Production of cast iron
About Production of cast iron
This cast iron came into the industry after World War II and, given its good mechanical properties, found significant applications in the industry, and because of its high utilization and good strength, it was gradually replaced by steel.
Reasons to replace ductile iron instead of steel :
1. In these castings, graphite is mainly spherical and with prefabricated perlite, and unlike malleable cast iron, these types of castings have high friction and flexibility. .
2. Compared to Mali-bone castings, these types of cast iron do not require a heat treatment cycle, so they are economically more economical, as well as by adding alloying elements during the melting of graphite The sheets It turns into spherical graphite In the chemical composition of these castings there are about 0.03% to 0.05% magnesium and the amount of sulfur in these castings is less than 0.01% Be .
Prepared and disposed of This type of cast iron is cast Similar to cast iron gray But with the difference in the melting process
Milling using alloying elements such as magnesium, graphite sheet to spherical graphite To be .
Note: The amount of molten expansion of the ductile iron is higher than gray cast iron and is therefore thrown in. It’s feeding Smaller ones Rhode and also in some cases without nutrition Power poured Gary did .
Types of furnaces for the production of Dactyl Cast Iron:
Coil ovens and flame furnaces And furnace Electrics Power to produce ductile iron :
Kupp Furnace: In Kupp kiln method, it is necessary to reduce the amount of sulfur and, secondly, Kupl kiln is one of the methods Some of you May cause the most sulfur in the melt due to the use of coal Therefore, it should be desulphurized before spinning graphite Did it .
Advantages of Kupple Furnace :
Reduction of melting cost and melting operations, dubbing of copper furnace: In this method, first the melt is prepared
In copper furnaces it is economical, but due to the high sulfur content, a sulfur deoxidation step and a carbon add-up step are carried out if carbon is low. Then, the melt is poured into the induction furnace and the melt is controlled in terms of chemical compositions. They do.
Charging materials for the production of ductile iron in induction furnaces :
Usually materials such as iron ingots, scrap steel, ferro-alloys, sponge iron are back Ductile iron cast iron Induction devices are used as charging .
Cast iron ingot: This ingot usually differs With a gray iron ingot, and is usually used in the production of gray iron from a long oven knife, which has a high sulfur content Be Cast iron ingots for dactyl casting usually have a lower sulfur content than gray cast iron ingots, which is usually less than 0.02% This bullion is usually cast in Brazilian and Canadian syringes To be In this bull Usually magnesium is used as an inoculum And the percentage of sulfur is considered low To prevent the loss of magnesium .
Steel scrap :
Due to the presence of low sulfur in the production of cast iron Ductile Application of this type of cast iron The industry is between 40% and 50% And its high point is the melting point and the carbon that is used to save on scrap energy. Before pouring Gary prehearses To make .
Direct Reduced Iron :
The product of the furnace Indirect use of which in the industry is between 10% and 15% Cause and cause
Its use is to reduce its cost The overall increase in temperature and the increase in the consumption of refractory materials .
Come back S :
This type of material in the industry accounts for about 30% of the charging of the furnace To be .
Ferro alloys :
Typically, these materials include Magnesium Ferro Silicom and Ferro Silica, in which Ferrocyclone Mimetic
It is used as spherical material And use silica as a germinant To be .
Advantages of ferroalloys :
- Generally, the loss of alloying elements is prevented To make .
- Cros silica increases the fluidity of the melt. And prevents the formation of carbide .
- Increases germination .
Preparation of the melt, which consists of three steps Be :
- Temperature control
- Chemical composition control
- Add spherical materials
1.Temperature control : The high temperature of the melt eliminates graphite stabilizing materials To be
Reduces the effect of inoculation On the other hand, low temperatures reduce the fluidity of the melt To be .
The temperature is usually used to prepare molten metal in dispersion ducts at a temperature range of 1450 to 1560
The temperature selection depends on the molten volume and the spherical method and the amount of spherical materials
Has a .
2. Chemical Composition Control : Sulfur is a spoiled material On the other hand, it causes the carbide phase stability If sulfur content is high, then desulphurisation is performed before adding spherical materials To be In order to perform the desulphurisation operation, two things must be followed. 1: The contact with molten sulfur must be as high as possible. 2 Time of reaction: If the time of desulphurisation is prolonged, it will re-enter sulfur from the slag into the melt Therefore, after the desulphurisation, slag operations should be performed immediately Take the patch to the pad .
Spherical elements: These substances include magnesium, serum and magnesium injected into coke Be Magnesium has a melting point of 620 ° C, which evaporates at 1100 ° C. To beAt this temperature, the internal pressure of magnesium reaches its maximum It seems that after adding to the melt, it sprays the melt, so adding alloys and amine to the mimesis Magnesium is used It is noteworthy that magnesium can be used in two forms To be .
1. Metal magnesium : Used at times Let the melt volume be low. These materials Can be used in the form of magnesium powder, magnesium ingot and magnesium scrap with iron and compressed magnesium brackets. .
2. Magnesium alloys : They are mainly divided into two groups To be .
A. Nickel magnesium alloys: nickel due to perlite properties Generation increases the mechanical properties of cast iron The only limitation of its use in the industry is its high cost Be It should be noted that nickel has a high price Usually to Nickel replaces the same elements (copper) for alloys To make Typically, magnesium nickel alloys are used in sandwich methods and soldered pots To make .
B. Magnesium Alloy Silicon Silicon Iron (Fermented Silicon Magnesium) (:
1. These types of alloys are cheaper in comparison to nickel alloys, and the silica in these alloys can be It can act as an inoculum agent, in addition, it has a strong spherical effect , so it is used in the industry and its chemical composition is 5% magnesium and 45% silicon and 5% iron Be .
2. Magnesium Injection Method : This technique is less commonly used The reason is that there is a lot of sulfur in the crust; this causes it To increase the amount of magnesium in this method .
1. Cerium: The evaporation temperature of this element is 3000 ° C, so magnesium problems in spherical But because it is a rare element, it is less used in the industry, and it is generally used in conjunction with magnesium in certain cases. .
Spreading method :
1. Soldier Pile Method : In this method, spherical materials are placed on a platter floor and melt is cast on these materials. To be In this way, it melts on magnesium And direct molar contact with magnesium Therefore, the recovery rate of magnesium in the melt is low It can be estimated that the recovery rate in this method is between 20% and 25%. In all methods of inoculum in the crucible, the ratio of the height of the patch to the diameter should be observed, which is the ratio of 3 to 1 m Be .
2. Sandwich method : In this method, the height is 3 times the diameter; with the difference that in the bottom of the cupboard Embedded in it That the spherical material is placed in this compartment and then coated with a coating of sand (steel sheet sandwich) To be Then the melt is poured into a pile and if it is used in sand, it will break the sand and cause the material to melt, but if the steel sheet is used, the melt will melt and the magnesium material will react with the melt. And also if it is done with ferrosilicon, the efficiency is increased and there are some advantages that, in addition to magnesium fosciallisim, germination is also carried out, which will increase the recovery rate in this method. The power is estimated to be between 45% and 40%. Another advantage of this method is that the loss of magnesium is greatly reduced due to the melting of magnesium ferrocylide and also due to the total outflow of oxygen. Also due to the low density of magnesium and its presence in the bottom of the bed after melting, the magnesium moves upwards and the inoculation is done completely. .
3. The method of immersion : In this method, the spherical material is embedded in the graphite compartment and when the cup is filled with molten material in a container, the recovery rate of magnesium in this method is 50 to 55%, which is usually the casting temperature In this method, the temperature drop in this method is 1560 ° C .
4. Rotor rotary method : In this method, after spinning materials are inserted into the conveyor, the rotator is rotated to about 90 degrees to make spherical materials melt, and the recovery rate in this method can be estimated to be about 60 percent. .
5. Magnesium powder Method: In this method, magnesium powder inside the chamber with inert gas is injected from the bottom of the ladle .
6. The template) Aynmvlt (recovery of magnesium in this method is about 100% of the time between inoculation and discharging molten lava in the least possible The less time this time is, the more spherical and uniform You’re better In this method, spherical materials are placed inside the system and during the flow of melt through the system, a spherical action plan is performed. To be .
Advantages of this method :
High levels of magnesium recovery to about. . 1%
Production of thin-sectioned parts
Elimination of environmental hazards
Reduce production steps
Increasing the mechanical properties of the piece
Facilitation in automation conditions
Disadvantages of this method :
1. The possibility of impurities entering To the mold casing if the false design of the mooring system .
2. The need for a precise and accurate design of the system that leads to increased production methods To be .
3. Need to use suitable alloy .
The phenomenon of depression :
The longer the time interval between the addition of spraying materials and melting is increased, the amount of their effect decreases, as well as the recovery rate of these materials decreases. .
Designing a Road System :
The design of the ductile cast iron system consists of two steps .
1. Interface compilation design
2. Design of the road
Interface compilation design that includes a feature Some are as follows Be :
A: The melt flow must be uniformly in contact with the level of spherical material .
B: Avoid carrying spherical material into the mold cavity .
Effective factors in choosing spherical method :
1. If the volume is high longitudinal method used for the globe To be .
2. The temperature of production, if high, is based on methods that have a minimum temperature .
3. ENVIRONMENTAL CONDITIONS: Techniques such as in-house minimize environmental damage .
4. Charging materials : If charging materials have a higher sulfur content, methods should be used to make spheroidization easier. .
5. Physical constraints
6. Casting time
Malt Dactyl Injection :
Ink ductile casting materials increase the number of cores per unit area, and therefore the spherical graphite distribution is more and more uniform. Which has a relatively high mechanical properties slow .
Inoculum In Dactyl Cast Iron :
These materials include aluminum silicon ferro-silicon sublimation. The in vitro practice of inoculation is less To be Generally, inoculation in ductile cast iron is more important than gray cast iron because it is spherical dactyl graphite in cast iron, but graphite in gray graphite gray sheet For this reason, the rate of inoculum in dactyl cast iron is lower than that of gray iron, which is why more nuclei are needed for dactyl inoculation. .
Inoculation methods :
1. Inoculation during melting
2. Insert inoculum materials on the mold surface and perform a vibrating system .
Control of the ductile cast iron production line includes controlling the charging materials of the furnace, controlling the operation of increasing magnesium, controlling inoculation, sproying and germination, controlling the effect of time, controlling the metallographic structure, controlling the metallographic properties Be .
1. Control of furnace charging materials includes: removal of non-iron materials from charging materials, removal of bearing parts, which due to lead lead to disintegration of graphite in ductile iron, removal of lead or lined lead or galvanized lead, control The dryness of the charge materials and the non-greasiness of these materials (this is due to preventing turbidity in the melt and reducing its mortality), drying the furnace coating, separating the rust or oxidized parts that increase the dissolution of oxygen and this Increases the loss of magnesium. To remove oxides and fats, charge materials before melting up to 300 to 400 I’m proud of .
2. Control of the operation of increasing magnesium and germination operations : control of the chemical composition of sulfur and harmful elements) At this stage, it is usually used to control the chemical composition of devices such as quantum oxometrometristometry, and atomic aberrozine and strains, which are now generally quantum Industry is used
Temperature control: The temperature of the magnesium is 1380 to 1450 degrees. Temperature control can also be made of thermocouple types And pyrometers .
The pyrometer is a device that uses it to rays It is possible to tell temperature without contact with the melt, which determines the temperature through the color of the alloy. The magnesium added to the melt is generally used in four ways :
2. It gets steam
3. Sulfide becomes
The magnesium residue remains (pulverized) causing graphite to spin Are you The amount of magnesium that is consumed by the molten magnesium is called pulverized or sulfided.Usually in unshakeable cast iron, such as the amount of sulfur 0.2% Mgs If desulphurization is done, it is zero To be .
3. Selection of Magnesium Magnesium Method
4. The geometric shape of the patch is controlled with a patch height of 3 times its diameter to prevent the loss of magnesium. .
5. Control of metallographic structure :
At the end of the sample production line for polishing and metallography, a microscope
The optical microstructure operation is performed .
6. Mechanical properties control :
For this purpose, a laboratory test such as strain testing hardness. . . . It is used that the tensile test is used for small units, but in large laboratories, the test of hardness test is taken out and the piece is alert .
* Cutting test : In the cast iron, the longer the cutting length is, the greater the fragmentation property. .
The tone test is: the harder the iron is, the more dull the iron is .
The basics of designing dashboard systems :
The roles of the system :
1. Melt transfer from bushes to molded compartment with max
2. Melting inside the system with minimal exhaustion and turbulence
The molten injection into the mold chamber should be such that the coolest part of the melt is in the outermost region
The mold is placed in the melt and the hottest part of the melt is inside the mast system
The dimensions of the guiding system must be designed in such a way that the mold of the mold cavity is in the form
Full fills the minimum return on the system .
Defects created in the design of the missile system :
1. Sanding sand and impurities into the mold chamber
2. Reduced surface quality of the production unit
Gas absorption in the melt and gas mist
Excessive oxidation of the melt
Creating contraction cavities in the production parts
5. Fill the template completely (do not go )
The introduction of pre-solid particles into the mold chamber
Two laws in physics are used to design a marching system
1. The energy conservation law ( Bernoulli law): Bernoulli’s relation has been extracted, which states that the amount of energy in a closed system is always constant, that the energies in this system can be introduced in the following way. .
2. Continuity law :
The law states that the amount of liquid flow in each section in a unit of time is constant .
Military system calculations :
1. Determine the rational system ratio :
Consisting of: a) push system; b) non-compression mooring system; c) a combined mooring system;
A: Compression system: In this system, the cross-sectional area from the barrage to the piece
The melt is pushed into the mold chamber by pressure .
1. The mosque is immediately filled with melt .
2. The solid melt volume in the marching system is minimal and increases the efficiency of the mooring system
To be The molten flow into the mold is more uniform .
1. This system causes turbulence and excitement within the system, causing the formation of gas deposits and sandblasting inside the system. .
2. Non- compression road system : The advantage of this type of system is to create a minimum of turbulence and expansion in the melt
And its disadvantages are the following: 1) the non-uniformity of the molten inlet from the 2nd incremental increase in weight
The system in this type of system should always be inside the mall
Note: Non-pressure compressed or non-iron alloys are used
Racking system components :
1. Thick pond
2. Barrice Road
Bottom of the pond
Primary and secondary canals
Interested in airing
Barris pond: To control the pouring speed and reduce the inlet pressure into the mold chamber and the molding system, it is usually used in cast iron and steel in the shape of a trapezoidal mold. The reason is the use of this type of slag collection at the melt surface and the control of the rolling speed of the propulsion board, which directs the melt from the funnel to the main platform. If the piece has a large dimension, it may be used simultaneously from two or more berths. And the cross-section of this type of platform They are usually rectangular, but in some cases, the circular cross-section is also used. To calculate the ratio of the barrage site, we must have the diameter of the input and output port. .
Pressure Feeding: The basis of this feeding method is based on the use of molten pressure at the melt expansion stage due to graphite deposition.
Effective factors in compression feeding :
1. Impression material: it should have sufficient strength to an expansion chamber liquid form to avoid dimensional changes .
2. Pressure feeding is used for the parts that are volummetric Up to two-Half
Practical cases for designing compression feeding :
1. Get the modulus of the largest part of the pieces if it is between . Up to 2 We will use this method
2. Modulus nutrition piece :
Obtain Nutrition Module
Gaining effective feeding volume
Gaining the height of the degree according to the volume of the feeding and the height between 1 to 1 it will be obtained. Using the thickness chart of the nutrition that is found in the vicinity of the frozen molding material
Feed diameter at stage, We add twice the thickness of the frozen equation. Feeding to a thicker portion of the feeding is hot and if you use large portion, use hot water. If the use of blind feeding is to be done, the feeding must be in contact with the atmosphere. The melting temperature should be the amount that is considered in the calculations.
History of Metallurgy
History of Metallurgy
The present-day use of metals is the culmination of a long path of development extending over approximately 6,500 years. It is generally agreed that the first known metals were gold, silver, and copper, which occurred in the native or metallic state, of which the earliest were in all probability nuggets of gold found in the sands and gravels of riverbeds. Such native metals became known and were appreciated for their ornamental and utilitarian values during the latter part of the Stone Age.
Gold can be agglomerated into larger pieces by cold hammering, but native copper cannot, and an essential step toward the Metal Age was the discovery that metals such as copper could be fashioned into shapes by melting and casting in molds; among the earliest known products of this type are copper axes cast in the Balkans in the 4th millennium bc. Another step was the discovery that metals could be recovered from metal-bearing minerals. These had been collected and could be distinguished on the basis of colour, texture, weight, and flame colour and smell when heated. The notably greater yield obtained by heating native copper with associated oxide minerals may have led to the smelting process, since these oxides are easily reduced to metal in a charcoal bed at temperatures in excess of 700° C (1,300° F), as the reductant, carbon monoxide, becomes increasingly stable. In order to effect the agglomeration and separation of melted or smelted copper from its associated minerals, it was necessary to introduce iron oxide as a flux. This further step forward can be attributed to the presence of iron oxide gossan minerals in the weathered upper zones of copper sulfide deposits.
In many regions, copper-arsenic alloys, of superior properties to copper in both cast and wrought form, were produced in the next period. This may have been accidental at first, owing to the similarity in colour and flame colour between the bright green copper carbonate mineral malachite and the weathered products of such copper-arsenic sulfide minerals as enargite, and it may have been followed later by the purposeful selection of arsenic compounds based on their garlic odour when heated.
Arsenic contents varied from 1 to 7 percent, with up to 3 percent tin. Essentially arsenic-free copper alloys with higher tin content—in other words, true bronze—seem to have appeared between 3000 and 2500 bc, beginning in the Tigris-Euphrates delta. The discovery of the value of tin may have occurred through the use of stannite, a mixed sulfide of copper, iron, and tin, although this mineral is not as widely available as the principal tin mineral, cassiterite, which must have been the eventual source of the metal. Cassiterite is strikingly dense and occurs as pebbles in alluvial deposits together with arsenopyrite and gold; it also occurs to a degree in the iron oxide gossans mentioned above.
While there may have been some independent development of bronze in varying localities, it is most likely that the bronze culture spread through trade and the migration of peoples from the Middle East to Egypt, Europe, and possibly China. In many civilizations the production of copper, arsenical copper, and tin bronze continued together for some time. The eventual disappearance of copper-arsenic alloys is difficult to explain. Production may have been based on minerals that were not widely available and became scarce, but the relative scarcity of tin minerals did not prevent a substantial trade in that metal over considerable distances. It may be that tin bronzes were eventually preferred owing to the chance of contracting arsenic poisoning from fumes produced by the oxidation of arsenic-containing minerals.
As the weathered copper ores in given localities were worked out, the harder sulfide ores beneath were mined and smelted. The minerals involved, such as chalcopyrite, a copper-iron sulfide, needed an oxidizing roast to remove sulfur as sulfur dioxide and yield copper oxide. This not only required greater metallurgical skill but also oxidized the intimately associated iron, which, combined with the use of iron oxide fluxes and the stronger reducing conditions produced by improved smelting furnaces, led to higher iron contents in the bronze.
It is not possible to mark a sharp division between the Bronze Age and the Iron Age. Small pieces of iron would have been produced in copper smelting furnaces as iron oxide fluxes and iron-bearing copper sulfide ores were used. In addition, higher furnace temperatures would have created more strongly reducing conditions (that is to say, a higher carbon monoxide content in the furnace gases). An early piece of iron from a trackway in the province of Drenthe, Neth., has been dated from 1350 bc, a date normally taken as the Middle Bronze Age for this area. In Anatolia, on the other hand, iron was in use as early as 2000 bc. There are also occasional references to iron in even earlier periods, but this material was of meteoric origin.
Once a relationship had been established between the new metal found in copper smelts and the ore added as flux, the operation of furnaces for the production of iron alone naturally followed. Certainly by 1400 bc in Anatolia, iron was assuming considerable importance, and by 1200–1000 bc it was being fashioned on quite a large scale into weapons, initially dagger blades. For this reason, 1200 bc has been taken as the beginning of the Iron Age. Evidence from excavations indicates that the art of iron making originated in the mountainous country to the south of the Black Sea, an area dominated by the Hittites. Later the art apparently spread to the Palestinians, for crude furnaces dating from 1200 bc have been unearthed at Gerar, together with a number of iron objects.
Smelting of iron oxide with charcoal demanded a high temperature, and, since the melting temperature of iron at 1,540° C (2,800° F) was not attainable then, the product was merely a spongy mass of pasty globules of metal intermingled with a semiliquid slag. This product, later known as bloom, was hardly usable as it stood, but repeated reheating and hot hammering eliminated much of the slag, creating wrought iron, a much better product.
The properties of iron are much affected by the presence of small amounts of carbon, with large increases in strength associated with contents of less than 0.5 percent. At the temperatures then attainable—about 1,200° C (2,200° F)—reduction by charcoal produced an almost pure iron, which was soft and of limited use for weapons and tools, but when the ratio of fuel to ore was increased and furnace drafting improved with the invention of better bellows, more carbon was absorbed by the iron. This resulted in blooms and iron products with a range of carbon contents, making it difficult to determine the period in which iron may have been purposely strengthened by carburizing, or reheating the metal in contact with excess charcoal.
Carbon-containing iron had the further great advantage that, unlike bronze and carbon-free iron, it could be made still harder by quenching—i.e., rapid cooling by immersion in water. There is no evidence for the use of this hardening process during the early Iron Age, so that it must have been either unknown then or not considered advantageous, in that quenching renders iron very brittle and has to be followed by tempering, or reheating at a lower temperature, to restore toughness. What seems to have been established early on was a practice of repeated coldforging and annealing at 600–700° C (1,100–1,300° F), a temperature naturally achieved in a simple fire. This practice is common in parts of Africa even today.
By 1000 bc iron was beginning to be known in central Europe. Its use spread slowly westward; iron making was fairly widespread in Great Britain at the time of the Roman invasion in 55 bc. In Asia iron was also known in ancient times, in China by about 700 bc.
While some zinc appears in bronzes dating from the Bronze Age, this was almost certainly an accidental inclusion, although it may foreshadow the complex ternary alloys of the early Iron Age, in which substantial amounts of zinc as well as tin may be found. Brass, as an alloy of copper and zinc without tin, did not appear in Egypt until about 30 bc, but after this it was rapidly adopted throughout the Roman world, for example, for currency. It was made by the calamine process, in which zinc carbonate or zinc oxide were added to copper and melted under a charcoal cover in order to produce reducing conditions. The general establishment of a brass industrywas one of the important metallurgical contributions made by the Romans.
Bronze, iron, and brass were, then, the metallic materials on which successive peoples built their civilizations and of which they made their implements for both war and peace. In addition, by 500 bc, rich lead-bearing silver mines had opened in Greece. Reaching depths of several hundred metres, these mines were vented by drafts provided by fires lit at the bottom of the shafts. Ores were hand-sorted, crushed, and washed with streams of water to separate valuable minerals from the barren, lighter materials. Because these minerals were principally sulfides, they were roasted to form oxides and were then smelted to recover a lead-silver alloy.
Lead was removed from the silver by cupellation, a process of great antiquity in which the alloy was melted in a shallow porous clay or bone-ash receptacle called a cupel. A stream of air over the molten mass preferentially oxidized the lead. Its oxide was removed partially by skimming the molten surface; the remainder was absorbed into the porous cupel. Silver metal and any gold were retained on the cupel. The lead from the skimmings and discarded cupels was recovered as metal upon heating with charcoal.
Native gold itself often contained quite considerable quantities of silver. These silver-gold alloys, known as electrum, may be separated in a number of ways, but presumably the earliest was by heating in a crucible with common salt. In time and with repetitive treatments, the silver was converted into silver chloride, which passed into the molten slag, leaving a purified gold. Cupellation was also employed to remove from the gold such contaminates as copper, tin, and lead. Gold, silver, and lead were used for artistic and religious purposes, personal adornment, household utensils, and equipment for the chase.
From 500 bc To ad 1500
In the thousand years between 500 bc and ad 500, a vast number of discoveries of significance to the growth of metallurgy were made. The Greek mathematician and inventor Archimedes, for example, demonstrated that the purity of gold could be measured by determining its weight and the quantity of water displaced upon immersion—that is, by determining its density. In the pre-Christian portion of the period, the first important steel production was started in India, using a process already known to ancient Egyptians. Wootz steel, as it was called, was prepared as sponge (porous) iron in a unit not unlike a bloomery. The product was hammered while hot to expel slag, broken up, then sealed with wood chips in clay containers and heated until the pieces of iron absorbed carbon and melted, converting it to steel of homogeneous composition containing 1 to 1.6 percent carbon. The steel pieces could then be heated and forged to bars for later use in fashioning articles, such as the famous Damascus swords made by medieval Arab armourers.
Arsenic, zinc, antimony, and nickel may well have been known from an early date but only in the alloy state. By 100 bc mercury was known and was produced by heating the sulfide mineral cinnabar and condensing the vapours. Its property of amalgamating (mixing or alloying) with various metals was employed for their recovery and refining. Lead was beaten into sheets and pipes, the pipes being used in early water systems. The metal tin was available and Romans had learned to use it to line food containers. Although the Romans made no extraordinary metallurgical discoveries, they were responsible for, in addition to the establishment of the brass industry, contributing toward improved organization and efficient administration in mining.
Beginning about the 6th century, and for the next thousand years, the most meaningful developments in metallurgy centred on iron making. Great Britain, where iron ore was plentiful, was an important iron-making region. Iron weapons, agricultural implements, domestic articles, and even personal adornments were made. Fine-quality cutlery was made near Sheffield. Monasteries were often centres of learning of the arts of metalworking. Monks became well known for their iron making and bell founding, the products made either being utilized in the monasteries, disposed of locally, or sold to merchants for shipment to more distant markets. In 1408 the bishop of Durham established the first water-powered bloomery in Britain, with the power apparently operating the bellows. Once power of this sort became available, it could be applied to a range of operations and enable the hammering of larger blooms.
In Spain, another iron-making region, the Catalan forge had been invented, and its use later spread to other areas. A hearth type of furnace, it was built of stone and was charged with iron ore, flux, and charcoal. The charcoal was kept ignited with air from a bellows blown through a bottom nozzle, or tuyere (see figure). The bloom that slowly collected at the bottom was removed and upon frequent reheating and forging was hammered into useful shapes. By the 14th century the furnace was greatly enlarged in height and capacity.
If the fuel-to-ore ratio in such a furnace was kept high, and if the furnace reached temperatures sufficiently hot for substantial amounts of carbon to be absorbed into the iron, then the melting point of the metal would be lowered and the bloom would melt. This would dissolve even more carbon, producing a liquid cast iron of up to 4 percent carbon and with a relatively low melting temperature of 1,150° C (2,100° F). The cast iron would collect in the base of the furnace, which technically would be ablast furnace rather than a bloomery in that the iron would be withdrawn as a liquid rather than a solid lump.
While the Iron Age peoples of Anatolia and Europe on occasion may have accidently made cast iron, which is chemically the same as blast-furnace iron, the Chinese were the first to realize its advantages. Although brittle and lacking the strength, toughness, and workability of steel, it was useful for making cast bowls and other vessels. In fact, the Chinese, whose Iron Age began about 500 bc, appear to have learned to oxidize the carbon from cast iron in order to produce steel or wrought iron indirectly, rather than through the direct method of starting from low-carbon iron.
During the 16th century, metallurgical knowledge was recorded and made available. Two books were especially influential. One, by the Italian Vannoccio Biringuccio, was entitled De la pirotechnia (Eng. trans., The Pirotechnia of Vannoccio Biringuccio, 1943). The other, by the German Georgius Agricola, was entitled De re metallica. Biringuccio was essentially a metalworker, and his book dealt with smelting, refining, and assay methods (methods for determining the metal content of ores) and covered metal casting, molding, core making, and the production of such commodities as cannons and cast-iron cannonballs. His was the first methodical description of foundry practice.
Agricola, on the other hand, was a miner and an extractive metallurgist; his book considered prospecting and surveying in addition to smelting, refining, and assay methods. He also described the processes used for crushing and concentrating the ore and then, in some detail, the methods of assaying to determine whether ores were worth mining and extracting. Some of the metallurgical practices he described are retained in principle today.
From 1500 to the 20th century, metallurgical development was still largely concerned with improved technology in the manufacture of iron and steel. In England, the gradual exhaustion of timber led first to prohibitions on cutting of wood for charcoal and eventually to the introduction of coke, derived from coal, as a more efficient fuel. Thereafter the iron industry expanded rapidly in Great Britain, which became the greatest iron producer in the world. The crucible process for making steel, introduced in England in 1740, by which bar iron and added materials were placed in clay crucibles heated by coke fires, resulted in the first reliable steel made by a melting process.
One difficulty with the bloomery process for the production of soft bar iron was that, unless the temperature was kept low (and the output therefore small), it was difficult to keep the carbon content low enough so that the metal remained ductile. This difficulty was overcome by melting high-carbon pig iron from the blast furnace in the puddling process, invented in Great Britain in 1784. In it, melting was accomplished by drawing hot gases over a charge of pig iron and iron ore held on the furnace hearth. During its manufacture the product was stirred with iron rabbles (rakes), and, as it became pasty with loss of carbon, it was worked into balls, which were subsequently forged or rolled to a useful shape. The product, which came to be known as wrought iron, was low in elements that contributed to the brittleness of pig iron and contained enmeshed slag particles that became elongated fibres when the metal was forged. Later, the use of a rolling mill equipped with grooved rolls to make wrought-iron bars was introduced.
The most important development of the 19th century was the large-scale production of cheap steel. Prior to about 1850, the production of wrought iron by puddling and of steel by crucible melting had been conducted in small-scale units without significant mechanization. The first change was the development of the open-hearth furnace by William and Friedrich Siemens in Britain and by Pierre and Émile Martin in France. Employing the regenerative principle, in which outgoing combusted gases are used to heat the next cycle of fuel gas and air, this enabled high temperatures to be achieved while saving on fuel. Pig iron could then be taken through to molten iron or low-carbon steel without solidification, scrap could be added and melted, and iron ore could be melted into the slag above the metal to give a relatively rapid oxidation of carbon and silicon—all on a much enlarged scale. Another major advance was Henry Bessemer’s process, patented in 1855 and first operated in 1856, in which air was blown through molten pig iron from tuyeres set into the bottom of a pear-shaped vessel called a converter. Heat released by the oxidation of dissolved silicon, manganese, and carbon was enough to raise the temperature above the melting point of the refined metal (which rose as the carbon content was lowered) and thereby maintain it in the liquid state. Very soon Bessemer had tilting converters producing 5 tons in a heat of one hour, compared with four to six hours for 50 kilograms (110 pounds) of crucible steel and two hours for 250 kilograms of puddled iron.
Neither the open-hearth furnace nor the Bessemer converter could remove phosphorus from the metal, so that low-phosphorus raw materials had to be used. This restricted their use from areas where phosphoric ores, such as those of the Minette range in Lorraine, were a main European source of iron. The problem was solved by Sidney Gilchrist Thomas, who demonstrated in 1876 that a basic furnace lining consisting of calcined dolomite, instead of an acidic lining of siliceous materials, made it possible to use a high-lime slag to dissolve the phosphates formed by the oxidation of phosphorus in the pig iron. This principle was eventually applied to both open-hearth furnaces and Bessemer converters.
As steel was now available at a fraction of its former cost, it saw an enormously increased use for engineering and construction. Soon after the end of the century it replaced wrought iron in virtually every field. Then, with the availability of electric power, electric-arc furnaces were introduced for making special and high-alloy steels. The next significant stage was the introduction of cheap oxygen, made possible by the invention of the Linde-Frankel cycle for the liquefaction and fractional distillation of air. The Linz-Donawitz process, invented in Austria shortly after World War II, used oxygen supplied as a gas from a tonnage oxygen plant, blowing it at supersonic velocity into the top of the molten iron in a converter vessel. As the ultimate development of the Bessemer/Thomas process, oxygen blowing became universally employed in bulk steel production.
Another important development of the late 19th century was the separation from their ores, on a substantial scale, of aluminum and magnesium. In the earlier part of the century, several scientists had made small quantities of these light metals, but the most successful was Henri-Étienne Sainte-Claire Deville, who by 1855 had developed a method by which cryolite, a double fluoride of aluminum and sodium, was reduced by sodium metal to aluminum and sodium fluoride. The process was very expensive, but cost was greatly reduced when the American chemist Hamilton Young Castner developed an electrolytic cell for producing cheaper sodium in 1886. At the same time, however, Charles M. Hall in the United States and Paul-Louis-Toussaint Héroult in France announced their essentially identical processes for aluminum extraction, which were also based on electrolysis. Use of the Hall-Héroult process on an industrial scale depended on the replacement of storage batteries by rotary power generators; it remains essentially unchanged to this day.
One of the most significant changes in the technology of metals fabrication has been the introduction of fusion welding during the 20th century. Before this, the main joining processes were riveting and forge welding. Both had limitations of scale, although they could be used to erect substantial structures. In 1895 Henry-Louis Le Chatelier stated that the temperature in an oxyacetylene flame was 3,500° C (6,300° F), some 1,000° C higher than the oxyhydrogen flame already in use on a small scale for brazing and welding. The first practical oxyacetylene torch, drawing acetylene from cylinders containing acetylene dissolved in acetone, was produced in 1901. With the availability of oxygen at even lower cost, oxygen cutting and oxyacetylene welding became established procedures for the fabrication of structural steel components.
The metal in a join can also be melted by an electric arc, and a process using a carbon as a negative electrode and the workpiece as a positive first became of commercial interest about 1902. Striking an arc from a coated metal electrode, which melts into the join, was introduced in 1910. Although it was not widely used until some 20 years later, in its various forms it is now responsible for the bulk of fusion welds.
The 20th century has seen metallurgy change progressively, from an art or craft to a scientific discipline and then to part of the wider discipline of materials science. In extractive metallurgy, there has been the application of chemical thermodynamics, kinetics, and chemical engineering, which has enabled a better understanding, control, and improvement of existing processes and the generation of new ones. Inphysical metallurgy, the study of relationships between macrostructure, microstructure, and atomic structure on the one hand and physical and mechanical properties on the other has broadened from metals to other materials such as ceramics, polymers, and composites.
This greater scientific understanding has come largely from a continuous improvement in microscopic techniques for metallography, the examination of metal structure. The first true metallographer was Henry Clifton Sorby of Sheffield, Eng., who in the 1860s applied light microscopy to the polished surfaces of materials such as rocks and meteorites. Sorby eventually succeeded in making photomicrographic records, and by 1885 the value of metallography was appreciated throughout Europe, with particular attention being paid to the structure of steel. For example, there was eventual acceptance, based on micrographic evidence and confirmed by the introduction of X-ray diffraction by William Henry and William Lawrence Bragg in 1913, of the allotropy of iron and its relationship to the hardening of steel. During subsequent years there were advances in the atomic theory of solids; this led to the concept that, in nonplastic materials such as glass, fracture takes place by the propagation of preexisting cracklike defects and that, in metals, deformation takes place by the movement of dislocations, or defects in the atomic arrangement, through the crystalline matrix. Proof of these concepts came with the invention and development of the electron microscope; even more powerful field ion microscopes and high-resolution electron microscopes now make it possible to detect the position of individual atoms.
Another example of the development of physical metallurgy is a discovery that revolutionized the use of aluminum in the 20th century. Originally, most aluminum was used in cast alloys, but the discovery of age hardening by Alfred Wilm in Berlin about 1906 yielded a material that was twice as strong with only a small change in weight. In Wilm’s process, a solute such as magnesium or copper is trapped in supersaturated solid solution, without being allowed to precipitate out, by quenching the aluminum from a higher temperature rather than slowly cooling it. The relatively soft aluminum alloy that results can be mechanically formed, but, when left at room temperature or heated at low temperatures, it hardens and strengthens. With copper as the solute, this type of material came to be known by the trade name Duralumin. The advances in metallography described above eventually provided the understanding that age hardening is caused by the dispersion of very fine precipitates from the supersaturated solid solution; this restricts the movement of the dislocations that are essential to crystal deformation and thus raises the strength of the metal. The principles of precipitation hardening have been applied to the strengthening of a large number of alloys.
Ferroalloy, alloys made of iron and one or more other elements And the easy conditions for the introduction of the element or elements to steel or molten iron are provided To make The role of these elements Can contain oxygen Dismantling or creating the desired structure and achieving the desired physical and chemical properties for certain types of steel and cast iron applications. These elements are: silicon, manganese, chromium, molybdenum, vanadium, titanium, cobalt, nickel and tungsten.
Add the above elements The following are not intended to be cast into alloys (steel and cast iron) for the following reasons:
1- Production of some metals in pure form is not economically feasible.
2- The price of alloying elements is very expensive in the pure form and the cost of their production.
3. The melting point of the elements in the pure state is greater than that of the alloy.
Therefore, creating the desired temperature for the melting of pure elements in addition to cost creation There are many technical problems for production, and the use of ferroalloys is essentially easy. It’s more than adding elements to the net. Some of the ferro-alloys play the role of detoxification of certain phases, including spherical graphite, or optimization and microstructure refinement in cast iron alloys. And to this alloys are inoculum or germination materials They say The major application of ferroalloys is in the casting and casting industry and electrodeposition industries.Consequently, ferroalloys play a unique role in the production of steel and castings of steel and cast iron. Therefore, the development of steel and cast iron production capacities in Iran, as in other countries, will be accompanied by an increase in ferroalloy consumption. Accordingly, the production of ferroalloys is quantitatively and qualitatively for the production of steel and the development of poured industries Gray is dependent on the production of steel and scrap Greased cast iron is more than ferroalloy Especially ferrosilicon will be higher.Since steel production plays an important role in economic development, production of ferroalloys is very important for the national economy. Due to the fact that the supply of raw materials and energy for the production of steel in Iran is not a problem and now almost the equivalent of the total domestic production of steel products, unfortunately comes from other countries. To be Certainly in the future with the way Size and interest Take the factory In the process of equipping steel production, the consumption of ferroalloys, especially ferosilicum, in the country should be increased. At present, 6 types of ferroalloy and molybdenum oxide are produced in 19 units of ferroalloy and molybdenum oxide in Iran. In the year 87 the production of ferroalloy and molybdenum oxide in Iran was about 75 thousand tons. History of Ferroalloy Production: In general, ferroalloys, which are silicon metal and ferrosilicon, are also classified in terms of production. Before the 1900s, such as Mint Iron or iron manganese stones Do it right now Graphite and in ground furnaces are produced with coke and other necessary materials. Products produced according to this method qualitatively only have industrial value in limited cases. By this method, ferrally alloys with high melting points could not be homogeneous due to lack of high temperatures. They gave. As a solution to the production of low-grade ferro-alloys, such as 45% fosciallisium. Obviously, the produced quantities did not cover the needs of rapidly expanding steel industries. Therefore, there should be other ways to make more production with lowering the price. Considering that the discussion of the day was the production of alloys of iron and another element. Therefore, ferroalloy production methods from iron and steel production methods could not be far off. Until 1920, iron was produced only in a long furnace. Therefore, in the furnace, instead of charging the ore Pure iron, manganese iron, chromium or titanium ore for the production of ferroalloys. They did.Production was not satisfactory, except in a few cases, so that, based on the production of large furnaces, there were huge industries (production of ferro-manganese and manganese); however, the production of other ferroalloys, ferrocylithium and silicon metal in the furnace had a lot of problems. Due to the type of building and type of furnace, they could not reach the high temperatures necessary for the restoration and melting of most ferroalloys. With the creation of generators and the creation of power generation industries, the history of ferroalloy production has evolved to a large extent. All elements which, due to the melting point and the high recovery temperature of their oxides, could not easily be produced in a long furnace, in a regular work by MOISSAN French Ferroalloy Production was performed in an electric arc furnace. The results of this person’s experiments by HEROULT The French were transferred to the industry. First, the production of calcium carbide 2 CaC This method became industrial and then other ferroalloys, including silicon metal and ferrosilicon, reached industrial production. Thus, the use of electric arc furnaces for the production of Ferrosilicon and Silicon Metal as the best way up to today.
Ferroalloy production in the world: According to reports in 2004, about 22.5 million tons of ferroalloy have been produced in the world, respectively, with China, South Africa, Ukraine accounting for 76% of the world’s ferroalloy production. China alone produced over 38.8 percent of the world’s ferroalloy production in 2004 with an annual production of more than 8.65 million tons of ferroalloy, and Iran’s share of ferroalloy production in the year (83) was about 46.0 percent of global production.
Ferroalloy production in Iran: In 2009, 6 types of ferroalloy and some types of germination are produced in 13 ferroalloy production units of Iran. The total amount of ferroalloy production in Iran in the year 84 was about 112 thousand tons, which has increased by 8 percent since 83 years. Considering that the nominal capacity of Iran’s ferroalloy production in 2004 was about 156 thousand tons, only about 72% of the capacity of existing equipment and facilities was used to produce ferroalloy this year. The status of production of each ferroalloy in Iran is now examined below:
Ferrosilicon Silicon is the most abundant element of the Earth’s crust after oxygen, and is usually found in quartz in nature. Today, silicon is widely used in the industry, but one of its alloys, which has been widely used, is ferrocyanic. Ferrocalcium is an amalgam of iron and silicon produced by heating, reclaiming and melting iron ore and carbon-silicon in electric arc furnaces. To be Ferrosilicon contains various percentages of iron and silicon, the amount of silicon in ferrosilicon, which usually indicates the type of ferrosilicon Be Amongst the different types of silica, ferrocyanic FeSi % 75 Commonplace It is said to contain at least 75% silicon. It was manufactured in the early 1910s by physicists and chemists from Sweden and Germany separately.
How to produce: The basis of Ferrocyanium production is cybernetic reactions. Here, based on a series of redox reactions of materials including silica (quartz stone) and iron oxide with energy addition Electric and remediation materials include carbon dioxide, which is recovered and produced by ferrosilicon. To be In this process, raw materials such as silica stone And oxide shells along with reducing agents such as charcoal Rock. Coke and charcoal are flooded into the furnace through a daily storage system through a transfer system To be This charge is reset and melted by electrodes with a current intensity of 120 kA and at a temperature such as 2500 ° C, during an electrometallurgical process. To be Melting operation In Iran, the ferroalloy processing plant was produced on average every two hours, and the produced fosilcium after being depleted in a special bed was frozen and then washed away by stone Breaking and crushing Different in bulk or in bagg bags To make.
How To Generate Forsellium: Charging Furnace: Stone Silica Stone (125 -25 mm) at the Azna and Semnan factories with coal (5-15 mm), coke (20 -5 mm), charcoal (10-80 mm), and iron oxide crust through the daily storage and through the transfer systems into the electric arc furnace smelting furnace To make Recovery and melt: This charge is powered by graphite electrodes at a current density of about 120,000 amps at a temperature of about 2500 ° C and during an electrometallurgical process in the cavity region Reaction and recovery To beMelt loading and transportation: Melting operation At Azna factory, the discharge is performed on average every 2 hours and through the kiln of the electric arc. To be Hole loading through the arc Electric or compressed air drill To be The used patch that is made of a steel shell and internal fireproof wall with a height of 3.2 and an average diameter of 9.1 meters is about 3 cubic meters of useful volume. To move a pad, use a wagon and a roof crane To be The maximum pellet weight is about 23 tons, with a minimum capacity of 25 tons for cranes and wagons. After filling the crater, the loading crater is again closed by throwing and knocking the carbon material. To be The main applications of Ferrosilicon in the casting and steel industries are as follows:
1- Oxygen depletion: Ferrocalcium is widely used in the steel industry as an oxygen-discharged.
2- Germination: Due to graphite High production of silicon, frucilcium as a germination in the production of all types of cast iron Gray is applicable.
3- Alloy element: Silicon is an important alloying element in iron and non-ferrous alloys. It uses silicon metal to add silicon to cast iron or alloy steel.
4- Production of refractory steel.
5- Reducing material in the production of other ferroalloys. When ferrosilicon is used in steel casting, its strength, hardness, elasticity and magnetic strength increase. Find It is also possible to add ferrocylases to the melt Can prevent the formation of unwanted carbides.
6- Chemical industry. Of course, the major use of Ferrosilicon in Iran is now oxygen Dismantling steel in steel pile and sprout Creation in the cast Cast iron Gray, used as an alloying element in alloy steels.