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Ferro Chrome Testing And Analysis Home / Ferro Chrome Testing & Analysis

Ferrochrome (FeCr) is an alloy of chromium and iron containing between 50% and 70% chromium. Ferrochrome production is essentially a carbothermic reduction operation taking place at high temperatures, most commonly in a electric arc furnace. Cr Ore (an oxide of chromium and iron) is reduced by coal and coke to form the iron-chromium alloy.

Though among the above HCFC is most commonly used in the Industry, higher percentage of carbon in ferrochrome creates several problems, for many purposes e. g. in final adjustment of stainless steel analysis, in extra low carbon alloy steels, special steels etc.when it is necessary to have very low carbon content in the alloy

Ferrochrome is often classified by the amount of carbon and chrome it contains. The vast majority of FeCr produced is charge chrome from Southern Africa. With high carbon being the second largest segment followed by the smaller sectors of low carbon and intermediate carbon material.

Over 80% of the world's ferrochrome is utilised in the production of stainless steel. FeCr from Southern Africa, known as 'charge chrome' and produced from a Cr containing ore with a low chrome content, is most commonly used in stainless steel production. Alternatively, high carbon FeCr produced from high grade ore found in India, Turkey & Kazakhstan (among other places) is more commonly used in specialist applications such as engineering steels where a high Cr to Fe ratio and minimum levels of other elements such as sulfur, phosphorus and titanium are important.

According to the C content, Ferro Chrome can be classified in 3 types:
HCFC : C % varies from 6 – 8%.
MCFC : C% varies from 0.5 – 1.5%
LCFC : C% below 0.5%

Carbon content of metal

EFFECT OF DIFFERENT PARAMETERS


Cr/Fe ratio : Cr/Fe ratio plays a role in the determination of the carbon content of the alloy. As chromium has more affinity to form carbides than iron, a higher Cr/Fe ratio means a higher carbon content of metal.

Si : A high MgO/Al2O3 ratio and a basic slag inhibit reduction of SiO2 to Si. Higher temperatures are required for the reduction of SiO2. Cr2O3 and FeO are reduced in solid state and in lower temperatures, thus there is very little opportunity for SiO2 to be reduced. Again a low Si content is a result of reduction of Cr2O3 and FeO in solid state and low temperatures.

S and P : Since the S and P content of the chrome ore is very low, introduction of S and P to metal is predominantly from the reductants. For example, a coke with a sulphur content of 0.6 to 1 percent will deliver a metal with a sulphur content of 0.014 to 0.025.

For dephosphorization the requirements include basic slags, lower temperatures and an oxidizing environment.. Even though most of the phosphorous enters the metal, the high basicity of the slag could result in a decrease in phosphorous content.

Sum of the alloy’s carbon and silicon contents has a negative correlation with the sulphur inside the alloy. In fact C and Si both are reducing agents and can meet one of the above conditions.

All of the above help to use cheaper reductants higher in S and P content. The P content of the alloy is 0.010 - 0.025 Slag characteristics : Slag composition under normal conditions has no big influence on slag Cr2O3 content. If the Cr2O3 content in the ore was high, some chromite was not totally reduced and could be observed in the tapped slag.

Slag can be determined in the metal by Gravity separation method or by Proportionate Al/Mg Method. While second method depends upon knowing the raw material characteristics, first method is more direct irrespective of raw material and production parameters.

Hence quality control of both input raw material and finished product are vert much necessary for manufacturing Ferrochrome of desired quality. MSK is having the capability of carrying out test of raw material and finished product. The trace elements like Ni, V, Co, Ti, Pb, B are very vital for specific application. MSK Central laboratory at Kolkata has developed the capability for a carrying out the trace elements by ICP –OES technology.
 

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