Ferro-alloys are mainly used as master alloys in the iron, foundry and steel industry, because it is the most economical way to introduce an alloying element into the steel melt. Besides this, special ferro-alloys are also needed for the production of aluminium alloys and as starting material in specific chemical reactions.
As an additive in steel production, ferro-alloys improve the properties, especially the tensile strength, wear and corrosion resistance. The effect of the improved properties of steel by using ferro-alloys as an alloying element depend more or less on the following influences:
- A change in the chemical composition of the steel.
- The removal or the tying up of harmful impurities such as oxygen, nitrogen, sulphur or hydrogen.
- A change in the nature of the solidification, for example, upon inoculation.
Depending on the production rate, ferro-alloys can be divided into two main categories: bulk alloys and special alloys. Bulk ferro-alloys (ferro-chrome, ferro-silicon, ferro-manganese, silico- manganese and ferro-nickel) account for about 90 % of the total production of ferro-alloys in the European Union.
Swissxer markets the following ferro-alloys worldwide:- Ferro-chrome
Along with nickel (ferro-nickel) is the major alloying element in the production of stainless steel. Stainless steel is used in a variety of areas from cutlery to aircraft engine turbine blades.
- Ferro-silicon and silicon alloys
Ferro-silicon, silicon metal and silico-calcium (CaSi) are used as additives in different industrial products. As an alloying element, ferro-silicon increases the strength of steel and is therefore used in steel that is needed to produce wire cords for tyres or ball bearings.
- Ferro-manganese and manganese alloys
Another bulk ferro-alloy of great importance, mainly in the steel and stainless steel industries. Initially employed as a deoxidising and desulphurising agent, today ferro-manganese is mostly used to improve the hardness and wear resistance of steel.
The addition of ferro-vanadium to a steel melt increases the tensile strength and the high temperature strength of carbon steel even if small amounts are added. Vanadium alloyed steel is therefore used for high speed cutting tools.
It can be produced either by the carbothermic or metallothermic reduction of molybdenum oxides. Because of practical reasons like the smelting equipment used for the process and the reduced manufacturing costs, the metallothermic production of ferro-molybdenum is much more important than the carbothermic reduction.
As well as tungstenmelting base (TMB), which is made from secondary raw material, is mainly used to improve the properties of steel. Tungsten as an alloying element forms stable carbides and therefore increases the hot strength and wear resistance of steel. Such steel (high speed steel) is needed to produce high speed cutting tools that can be used up to temperatures of about 600 oC. Tungsten will also increase a number of other properties of the steel, such as the hardness, yield strength and the ultimate tensile strength.
It can be produced either from primary or secondary raw material, and is used for a variety of different purposes. As an alloying element, it increases yield strength and reduces the cracking tendency. In the production of stainless steel with a high chrome and nickel content, ferro-titanium is used to bond the sulphur.
Mainly used as anadditive in steel making to increase the hardenability, creep resistance and hot work ability because boron-alloyed steel is oxidation-resistant up to 900 oC. The raw materials needed to produce ferro-boron are boric oxides and boricacid. Carbon (charcoal), aluminium or magnesium are used as a reducing agent. The alloys can be produced by carbo-thermic or metallo-thermic reduction processes.- Ferro-niobium
As an alloying agent improves the corrosion resistance and weldability of steel and prevents, especially, the inter-crystalline corrosion of stainless chrome-nickel steel. The raw materials needed to produce ferro-niobium are ores and concentrates that contain niobium and iron oxide. The reduction occurs as an alumino-thermic process. The reaction normally takes place in a refractory-lined crucible, where the whole charge can be ignited or just a part of it that then serves as a starting mixture.
© Swissxer S.A. All rights reserved. | Site Index