Not all steel is the same: in principle, the versatile and almost ubiquitous metal always consists of iron and a small amount of carbon. Various further accompanying alloying elements significantly influence the material properties. However, there are many processing methods to produce steel from pig iron. What they all have in common is that the very specific quality of the end product is determined by the post-treatment, the so-called secondary metallurgy.
The main focus in secondary metallurgy is to effectively reduce the levels of quality-reducing by-products such as sulfur and oxygen. This is where calcium carbide comes into play: Thanks to its high affinity for oxygen and sulfur, calcium carbide is used as a highly efficient agent in various secondary metallurgy applications. As a strong reducing agent, it is particularly suitable for desulfurization and deoxidation - where low sulfur and oxygen content are specified - of steel, as well as excellent for slag treatment.
For deoxidation and desulfurization, calcium carbide is added as a fine powder; however, for slag treatment, the active ingredient shows its highest efficiency in a coarser form.
The advantages of calcium carbide in secondary metallurgy at a glance:
high potential for cost savings
improved metal purity due to efficient deoxidation and desulfurization
reduced consumption of synthetic slag and other slag formers
recovery of oxidized metals such as chromium, manganese, silicon, iron
rapid reduction of aggressive furnace slag and thus longer service life of refractory materials
minimum sulfur content and high sulfur capacity of the slag
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Alzchem offers further products based on calcium carbide. These products are CaD® for desulfurization of pig iron as well as CalciPro®, developed for Calcium-treatment via cored wire. In addition, we have in our product portfolio for the steel industry Calzot®: this product is based on calcium cyanamide and is used for alloying nitrogen.
In modern steelmaking operations, the need for lower sulfur steels demanded by modern continuous casting operations and specialty applications has increased calcium carbide's appeal as a hot metal desulfurizer.
As late as , most blast furnace iron was desulfurized in the torpedo car as shown above. In the integrated steel mill, this practice has now been largely replaced by the use magnesium to remove an initial amount of sulfur in the transfer ladle, and the use of carbide as a steel ladle deoxidizer and slag conditioner to obtain the final sulfur specification.
In ductile iron foundries, liquid iron must be desulfurized before specialized inoculation treatments can be employed. This desulfurization is frequently performed by feeding granular forms of calcium carbide onto the surface of the liquid iron, which is contained in specially designed mixing units.
Purity and particle size are the key parameters for optimum effectiveness in these applications. Particle sizing is carefully selected to provide maximum contact with carbide particles without incurring excessive dust losses.
Carbide Industries manufactures three standard sized products for ductile iron desulfurization, generally within the range of 8 to 80 US-mesh (2.5 to 0.2 mm). In addition, two patented specialty products are available to meet specific customer requirements. These specialized products are formulated to help eliminate the retention of unreacted carbide in the resulting desulfurization slags and also to minimize slag odor.
For subsurface injection, a powdered carbide is manufactured by ball milling selected sizes of carbide to less than 140 US-mesh (<105 microns). The milled carbide can then be custom blended with a wide range of other powder additives, such as lime, limestone, and fluorspar to meet customer specified formulations. The milled carbide is treated with special additives to significantly improve flow characteristics.
Because of their reactivity, calcium carbide powders are manufactured, mixed, loaded, and transported in either 20 ton pressure differential trailers or 90 ton railcars, under an inert nitrogen atmosphere.
For more information, please visit Calcium Carbide for Desulfurizer.