Steelmaking, Refining and Casting of Auto Steel

摘要

In the making of steel for auto industry, challenges faced in long products domain includes improving the fatigue life of components such as bearing and crankshaft, torsional resistance in springs made of high carbon steel axle shaft, reduction in noise level of gear box, machinability for making intricate precision components, cost reduction in processing through microalloys, improved reliability of components through control of internal and surface cracks and high- strength to weight ratio for fuel efficiency. Steels with consistent chemical composition and suitable heat treatment ensure fine microstructure in the steel matrix. Besides this, steel cleanliness plays a major role in the improvement of fatigue life. Need of the day is to standardise the secondary refining practice involving de-oxidation with aluminium/silicon as appropriate, inert gas bubbling with bubble size control and multiple porous plugs, vacuum degassing, slag engineering to target lower oxygen levels, etc. The level of oxygen, hydrogen and nitrogen has comedown drastically in recent times. Sulphur and phosphorus reductions pose different type of challenges. Levels of micro and macro inclusions as well as the carbide banding have gone down less than 50% of what it was. Testing equipment like SEMs, Phased Array UT, MFL, Infrared Surface Detection, Immersion Ultrasonic, etc. are replacing conventional equipment, today.