Abstract
Because of its superior properties, stainless steel has been widely used for many applications. Nonmetallic inclusions can influence the quality of stainless steel products. A set of samples was used to track the response of inclusion composition during processing of a heat of titanium-bearing 18% chromium steel, from deoxidation after decarburization, to the solidified slab. The oxide inclusions responded as expected to additions of deoxidizers and calcium treatment, changing from silica to alumina and spinels, and then to calcium aluminates. The samples confirmed that titanium nitride can nucleate on liquid calcium aluminate during steel solidification.
Highlights
Nonmetallic inclusions that can be present in stainless steels include oxides, nitrides, and sulphides (Park and Kang, 2017)
Titanium nitride inclusions are very hard – titanium nitride coatings extend the life of cutting tools – and such hard inclusions play an important role in microcrack formation in steel (Fairchild, Howden, and Clark, 2000)
The additions of deoxidizers and calcium during processing of an 18% Cr ferritic stainless steel resulted in the expected change in the composition of the oxide inclusions – from silica after deoxidation with ferrosilicon to alumina and spinel after deoxidation with aluminium, and to calcium aluminates upon calcium treatment
Summary
Nonmetallic inclusions that can be present in stainless steels include oxides, nitrides, and sulphides (Park and Kang, 2017). In this work we studied changes in oxide inclusions and the associated formation of titanium nitride and niobium carbonitride during processing of a ferritic stainless steel (containing 18% Cr). The investigation was based on a previous study that considered the change in oxide inclusions when processing a similar ferritic stainless steel in the same plant (Kruger and Garbers-Craig, 2017). In ferritic stainless steel (based on binary FeCr alloys), titanium is frequently added to bind nitrogen as titanium nitride. In such steels, titanium nitride (TiN) normally precipitates during solidification. The effect of angular inclusions on the mechanical behaviour of the steel can be strong: In bearing steels the deleterious effect of 6 μm TiN inclusions on the fatigue life of steel is equivalent to that of 25 μm globular oxide inclusions (Monnot, Heritier, and Cogne, 1988)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
