High strength medium carbon austenitic stainless steels have been developed through partial and total replacement of nickel by nitrogen. Stainless steels containing 0.4% carbon with different combinations of nickel and nitrogen were produced in 10kg induction furnace under different nitrogen pressures. The produced stainless steels were cast and hot forged and the total nitrogen was determined. Furthermore, the produced forged steels were subjected to either only solution treatment or solution treatment followed by ageing process.

Nonmetallic inclusions such as carbides and nitrides were separated by electrolytic dissolution. Nitrogen as nitrides was determined and soluble nitrogen was calculated. XRD technique was used to investigate the types of nonmetallic inclusions. The microstructure of produced stainless steels was observed and the grain size was measured. The tensile properties at room temperature were determined. The influence of grain size, total nitrogen, insoluble and soluble nitrogen on tensile strength was investigated. All produced stainless steels as-quenched were aged at temperatures range from 450°C to 950°C for different times. Hardness test was carried out for aged stainless steels and the optimum ageing conditions were determined.

After solution treatment of the investigated stainless steels at 1050°C, a great portion of alloy carbides and nitrides is observed to be taken into solution. Nitrogen in solid solution increases both yield and tensile strengths. At optimum ageing temperature, this portion in solution precipitates, mainly as Cr2N, was causing higher precipitation strengthening. The yield strength and ultimate tensile strength of the aged stainless steels were found to increase at average rates of 706 MPa/1 mass % nitrogen and 723 MPa/1 mass % nitrogen, respectively. On the other hand, the increase of nitrogen content deteriorates the steel ductility.

Please login / register to post comments

news in steel

ECS scrap preheating and zero bucket: the most sustainable way to produce steel

The first Danieli Zero-bucket EAF with ECS scrap preheating in China is in operation Chizhou City.

What's new in continuous casting: SMS Concast develops actuator-driven oscillation with direct drives by KOLLMORGEN

Shape is given to the molten steel by the casting die in continuous casting. The casting die can be compared to a mold made of water-cooled copper in which targeted extraction of heat causes the steel to form an outer skin – at first as delicate as a raw egg.

New Scan System with 20-Millimeter Aperture Broadens Product Portfolio

Laser technology manufacturer SCANLAB GmbH is extending its premium-segment product family with the excelliSCAN 20. This new scan system targets exceptionally demanding applications such as micromachining and additive manufacturing (3D printing).

Bucket manufacturer Lennéers chooses Hardox wear plate from SSAB for increased wear resistance and reduced weight

Swedish bucket manufacturer Lennéers uses Hardox wear plate from SSAB in all its products. Hardox abrasion-resistant steel enables Lennéers to deliver top-quality construction and agricultural equipment that is strong, light, and long lasting.