Manufacture of sheets of 1Kh21N5T at Zaporozhstal' Plant

Conclusions

• 1. The technological usability of 1Kh21N5T steel during hot rolling of ingots in a slab mill, or of slabs in a thin-sheet continuous mill, is determined by the chemical composition of the metal and austenite-ferrite phase ratio, and is a function of the heating temperature of the metal. But if the steel contains >0.55% Ti and ≤5.3% Ni, the application of high heating temperatures leads to overheating of the metal (the formation of large-grain ferrite structure and absence of austenite). Steel with a structure of this kind exhibits heightened susceptibility to embrittiement.

• 2. The embrittlement of hot-rolled strip is evidently connected with 475-degree brittleness inherent in ferrite and ferrite-austenite steels. An increased titanium content, which promotes the formation of a ferrite structure, increases the likelihood of embrittlement.

• 3. Reduction of the titanium content to ≤0.50% at 4.8–5.3% Ni makes it necessary hot-rolling of the metal in continuous and slab mills under high-temperature conditions (close to the technology for Kh18N10T). With this, composition stability of the mechanical properties is attained.