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Stainless steel pipe why solution annealing treatment?

Stainless steel pipe why solution annealing treatment?

Time:2022-03-18 Source:China Wuxi JiaNuo Special Steel Co.

Austenitic stainless steel after solid solution treatment to soften, generally stainless steel pipe heated to about 950 ~ 1150 ℃, holding a period of time, so that carbide and a variety of alloying elements fully and uniformly dissolved in austenite, and then quickly quenched water cooling, carbon and other alloying elements can not be divided, to obtain pure austenite arrangement, called solid solution treatment.

The role of solid solution treatment has three points.

One. So that the steel arrangement and composition of uniform common, which is particularly important for the material, because the hot-rolled wire sections of the rolling temperature and cooling rate is not the same, constituting a common arrangement structure. Atomic activity at high temperatures increased, σ phase dissolution, chemical composition tends to be uniform, rapid cooling to obtain a uniform single-phase arrangement.

II. Eliminate process hardening to facilitate continued cold processing.

After solid solution treatment, the distorted lattice recovery, elongation and broken grains from scratch crystallization, internal stress elimination, steel tensile strength decreases, elongation rises.

Three. Rehabilitation of stainless steel inherent corrosion resistance.

Because the cold processing constitutes a carbide split, lattice shortcomings, so that the corrosion resistance of stainless steel decreased. Solid solution treatment of steel pipe corrosion resistance recovery to the best condition.

On the stainless steel pipe, the three elements of solution treatment is the temperature, holding time and cooling rate. Solution temperature is based on the chemical composition of the primary determination.

Generally speaking, the variety of alloying elements, high content of the trademark, solid solution temperature to progress accordingly. In particular, manganese, molybdenum, nickel, silicon content of high steel, as long as the progress of solid solution temperature, so that the full dissolution, in order to reach the softening effect.

But the stabilization steel, such as 1Cr18Ni9Ti, the solid solution temperature is high when the carbide of the stabilization element is fully dissolved in austenite, in the subsequent cooling will be divided in the shape of Cr23C6 in the grain boundary, constituting intergranular corrosion. In order to stabilize the carbides of the elements (TiC and Nbc) do not divide, not solid solution, generally choose the lower limit of solid solution temperature.

Stainless steel is commonly known as the steel that does not rust easily, in practice there is a part of the stainless steel, containing both stainless and acid resistance (corrosion resistance). Stainless steel stainless and corrosion resistance because of its surface chromium-rich oxide film (passivation film) composition. The stainlessness and corrosion resistance are relative.

The test proves that the steel in the atmosphere, water and other weak media and nitric acid and other oxidizing media, its corrosion resistance will be proportional to the increase in chromium content of steel and progress. When the chromium content reaches a certain percentage, the corrosion resistance of steel on the sudden change, that is, from rust-prone to rust-prone, from corrosion resistance to corrosion resistance.