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Why do a Strong Steel Pipe Need Bright Annealing Solution?

Source:Iris Liang Time:2018-10-12 8:35:07

Why do a Strong Steel Pipe Need Bright Annealing Solution?

What is bright annealing solution?
The bright annealing solution process eliminates residual stress, obtains a single austenite structure, and makes the surface of the welded pipe white and smooth.
The bright annealing solution treated steel pipe has good bending, stretching, pierhead and corrosion resistance!

SEKO Machienry Online bright annealing treatment
During the production process, the welded pipe is affected by the high temperature during rolling, drawing and welding. The microstructure and mechanical properties of the material will change, which will seriously affect the quality of the pipe. These changes mainly include: cold work hardening, that is, a column in the crystal. Or if the column atoms are regularly staggered, the crystal lattice is distorted to form a stress concentration zone, which is also called a dislocation. Because high temperature and uneven cooling produce weld stress and ferrite is generated in the original single austenite structure, uneven structure such as carbide occurs. In order to improve production efficiency, ensure the surface of the welded pipe is bright, and the residual stress is eliminated, and a single austenite is obtained. Body tissue, for the production of high quality welded pipes, must be implemented by online bright solution treatment.
1.Protective gas effect

The liquid ammonia decomposition gas is used as a protective atmosphere, and the liquid ammonia at 400 ° C or higher will undergo the following decomposition reaction:
2NH3→3H2+N2. Hydrogen is a reducing gas, and certain metals can be reduced under certain conditions, and nitrogen is a neutral gas. The liquid ammonia decomposes the atmosphere as a shielding gas, which makes the surface of the welded pipe white and smooth, and thus is the most economical and ideal protective gas.
2.Solution treatment temperature

Solution treatment temperature is one of the most important parameters of solid-liquid treatment process. Too high or too low will directly affect the quality of welded pipe. The temperature of the welded pipe is coarse, the performance is degraded, the temperature is too low, and the solid solution is incomplete. Incomplete removal, use 1080 ° C ± 10 ° C, and appropriate insulation, the carbide is fully dissolved.
3.Cooling rate

Austenitic stainless steel in the range of 650 ° C -850 ° C, σ phase brittle change, usually in the form of needle-like flakes in the austenite crystal or grain boundary, so that plasticity, toughness, strength is greatly reduced, at 450 °C-850 °C is also the intergranular corrosion sensitive zone of the low-profile stainless steel. The essence is that the supersaturated solid solution carbon atoms in the metal grains in the temperature zone gradually diffuse toward the edge of the grain, forming carbides with the chromium atoms in the edge layer. And precipitation along the grain boundary, causing the edge of the grain to be depleted of chromium and losing corrosion resistance. When the austenitic steel is heated to 1080 ° C ± 10 ° C, the carbide in the steel is fully dissolved and then rapidly cooled. Avoid steel staying in the 450°C-850°C range, thus preventing the occurrence of σ phase and intergranular corrosion without precipitating carbides along the austenite grain boundaries to obtain the uniform saturated single austenite we need. organization.

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Iris Liang
SEKO Machinery & Technology Co., Ltd
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