Improvement of the purity of stainless steel welded pipe

Posted by zora li on October 28th, 2022

If the stainless steel tube contains impurities, not only its surface quality, but also its performance is immeasurable. In order to reduce the impurities of seamless steel pipes and improve their purity, we must start with the production process. The following are ways to improve the purity of stainless steel pipes.

1. Avoid impurities entering the steel.
One. Manufacturers purchase raw materials (scrap steel, ferroalloy, etc.), slagging materials (lime, fluorite, etc.), quality of deoxidation materials, baking and drilling;
b. Manufacturer of refractory materials and baking quality stainless steel pipes for linings, ladles, gating systems in steelmaking workshops;
C. Improve the purity of steelmaking gas (argon, oxygen, nitrogen, etc.) (no water, etc.);
d. Avoid secondary oxidation of molten steel during tapping and pouring.

2. Remove from steel. Manufacturers use AOD, VOD and other out-of-furnace fines in the production method; for those with special requirements, they can also be used in electroslag remelting vacuum electric arc furnaces. VOD and three-step refining can reach lower levels of steel oxygen, nitrogen and carbon than AOD refining, which is especially important for ferritic stainless steel pipes; electric furnace steel C, S, and N are much higher than AOD furnace steel, AOD steel After carbon content ≤ 0.02%. Studies have shown that the pitting corrosion resistance of the 18-8 type chrome-nickel stainless steel pipe that has been remelted by electroslag in an electric furnace is better than that of electric single steel. There are many harmful impurities in non-ferrous metals, the elements have low melting point and high vapor pressure, so they are easy to volatilize at high temperature. In the essential process of AOD and VOD, due to the carbon-oxygen reaction at high temperature and the mixing of argon, oxygen and other gases, it is beneficial to accelerate the removal of these harmful impurities by evaporation. The essence of VOD is more favorable in this regard. Comparison of non-metallic inclusion content in seamless carbon steel pipe after refining, comparison of electric arc furnace and AOD steel. It is found that the non-metallic inclusions in AOD intrinsic steel are much lower than that in EAF steel. In the comparison of the grinding rate of EAF steel and AOD secondary fine steel, the grinding rate of AOD fine steel is obviously lower than that of EAF steel.

Read more ：Heat treatment defects and prevention of seamless steel pipes