Processing technology of u-shaped seamless stainless steel pipe and stainless steel pipe

Abstract

The invention discloses a U-shaped seamless stainless steel pipe processing technology and the stainless steel pipe. The raw material of the round steel billet is cross-rolled, hot-perforated, multi-pass cold-rolled and heat-treated, and finally the finished product is formed by large-deformation cold-rolling and coreless cold-bending. At the same time, focus on controlling the relationship between the diameter reduction and wall reduction of the finished product, introduce the concept of Q value, ensure that the Q value is between 0.8 and 1.5, optimize the matching tool and mold curve design scheme, ensure excellent surface quality, and the inner surface roughness can reach 0.5 μm the following. The cross-sectional area of ​​the U-shaped seamless stainless steel pipe is a closed ring or an approximate ring. The diameter is between 10.1mm and 25.4mm, and the length of the U-shaped tube can be up to 50m after deployment. The processing technology has high production efficiency, flexible adjustment of finished product specifications, and the surface roughness that can be made is ≤0.5μm. There is no oxidation color and nitriding layer on the surface, so it has excellent corrosion resistance. U-shaped seamless stainless steel pipe with high dimensional accuracy product.

Description

technical field [0001] The invention belongs to the technical field of steel pipe processing, and in particular relates to a processing technology of a U-shaped seamless stainless steel pipe mainly used for heat exchange equipment in thermal power, petroleum, chemical and nuclear power industries and the stainless steel pipe. Background technique [0002] With the development of modern industry, U-shaped seamless stainless steel tubes have been widely used in heat exchange equipment in thermal power, petroleum, chemical, nuclear power and other industries. The raw material tube blank is processed to the finished straight tube specification, and the mixed gas of nitrogen and hydrogen after ammonia decomposition is used for atmosphere protection heat treatment, and then the U-shaped tube is bent by using the bending mold, and then the stress relief heat treatment of the elbow part without protective atmosphere is carried out , Finally, pickling and passivation treatment of the...

AI Technical Summary

Problems solved by technology

The processing process is single, the deformation of each pass is small, and the production efficiency is low; the feeding length of the existing rolling mill is limited (usually within 12 meters), and the deformation of conventional cold rolling is 40% to 60%. Under this deformation, the corresponding The maximum elongation rate of 2.5 times can only achieve a finished product with a length of about 30 meters. Generally, the inner surface roughness of seamless stainless steel pipes can only reach the level of 0.8-1.6 μm, and it is difficult to further reduce the roughness value; under the protection of a hydrogen and nitrogen mixed atmosphere There is a risk of nitriding on the stainless steel surface after heat treatment, which reduces the corrosion resistance; the existing process elbow mold is made of stainless steel or bakelite, and the stainless steel mold has high strength, but it is easy to leave scratches on the surface of the steel pipe, without using surface quality control, and The inner profile is poor, easy to wrinkle, and the toughness of the bakelite mold is poor, but it is easy to crack under force, so it is not used for long-term bending; after the U-shaped seamless stainless steel pipe is formed, the U-shaped part has a large ellipse, perpendicular to the U-shaped pipe The outer diameter in the plane direction increases, and the outer diameter parallel to the plane direction of the U-shaped tube decreases. Usually, the ellipticity control level is 5% to 7%, which cannot meet the high-precision elbow size requirements; , while the U-shaped part increases in ellipticity, the amount of wall thickness thinning increases. After bending, the U-shaped tube forms a weak area, which is prone to damage and blockage; the bent tube without a protective atmosphere is bent after stress-relieving heat treatment The surface of the tube is severely oxidized. If it is not treated, it will affect the corrosion resistance of the U-shaped tube. After pickling and passivation treatment, the surface roughness is poor and there is a risk of overacid

Images