Machining process of U-shaped seamless stainless steel tube and stainless steel tube

Abstract

The invention discloses a machining process of a U-shaped seamless stainless steel tube and the stainless steel tube. According to the machining process, a round steel tube blank raw material is subjected to skew rolling hot piercing and multi-pass cold rolling heat treatment, and finally subjected to finished product large-deformation cold rolling and coreless cold bending machining forming; andmeanwhile, the relation between the finished product diameter reduction amount and the wall reduction amount is mainly controlled, the Q value concept is introduced, it is ensured that a Q value ranges from 0.8 to 1.5, a tool and die curve design scheme is optimized and matched, it is ensured that the surface quality is excellent, and the inner surface roughness can reach 0.5 micron or below. Thecross section area of each part of the U-shaped seamless stainless steel tube is in a closed circular ring shape or an approximate circular ring shape, the whole steel tube is in a U shape or an approximate U shape, the wall thickness ranges from 0.5 mm to 2.5 mm, the outer diameter of the tube ranges from 10.1 mm to 25.4 mm, and the maximum length of the U-shaped tube can reach 50 m after the U-shaped tube is unfolded. The machining process is high in production efficiency, the specification of the finished product is flexibly adjusted, and the U-shaped seamless stainless steel tube product with surface roughness smaller than or equal to 0.5 micron, no oxidation color or nitriding layer on the surface, excellent corrosion resistance and high U-shaped tube dimensional precision can be manufactured.

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...

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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

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