Process for improving wall thickness accuracy of medium-thick wall pipe

Abstract

The invention discloses a process for improving the wall thickness accuracy of a medium-thick wall pipe, comprising the following steps: S1, steel pipe casting: selecting a suitable steel ingot and melting the steel ingot and pouring the melted ingot to produce a pipe blank; S2, piercing machine correction: setting a keyway of a connecting sleeve at the top of a piercing machine as a semicircularkeyway; S3, cold centering machine punching detection: detecting punching of a perforator; S4, coefficient modification: changing the frame speed and tension coefficient of the hole type to 0.05+/-0.01; S5, centerline adjustment: ensuring that the rolling centerline of the piercing machine is consistent with the centerline of a piercing trolley, so that the force applied to the pipe blank during piercing is uniform. Through head technical modification, the system specification of the centering hole and the optimization of the tension coefficient of the sizing mill, the yield of the medium-thick wall pipe with the wall thickness of 16 to 35 of 273 pipes can be stabilized at 93 percent or more.

Description

technical field [0001] The invention relates to the technical field of steel pipe production and processing, in particular to a process for improving the wall thickness accuracy of medium-thick-wall pipes. Background technique [0002] Stainless steel seamless pipes are made from solid blanks, and steel pipes are produced by hot piercing, hot rolling or cold working. The type and level of the unit mainly depend on hot working, cold working (the main methods are cold rolling and cold drawing) and heat treatment process. Therefore, the production and product quality of stainless steel seamless pipes mainly depend on the main links of raw materials, hot processing and cold processing. It is in these main links that there is a big gap in the production technology of stainless steel seamless pipes in our country. [0003] my country's stainless steel smelting process is backward. Not only does it not have the latest "three-step" smelting process equipment, but also uses electri...

AI Technical Summary

Problems solved by technology

The factors affecting the production of stainless steel pipes by cross-rolling and piercing technology are as follows: (1) Hot-rolled finished pipes cannot be produced, and only billets can be provided for cold processing, which has led to the existence of "cold processing" in the field of stainless steel pipes in my country. The unreasonable phenomenon of "generation heat"

(2) The quality of stainless steel pipes is difficult to guarantee, because of the "Mannesmann effect" in the process of cross-rolling and piercing, the low plasticity of stainless steel, the narrow heating temperature range, and the temperature rise during deformation, it is difficult to guarantee the quality of stainless steel pipes

(3) For some hard-to-deform alloys, such as nickel-based superalloy GH39 and 25-20 stainless heat-resistant steel with high Si content, it is difficult or impossible to produce by cross-rolling and piercing. rate is extremely low

(4) Since the production of stainless steel pipes in my country only uses the Mans piercing machine in the automatic pipe rolling unit and does not use the following rolling pipes, leveling machines and sizing machines, the dimensional accuracy of the produced waste pipes is poor, and the wall thickness is poor. thicker, which adds a lot of deformation to cold working

(5) The cross-rolling and piercing process cannot produce special-shaped cross-section pipes

[0005] The problem of wall deviation of medium and thick wall pipes has always been the main problem affecting the quality of 273 pipe wall thickness. The wall thickness deviation has a great impact on the geometric dimensions, cutting rate and yield of steel pipes. After on-site investigation, two comparisons were found. The outstanding problems are: first, the assembly gap between the punching machine head and the ejector pin is relatively large, and second, the cold centering machine has poor drilling accuracy, which leads to a growth rate of 91.5%-93% for medium-thick pipe walls