Stainless steel welded pipe refers to a steel pipe with strict internal and external dimensional accuracy (tolerance range), good internal and external surface finish, roundness, straightness, and uniform wall thickness. The main technical indicators of stainless steel welded pipe produced by this technology have reached or partially exceeded the national Standard GB12771-2002 and standard ISO4394/I-1980 (E) requirements. How to control the accuracy of stainless steel welded pipe is a key issue.
Due to the relatively high surface density of stainless steel welded pipes, even if the outer surface is not polished, it can generally reach about 260 mesh. If the stainless steel welded pipe is polished internally and externally, its straightness will decrease. Therefore, if there are special requirements for the straightness of the steel pipe, polishing is generally not recommended. The polished surface of the stainless steel welded pipe is already very bright. The cold-rolled stainless steel welded pipe has excellent comprehensive performance, can withstand high pressure, cold-formed, flared, and flattened without cracking or wrinkling. It can do various complex deformations and mechanical processing. After the stainless steel welded pipe is vacuum annealed, the steel pipe can be processed.
Stainless steel welded pipes are generally used to manufacture mechanical structures, hydraulic equipment, machinery and other production fields. In the fields of instrumentation, medical equipment, precision equipment, electronic equipment, aerospace, thin-walled water supply pipelines and heat exchangers, the welded pipes used are required to have high outer diameter dimensional accuracy. Ordinary welded pipe mills cannot meet this requirement. SEKO Machinery takes you to analyze how welded pipe equipment and production factors affect the dimensional accuracy of stainless steel welded pipe outer diameter.
1. The dimensional accuracy requirements of high-precision stainless steel welded pipes
From GB/T 3639-2000 "Cold-drawn or cold-rolled precision seamless steel pipes" and ASTM A1016, GB/T 12770-2002 "Stainless steel welded pipes for mechanical structures" and other standards, it can be seen that the relevant standards have an impact on precision stainless steel welded pipes. Allowable deviation of diameter (table 1) and wall thickness deviation (table 2) requirements. The inner diameter tolerance of welded pipe is mainly affected by outer diameter tolerance and wall thickness tolerance. This article does not discuss the issue of inner diameter tolerance.
2. Analysis of factors affecting the dimensional accuracy of the outer diameter of stainless steel welded pipes
2.1 The influence of steel strip thickness and width accuracy
2.2 The outside diameter tolerance of welded pipe before sizing and the influence of sizing amount
1) Dimension tolerance of welded pipe outside diameter before sizing
The outer diameter tolerance of the welded pipe before sizing is affected by the superposition of many factors such as the tolerance of the steel strip, the dimensional accuracy of the welding roll and its gap.
2) The influence of sizing amount on the dimensional accuracy of welded pipe outer diameter
The sizing amount of high-precision welded pipe should be slightly larger than that of ordinary welded pipe. The principle of determining the sizing amount is: ①The sizing amount should be greater than the tolerance of the outer diameter of the welded pipe before the diameter; ②Sufficient sizing amount and pass times.
2.3 The frame stiffness of the sizing machine and the influence of equipment size
2.3.1 Frame stiffness
The elastic deformation of the base of the welded pipe sizing machine is equal to the sum of the elastic deformation of a series of stressed parts in the base.
2.3.2 Sizing rolling force
1) Average unit pressure
2) Contact area
3) Sizing rolling force
2.3.3 Elastic deformation of the sizing machine base
2.4 The influence of sizing machine equipment manufacturing accuracy
The equipment manufacturing accuracy of the sizing machine directly affects the outer diameter tolerance of the welded pipe
The accuracy of the thickness and width of the steel strip only affects the accuracy of the outer diameter of the welded pipe before sizing, but not much during the sizing process. The sizing pass and the sizing amount are mainly determined according to the outer diameter tolerance of the welded pipe before sizing. Sufficient sizing pass and sizing amount are the basic guarantee for improving the outer diameter accuracy of the welded pipe finished product. The main factors affecting the accuracy of the outer diameter of the welded pipe are the size of the sizing machine and the accuracy of the equipment manufacturing. Hangao Tech (SEKO Machinery) precision high-speed stainless steel industrial pipe machine, model and mold design are precisely controlled, and a series of processes including welding forming, annealing bright, precise sizing, etc. can be completed online, which can meet 24-hour continuous production. For more details, please consult!
