Crack Analysis and Control of 40Cr Seamless Steel Pipe
Crack Analysis and Control of 40Cr Seamless Steel Pipe of 40Cr seamless steel pipe—crack is comprehensively analyzed, and the cause of the crack is found out. The oblique crack is caused by the tube blank; the longitudinal crack is caused by the unreasonable temperature control of the steel pipe production process and heat treatment process. By adopting control measures such as reducing inclusions in molten steel, optimizing continuous casting process, and optimizing thermal system for tube billet production, the production process was adjusted to effectively control the continued generation of cracks in 40Cr seamless steel pipes and improve the quality of steel pipes.
Key words seamless steel pipe crack pipe billet heat treatment temperature control
The 40Cr round tube billet produced by is sold to the rolling mill to produce seamless steel tubes. With the continuous improvement of the production process level, the quality of 40Cr pipe blanks is continuously improved, the quality of seamless steel pipes is also continuously improved, and the scope of application of products is also expanding. However, crack defects in steel pipes occur from time to time, which restricts the further improvement of steel pipe quality. Improvement, resulting in a batch of quality objections. In order to solve the problem of 40Cr steel pipe cracks, our company and the pipe rolling factory jointly organized personnel to conduct detailed analysis of these crack defects, starting from the crack shape, with the help of various analytical instruments, combined with production records, to find the cause of cracks, improve production technology, control Crack defects, improve the quality of 40Cr steel pipe.
40Cr seamless steel pipe production process
Molten iron — converter smelting — external refining — heating of continuous casting round billet heating furnace — piercing by piercing machine — three-roll cross rolling (pipe removal) —sizing and reducing) —cooling — quenching and tempering — straightening — flaw detection (pressing) Inspection — Identify storage.
- 40Cr Seamless Steel Pipe Crack Cause Analysis
- crack pattern
40Cr seamless steel pipe cracks can be mainly divided into two categories:
( 1 ) oblique cracks and outward folds). This defect appears on the steel pipe before heat treatment, and some cracks are distributed in a spiral shape. The crack extends spirally at a certain angle with the steel pipe axis, the crack is generally thick, and there is serious oxidation in the crack.
( 2 ) Longitudinal cracks. It often appears on the steel pipe after heat treatment, and the crack extends along the axial direction of the steel pipe. Among them, the cracks that appear during the pressing process are concentrated in the processing and connection parts of the steel pipe, such as the end of the steel pipe or the drilling processing part of the steel pipe. The cracks are slender and distributed in a tear shape, and the starting part of the crack can be clearly seen. The longitudinal cracks found during heat treatment are very slender with small tails, and the inside of the cracks are very clean. The above two kinds of cracks are produced independently, and it is rare to find that the two kinds of cracks appear at the same time.
40Cr Seamless Steel Pipe Control effect
After the process improvement, the quality of 40Cr steel tube blank and steel pipe has been significantly improved, cracks have been effectively controlled, the qualified rate of tube blank has increased by 1.05% , reaching 99.95% , the crack problem of 40Cr steel tube has also been solved, and no cracks have occurred in 40Cr steel tube There are quality issues, and the performance of the steel pipe after heat treatment has also met the requirements for use.
40Cr steel tube in conclusion
1The distribution of oblique cracks (spiral cracks) in steel pipes and the serious oxidation around the cracks all indicate that the cracks already existed before the billet was heated and rolled, so the oblique cracks in steel pipes are mostly caused by quality defects in the billet.
3.steel pipe, no obvious oxidation phenomenon, and abnormal structure and other characteristics indicate that the straight cracks of the steel pipe are mostly caused by unreasonable rolling and heat treatment processes.
3By optimizing the steelmaking and continuous casting process, improving the quality of the tube billet, and adjusting the tube rolling and heat treatment process, the crack problem of the steel tube was solved.
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