Seamless pipes (SMLS pipe) sometimes crack during production and use, which will not only affect their service life, but also affect the normal operation of related equipment. This article will explore the causes of cracking of carbon steel seamless pipes in order to provide reference for related companies and personnel.
Causes of cracks in seamless pipes during production:
1. Selection of raw materials
Seamless pipes are made of steel billets through perforation, so the quality of the raw materials of the steel billets has a vital impact on the quality of the steel pipes. If there are quality problems with the steel billets, such as uneven composition and high impurity content, cracking will occur during the perforation process. In addition, brittle inclusions and carbide segregation contained in the material will also affect the toughness of the seamless steel pipe, making it easy to crack.
In order to save costs, some seamless pipe manufacturers use round steel produced by small steel mills for processing. However, the round steel produced by these small steel mills contains more impurities, bubbles, interlayers, pores, etc., and it is easy to crack after post-processing.
2. Improper heat treatment control
Heat treatment is an important step in the production process of seamless pipes. Improper heat treatment can also cause cracking of steel pipes. For example, during quenching, if the cooling speed is too fast or the temperature is too low, stress concentration will occur inside the steel pipe, leading to cracking. In addition, if the tempering temperature is too low or the tempering time is insufficient, it will also affect the toughness of the steel pipe and make it easy to crack.
The manufacturer does not have professional production experience and technology. The workshop workers cannot ensure whether the heat treatment of the steel pipe is in place simply by relying on the heating temperature and time. Heat treatment will change the mechanical properties of the steel pipe, but generally some small manufacturers do not have clear indicators for different steel grades, wall thickness, mechanical properties, etc., and there is no testing equipment to judge whether the pipe meets the performance indicators required by customers.
3. Processing problems
During the processing of seamless steel pipes, if the operation is improper, cracks will also be caused. For example, excessive widening of the orifice during processing, tool damage, unreasonable forging process, excessive heating during processing, etc., will cause local overload or residual stress after welding of the steel pipe, causing cracks in the steel pipe.
For example:
a. During the perforation process of seamless pipes, if the perforation speed is too fast or the perforation temperature is too low, cracks will appear on the surface of the steel pipe, leading to cracking. In addition, if the extrusion speed is too fast or the bending radius is too small, stress concentration will occur inside the steel pipe, leading to cracking.
b. During the straightening process of steel pipes, straightening is equivalent to secondary deformation. Bidirectional force is applied during straightening. If the operator is inexperienced, the straightening force is too large, and the strength of the thick-walled pipe is not well controlled, it will cause damage and cracks inside the thick-walled pipe, which is also the reason for the cracking of the steel pipe in the later stage.
4. Equipment factors
In the production process of seamless steel pipes, starting from the furnace, every equipment component will have an impact on the final quality of the pipe. For example, if the equipment parts are scratched, this will cause pits and scratches on the surface of the pipe, which will affect the appearance and performance of the pipe.
Reasons for cracking of seamless pipes in practical applications:
1. Environmental issues
Seamless steel pipes will be affected by environmental factors during use. For example, in harsh environments such as high temperature, high pressure, and corrosion, steel pipes will corrode and oxidize faster and are prone to cracking. In addition, steel pipes may also crack or break under the influence of natural disasters such as earthquakes and sandstorms.
Although seamless steel pipes have a long service life, they are also prone to cracks when the use environment is harsh. Long-term use may also cause pipe fatigue and cause cracks. During use, the steel pipe should be avoided from collision and extrusion with other objects as much as possible. Some protective measures can be taken or regular maintenance and care can be performed, such as installing protective sleeves.
2. Product quality problems
The quality problem of the purchased seamless pipe itself is also one of the main causes of cracks. It is mainly manifested in defects caused by factors such as surface unevenness, bad impurities, surface hardness, and large pores. These problems will cause surface damage and internal stress concentration of the steel pipe, and eventually lead to cracks, affecting the progress of the project.
Prevention methods for cracks in seamless pipes:
1. Pay attention to quality when purchasing materials
When purchasing materials, pay attention to quality and choose steel pipe materials manufactured by regular steel pipe manufacturers. And carry out necessary tests to ensure that the quality of the materials is qualified and avoid cracks caused by material problems.
2. Defect detection must be strict
In the process of manufacturing seamless pipes, the defects of steel pipes must be strictly detected. Use high-quality testing equipment, such as
ultrasonic flaw detection, radiographic flaw detection, etc., to conduct a comprehensive inspection of the steel pipe to eliminate problems in the manufacturing process of the steel pipe as much as possible.
3. Processing operations should be standardized
During the processing process, personnel with standardized operations and high technical levels should be trained, and high-quality processing equipment and cutting tools should be used. For different types of steel pipes, different production processes and working parameters are used to avoid cracks caused by processing.
4. The use environment should be reasonable
When using seamless steel pipes, it is necessary to choose appropriate occasions and environments to avoid damage to the steel pipes, strengthen the inspection and maintenance of seamless steel pipes, and clean and repair them in time to avoid cracks caused by environmental problems.
5. Strengthen quality management
In the production process, manufacturers should strictly follow quality management specifications, strengthen quality control, inspection processes and records, and promptly discover and correct problems to ensure that the quality of seamless steel pipes produced is stable and excellent.
Conclusion:
The generation of cracks in seamless steel pipes during production and use is related to many aspects such as seamless pipe raw materials, heat treatment processes, processing, equipment factors, use environment, and product quality. In order to prevent the generation of cracks in seamless steel pipes, manufacturers should start from materials, quality management, processing operations, etc., strengthen the quality management of the manufacturing process, and conduct all-round inspection and maintenance of steel pipes. At the same time, users should also pay attention to the scientific methods and correct operation of seamless steel pipes to avoid damage to the steel pipes and cracks.
Read more: ASTM Standard Seamless Steel Pipe Quality Inspection or Seamless Steel Pipe Manufacturing Process
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