What causes cold drawn seamless tubes to crack?
1) Material issues
Cold drawn seamless tube materials may have the following problems, leading to cracking:
1. Material problem: The quality of the raw materials is not up to standard, or unsuitable materials are selected, and their hardness, strength, toughness and other properties cannot meet the usage requirements.
2. Inclusion problem: Inclusions are a form of impurities in cold-drawn seamless steel pipes. When the volume of inclusions is too large, it will affect the strength and plasticity of the steel pipe, leading to cracks.
3. Bubble problem: Bubbles are formed during the manufacturing process. The existence of bubbles will reduce the strength and stiffness of the material, leading to cracks.
2) Manufacturing process issues
The manufacturing process of cold drawn seamless steel tubes may have the following problems, leading to cracking:
1. Improper heat treatment control
The merchants do not have professional production experience and technology. Workshop workers cannot ensure whether the heat treatment of the steel pipe is in place simply by relying on heating temperature and time. Heat treatment will change the mechanical properties of the steel pipe. However, general merchants do not have clear indicators for different steel types, wall thicknesses, mechanical properties, etc., and they do not have testing equipment to determine whether the pipes meet the performance indicators required by customers.
2. Problem of excessive cold drawing
When cold drawing is excessive, it will cause the steel pipe to crack. This is because excessive cold drawing causes excessive stress inside the steel pipe, which leads to cracking.
3. Improper control of the steel pipe stretching process
If the steel pipe is not properly controlled during the stretching process, it will cause stress concentration and cause cracks.
4. Straightening strength
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 internal damage and cracks in the thick-walled pipe. This is also the reason for the later cracking of steel pipes.
5. Production process issues
Unreasonable production processes, such as improper use of molds or poor cooling conditions, may also lead to cracking.
3) Usage environment issues:
The following problems may occur during the use of cold drawn seamless steel tubes, leading to cracking:
1. Temperature problems: Such as harsh environmental conditions (such as excessive temperature, humidity) or wear and tear, these may cause the cold-drawn steel pipe to crack. Some cold-drawn seamless steel pipes need to be used in low-temperature environments. If their temperature tolerance is exceeded, the steel pipe will crack.
2. Scratch problem: Scratches on the surface of the steel pipe will cause surface cracks, accelerate the cracking and expansion, and cause the steel pipe to crack.
3. Spare parts installation problems: Improper installation of spare parts will cause stress concentration, cause cracks, and lead to cracking of the steel pipe.
Conclusion:
To sum up, the causes of cracking of cold drawn seamless tubes (ASTM A106) mainly come from material problems, manufacturing process problems and usage environment problems. The key to solving these problems is to start from improving the quality of raw materials, improving production processes and improving usage conditions to achieve the goal of preventing and controlling cracking problems.
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