Direction of layered crack in Zhangye steel: Root-
Directional crack, blunt crack tip.
After the stainless steel rod is treated on the surface, the crack at its end is smaller than the end of the previous hair, and the crack tip opens.
The Ax crack tip is smaller than the previous crack at the crack tip to produce a passivation smaller than the first part.
Secondary layered crack.
The crack between the second layer layered crack and the first layer of material stainless steel rod is broken, the main crack, and the main crack is broken in a direction of 450.
The expansion of the peak crack along the straight path does not extend, forming an oblique shear failure surface between layered cracks.
Master the direction of the crack stratification of Ding main vertical crack, and its expansion in the material needs to consume more energy to make it more difficult to crack.
Therefore, weak pipeline layered cracks and thickness at the crack interface caused by pipe surface defects or cracks penetrating the surface wall-
The seamless evolution of the wall hinders a beneficial effect on the formation of resistance I bu cracks and leakage pipes.
Regardless of the orientation of the sample, it is thick in layered cracks-
Seamless Wall rich.
During the fracture process, the stress state has a great influence on the layered crack tip, which has a huge impact on the fracture.
In normal use, there is no layered crack in the feed pipe tree, thick-
The layered crack of the wall is only towel during the fracture process, and the layered crack fracture has no effect on the normal use of the pipeline.
In addition, when layered crack breaks need to consume more energy, and layered crack cracks penetrate the body to reduce its effective thickness, the vertical layered crack and the direction of crack growth of the surface crack body, all of these factors make the crack more difficult and the toughness of the material is improved.
The main purpose of steel is high
The disadvantage layering mechanism is generally considered non-
The metal inclusion in the tube can destroy the continuity and tightness of the pipe, and even produce serious inclusions in the internal stratification.
The other is considered hydrogen.
Induced cracks, that is, due to the excessive formation of white points in the steel pipe, the accumulation of hydrogen in the gas pressure inside the steel metal, the crack expansion occurs during the rolling process, and finally a layered defect is formed.
In addition, uneven deformation of the rotational perforation strength of the plastic with a stress of more than two rolls can also cause layering.
In the case of strict control of smelting, the control measures taken are to improve the cleanliness of molten steel and reduce harmful inclusions;
Increase the proportion of the crystal axis of the plate, reduce the central segregation and the central air hole;
Adopt a reasonable cooling system to avoid Flower cracking;
The off-line cooling process is adopted to reduce the internal stress, thus ensuring that the organizational and mechanical properties of the finished pipe meet the technical standards.
Select the best heating temperature by measuring the thermoplastic curve.
Please also note that there is sufficient heating tube holding time in order to reduce the plastic deformation resistance and improve the toughness.
Roll speed is a key parameter of the perforation process in which the roll speed changes from low to high and there is a critical start-up layered roll speed.
The rolling speed is low and the pipe hole is easy to form;
High rolling speed, easy to form a capillary with layered defects.
In order to eliminate the layered defects and capillary tubes, the roller speed should be lowered to the beginning of the critical layered Roller speed.