Hot rolling is relative to cold rolling. Cold rolling is rolling below the recrystallization temperature, while hot rolling is rolling above the recrystallization temperature. So what are the advantages and disadvantages of hot rolling?
Advantages of hot rolled steel pipe:
① After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, and silicates) inside the steel are pressed into thin sheets, and stratification (interlayer) occurs. Delamination deteriorates the steel's ability to be stretched through the thickness and has the potential for interlaminar tearing as the weld shrinks. The local strain induced by the shrinkage of the weld often reaches several times the strain at the yield point, which is much larger than the strain caused by the load;
② Residual stress caused by uneven cooling. Residual stress is the internal self-equilibrium stress without external force. Hot-rolled steel sections of various sections have this kind of residual stress. Generally, the larger the section size of the section steel, the greater the residual stress. Although the residual stress is self-equilibrium, it still has a corresponding influence on the performance of the steel member under the action of external force. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc.
Disadvantages of hot rolled steel pipe:
① After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (interlayer) occurs. Delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible that interlayer tearing may occur when the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by the load;
②Residual stress caused by uneven cooling. Residual stress is the internal self-balanced stress without external force. Hot-rolled steel sections of various sections have such residual stresses. Generally, the larger the section size of the steel section, the larger the residual stress. Although the residual stress is self-balanced, it still has a certain influence on the performance of steel components under external force. For example, it may have adverse effects on deformation, stability, and fatigue resistance.
③The thickness and edge width of hot rolled steel products are not easy to control. We are familiar with thermal expansion and contraction. Since at the beginning, even if the length and thickness are up to the standard, there will be a certain negative difference after cooling. The wider the negative difference, the more obvious the thicker the thickness. Therefore, for large steel, the side width, thickness, length, angle, and sideline of the steel cannot be too accurate.
The structure of hot rolled steel pipe:
Mainly used for mechanical structures, carbon press equipment, steel pipes with required dimensions and good surface finish.
It is mainly used to make coal mine hydraulic supports, cylinders and columns, and other hydraulic cylinders and columns.
It is mainly used to make carbon structural steel and alloy structural steel hot-rolled seamless steel pipes for automobile half-axle casings and drive axle housing shaft pipes.
It is mainly used to make cold drawn seamless tubing with inner diameters for hydraulic and pneumatic cylinders.
Advantages of hot rolled steel pipe:
① After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, and silicates) inside the steel are pressed into thin sheets, and stratification (interlayer) occurs. Delamination deteriorates the steel's ability to be stretched through the thickness and has the potential for interlaminar tearing as the weld shrinks. The local strain induced by the shrinkage of the weld often reaches several times the strain at the yield point, which is much larger than the strain caused by the load;
② Residual stress caused by uneven cooling. Residual stress is the internal self-equilibrium stress without external force. Hot-rolled steel sections of various sections have this kind of residual stress. Generally, the larger the section size of the section steel, the greater the residual stress. Although the residual stress is self-equilibrium, it still has a corresponding influence on the performance of the steel member under the action of external force. For example, it may have adverse effects on deformation, stability, fatigue resistance, etc.
Disadvantages of hot rolled steel pipe:
① After hot rolling, the non-metallic inclusions (mainly sulfides and oxides, as well as silicates) inside the steel are pressed into thin sheets, and delamination (interlayer) occurs. Delamination greatly deteriorates the tensile properties of the steel in the thickness direction, and it is possible that interlayer tearing may occur when the weld shrinks. The local strain induced by weld shrinkage often reaches several times the yield point strain, which is much larger than the strain caused by the load;
②Residual stress caused by uneven cooling. Residual stress is the internal self-balanced stress without external force. Hot-rolled steel sections of various sections have such residual stresses. Generally, the larger the section size of the steel section, the larger the residual stress. Although the residual stress is self-balanced, it still has a certain influence on the performance of steel components under external force. For example, it may have adverse effects on deformation, stability, and fatigue resistance.
③The thickness and edge width of hot rolled steel products are not easy to control. We are familiar with thermal expansion and contraction. Since at the beginning, even if the length and thickness are up to the standard, there will be a certain negative difference after cooling. The wider the negative difference, the more obvious the thicker the thickness. Therefore, for large steel, the side width, thickness, length, angle, and sideline of the steel cannot be too accurate.
The structure of hot rolled steel pipe:
Mainly used for mechanical structures, carbon press equipment, steel pipes with required dimensions and good surface finish.
It is mainly used to make coal mine hydraulic supports, cylinders and columns, and other hydraulic cylinders and columns.
It is mainly used to make carbon structural steel and alloy structural steel hot-rolled seamless steel pipes for automobile half-axle casings and drive axle housing shaft pipes.
It is mainly used to make cold drawn seamless tubing with inner diameters for hydraulic and pneumatic cylinders.
