The difference between hot-rolled and cold-rolled seamless steel pipe

The difference between hot-rolled seamless steel pipe and cold-rolled seamless steel pipe:

1) Cold-rolled seamless steel pipes tend to be of small diameter, and hot-rolled seamless steel pipes tend to be of large diameter.

2) The precision of cold-rolled seamless steel pipe is higher than that of hot-rolled seamless steel pipe, and the price is also higher than that of hot-rolled seamless steel pipe.
3) Hot-rolled seamless pipes are divided into general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, geological steel pipes and other steel pipes.
4) In addition to general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, petroleum cracking pipes, and other steel pipes, cold-rolled seamless steel pipes also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, non-ferrous steel pipes, etc. Rust thin-walled steel pipe, special-shaped steel pipe.
5) In addition to general steel pipes, low and medium pressure boiler steel pipes, high pressure boiler steel pipes, alloy steel pipes, stainless steel pipes, oil cracking pipes, and other steel pipes, cold-rolled seamless steel pipes also include carbon thin-walled steel pipes, alloy thin-walled steel pipes, non-ferrous steel pipes, etc. Rust thin-walled steel pipe, special-shaped steel pipe.

Process flow:

Hot rolling (extruded seamless steel pipe): round tube billet → heating → perforation → three-roller skew rolling, continuous rolling or extrusion → tube removal → sizing (or diameter reduction) → cooling → billet tube → straightening → water pressure Test (or flaw detection) → mark → storage.

Cold-rolled seamless steel pipe: round tube billet → heating → perforation → heading → annealing → pickling → oiling (copper plating) → multi-pass cold drawing (cold rolling) → billet → heat treatment → straightening → hydraulic test ( Flaw detection) → marking → storage.

Hot rolling is relative to cold rolling, cold rolling is rolling below the recrystallization temperature, and hot rolling is rolling above the recrystallization temperature.

Hot rolled seamless tube:

Advantages:

It can destroy the casting structure of the ingot, refine the grain of the steel, and eliminate the defects of the microstructure, so that the steel structure is dense and the mechanical properties are improved. This improvement is mainly reflected in the rolling direction, so that the steel is no longer isotropic to a certain extent; the bubbles, cracks and porosity formed during casting can also be welded under the action of high temperature and pressure.

Disadvantages:

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 the phenomenon of delamination (interlayer) occurs. Delamination greatly deteriorates the tensile properties of the steel through the thickness, and there is the potential for interlaminar tearing as 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 induced by the load;

2. Residual stress caused by uneven cooling. Residual stress is the stress of internal self-phase equilibrium without external force. Hot-rolled section steel of various sections has such residual stress. Generally, the larger the section size of the section steel, the greater the residual stress. Although the residual stress is self-balanced, it still has a certain 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.

3. Hot-rolled steel products are difficult to control in terms of thickness and side width. We are familiar with thermal expansion and cold contraction. Even if the length and thickness are up to standard at the beginning of hot rolling, there will still be a certain negative difference after cooling. The wider the side width of this negative difference, the thicker the thickness, the more obvious the performance. Therefore, for large steel, the width, thickness, length, angle, and edge of the steel cannot be too precise.

Hunan Standard Steel Co.,Ltd: https://www.hu-steel.com
Address: 22nd floor golden tower, Changsha West International Central Mansion, Yuelu District, Changsha, Hunan, China
Postcode:410205
Tel: 0086-731-88787781
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E-mail: info@hu-steel.com
Seamless steel pipe: https://www.hu-steel.com/product85.html
ERW welded pipe: https://www.hu-steel.com/product90_985.html

Hunan Standard Steel Co.,Ltd is a as the professional manufacturer of seamless steel pipe, welded steel pipe and pipe fittings.Please refer to: https://www.hu-steel.com

This release was published on openPR.