Hot rolling and cold rolling are the forming processes of two kinds of shape steel or steel plate for sanitary pipe fittings. Heat treatment can have a great influence on the structure and properties of steel. Hot rolling is the main method of steel rolling, and cold rolling is only used to produce small section steel and thin plate. So what do you know about the heat treatment methods of sanitary pipe fittings?

1、 Hot rolling

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

Disadvantages: 1. After hot rolling, the non-metallic mixture inside the steel (mainly sulfide and oxide, and silicate) is pressed into thin sheets, showing the sign of delamination (interlayer). Delamination greatly deteriorates the tensile properties of the steel along the thickness, and there may be interlaminar tearing during weld tightening.

2. Slag stress caused by uneven cooling. The slag stress is the stress of self-equilibrium in the internal without external force. All kinds of hot-rolled steel sections have this kind of slag stress. The larger the section size of ordinary section steel is, the greater the slag stress is. Although the slag stress is self-equilibrium.

2、 Cold rolling

Advantages: rapid forming speed, high yield, and no damage to the coating, can be made into a variety of cross-section situations to meet the needs of utilization conditions; cold rolling can make the steel produce a large plastic deformation, thus improving the yield point of steel.

Disadvantages: 1. Although there is no hot plastic compression in the forming process, there is still slag stress in the cross-section, which definitely affects the bulk and local buckling characteristics of steel.

2. The wall thickness of cold-rolled formed steel is small, and there is no thickening at the corner of plate joint, so the ability to bear local convergence load is weak.

3. The cold rolled section is usually open section, which makes the free rotation stiffness of the section low. Rotation is easy to occur in bending, bending and torsion buckling are easy to occur under compression, and the torsional performance is poor.