Thick-walled mild steel pipe tube heat treatment prior to cold working the hot-rolled tube for a heat treatment, its main purpose is to eliminate internal stress tube, lower hardness, improved ductility, so that the cold working properties to meet the cold deformation. Tube mainly for the treatment alloy steel and high carbon steel. Low carbon steel tube heat tube is generally not performed.
As the heat-treated steel easily deformed, so it needs to be further finishing. In some steel heat treatment production line, in furnace set at the discharge port pipe sizing machine for sizing. The main role of sizing are two: First, to ensure accuracy of the geometry of pipe diameter; two is to ensure that steel has a smaller ellipse, which need to be tapped holes for casing and tubing is very beneficial, in order to ensure quality of the thread creation the conditions.
Pipe deformation will occur after the heat treatment, the bending and ellipticity increases. Difficult to meet the relevant standards and requirements after the procedure, therefore, straightening process is essential. Straightening process can eliminate or reduce this distortion, the bending of the product and the ellipticity meet the standard requirements. Commonly used steel straightening machine for the oblique roll straightening machines and pressure straightening machine, oblique roller straightening machine efficiency should be high, straightening effect, not only to get the bending of straight pipe, but also improve the pipe ovality. But should skew roller straightening machine for steel pipe ends bent (goose head bent) straightening effect is not ideal, is usually required pressure straightening machine straightening. Right oblique roll straightener, the pipe bending and flattening only under conditions to achieve the straightening effect. Pipe straightening parameters affecting the quality of the amount of reduction of the rollers, deflection of the intermediate rolls, straightening temperature of steel pipe, specifications and straightening speed.
Bend to the straight pipe straightening process is actually a plastic deformation process, and the deformation force must meet or exceed the yield strength of steel to produce plastic deformation. In the heat treatment is usually arranged in line leveler back behind the stove, the stove pipe out the back, the temperature should be slightly adjusted that for Johnson, called "hot correction" or "temperature correction." The strength of steel with the temperature increase and decrease, and different kinds of steel strength at the same temperature difference is large, so adjusting the straightening machine, the amount of reduction of the rollers and due to the deflection of the lower roll and straightening of steel Straight vary by temperature.
