Cold-rolled steel strip for double-layer welded tube and its manufacture mathod

Abstract

The invention relates to a cold-rolled steel strip, and especially relates to a cold-rolled steel strip for a double-layer welded tube and its manufacturing method to mainly solve technical problems comprising bad product yield and bad performance uniformity because of cover annealing generally adopted in the manufacturing of the double-layer welded tube. The chemical components of the cold-rolled steel strip for the double-layer welded tube comprise 0.015-0.054wt% of C, 0.034wt% or less of Si, 0.15-0.25wt% of Mn, 0.020wt% or less of P, 0.020wt% or less of S, 0.015-0.050wt% of Alt, and the balance Fe and inevitable impurity elements. In the invention, low carbon and low silicon are adopted, aluminum deoxidization is adopted as a crystal grain refinement element, and impurity form control, hot continuous rolling control cooling, continuous annealing temperature control and continuous flattening technologies are utilized to produce, so it is helpful for the guarantee of the yield strength, the percentage elongation after fracture and the hardness of the steel in prescribed requirement ranges. The cold-rolled steel strip makes the tube manufactured through using it have the advantages of good full-length performance uniformity, good roll bend formability, good tube barrel lap rebound controllability, good weldability, and good tube bending performance, and can guarantee the yield in the complete tube manufacturing flow.

Description

technical field [0001] The invention relates to a cold-rolled steel strip, in particular to a cold-rolled steel strip for a double-layer coiled welded pipe, and also relates to a manufacturing method thereof. Background technique [0002] Double-layer coiled welded pipes are mainly used to produce automotive brake oil circuits, brake pipes, and refrigerator condensation systems. Due to the particularity of their service environment, they are required to have very good safety during use. Based on the process of double-layer welded pipe, the production process of strip uncoiling-720℃ rolling forming-high temperature brazing-annealing-coiling is generally adopted. The product has high processing and formability requirements for raw steel plates, and the yield strength is required to be maintained at 170. -260MPa, the tensile strength is guaranteed to be 270-370MPa, the elongation after fracture is >32%, and the hardness is guaranteed to be within the range of 40-52HR30T. In...

AI Technical Summary

Problems solved by technology

[0003] The object of the present invention is to provide a cold-rolled double-layer welded pipe whose yield strength is controlled at 170-260 MPa, tensile strength is guaranteed at 270-370 MPa, elongation after fracture is >32%, and hardness HR30T is guaranteed to be within the range of 40-52. The strip steel and its manufacturing method mainly solve the technical problems that bell annealing is commonly used for the existing double-layer welded pipe steel, and the product yield and performance uniformity are poor

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