A method for producing cold-drawn steel pipes by two-pass continuous drawing

Abstract

The invention discloses a two-pass continuous drawing method for producing a cold-drawn steel pipe. The method comprises the steps of pretreatment, pickling, phosphating, lubrication, cold drawing of rod with mandrel, drawing, and heat treatment. By changing the interaction of pickling, phosphating and lubrication, the physical and chemical properties of the pierced billet are improved greatly, especially the extension and isotropy are greatly improved greatly. Finally, the time and temperature of the heat treatment are controlled to eliminate internal stress of the product. The above processes as an organic continuous production process are indispensable to ensure parameters of each part and to obtain product with good mechanical properties and certain antirust ability, thereby reducing the pass frequency of cold drawing and reducing production cost.

Description

technical field [0001] The invention belongs to the technical field of metal material forming, and in particular relates to a method for producing cold-drawn steel pipes by two-pass continuous drawing. Background technique [0002] As a fluid conveying material, cold-drawn steel pipes have been widely used in production, such as high-pressure boiler pipes, petroleum cracking pipes, high-pressure fertilizer pipes, low and medium pressure boiler pipes, etc. At present, the method of producing cold-drawn steel pipes is to use large-diameter pipe materials as raw materials, undergo pretreatments such as pickling and phosphating, and then draw through multiple passes (at least three passes) to obtain the design. Cold-drawn steel pipes of fixed diameter. [0003] This multi-pass cold drawing process has three major defects: First, because each pass in the multi-pass cold drawing process reduces the outer diameter and wall thickness of the pipe material, the continuous drawing rat...

AI Technical Summary

Problems solved by technology

[0003] This multi-pass cold drawing process has three major defects: First, because each pass in the multi-pass cold drawing process reduces the outer diameter and wall thickness of the pipe material, the continuous drawing rate is also very low, resulting in The production cycle of the product is long, which seriously limits the output

The second is that the actual outer diameter and wall thickness reduction value of each pass of cold drawing will have an error with the set value. The more passes, the greater the cumulative effect of the error, which will also affect the pass rate of the product.

The third is that due to the lack of extensibility of the waste pipe, defects will be generated during the drawing process, and it is necessary to heat-treat the waste pipe between two passes before performing subsequent drawing passes, making the production process discontinuous and causing Affect the yield of the product

[0004] Therefore, reducing the number of cold-drawing passes of cold-drawn steel pipes can improve production efficiency and product qualification rate. However, in actual production, reducing the number of cold-drawing passes is likely to cause straight lines, shaking lines, transverse cracks, extrusion lines, and pits on the inner and outer surfaces of steel pipes. and other defects, leading to an increase in the scrap rate

Images