Cold drawing process for austenitic stainless asymmetric wall thickness steel pipe

Abstract

This invention discloses a cold drawing process for austenitic stainless steel pipes with asymmetrical wall thickness. The process includes the following steps: Step 1: Selecting an asymmetrical cold drawing outer die with a tapered inlet hole; Step 2: Selecting a tapered cold drawing inner die; Step 3: Assembling the cold drawing outer and inner dies with a hydraulic drawing machine; Step 4: Feeding the austenitic stainless steel pipe into the hydraulic drawing machine and performing three passes of cold drawing with the outer and inner dies. Compared with traditional machining, this invention significantly shortens the production cycle of asymmetric wall thickness steel pipes and improves production efficiency. Through the cooperation of the inner and outer dies, the product's dimensions and wall thickness accuracy can be effectively controlled, resulting in a bright and smooth surface finish. Furthermore, this process saves considerable raw material consumption and reduces labor costs during cold drawing.

Description

Technical Field

[0001] This invention relates to the technical field of steel pipe processing, and in particular to a cold drawing process for austenitic stainless steel pipe with asymmetric wall thickness. Background Technology

[0002] In the electronics industry, some parts are made of stainless steel (such as austenitic stainless steel). These products have regular shapes, irregular internal holes, and non-uniform wall thicknesses. They also have high requirements for dimensional accuracy, surface quality, and hardness (external 210-330 HV1, internal 175-265 HV1). Currently, they are mainly processed by machining, which has a long processing cycle, high raw material consumption, high cost, and low production efficiency in mass production, resulting in a low product yield (25-35%).

[0003] To overcome the shortcomings of current machining methods, shorten the processing cycle, reduce raw material consumption, improve production efficiency, reduce production costs, and increase product yield, it is necessary to design a cold drawing process for austenitic stainless steel pipes with asymmetric wall thickness for cold working of such products. Summary of the Invention

[0004] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0005] In view of the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of this invention is to provide a cold drawing process for austenitic stainless steel pipes with asymmetric wall thickness, in order to solve the problems of long processing cycle, high raw material consumption, high cost, and low production efficiency in mass production of asymmetric wall thickness steel pipes.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a cold drawing process for austenitic stainless steel pipe with asymmetric wall thickness, the steps of which are as follows:

[0008] Step 1: Select an asymmetrical cold-drawn outer mold with a tapered inlet hole;

[0009] Step 2: Select a cold-drawn inner mold with a conical shape and a tapered angle;

[0010] Step 3: Assemble the cold-drawn outer mold and the cold-drawn inner mold with the hydraulic drawing machine;

[0011] Step 4: Feed the austenitic stainless steel tube into the hydraulic drawing machine and perform three cold drawing passes using the cold drawing outer die and the cold drawing inner die.

[0012] Each pass involves a reasonable allocation of cold drawing deformation rate, and a pressing device is added outside the cold drawing outer die exit end to keep the steel pipe centerline aligned with the drawing centerline, matching appropriate drawing speed and deformation rate. Cold drawing lubricant needs to be added during the cold drawing process.

[0013] As a preferred embodiment of the cold drawing process for an austenitic stainless steel pipe with asymmetric wall thickness as described in this invention, the cold drawing outer mold has an asymmetric hole, which includes an outlet hole section, a sizing hole section and an inlet hole section, and the taper angles of the two opposite faces of the inlet hole section are α and β, respectively, and the value is 6-9°.

[0014] As a preferred embodiment of the cold drawing process for an austenitic stainless steel pipe with asymmetric wall thickness as described in this invention, the cold drawing inner mold comprises four integrally formed sections: a sizing section, a reverse tapered section, a chamfered section, and a threaded section, wherein the taper angle of the reverse tapered section of the cold drawing inner mold is 7 to 10°.

[0015] As a preferred embodiment of the cold drawing process for an austenitic stainless steel asymmetric wall thickness steel pipe described in this invention, the process further includes, between the three cold drawing passes, the inner and outer surfaces of the austenitic stainless steel pipe undergoing solution treatment; the solution treatment temperature is 1040℃-1100℃.

[0016] As a preferred embodiment of the cold drawing process for an austenitic stainless steel pipe with asymmetric wall thickness as described in this invention, wherein: after each solution treatment, the pipe is cooled to below 200°C using an extremely rapid cooling method, the cooling medium is circulating cooling water, and the cooling rate is controlled at 100-300°C / min.

[0017] As a preferred embodiment of the cold drawing process for austenitic stainless steel pipe with asymmetric wall thickness as described in this invention, in step four, the deformation rate of the three cold drawing passes is controlled as follows: 25.54% for the first pass, 8.25% for the second pass, and 5.59% for the third pass.

[0018] The beneficial effects of this invention are as follows: Compared with traditional machining, the process of this invention greatly shortens the production cycle of asymmetric wall thickness steel pipes and improves production efficiency. Through the cooperation of inner and outer molds, the product's external dimensions and wall thickness accuracy can be effectively controlled, and the product surface quality is bright and smooth. Due to the characteristics of this process, it can save a lot of raw material consumption and reduce labor costs during cold drawing, thereby reducing the product production cost. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0020] Figure 1 This is a schematic diagram of the outer mold structure for a cold drawing process of austenitic stainless steel pipe with asymmetric wall thickness proposed in this invention.

[0021] Figure 2 This is a schematic diagram of the inner mold structure for a cold drawing process of austenitic stainless steel pipe with asymmetric wall thickness proposed in this invention.

[0022] Figure 3 This is a schematic diagram of the steel pipe cross-section change process in the cold drawing process of an austenitic stainless asymmetric wall thickness steel pipe proposed in this invention.

[0023] Figure 4 This is a schematic diagram of the final steel pipe product structure of the cold drawing process of an austenitic stainless asymmetric wall thickness steel pipe proposed in this invention. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Reference Figure 1-4 As an embodiment of the present invention, a cold drawing process for austenitic stainless steel pipe with asymmetric wall thickness is provided, the steps of which are as follows:

[0028] Step 1: Refer to the appendix Figure 1An asymmetrical cold-drawn outer die with a tapered inlet hole is selected. Specifically, the cold-drawn outer die has asymmetrical orifices inside, including: an outlet hole section 1, a sizing hole section 2, and an inlet hole section 3. The taper angles of the two opposite faces of the inlet hole section 3 are α and β, respectively, and the values ​​are 6-9°. Figure 1 It can be seen that β > α.

[0029] Step Two: Refer to Appendix Figure 2 A cold-drawn inner mold with a conical shape and taper is selected, referring to... Figure 2 The cold-drawing inner die includes: a sizing section L1, which is used to control the wall thickness and inner hole size of the steel pipe; a reverse tapered section L2, which is used to reduce the wall deformation of the steel pipe; a chamfered section L3 for transition; and a threaded section L4 for connection and fixation. The four sections are integrally formed. The taper angle c of the reverse tapered section of the cold-drawing inner die is 7 to 10°.

[0030] Step 3: Assemble the cold-drawn outer mold and the cold-drawn inner mold with the hydraulic drawing machine;

[0031] Step 4: Feed the austenitic stainless steel tube into the hydraulic drawing machine and perform three cold drawing passes using the cold drawing outer die and the cold drawing inner die.

[0032] The cold drawing deformation rate is reasonably allocated for each pass, namely: 25.54% for the first pass, 8.25% for the second pass, and 5.59% for the third pass. A pressing device is added to the outside of the cold drawing outer die exit to keep the center line of the steel pipe consistent with the drawing center line, and to match the appropriate drawing speed and deformation rate. Cold drawing lubricant needs to be added during the cold drawing process.

[0033] Between the three cold drawing processes, the austenitic stainless steel tube undergoes internal and external surface treatment and solution treatment. The solution treatment temperature is 1040℃-1100℃. After each solution treatment, the tube is rapidly cooled to below 200℃ using a circulating cooling water medium, with a cooling rate controlled at 100~300℃ / min.

[0034] In summary, the process of this invention significantly shortens the production cycle of asymmetric wall thickness steel pipes compared to traditional machining, improves production efficiency, and through the cooperation of inner and outer molds, the product's external dimensions and wall thickness accuracy can be effectively controlled, resulting in a bright and smooth product surface. Furthermore, the process saves considerable raw material consumption and reduces labor costs during cold drawing, thereby lowering the product's production cost.

[0035] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A cold drawing process for austenitic stainless steel pipe with asymmetric wall thickness, characterized in that, The steps of this process are as follows: Step 1: Select an asymmetrical cold-drawn outer mold with a tapered inlet hole; Step 2: Select a cold-drawn inner mold with a conical shape and a tapered angle; Step 3: Assemble the cold-drawn outer mold and the cold-drawn inner mold with the hydraulic drawing machine; Step 4: Feed the austenitic stainless steel tube into the hydraulic drawing machine and perform three cold drawing passes using the cold drawing outer die and the cold drawing inner die. Each pass involves a reasonable allocation of cold drawing deformation rate, and a pressing device is added outside the cold drawing outer die exit end to keep the steel pipe centerline consistent with the drawing centerline, match the appropriate drawing speed and deformation rate, and add cold drawing lubricant during the cold drawing process. The cold-drawn outer mold has asymmetrical holes, including: an outlet hole section (1), a sizing hole section (2) and an inlet hole section (3), and the taper angles of the two opposite faces of the inlet hole section (3) are α and β, respectively, and the values ​​are 6-9°. The cold-drawn inner mold comprises four integrally formed sections: a sizing section, a reverse tapered section, a chamfered section, and a threaded section. The taper angle of the reverse tapered section of the cold-drawn inner mold is 7 to 10 degrees.

2. The cold drawing process for an austenitic stainless steel pipe with asymmetric wall thickness according to claim 1, characterized in that: Between the three cold drawing processes, the austenitic stainless steel tube undergoes solution treatment on both its inner and outer surfaces; the solution treatment temperature is 1040℃-1100℃.

3. The cold drawing process for an austenitic stainless steel pipe with asymmetric wall thickness according to claim 2, characterized in that: After each solution treatment, the temperature is rapidly cooled to below 200°C using a circulating cooling water medium, with the cooling rate controlled at 100–300°C / min.

4. The cold drawing process for an austenitic stainless steel pipe with asymmetric wall thickness according to claim 1, characterized in that: In step four, the deformation rate of the three cold drawing passes is controlled as follows: 25.54% for the first pass, 8.25% for the second pass, and 5.59% for the third pass.

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