Pipe inner wall surface quenching process

Abstract

The invention relates to a process for quenching the inner wall surface of a pipe, which is particularly suitable for a pipe made of a 42MnCr52 material. The process is realized through the following steps: vertically placing a pipe on a rotating tool, arranging an electric coil at a position about 30mm away from the bottom of the pipe, and configuring an inner and outer wall cooling device; and after the electric coil is preheated, the electric coil is heated at high frequency and passes through the inner hole of the pipe at the speed of 4-8 mm / s, meanwhile, water is introduced into the copper pipes on the inner wall and the outer wall for cooling, and the pipe rotates at the speed of 150-250 r / min. And after the electric coil completely passes through, cooling continues to be kept for 10-20 seconds so as to strengthen the quenching effect. Optionally, a destressing treatment is performed to ensure the dimensional stability of the tubing. The technical indexes that the hardness of a hardening layer is larger than or equal to 78 HRA, the depth ranges from 0.8 mm to 1.4 mm, and the inner hole diameter shrinkage ranges from 0.15 mm to 0.3 mm are achieved, the problem that deformation is large after the cylinder sleeve is quenched is effectively solved, and the pipe performance is improved.

Description

Technical Field

[0001] The present invention relates to the field of metal surface treatment processes, and particularly to a surface quenching process for the inner wall of a pipe. Background Art

[0002] In the fields of mechanical manufacturing and metal processing, surface quenching treatment of the inner wall of a pipe is an important means to improve its wear resistance, hardness, and service life. Especially for pipes made of alloy steel such as 42MnCr52, due to their excellent mechanical properties and heat treatment properties, they are widely used in various occasions requiring high strength and wear resistance. However, traditional inner wall quenching processes for pipes often have some problems, such as large deformation after quenching, difficulty in controlling the thickness and hardness of the hardened layer, etc., which seriously affect the quality and performance of the products.

[0003] Especially when quenching the inner wall of a pipe made of 42MnCr52 material, due to the particularity of the material and the limitations of the quenching process, it is often difficult to simultaneously meet the requirements of multiple aspects such as the hardness of the hardened layer, the depth of the hardened layer, and the deformation of the pipe. Traditional quenching processes often use a single quenching frequency and cooling method, resulting in unsatisfactory quenching effects and easy generation of large deformations, thus affecting the use effect and service life of the products. Summary of the Invention

[0004] The purpose of the present invention is to provide a surface quenching process for the inner wall of a pipe to solve the problems of large deformation after quenching and difficulty in controlling the thickness and hardness of the hardened layer in the prior art.

[0005] The present invention is realized by the following technical solutions: A surface quenching process for the inner wall of a pipe, characterized by comprising the following steps: S1. Preparation stage: Vertically place a pipe made of 42MnCr52 material on a rotating fixture. Set the initial position of the induction coil at a position about 30 mm from the bottom of the pipe, and connect a ring-shaped copper pipe with the same diameter at the bottom. A circle of small holes is drilled on the copper pipe for water cooling of the inner wall of the pipe; At a horizontal position about 50 mm from the induction coil, configure a circle of perforated copper pipes for water cooling of the outer wall of the pipe; S2. Preheating stage: Preheat the induction coil for 10 - 20 seconds to make the induction coil, the air around it, and the pipe reach a certain initial temperature; S3. Heating and cooling stage: After the induction coil is heated by high frequency, pass through the inner hole of the pipe at a rate of 4 - 8 mm / s to heat the inner wall of the pipe. At the same time, start water cooling for the inner and outer wall copper pipes, and the pipe rotates at a rate of 150 - 250 r / min; S4. Intensified cooling and unloading stage: After the induction coil completely passes through the upper end of the pipe, continue to keep the inner and outer wall copper pipes for water cooling for 10 - 20 seconds, and then unload the quenched pipe; S5. Inspection and Quality Control Stage: Use appropriate testing methods to inspect the hardness and depth of the hardened layer, and measure and record the diameter shrinkage of the inner hole of the pipe after quenching.

[0006] Further, in step S3, the heating frequency is controlled within 20000 - 22000 HZ.

[0007] Further, in step S5, the hardness requirement of the hardened layer is ≥78 HRA, and the depth of the finished hardened layer is 0.8 - 1.4 mm.

[0008] Further, the pipe rotates at a rate of 150 - 250 r / min during the heating and cooling stages to ensure uniform cooling.

[0009] Further, in step S3, the temperature of the cooling water needs to be controlled at ≤50 °C to ensure the cooling effect.

[0010] Further, it also includes stress relief treatment. For the stress that may be generated during the quenching process, an appropriate stress relief process is adopted for treatment.

[0011] Further, in step S5, the measured and recorded diameter shrinkage of the inner hole of the pipe after quenching should be within the range of 0.15 - 0.3 mm.

[0012] A surface quenching process for the inner wall of a pipe according to the present invention has the following beneficial effects: Improved hardness and depth of the hardened layer: By adjusting the quenching frequency and cooling method, the present invention has successfully increased the hardness of the hardened layer to ≥78 HRA, and the depth of the finished hardened layer is controlled between 0.8 - 1.4 mm, meeting the requirements of the product drawing.

[0013] Reduced deformation of the pipe: By optimizing the quenching process and adapting the stress relief process, the present invention effectively reduces the deformation of the pipe during quenching, thereby improving the quality and stability of the product.

[0014] Improved production efficiency: The quenching process of the present invention is simple to operate, easy to control, and can achieve uniform quenching treatment of the inner wall of the pipe, thereby improving the production efficiency.

[0015] Reduced production cost: Since the present invention can effectively control various parameters during the quenching process, it avoids the increase in the rejection rate caused by poor quenching, thereby reducing the production cost. Description of the Drawings

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. The accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0017] Figure 1 It is a process flow chart for surface quenching of the inner wall of a pipe. Detailed implementation manners

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Generally, the components of the embodiments of the present invention described and illustrated in the accompanying drawings here can be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0020] As Figure 1 shown, a surface quenching process for the inner wall of a pipe includes the following steps: I. Preparation stage: Placement of the pipe: Vertically and stably place the 42MnCr52 material pipe to be quenched on the rotating fixture to ensure that the pipe does not shake during the quenching process to guarantee the uniformity of the quenching effect.

[0021] Setting of the electric coil and the cooling device: Set an electric coil at a position about 30 mm from the bottom of the pipe. Connect a copper pipe with the same diameter below the electric coil. A circle of small holes is drilled on the copper pipe for water cooling of the inner wall of the pipe. At the same time, configure a circle of perforated copper pipes at a horizontal position about 50 mm from the electric coil for water cooling of the outer wall of the pipe.

[0022] II. Preheating stage: Preheat the electric coil for 10 - 20 seconds to make the electric coil, the air around it, and the pipe reach a certain initial temperature. The purpose of this step is to reduce the thermal stress during the subsequent heating process and ensure the stability of the quenching effect and the integrity of the pipe.

[0023] III. Heating and cooling stage: High-frequency heating: After the electric coil is heated by high frequency, it starts to pass through the inner hole of the pipe from the initial position at a rate of 4 - 8 mm / s to heat the inner wall of the pipe. The heating frequency is controlled at 20000 - 22000 HZ to ensure the uniformity and stability of the heating effect.

[0024] Simultaneous cooling of the inner and outer walls: While the electric coil passes through the inner hole of the pipe, the copper pipes on the inner and outer walls start to supply water for cooling. The pipe rotates at a rate of 150 - 250 r / min to ensure uniform cooling. The temperature of the cooling water needs to be controlled at ≤50 °C to ensure the cooling effect.

[0025] IV. Strengthened cooling and unloading stage: After the electric coil completely passes through the upper end of the pipe, continue to keep the copper pipes on the inner and outer walls supplying water for cooling for 10 - 20 seconds to further consolidate the quenching effect. After the strengthened cooling is completed, unload the quenched pipe.

[0026] V. Stress relief treatment (selected according to actual needs): For the stress that may be generated during the quenching process, an appropriate stress relief process is used for treatment. This step is optional. Whether stress relief treatment is required specifically should be determined according to actual needs.

[0027] VI. Inspection and quality control: Inspect the hardened layer: Use appropriate detection methods, such as hardness testing, metallographic analysis, etc., to inspect the hardness (≥78 HRA) and depth (0.8 - 1.4 mm) of the hardened layer. This is an important step to ensure that the quenching effect meets the requirements of the product drawing.

[0028] Measure the shrinkage of the inner hole diameter: Measure and record the shrinkage of the inner hole diameter of the pipe after quenching to ensure that it is within the range of 0.15 - 0.3 mm. The purpose of this step is to ensure that the deformation of the pipe during quenching is controlled within a reasonable range.

[0029] In the above embodiments, the basic principles, main features, and advantages of the present invention are described. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications and changes made by those skilled in the art that do not depart from the spirit and scope of the present invention should fall within the protection scope of the appended claims of the present invention.

Claims

1. A quenching process for the inner wall surface of a pipe, characterized in that, It includes the following steps: S1. Preparation stage: Vertically place the pipe made of 42MnCr52 material on the rotating fixture. Set the initial position of the induction coil at about 30 mm from the bottom of the pipe, and connect a ring-shaped copper pipe with the same diameter at the bottom. A circle of small holes is drilled on the copper pipe for water cooling of the inner wall of the pipe. At a horizontal position about 50 mm from the induction coil, a circle of perforated copper pipes is arranged for water cooling of the outer wall of the pipe. S2. Preheating stage: Preheat the induction coil for 10 - 20 seconds to make the induction coil, the air around it and the pipe reach a certain initial temperature. S3. Heating and cooling stage: After the induction coil is heated by high frequency, it passes through the inner hole of the pipe at a rate of 4 - 8 mm / s to heat the inner wall of the pipe. At the same time, the copper pipes on the inner and outer walls start to supply water for cooling, and the pipe rotates at a rate of 150 - 250 r / min. S4. Intensified cooling and unloading stage: After the induction coil completely passes through the upper end of the pipe, continue to keep the copper pipes on the inner and outer walls supplying water for cooling for 10 - 20 seconds, and then unload the quenched pipe. S5. Inspection and quality control stage: Use appropriate detection methods to inspect the hardness and depth of the hardened layer, and measure and record the diameter shrinkage of the inner hole of the pipe after quenching.

2. A surface quenching process for the inner wall of a pipe according to claim 1, characterized in that, In step S3, the heating frequency is controlled within 20000 - 22000 HZ.

3. A surface hardening process for the inner wall of a pipe according to claim 1, characterized in that, In step S5, the hardness requirement of the hardened layer is ≥78 HRA, and the depth of the finished hardened layer is 0.8 - 1.4 mm.

4. A quenching process for the inner wall surface of a pipe according to claim 1, characterized in that, During the heating and cooling stage, the pipe rotates at a rate of 150 - 250 r / min to ensure uniform cooling.

5. A quenching process for the inner wall surface of a pipe according to claim 1, characterized in that, In step S3, the temperature of the cooling water needs to be controlled at ≤50 °C to ensure the cooling effect.

6. A quenching process for the inner wall surface of a pipe according to claim 1, characterized in that, It also includes stress relief treatment. For the stress that may be generated during the quenching process, an appropriate stress relief process is adopted for treatment.

7. A quenching process for the inner wall surface of a pipe according to claim 1, characterized in that, In step S5, the measured and recorded diameter shrinkage of the inner hole of the pipe after quenching should be within the range of 0.15 - 0.3 mm.

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