A high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe and its preparation method

Abstract

The present invention discloses a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe and a preparation method thereof. The structural form of the composite pipe is that hard high chromium cast iron is diffusely embedded inside the high manganese steel matrix; the preparation method of the composite pipe is as follows: a composite pipe blank with 5 to 11 layers is cast layer by layer by means of centrifugal casting; the centrifugally cast composite pipe blank is subjected to heat treatment to enable the high manganese steel to obtain a single austenite structure; the heat-treated composite pipe blank is subjected to hot rolling deformation so that the high chromium cast iron plates inside the pipe blank are fractured and broken during the rolling process and embedded in the high manganese steel; the composite pipe is subjected to quenching and tempering treatments, thereby obtaining a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe. The high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe of the present invention has good wear resistance and toughness. The manufacturing method of the wear-resistant composite pipe is simple, without the need for major equipment modification, and is easy to realize mass production.

Description

Technical Field

[0001] The present invention belongs to the technical field of bimetallic composite pipes, and particularly relates to a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe and a preparation method thereof. Background Art

[0002] Bimetallic composite pipes are usually composed of two different metal materials combined together through a certain connection technology, which can combine the advantages of the two component metal materials in terms of structure and performance. At present, they have been widely used in industries such as mining equipment, coal transportation, petroleum, chemical industry, and electric power.

[0003] In important equipment such as material transportation, oil and gas extraction, wear-resistant metal pipe fittings with excellent comprehensive performance are required. These metal pipe fittings are often under complex combined stress during use, and not only need to have high hardness and good wear resistance, but also need to have a certain degree of toughness. High chromium cast iron is a wear-resistant metal material widely used in industry, and the wear-resistant metal pipes prepared from it have obtained certain applications in the material transportation industry. However, the high chromium cast iron has low impact resistance and fatigue resistance, and often fails due to impact fracture under high stress loads, resulting in the inability to fully exert its excellent wear resistance. At present, high chromium cast iron and ductile alloy steel are usually prepared into a bimetallic layered structure composite pipe through connection processes such as surfacing composite, casting composite, and powder metallurgy composite to obtain good comprehensive mechanical properties. However, the traditional preparation process of high chromium cast iron composite pipes is difficult to promote, and the brittle and hard high chromium cast iron wear-resistant layer is prone to problems such as cracking along the bonding interface or delamination and spalling under large impact loads, resulting in unstable performance of the composite pipe fittings and low service safety.

[0004] High manganese steel is an excellent wear-resistant alloy. After water toughening treatment, high manganese steel can obtain a single austenite structure and has good impact resistance. At the same time, under the action of large impact loads or contact stresses, its surface rapidly undergoes work hardening, while the inner layer of austenite still maintains good toughness. However, when the applied impact load is small, its work hardening ability is insufficient, and it often exhibits low wear resistance, resulting in rapid wear of the material. By embedding high chromium cast iron with excellent wear resistance into the high manganese steel matrix with excellent toughness and work hardening performance through a certain technology and process, the advantages of the two metal materials in terms of performance and function can be fully exerted. Summary of the Invention

[0005] The purpose of the present invention is to provide a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe. The present invention mainly obtains a bimetallic composite pipe with high chromium cast iron embedded in the high manganese steel matrix, so that it has both good wear resistance and impact resistance.

[0006] Another object of the present invention is to provide a method for preparing a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe to overcome the disadvantages of low bonding strength at the interface between the two metals and poor comprehensive performance in the existing production technology.

[0007] In order to achieve the above object of the invention, the technical solution of the present invention is as follows:

[0008] The present invention provides a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe. The structural form of the composite pipe is that high chromium cast iron with excellent wear resistance is dispersed and embedded in ductile high manganese steel; the high manganese steel contains the following chemical components by weight percentage: C: 0.9%, Si: 0.42%, Mn: 13%, Al: <0.05%, S <: 0.01%, P: <0.2%, and the rest is Fe; the high chromium cast iron contains the following chemical components by weight percentage: C: 2.8%, Cr: 28%, Mn: 0.6%, Si: 0.5%, S: <0.05%, P: <0.1%, and the rest is Fe.

[0009] Another object of the present invention is to provide a method for preparing a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe, which specifically includes the following steps:

[0010] S1: Take two sets of casting systems and use the centrifugal casting method to layer-cast a composite pipe blank with 5 to 11 layers. The outermost and innermost layers of the composite pipe blank are high manganese steel layers, and the cast high chromium cast iron layer is located between the two high manganese steel layers;

[0011] S2: Heat the centrifugally cast composite pipe blank to 1050 °C, hold for 1 to 2 h, and then quickly water-cool to make the high manganese steel obtain a single austenite structure. Mechanically polish the inner and outer surfaces of the heat-treated composite pipe blank to remove external impurities;

[0012] S3: Heat the above-treated composite pipe blank to 1150 - 1200 °C, hold for 0.5 to 2 h, and then perform multi-pass hot rolling. The rolling temperature is 1000 - 1150 °C, and the reduction per pass is 10% - 25%. Under the action of the rolling pressure, the high chromium cast iron layer with poor deformability in the composite pipe blank fractures and is embedded in the ductile high manganese steel;

[0013] S4: Heat the rolled composite pipe to 1050 °C, hold for 1 to 3 h, oil-quench and cool to room temperature, then heat the composite pipe to 350 °C, hold for 1 to 3 h, air-cool to room temperature, and then mechanically polish the inner and outer layers of the composite pipe to obtain a bimetallic wear-resistant composite pipe with a hard high chromium cast iron-reinforced high manganese steel matrix.

[0014] Among them, in step S1, the thickness of the high manganese steel layer is 5 - 20 mm, the thickness of the high chromium cast iron layer is 5 - 10 mm, and the thickness ratio of the high manganese steel to the high chromium cast iron layer is 1 - 2.

[0015] In step S1, the casting temperature of the high manganese steel layer is 1600 - 1700 °C, and the rotational speed of the centrifuge is 400 - 600 revolutions per minute; the casting temperature of the high chromium cast iron is 1350 - 1400 °C, and the rotational speed of the centrifuge is 500 - 700 revolutions per minute; the time interval between the casting of the two metal melts is 80 s - 120 s.

[0016] The present invention has the following beneficial effects:

[0017] 1. For the bimetallic wear-resistant composite pipe of the present invention, the high chromium cast iron is embedded in the high manganese steel matrix as a reinforcement. Under low stress, the hard high chromium cast iron can effectively protect the high manganese steel matrix from wear. Under high stress, the high manganese steel matrix can achieve good work hardening and resist external wear together with the hard high chromium cast iron.

[0018] 2. The present invention provides a preparation method for a bimetallic wear-resistant composite pipe with high chromium cast iron dispersed and embedded in a high manganese steel matrix. By adjusting the thickness ratio of the two metal layers during centrifugal casting, the specifications and comprehensive properties of the prepared bimetallic composite pipe can be regulated.

[0019] 3. By combining the bimetallic casting composite and rolling deformation processes, embedding the hard high chromium cast iron in the high manganese steel to form a three-dimensional composite structure of the two metals, problems such as the low interfacial bonding strength between the hard wear-resistant layer and the matrix, cracking or delamination and spalling of the wear-resistant layer along the interface in the traditional bimetallic laminated composite pipe can be overcome. At the same time, this soft-hard alternating three-dimensional composite structure can utilize the large-area continuous ductile high manganese steel matrix to improve the damage tolerance of the composite material, and has good engineering application value. Description of the Drawings

[0020] Figure 1 It is a schematic diagram of a centrifugally cast composite pipe blank; Figure 2 It is a schematic diagram after hot rolling forming of the composite pipe blank; Figure 3 It is a scanning electron microscope micrograph of the bimetallic composite pipe in Example 1.

[0021] In the figure, D1 - the outer diameter of the centrifugally cast composite pipe, d1 - the inner diameter of the centrifugally cast composite pipe, M1, M2, M3 - the first, second, and third layers of high manganese steel cast, G1, G2 - the first and second layers of high chromium cast iron cast, 1 - the high manganese steel matrix after hot rolling forming, 2 - the high chromium cast iron embedded in the high manganese steel, D2 - the outer diameter of the composite pipe after hot rolling, d2 - the inner diameter of the composite pipe after hot rolling. Detailed Embodiments

[0022] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments, but the present invention is not limited to this specific embodiment.

[0023] The present invention provides a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe. As Figure 2 shown, the structural form of the composite pipe is that high chromium cast iron with excellent wear resistance is dispersed and embedded in ductile high manganese steel; the high manganese steel contains the following chemical components by weight percentage: C: 0.9%, Si: 0.42%, Mn: 13%, Al: <0.05%, S: <0.01%, P: <0.2%, and the rest is Fe; the high chromium cast iron contains the following chemical components by weight percentage: C: 2.8%, Cr: 28%, Mn: 0.6%, Si: 0.5%, S: <0.05%, P: <0.1%, and the rest is Fe.

[0024] Another object of the present invention is to provide a method for preparing a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe, which includes the following steps:

[0025] S1: Take two sets of casting systems and layer-cast a composite pipe blank with 5 to 11 layers by centrifugal casting method. The outermost layer and the innermost layer of the composite pipe blank are high manganese steel layers, and the cast high chromium cast iron layer is located between the two high manganese steel layers;

[0026] S2: Heat the centrifugally cast composite pipe blank to 1050 °C, keep it warm for 1 to 2 h, and then rapidly water-cool it so that the high manganese steel obtains a single austenite structure. Mechanically polish the inner surface and the outer surface of the heat-treated composite pipe blank to remove external impurities;

[0027] S3: Heat the above-treated composite pipe blank to 1150 - 1200 °C, keep it warm for 0.5 to 2 h, and then perform multi-pass hot rolling. The rolling temperature is 1000 - 1150 °C, and the reduction per pass is 10% - 30%. Under the action of rolling pressure, the high chromium cast iron layer with poor deformability in the composite pipe blank fractures and breaks and is embedded in the ductile high manganese steel;

[0028] S4: Heat the rolled composite pipe to 1050 °C, keep it warm for 1 to 3 h, oil-quench it to room temperature, then heat the composite pipe to 350 °C, keep it warm for 1 to 3 h, air-cool it to room temperature, and then mechanically polish the inner layer and the outer layer of the composite pipe to obtain a bimetallic wear-resistant composite pipe with a hard high chromium cast iron-reinforced high manganese steel matrix.

[0029] Among them, the thickness of the high manganese steel layer described in step S1 is 5 - 20 mm, the thickness of the high chromium cast iron layer is 5 - 10 mm, and the thickness ratio of the high manganese steel to the high chromium cast iron layer is 1 - 2.

[0030] In step S1, the casting temperature of the high manganese steel layer is 1600 - 1650 °C, and the centrifuge speed is 400 - 600 revolutions per minute; the casting temperature of the high chromium cast iron is 1350 - 1400 °C, and the centrifuge speed is 500 - 700 revolutions per minute; the time interval between the casting of the two metal liquids is 80s - 120s.

[0031] Example 1

[0032] A high manganese steel - high chromium cast iron bimetallic wear - resistant composite pipe is prepared by using casting composite and rolling forming processes. The specific preparation method is as follows:

[0033] Select two sets of medium - frequency induction melting furnaces, melt high manganese steel and high chromium cast iron according to the requirements of composition design. The chemical composition of the melted high manganese steel is: C: 0.9%, Si: 0.42%, Mn: 13%, Al: <0.05%, S: <0.01%, P: <0.2%, and the rest is Fe. The chemical composition of the melted high chromium cast iron is: C: 2.8%, Cr: 28%, Mn: 0.6%, Si: 0.5%, S: <0.05%, P: <0.1%, and the rest is Fe.

[0034] Use a horizontal cantilever centrifugal casting machine for centrifugal casting. First, cast the outer high manganese steel layer. The casting temperature is 1600 °C, the centrifuge speed is 600 revolutions per minute, and the casting thickness is 10 mm. After waiting for an interval of 120 s, cast the second high chromium cast iron layer. The casting temperature is 1400 °C, the centrifuge speed is 700 revolutions per minute, and the casting thickness is 10 mm. After waiting for an interval of 120 s, cast the third high manganese layer. According to the above process parameters, cast a five - layer high manganese steel / high chromium cast iron / high manganese steel / high chromium cast iron / high manganese steel composite pipe blank as Figure 1 shown. The thickness of each cast high manganese steel layer is 10 mm, and the thickness of each cast high chromium cast iron layer is 10 mm. The thickness ratio of each metal layer of the five - layer cast composite pipe is 1:1:1:1:1. During the casting process, argon is used for protection. The outer diameter of the five - layer cast composite pipe blank is 200 mm, and the total thickness is 50 mm.

[0035] Heat the centrifugally cast five - layer composite pipe blank to 1050 °C, keep it warm for 1 h, and then rapidly water - cool it to obtain a single austenite structure for the high manganese steel. Grind the inner and outer surfaces of the heat - treated composite pipe blank to remove external impurities.

[0036] Heat the above - treated composite pipe blank to 1150 °C, keep it warm for 1 h, and then perform 6 - pass hot rolling. The rolling temperature is controlled at 1000 - 1150 °C, and the reduction per pass is 25%, 20%, 20%, 15%, 13%, 10% respectively. Under the action of rolling pressure, the high chromium cast iron layer with poor deformability in the composite pipe blank fractures and is embedded in the ductile high manganese steel, as Figure 2 shown.

[0037] The composite pipe after rolling forming is heated to 1050 °C, held for 1 h, quenched in oil to room temperature, and then the composite pipe is heated to 350 °C, held for 1 h, and air-cooled to room temperature. The inner and outer layers of the heat-treated composite pipe are mechanically polished to obtain a bimetallic wear-resistant composite pipe with a hard high-chromium cast iron reinforced high-manganese steel matrix. In the bimetallic wear-resistant composite pipe prepared in this example, the two metals are tightly bonded, and there are no voids and cracks at the bonding interface, as Figure 3 shown. After testing, the average hardness of the high-manganese steel is 200 HB, and the average hardness of the high-chromium cast iron is 54 HRC.

[0038] Example 2

[0039] Two sets of intermediate frequency induction melting furnaces are selected to melt high-manganese steel and high-chromium cast iron according to the composition design requirements. The chemical composition of the melted high-manganese steel is: C: 0.9%, Si: 0.42%, Mn: 13%, Al: <0.05%, S: <0.01%, P: <0.2%, and the rest is Fe. The chemical composition of the melted high-chromium cast iron is: C: 2.8%, Cr: 28%, Mn: 0.6%, Si: 0.5%, S: <0.05%, P: <0.1%, and the rest is Fe.

[0040] Horizontal cantilever centrifugal casting machine is used for centrifugal casting. First, the outer high-manganese steel layer is cast, the casting temperature is 1700 °C, the centrifuge speed is 400 r / min, and the casting thickness is 10 mm. After waiting for an interval of 120 s, the second high-chromium cast iron layer is cast, the casting temperature is 1350 °C, the centrifuge speed is 500 r / min, and the casting thickness is 5 mm. After waiting for an interval of 80 s, the third high-manganese layer is cast. According to the above process parameters, an 11-layer high-manganese steel / high-chromium cast iron composite pipe blank is cast. The outermost and innermost layers of the composite pipe blank are high-manganese steel layers, the high-chromium cast iron layer is located between the two high-manganese steel layers, the thickness of the high-manganese steel layer is 10 mm, the thickness of the high-chromium cast iron layer is 5 mm, and the thickness ratio of the two metal layers of high-manganese steel and high-chromium cast iron is 2:1. During the casting process, argon is used for protection. The outer diameter of the 11-layer composite pipe blank is 400 mm and the total thickness is 85 mm.

[0041] The 11-layer composite pipe blank obtained by centrifugal casting is heated to 1050 °C, held for 2 h, and then rapidly water-cooled to obtain a single austenite structure for the high-manganese steel. The inner and outer surfaces of the heat-treated composite pipe blank are polished to remove external impurities.

[0042] The above-treated composite pipe blank is heated to 1200 °C, held for 2 h, and then hot-rolled for 5 passes. The rolling temperature is controlled at 1000-1150 °C, and the reduction per pass is 25%, 20%, 20%, 15%, 15% respectively.

[0043] The composite tube after rolling forming is heated to 1050 °C, held for 2 h, quenched in oil and cooled to room temperature. Then the composite tube is heated to 350 °C, held for 2 h, and air-cooled to room temperature. Then the inner and outer layers of the composite tube are mechanically polished to obtain a bimetallic wear-resistant composite tube with a hard high-chromium cast iron reinforced high-manganese steel matrix. In the bimetallic wear-resistant composite tube prepared in this example, the high-manganese steel and the high-chromium cast iron are well combined and no interfacial cracks are generated. The average hardness of the high-manganese steel matrix is 205 HB, and the average hardness of the high-chromium cast iron is 55 HRC.

[0044] The high-chromium cast iron 2 described above is used as the reinforcement and is dispersed and embedded inside the high-manganese steel matrix 1.

[0045] The above examples are only used to illustrate the technical solution of the present invention rather than to limit it. By the thickness dimensions of the high-manganese steel and the high-chromium cast iron plate during centrifugal casting, the present invention can adjust the volume ratio of the reinforcement to the ductile matrix after rolling forming, and thus different specifications and properties of the bimetallic composite tube can be obtained.

Claims

1. A preparation method of a high manganese steel - high chromium cast iron bimetallic wear - resistant composite pipe, characterized in that: High chromium cast iron (2) is used as a reinforcement and is diffusely embedded inside the high manganese steel matrix (1); The high manganese steel contains the following chemical components by weight percentage: C: 0.9%, Si: 0.42%, Mn: 13%, Al: <0.05%, S: <0.01%, P: <0.2%, and the rest is Fe; The high chromium cast iron contains the following chemical components by weight percentage: C: 2.8%, Cr: 28%, Mn: 0.6%, Si: 0.5%, S: <0.05%, P: <0.1%, and the rest is Fe; And it is implemented according to the following steps: S1: Using the centrifugal casting method, a composite pipe blank with 5 - 11 layers is cast layer by layer with high manganese steel and high chromium cast iron. The outer layer and the inner layer of the composite pipe blank are both high manganese steel layers, and the cast high chromium cast iron layer is located between two adjacent high manganese steel layers; S2: Heat the composite pipe blank obtained by centrifugal casting to 1050 °C, hold for 1 - 2 h, and then cool it with water to make the high manganese steel obtain a single austenite structure. Mechanically polish the inner surface and the outer surface of the heat - treated composite pipe blank to remove surface impurities; S3: Heat the above - treated composite pipe blank to 1150 - 1200 °C, hold for 0.5 - 2 h, and then perform multi - pass hot rolling. The rolling temperature is 1000 - 1150 °C, and the reduction per pass is 10% - 25%. Under the action of the rolling pressure, the high chromium cast iron layer in the composite pipe blank fractures and breaks and is embedded in the ductile high manganese steel; S4: Heat the rolled composite pipe to 1050 °C, hold for 1 - 3 h, quench it in oil and cool it to room temperature, then heat the composite pipe to 350 °C, hold for 1 - 3 h, air - cool it to room temperature, and then mechanically polish the inner layer and the outer layer of the composite pipe to obtain a high chromium cast iron bimetallic wear - resistant composite pipe based on high manganese steel.

2. The preparation method of a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe according to claim 1, characterized in that: In S1, the thickness of the high manganese steel layer is 5 - 20 mm, the thickness of the high chromium cast iron layer is 5 - 10 mm, and the thickness ratio of the high manganese steel to the high chromium cast iron layer is 1 - 2.

3. The preparation method of a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe according to claim 2, characterized in that: In S1, the casting temperature of the high manganese steel layer is 1600 - 1700 °C, and the rotation speed of the centrifuge is 400 - 600 revolutions per minute; the casting temperature of the high chromium cast iron layer is 1350 - 1400 °C, and the rotation speed of the centrifuge is 500 - 700 revolutions per minute; the time interval between the casting of the two metal liquids is 80 s - 120 s.

4. The preparation method of a high manganese steel-high chromium cast iron bimetallic wear-resistant composite pipe according to claim 2 or 3, characterized in that: In S3, the high manganese steel matrix and high chromium cast iron bimetallic composite pipe are hot - rolled for 6 passes, and the rolling temperature is controlled at 1000 - 1150 °C, and the reduction per pass is 25%, 20%, 20%, 15%, 13%, 10% respectively.

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