A method for manufacturing a stainless steel and carbon steel composite profile

Abstract

The application discloses a preparation method of stainless steel and carbon steel composite section, which comprises the following steps: preparing a stainless steel and carbon steel composite ingot by a centrifugal composite casting process, annealing the composite ingot, heating and keeping the composite ingot, and rolling or forging the composite ingot into a stainless steel and carbon steel composite section. The application solves the technical problem of the tightness of the bimetallic composite interface by adopting the centrifugal composite casting process to centrifugally cast the stainless steel and carbon steel composite ingot. The stress relieving process is adopted to eliminate the rolling or forging cracking problem caused by the solidification stress. The surface low-temperature rolling or forging process is adopted to ensure the uniformity of the deformation of the outer composite layer and the core metal in the process of rolling or forging the stainless steel and carbon steel composite section. The stainless steel and carbon steel composite section produced by the preparation method of the stainless steel and carbon steel composite section can replace the stainless steel used in special environments, and the manufacturing and using costs are significantly reduced.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel composite profile production technology, specifically relating to a method for preparing stainless steel and carbon steel composite profiles. Background Technology

[0002] Stainless steel contains certain amounts of precious alloying elements such as chromium and nickel. Compared with carbon steel, stainless steel has better corrosion resistance, high temperature resistance, and ease of processing, and is widely used in various fields of economic and social life. However, stainless steel is relatively expensive, increasing the cost of use. Carbon steel has good strength and toughness and is inexpensive, but its corrosion resistance is poor in certain special environments, which seriously affects its service life. Using stainless steel as a substitute would significantly increase manufacturing costs.

[0003] Therefore, in order to improve the service life of carbon steel in certain special environments, a composite production process of stainless steel and carbon steel can be used to coat the surface of carbon steel with a certain thickness of stainless steel, thereby protecting the carbon steel and significantly improving its service life in special environments.

[0004] There are various methods for bonding stainless steel and carbon steel, such as explosive bonding, vacuum welding bonding, solid-state diffusion bonding, plastic forming bonding, centrifugal casting, casting bonding, and electroslag bonding. Among existing technologies, centrifugal casting is commonly used to produce billets for composite profiles. The bonding of stainless steel and carbon steel requires ensuring the thickness of the outer stainless steel composite layer to protect the carbon steel, and also ensuring a tight composite interface to prevent cracking during subsequent rolling.

[0005] However, existing technologies lack effective process measures to ensure a tight bond at the bimetallic composite interface and to ensure uniform deformation of the outer composite layer and the core metal during the rolling or forging of stainless steel and carbon steel composite profiles. Summary of the Invention

[0006] To address the aforementioned technical problems in the existing technology, the present invention provides a method for preparing a stainless steel and carbon steel composite profile, comprising the following steps:

[0007] (1) A composite ingot of stainless steel and carbon steel is centrifugally cast using a centrifugal composite casting process. The composite ingot is cylindrical, and the relationship between the cross-sectional diameter of the composite ingot and the cross-sectional diameter of the composite profile to be produced is as follows: D 铸锭 = (3~5)×D 型材 D 铸锭 D is the cross-sectional diameter of the composite ingot, in mm. 型材The cross-sectional diameter of the composite profile to be produced is in mm; the centrifugal casting of stainless steel and carbon steel composite ingots specifically includes: separately smelting stainless steel and carbon steel, centrifugally casting the stainless steel outer layer, centrifugally casting the carbon steel core after a predetermined interval, allowing it to solidify, and demolding; the initial casting temperature of the stainless steel outer layer is T. SS Control is T SS =T 不锈钢液相线 +t 不锈钢 ×(25~35℃) / min, T 不锈钢液相线 The liquidus temperature of stainless steel is expressed in °C (°C) or t (t). 不锈钢 The casting time for the stainless steel outer layer is in minutes; the predetermined interval time is t. 间隔 = (3~5) min / ton × G, where G is the amount of molten stainless steel being cast, in tons; T is the initial casting temperature of the core carbon steel. CS Control is T CS =T 碳钢液相线 +(30~45℃),T 碳钢液相线 This is the liquidus temperature of carbon steel, in °C.

[0008] (2) Annealing heat treatment of stainless steel and carbon steel composite ingots, wherein the composite ingots are heated to 700-750°C within 3-4 hours, and then held at that temperature for a duration of t. 保温 Controlled by t 保温 = (0.6~1.0)min / mm×D 铸锭 After the heat preservation is completed, it is cooled with the furnace;

[0009] (3) The stainless steel and carbon steel composite ingot is heated and held at a certain temperature, and then rolled or forged into stainless steel and carbon steel composite profiles. The target temperature T for heating the composite ingot is... 加热 Control is T 加热 =T 碳钢固相线 -(200~300℃), T 碳钢固相线 The solidus temperature of carbon steel is expressed in °C. The holding time is controlled at 4 to 6 hours. After the holding time is completed, the steel should be left to stand on the transport track for 5 to 10 minutes.

[0010] Furthermore, in the above-mentioned method for preparing stainless steel and carbon steel composite profiles, in the step of centrifugally casting the stainless steel and carbon steel composite ingot, the thickness H of the stainless steel outer layer of the composite ingot is... SS Controlled as H SS = (0.1~0.4)×D 铸锭 The thickness H of the fusion transition layer at the bimetallic interface 过渡 Controlled as H 过渡 ≤(0.01~0.05)×D 铸锭 .

[0011] The method for preparing the stainless steel and carbon steel composite profile of the present invention has the following beneficial effects:

[0012] This invention solves the technical problem of tight bonding at the interface of bimetallic composites by using a centrifugal composite casting process to centrifugally cast stainless steel and carbon steel composite ingots.

[0013] This invention eliminates the problem of rolling or forging cracks caused by solidification stress by using a steel ingot annealing process to relieve stress.

[0014] This invention ensures the uniformity of deformation of the outer composite layer and the core metal during the rolling or forging of stainless steel and carbon steel composite profiles by employing a surface low-temperature rolling or forging process.

[0015] The stainless steel and carbon steel composite profiles produced by the preparation method of the present invention can replace stainless steel used in special environments, significantly reducing manufacturing and usage costs. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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. In the drawings:

[0017] Figure 1 This is a low-magnification microstructure of the stainless steel and carbon steel composite ingot prepared by centrifugal composite casting process in the preparation method of stainless steel and carbon steel composite profile of the present invention.

[0018] Figure 2 This is a low-magnification cross-sectional microstructure image of a stainless steel and carbon steel composite profile in bar form prepared by the method of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] In general, the main process flow of the method for preparing stainless steel and carbon steel composite profiles provided by the present invention includes: preparing stainless steel and carbon steel composite ingots by centrifugal composite casting process, annealing heat treatment of composite ingots, heating and holding composite ingots and rolling or forging them into stainless steel and carbon steel composite profiles.

[0021] Centrifugal composite casting process is used for centrifugal casting of bimetallic composite ingots. Its basic principle is as follows: Select a suitable casting ingot mold according to the profile of the intended production specifications, place the ingot mold on a centrifugal casting machine, and pour molten stainless steel, which is used as the outer layer, into the ingot mold. When the centrifugal casting machine is running, under the action of centrifugal force, the molten steel injected into the ingot mold adheres tightly to the inner wall of the ingot mold. After the stainless steel injected into the ingot mold solidifies, molten carbon steel, which is used as the core, is injected into the ingot mold. After the centrifugal casting machine runs for a certain period of time, it is left to stand until all the molten steel in the ingot mold has solidified, forming a stainless steel and carbon steel composite ingot with a stainless steel outer layer and a carbon steel core.

[0022] In centrifugal composite casting, the preparation of stainless steel and carbon steel composite ingots requires selecting appropriate ingot molds and controlling the thickness of the stainless steel layer according to the specifications of the profile to be produced. To ensure the compactness of the internal structure of the composite ingot, especially the tight bonding of the bimetallic interface, a metal fusion method is used at the bimetallic interface. However, the metal fusion method results in the existence of a fusion transition layer between the two metals. A large transition layer thickness will reduce the thickness of the stainless steel outer layer, affecting the thickness of the stainless steel layer on the surface of the profile after rolling or forging. Therefore, to reduce the thickness of the fusion transition layer while ensuring a tight bond between the two metals, it is necessary to control the bimetallic casting temperature and allow a certain solidification time after casting the stainless steel outer layer.

[0023] Specifically, the preparation method of the stainless steel and carbon steel composite profile of the present invention includes the following steps:

[0024] (1) A composite ingot of stainless steel and carbon steel is centrifugally cast using a centrifugal composite casting process, wherein:

[0025] The stainless steel and carbon steel composite ingot is cylindrical. The relationship between the cross-sectional diameter of the composite ingot and the cross-sectional diameter of the composite profile to be produced is set as: D 铸锭 = (3~5)×D 型材 D 铸锭 D is the cross-sectional diameter of the composite ingot, in mm. 型材 The cross-sectional diameter of the composite profile to be produced is in mm;

[0026] The centrifugal casting of stainless steel and carbon steel composite ingots specifically includes: smelting stainless steel and carbon steel separately, centrifugally casting the stainless steel outer layer, centrifugally casting the carbon steel core after a predetermined interval, allowing it to solidify, and demolding.

[0027] Stainless steel outer layer casting start temperature T SS Control is T SS =T 不锈钢液相线 +t 不锈钢 ×(25~35℃) / min, T 不锈钢液相线 The liquidus temperature of stainless steel is expressed in °C (°C) or t (t). 不锈钢 This refers to the casting time of the stainless steel outer layer, in minutes.

[0028] Predetermined interval time t 间隔 = (3~5) min / ton × G, where G is the amount of molten stainless steel to be cast in tons, and this predetermined interval time corresponds to the solidification waiting time of the molten stainless steel.

[0029] The initial casting temperature of the core carbon steel is T. CS Control is T CS =T 碳钢液相线 +(30~45℃),T 碳钢液相线 This is the liquidus temperature of carbon steel, in °C.

[0030] The thickness H of the stainless steel outer layer of the composite ingot is determined by controlling the amount of molten stainless steel poured, based on the outer diameter of the casting ingot mold. SS Controlled as H SS = (0.1~0.4)×D 铸锭 By controlling parameters such as the predetermined interval time and the initial casting temperature of the core carbon steel, the thickness H of the fusion transition layer at the bimetallic interface is controlled. 过渡 Controlled as H 过渡 ≤(0.01~0.05)×D 铸锭 .

[0031] (2) Annealing heat treatment of stainless steel and carbon steel composite ingots: When preparing composite profiles using centrifugal casting of composite ingots, solidification stress exists in the composite ingots during centrifugal casting. Direct rolling or forging can lead to cracking. Therefore, annealing heat treatment is required before rolling or forging to eliminate solidification stress. In the annealing heat treatment of stainless steel and carbon steel composite ingots, the composite ingots are heated to 700-750℃ within 3-4 hours and then held at that temperature for a duration of t. 保温 Controlled by t 保温 = (0.6~1.0)min / mm×D 铸锭 After the heat preservation is completed, it is cooled with the furnace.

[0032] (3) The stainless steel and carbon steel composite ingot is heated and held at a certain temperature, and then rolled or forged into a stainless steel and carbon steel composite profile. During the rolling or forging process, due to the significant difference in melting points between the outer stainless steel and the core carbon steel, if the rolling or forging is carried out at the same heating temperature, the strength of the outer stainless steel is lower than that of the core carbon steel. Therefore, under the same pressure during the rolling or forging process, the deformation of the outer stainless steel is greater than that of the core carbon steel, resulting in uneven deformation of the outer and core bimetallic layers during the rolling or forging process. Therefore, in order to ensure uniform deformation of the outer and core bimetallic layers during the rolling or forging process, after heating and holding at the processing temperature of the core carbon steel, the ingot is placed on the conveyor roller for a certain period of time before rolling or forging to lower the temperature of the outer stainless steel and increase its strength to be comparable to that of the core carbon steel. This ensures that the deformation of the outer and core bimetallic layers is synchronous and uniform during the rolling or forging process. The target temperature T for heating the stainless steel and carbon steel composite ingot is... 加热 Control is T 加热 =T 碳钢固相线 -(200~300℃), T 碳钢固相线 The solidus temperature of carbon steel is expressed in °C. The holding time is controlled at 4 to 6 hours. After the holding time is completed, the steel is left to stand on the conveying track for 5 to 10 minutes, and then rolled or forged into stainless steel and carbon steel composite profiles of specified specifications.

[0033] The following detailed description of the preparation method of the stainless steel and carbon steel composite profile of the present invention is provided in conjunction with the embodiments.

[0034] Example 1

[0035] The method for preparing stainless steel and carbon steel composite profiles in Embodiment 1 of this invention is used to prepare stainless steel and carbon steel composite profiles with an outer layer of 304 stainless steel and a core of Q235 carbon steel. The profiles are φ220mm bars. The specific implementation process includes:

[0036] (1) A composite ingot of stainless steel and carbon steel was centrifugally cast using a centrifugal composite casting process. The cross-sectional diameter of the composite ingot was 700 mm, the thickness of the stainless steel layer was 120 mm, the initial casting temperature of the outer stainless steel layer was 1495℃, the casting time was 1.5 min, the casting weight was 4 tons, the predetermined interval after the outer stainless steel layer casting was completed was 15 min, and the initial casting temperature of the carbon steel core was 1552℃.

[0037] The low-magnification microstructure of the stainless steel and carbon steel composite ingot prepared in Example 1 is shown in the image below. Figure 1 .

[0038] (2) Annealing heat treatment of stainless steel and carbon steel composite ingots: the annealing temperature of the ingots is 730℃, the heating time is 3.4 hours, the annealing holding time is 8 hours, and the ingots are cooled with the furnace after the holding time is completed.

[0039] (3) The stainless steel and carbon steel composite ingot is heated and kept warm, and then rolled or forged into stainless steel and carbon steel composite profiles. The target heating temperature of the composite ingot is 1250℃, the holding time is 4.2 hours, and after the holding time is completed, it is left to stand for 5 minutes before rolling or forging, and then rolled or forged into φ220mm bars.

[0040] A low-magnification microstructure diagram of the cross-section of the stainless steel-carbon steel composite profile in bar form prepared using Example 1 is shown below. Figure 2 .

[0041] Example 2

[0042] The method for preparing the stainless steel and carbon steel composite profile of Embodiment 2 of the present invention is used to prepare a stainless steel and carbon steel composite profile with an outer layer of 304 stainless steel and a core of Q235 carbon steel. The profile is a φ250mm bar. The specific implementation process includes:

[0043] (1) A composite ingot of stainless steel and carbon steel was centrifugally cast using a centrifugal composite casting process. The cross-sectional diameter of the composite ingot was 800 mm, the thickness of the stainless steel layer was 140 mm, the initial casting temperature of the outer stainless steel layer was 1498℃, the casting time was 2 min, the casting weight was 5 tons, the predetermined interval after the outer stainless steel layer casting was completed was 18 min, and the initial casting temperature of the carbon steel core was 1553℃.

[0044] (2) Annealing heat treatment of stainless steel and carbon steel composite ingots: the annealing temperature of the ingots is 730℃, the heating time is 3.6 hours, the annealing holding time is 9 hours, and the ingots are cooled with the furnace after the holding time is completed.

[0045] (3) The stainless steel and carbon steel composite ingot is heated and kept warm, and then rolled or forged into stainless steel and carbon steel composite profiles. The target heating temperature of the composite ingot is 1250℃, the holding time is 5 hours, and after the holding time is completed, it is left to stand for 7 minutes before rolling or forging, and then rolled or forged into φ250mm bars.

[0046] In summary, the method for preparing stainless steel and carbon steel composite profiles of the present invention solves the technical problem of tight bonding at the bimetallic composite interface by centrifugally casting stainless steel and carbon steel composite ingots using a centrifugal composite casting process. Stress relief through ingot annealing eliminates the problem of rolling or forging cracking caused by solidification stress. The use of surface low-temperature rolling or forging ensures the uniform deformation of the outer composite layer and the core metal during the rolling or forging process of the stainless steel and carbon steel composite profiles. The stainless steel and carbon steel composite profiles produced using the method of the present invention can replace stainless steel used in special environments, significantly reducing manufacturing and usage costs.

[0047] It should be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that an article or device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such an article or device.

[0048] It should also be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the present invention.

Claims

1. A method for preparing a stainless steel and carbon steel composite profile, characterized in that, Includes the following steps: (1) A composite ingot of stainless steel and carbon steel is centrifugally cast using a centrifugal composite casting process. The composite ingot is cylindrical, and the relationship between the cross-sectional diameter of the composite ingot and the cross-sectional diameter of the composite profile to be produced is as follows: D 铸锭 = (3~5)×D 型材 D 铸锭 D is the cross-sectional diameter of the composite ingot, in mm. 型材 The cross-sectional diameter of the composite profile to be produced is in mm; the centrifugal casting of stainless steel and carbon steel composite ingots specifically includes: separately smelting stainless steel and carbon steel, centrifugally casting the stainless steel outer layer, centrifugally casting the carbon steel core after a predetermined interval, allowing it to solidify, and demolding; the initial casting temperature of the stainless steel outer layer is T. SS Control is T SS =T 不锈钢液相线 +t 不锈钢 ×(25~35℃) / min, T 不锈钢液相线 The liquidus temperature of stainless steel is expressed in °C (°C) or t (t). 不锈钢 The casting time for the stainless steel outer layer is in minutes; the predetermined interval time t 间隔 = (3~5) min / ton × G, where G is the amount of molten stainless steel being cast, in tons; T is the initial casting temperature of the core carbon steel. CS Control is T CS =T 碳钢液相线 +(30~45℃),T 碳钢液相线 This is the liquidus temperature of carbon steel, in °C. (2) Annealing heat treatment of stainless steel and carbon steel composite ingots, wherein the composite ingots are heated to 700-750°C within 3-4 hours, and then held at that temperature for a duration of t. 保温 Controlled by t 保温 = (0.6~1.0)min / mm×D 铸锭 After the heat preservation is completed, it is cooled with the furnace; (3) The stainless steel and carbon steel composite ingot is heated and held at a certain temperature, and then rolled or forged into stainless steel and carbon steel composite profiles. The target temperature T for heating the composite ingot is... 加热 Control is T 加热 =T 碳钢固相线 -(200~300℃), T 碳钢固相线 The solidus temperature of carbon steel is expressed in °C. The holding time is controlled at 4 to 6 hours. After the holding time is completed, the steel should be left to stand on the transport track for 5 to 10 minutes.

2. The method for preparing the stainless steel and carbon steel composite profile according to claim 1, characterized in that, In the centrifugal casting process of stainless steel and carbon steel composite ingots, the thickness H of the stainless steel outer layer of the composite ingot is... SS Controlled as H SS = (0.1~0.4)×D 铸锭 The thickness H of the fusion transition layer at the bimetallic interface 过渡 The control value is ≤(0.01~0.05)×D 铸锭 .

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