Preparation method of stainless steel and carbon steel composite profile

Abstract

The invention discloses a preparation method of a stainless steel and carbon steel composite profile. The preparation method comprises the following steps: preparing a stainless steel and carbon steel composite cast ingot through a centrifugal composite casting process, carrying out annealing heat treatment on the composite cast ingot, carrying out heating and heat preservation on the composite cast ingot, and rolling or forging to obtain the stainless steel and carbon steel composite profile. The stainless steel and carbon steel composite cast ingot is centrifugally cast by adopting a centrifugal composite casting process, so that the technical problem of bonding tightness of a bimetal composite interface is solved; stress is eliminated by adopting a steel ingot annealing process, so that the problem of rolling or forging cracking caused by solidification stress is solved; by adopting a surface layer low-temperature rolling or forging process, the deformation uniformity of an outer composite layer and core metal in the process of rolling or forging the stainless steel and carbon steel composite profile is ensured. The stainless steel and carbon steel composite section bar produced by using the preparation method of the stainless steel and carbon steel composite section bar can replace stainless steel used in a special environment, and the manufacturing and using cost is remarkably reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of stainless steel composite profile production, and specifically relates to a method for preparing a stainless steel and carbon steel composite profile. Background Art

[0002] Stainless steel contains a certain amount of precious alloy elements such as chromium and nickel. Compared with carbon steel, stainless steel has corrosion resistance, high temperature resistance, and easy processing. It is widely used in various fields of economic and social life, but the price of stainless steel is relatively high, which increases the cost of use. Carbon steel has good strength and toughness, and its price is low, but in some special environments, carbon steel has poor corrosion resistance, which seriously affects the service life of carbon steel, and using stainless steel instead will greatly increase the manufacturing cost.

[0003] Therefore, in order to increase the service life of carbon steel in certain special environments, the composite production process of stainless steel and carbon steel can be used to wrap a certain thickness of stainless steel on the surface of carbon steel, thereby protecting the carbon steel, thereby greatly increasing the service life of carbon steel in special environments.

[0004] There are many methods for compounding stainless steel and carbon steel, such as blasting compounding, vacuum welding compounding, solid diffusion bonding, plastic forming bonding, centrifugal casting, casting compounding and electroslag compounding. In the prior art, centrifugal casting is often used to produce blanks for composite profiles. The compounding of stainless steel and carbon steel requires ensuring the thickness of the outer stainless steel composite layer to ensure that the stainless steel can protect the carbon steel, and also requires ensuring the tightness of the composite interface to ensure that the bonding interface does not crack during the subsequent rolling process.

[0005] However, the prior art lacks effective process measures to ensure the close bonding of the bimetallic composite interface and to ensure uniform deformation of the outer composite layer and the core metal during rolling or forging of stainless steel and carbon steel composite profiles. Summary of the invention

[0006] In order to solve the above technical problems existing in the prior art, the present invention provides a method for preparing a stainless steel and carbon steel composite profile, comprising the following steps:

[0007] (1) Centrifugally casting a stainless steel and carbon steel composite ingot by a centrifugal composite casting process, wherein the composite ingot is cylindrical, and the cross-sectional diameter of the composite ingot and the cross-sectional diameter of the composite profile to be produced are related to each other as follows: D 铸锭 =(3~5)×D 型材 , D 铸锭 is the cross-sectional diameter of the composite ingot, in mm, D 型材is the cross-sectional diameter of the composite profile to be produced, in mm; centrifugal casting of stainless steel and carbon steel composite ingots specifically includes: smelting stainless steel liquid and carbon steel liquid, centrifugal casting of stainless steel outer layer, centrifugal casting of core carbon steel after a predetermined interval, static solidification, and demoulding; the stainless steel outer layer casting starting 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 is the liquidus temperature of stainless steel, in °C, t 不锈钢 is the casting time of the stainless steel outer layer, in min; the predetermined interval time t 间隔 = (3-5) min / ton × G, G is the amount of molten steel for casting stainless steel, in tons; the core carbon steel starting casting temperature T CS Control is T CS =T 碳钢液相线 +(30~45℃),T 碳钢液相线 is the liquidus temperature of carbon steel, in °C;

[0008] (2) Annealing heat treatment of the composite ingot of stainless steel and carbon steel, wherein the composite ingot is heated to 700-750° C. within 3-4 hours and then kept at this temperature for a holding time of t 保温 Controlled by t 保温 =(0.6~1.0)min / mm×D 铸锭 , after the insulation is completed, cool down with the furnace;

[0009] (3) heating and heat-insulating the composite ingot of stainless steel and carbon steel, and then rolling or forging it into a composite profile of stainless steel and carbon steel, wherein 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 It is the solidus temperature of carbon steel in °C. The holding time is controlled at 4 to 6 hours. After the holding is completed, it is allowed to stand on the conveyor track for 5 to 10 minutes.

[0010] Furthermore, in the method for preparing the above-mentioned stainless steel and carbon steel composite profile, 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 Control is H SS =(0.1~0.4)×D 铸锭 , the thickness of the fusion transition layer at the bimetallic bonding interface H 过渡 Control is 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] The present invention solves the technical problem of tightness of the bimetallic composite interface by centrifugally casting a stainless steel and carbon steel composite ingot using a centrifugal composite casting process.

[0013] The present invention eliminates the rolling or forging cracking problem caused by solidification stress by adopting the steel ingot annealing process to eliminate stress;

[0014] The present invention ensures the uniformity of deformation of the outer composite layer and the core metal during the rolling or forging of the stainless steel and carbon steel composite profile by adopting the surface low temperature rolling or forging process;

[0015] The stainless steel and carbon steel composite profile produced by the method for preparing the stainless steel and carbon steel composite profile of the present invention can replace the stainless steel used in special environments, thereby significantly reducing the manufacturing and use costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0017] Figure 1 A macrostructure diagram of a stainless steel and carbon steel composite ingot prepared by a centrifugal composite casting process in the method for preparing a stainless steel and carbon steel composite profile of the present invention;

[0018] Figure 2 The present invention is a cross-sectional low-magnification structure diagram of a stainless steel and carbon steel composite profile in the form of a rod prepared by the method for preparing the stainless steel and carbon steel composite profile of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0020] In general, the main process flow of the preparation method of the stainless steel and carbon steel composite profile provided by the present invention includes: 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 warm, and rolling or forging it into a stainless steel and carbon steel composite profile.

[0021] The centrifugal composite casting process is used for centrifugal casting of bimetallic composite ingots. Its basic principle is: select a suitable casting ingot mold according to the profile specifications to be produced, place the ingot mold on a centrifugal casting machine, and cast the stainless steel liquid used as the outer layer into the ingot mold. The centrifugal casting machine is running. Under the action of centrifugal force, the molten steel injected into the ingot mold is tightly attached to the inner wall of the ingot mold. After the stainless steel injected into the ingot mold solidifies, the carbon steel liquid used as the core is injected into the ingot mold. The centrifugal casting machine is allowed to stand still after running for a certain period of time, and waits for all the molten steel in the ingot mold to solidify to form a stainless steel and carbon steel composite ingot, with the outer layer being a stainless steel layer and the core being carbon steel.

[0022] In the centrifugal composite casting process, the preparation of stainless steel and carbon steel composite ingots requires the selection of appropriate ingot molds and the control of reasonable stainless steel layer thickness according to the specifications of the profile to be produced. In order to ensure the compactness of the internal structure of the composite ingot, especially the tight bonding of the bimetallic composite interface, the metal fusion method is used at the bimetallic bonding interface, but the use of the metal fusion method will result in the presence of a fusion transition layer in the bimetal. A larger transition layer thickness will reduce the thickness of the stainless steel outer layer, and affect the thickness of the stainless steel layer on the surface of the profile after rolling or forging. Therefore, in order to reduce the thickness of the fusion transition layer while ensuring that the bimetal can be tightly bonded, it is necessary to control the bimetal casting temperature and allow a certain solidification time after casting the stainless steel outer layer.

[0023] Specifically, the method for preparing the stainless steel and carbon steel composite profile of the present invention comprises the following steps:

[0024] (1) Centrifugally casting a composite ingot of stainless steel and carbon steel by a centrifugal composite casting process, wherein:

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

[0026] The centrifugal casting of stainless steel and carbon steel composite ingot specifically includes: smelting stainless steel liquid and carbon steel liquid respectively, centrifugal casting of stainless steel outer layer, centrifugal casting of core carbon steel after a predetermined interval, static solidification, and demoulding;

[0027] Stainless steel outer layer casting 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 is the liquidus temperature of stainless steel, in °C, t 不锈钢 is the casting time of the stainless steel outer layer, in min;

[0028] Predetermined interval time t 间隔 =(3-5)min / ton×G, G is the amount of molten stainless steel cast, in tons, and the predetermined interval time corresponds to the waiting time for the molten stainless steel to solidify;

[0029] Core carbon steel casting start temperature T CS Control is T CS =T 碳钢液相线 +(30~45℃),T 碳钢液相线 is the liquidus temperature of carbon steel, in °C;

[0030] Based on the outer diameter of the casting ingot mold, the thickness H of the stainless steel outer layer of the composite ingot is controlled by controlling the amount of stainless steel liquid cast. SS Control is H SS =(0.1~0.4)×D 铸锭 By controlling the above-mentioned predetermined interval time and the core carbon steel casting temperature and other parameters, the thickness H of the fusion transition layer at the bimetallic bonding interface is adjusted. 过渡 Control is H 过渡 ≤(0.01~0.05)×D 铸锭 .

[0031] (2) Annealing heat treatment of the composite ingot of stainless steel and carbon steel. When the composite profile is prepared by centrifugal casting composite ingot, since the composite ingot has solidification stress during the centrifugal casting process, direct rolling or forging will cause cracking. Therefore, it is necessary to perform annealing heat treatment on the composite ingot before rolling or forging to eliminate the solidification stress. In the annealing heat treatment process of the composite ingot of stainless steel and carbon steel, the composite ingot is heated to 700-750°C within 3-4 hours and then kept warm for a holding time of t 保温 Controlled by t 保温 =(0.6~1.0)min / mm×D 铸锭 After the insulation is completed, cool down with the furnace.

[0032] (3) The stainless steel and carbon steel composite ingot is heated and kept warm, and then rolled or forged into a stainless steel and carbon steel composite profile. During the rolling or forging process, due to the large difference in melting point between the outer stainless steel and the core carbon steel, if the rolling or forging is performed at the same heating temperature, the strength of the outer stainless steel is lower than the strength of the core carbon steel. Therefore, under the same pressure during the rolling or forging process, the deformation of the outer layer of the stainless steel is greater than the deformation of the core carbon steel, resulting in uneven deformation of the outer layer and the core bimetal during the rolling or forging process. Therefore, in order to make the outer layer and the core bimetal uniformly deform during the rolling or forging process, after heating and keeping warm according to the processing temperature of the core carbon steel, it is placed on the conveying roller for a certain period of time before rolling or forging, so that the temperature of the outer layer of the stainless steel is reduced and the strength is increased to be equivalent to the strength of the core carbon steel, thereby ensuring that the outer layer and the core bimetal are deformed synchronously and uniformly during the rolling or forging process. Among them, 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 is the solidus temperature of carbon steel, in degrees Celsius. The holding time is controlled at 4 to 6 hours. After the holding is completed, it is allowed to stand on the conveyor track for 5 to 10 minutes, and then rolled or forged into stainless steel and carbon steel composite profiles of specified specifications.

[0033] The preparation method of the stainless steel and carbon steel composite profile of the present invention is described in detail below with reference to the embodiments.

[0034] Example 1

[0035] The method for preparing the stainless steel and carbon steel composite profile of Example 1 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, and the profile is a φ220 mm bar. The specific implementation process includes:

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

[0037] The macrostructure diagram of the stainless steel and carbon steel composite ingot prepared in Example 1 is shown in Figure 1 .

[0038] (2) Annealing heat treatment of stainless steel and carbon steel composite ingots: the ingot annealing temperature is 730°C, the heating time is 3.4 hours, the annealing holding time is 8 hours, and the ingot is 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 a stainless steel and carbon steel composite profile. The heating target temperature of the composite ingot is 1250°C, and the holding time is 4.2 hours. After the holding is completed, it is allowed to stand for 5 minutes before rolling or forging, and then rolled or forged into a φ220 mm bar.

[0040] The cross-sectional macrostructure diagram of the stainless steel and carbon steel composite profile in the form of a rod prepared by Example 1 is shown in Figure 2 .

[0041] Example 2

[0042] The method for preparing the stainless steel and carbon steel composite profile of Example 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, and the profile is a φ250 mm bar. The specific implementation process includes:

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

[0044] (2) Annealing heat treatment of stainless steel and carbon steel composite ingots: the annealing temperature of the ingots is 730°C, 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 a stainless steel and carbon steel composite profile. The heating target temperature of the composite ingot is 1250°C, and the holding time is 5 hours. After the holding is completed, it is allowed to stand for 7 minutes before rolling or forging, and then rolled or forged into a φ250 mm bar.

[0046] In summary, the preparation method of the stainless steel and carbon steel composite profile of the present invention solves the technical problem of the tightness of the bimetallic composite interface by adopting a centrifugal composite casting process to centrifugally cast the stainless steel and carbon steel composite ingot, and eliminates the rolling or forging cracking problem caused by solidification stress by adopting a steel ingot annealing process. By adopting a surface low-temperature rolling or forging process, the deformation uniformity of the outer composite layer and the core metal during the rolling or forging of the stainless steel and carbon steel composite profile is ensured. The stainless steel and carbon steel composite profile produced by the preparation method of the stainless steel and carbon steel composite profile of the present invention can replace the stainless steel used in special environments, which significantly reduces the manufacturing and use costs.

[0047] It should be noted that, in this article, the term "comprise" or any other variation thereof is intended to cover non-exclusive inclusion, so that an article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such 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, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements 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: The steps include: (1) Centrifugally casting a stainless steel and carbon steel composite ingot by a centrifugal composite casting process, wherein the composite ingot is cylindrical, and the cross-sectional diameter of the composite ingot and the cross-sectional diameter of the composite profile to be produced are related to each other as follows: D 铸锭 =(3~5)×D 型材 , D 铸锭 is the cross-sectional diameter of the composite ingot, in mm, D 型材 is the cross-sectional diameter of the composite profile to be produced, in mm; centrifugal casting of stainless steel and carbon steel composite ingots specifically includes: smelting stainless steel liquid and carbon steel liquid, centrifugal casting of stainless steel outer layer, centrifugal casting of core carbon steel after a predetermined interval, static solidification, and demoulding; the stainless steel outer layer casting starting 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 is the liquidus temperature of stainless steel, in °C, t 不锈钢 is the casting time of the stainless steel outer layer, in min; the predetermined interval time t 间隔 = (3-5) min / ton × G, G is the amount of molten steel for casting stainless steel, in tons; the core carbon steel starting casting temperature T CS Control is T CS =T 碳钢液相线 +(30~45℃),T 碳钢液相线 is the liquidus temperature of carbon steel, in °C; (2) Annealing heat treatment of the composite ingot of stainless steel and carbon steel, wherein the composite ingot is heated to 700-750° C. within 3-4 hours and then kept at this temperature for a holding time of t 保温 Controlled by t 保温 =(0.6~1.0)min / mm×D 铸锭 , after the insulation is completed, cool down with the furnace; (3) heating and heat-insulating the composite ingot of stainless steel and carbon steel, and then rolling or forging it into a composite profile of stainless steel and carbon steel, wherein 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 It is the solidus temperature of carbon steel in °C. The holding time is controlled at 4 to 6 hours. After the holding is completed, it is allowed to stand on the conveyor 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 step of the composite ingot of stainless steel and carbon steel, the thickness H of the outer layer of the composite ingot is SS Control is H SS =(0.1~0.4)×D 铸锭 , the thickness of the fusion transition layer at the bimetallic bonding interface H 过渡 Controlled to ≤(0.01~0.05)×D 铸锭 .

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