Preparation method of stainless steel layered composite plate

Abstract

The invention discloses a preparation method of a stainless steel layered composite plate, which comprises the following steps: (1) grinding the surfaces of a stainless steel plate and a carbon steel plate which need to be compounded, then forming air exhaust holes in the edges of the opposite positions of the same ends of the stainless steel plate and the carbon steel plate, and laminating the stainless steel plate and the carbon steel plate to form an initial layered plate; (2) sealing and welding the periphery of the initial laminated plate; (3) the initial layered plate is subjected to air exhaust treatment through the air exhaust holes, and a layered composite plate blank is obtained; and (4) carrying out hot isostatic pressing treatment on the layered composite plate blank, after the hot isostatic pressing treatment is finished, carrying out pressure relief, cooling, discharging and air cooling to room temperature, then carrying out heating and hot rolling treatment, and finally straightening. By means of the method, the stainless steel layered composite plate with the large-range thickness can be prepared, the plate shape is good, stainless steel and carbon steel form compact and inclusion-free metallurgical bonding, the bonding strength reaches 360 MPa or above, the tensile strength and impact toughness of the composite plate are good, and the stainless steel intergranular corrosion performance is qualified.

Description

Technical Field

[0001] The invention relates to the technical field of composite materials, and in particular to a method for preparing a stainless steel layered composite plate. Background Art

[0002] Deep-processed steel products with high added value have been vigorously developed, such as stainless steel layered composite plates, composite pipes, composite rods, etc. prepared by combining stainless steel and carbon steel. Compared with pure stainless steel plates, stainless steel layered composite plates have significant advantages of high specific strength, good corrosion resistance and low cost, and have been widely used in chemical, bridge, shipbuilding, nuclear power and other fields. At present, the preparation methods of stainless steel layered composite plates mainly include explosive composite method, hot rolling composite method and solid-liquid casting composite method. The explosive composite method is mainly used for the composite of thick plates of difficult-to-deform metals, but the plate shape of the composite plate is poor, and the production process has a great impact on the environment. The composite plate obtained by the hot rolling composite method has a good plate shape and a wide range of sizes, but the production process is long and the interface bonding strength is not high enough. The solid-liquid composite method has limitations such as complex process control and a small number of applicable metal types, and its application range is relatively small.

[0003] Hot isostatic pressing diffusion bonding technology can play a huge role in the solid-state composite of materials of different materials and sizes, especially the composite of hard metals. Under the action of static pressure, the composite interface obtains element diffusion and solid metallurgical bonding, especially to form a high-strength bond between thicker sheets or billets with special shapes. At present, hot isostatic pressing technology has been maturely applied in the preparation of composite materials for nuclear power and military purposes.

[0004] The invention patent with publication number CN114193096A discloses a hot isostatic pressing diffusion connection method for vanadium alloy and steel. Through the hot isostatic pressing of the sheath, the element transition of the vanadium-steel connection interface can be uniform, no intermediate phase is generated, and the connector has a high bonding strength, but the composite material preparation method requires the use of a sheath, and the size of the composite workpiece is limited. The invention patent with publication number CN115156837A discloses a hot isostatic pressing repair method for the surface connection defects of aluminum alloy castings. This method infiltrates the impregnation liquid into the through pores of the parts and solidifies them before being placed in a hot isostatic pressing furnace for treatment, thereby repairing the through defects on the surface of the casting. This method is suitable for solid-state repair of local defects and does not involve the preparation of large-size surface covering layers. The invention patent with publication number CN113458737A discloses a preparation process for a double-wall cooling tube suitable for fusion reactor cladding, which is composed of an alloy steel inner tube, an outer tube and an intermediate layer of copper, nickel, etc. The tube ends are sealed and vacuumed and then hot isostatic pressing is performed to obtain a double-wall tube. This method does not involve the preparation of composite plates. The invention patent with publication number CN108067621A discloses a hot isostatic pressing repair method for the connection interface of copper-chromium-zirconium-stainless steel explosion-welded composite plates, which solves the layered interface defect problem of explosion-welded composite plates and improves the yield rate of composite plates. This method is to repair the composite interface that has been solid-state connected and does not involve the diffusion connection preparation process of dissimilar metals.

[0005] According to relevant literature, the conventional solid-state pressure composite process of stainless steel and carbon steel completely relies on the huge plastic deformation and atomic diffusion reaction behavior between metal layers, and the product performance still has room for improvement. The present invention proposes to use hot isostatic pressing technology to prepare the intermediate blank of stainless steel / carbon steel composite plate, and then prepare the finished composite plate through hot rolling deformation, so as to obtain a layered interface without inclusions, dense structure and metallurgical bonding, and optimize the various properties of the composite plate. Summary of the invention

[0006] Purpose of the invention: In order to solve the problem of interface defects that are easily generated in the solid-state composite preparation process of stainless steel and carbon steel in the prior art, the present invention aims to provide a method for preparing a stainless steel layered composite plate that can improve the density, cleanliness and bonding strength of the layered composite interface.

[0007] Technical solution: The method for preparing the stainless steel layered composite plate provided by the present invention comprises the following steps:

[0008] (1) Take a stainless steel plate and a carbon steel plate of equal size, grind the surfaces to be composited, and then respectively open exhaust grooves at the edges of the stainless steel plate and the carbon steel plate at opposite positions at the same end, and the opposite exhaust grooves form exhaust holes. After completion, the stainless steel plate and the carbon steel plate are laminated to form an initial layered plate;

[0009] (2) The initial layered plate is sealed and welded around, leaving only the exhaust hole connected to the outside world;

[0010] (3) exhausting the initial layered plate through the exhaust holes, and sealing the exhaust holes after the exhaust is completed to obtain a layered composite plate blank;

[0011] (4) The layered composite plate is subjected to hot isostatic pressing, and after the pressing is completed, it is unloaded and cooled, and then taken out of the furnace and air-cooled to room temperature, and then heated and hot-rolled, and finally straightened to obtain a stainless steel layered composite plate.

[0012] Furthermore, in step (1), the stainless steel plate is a hot-rolled 316L plate with a thickness of 3-10 mm, and the carbon steel plate is a hot-rolled normalized Q370qE plate with a thickness of 16-48 mm; the grinding process is as follows: grinding the raw material plate with a grinder until the surface roughness reaches Ra0.8-1.6, which is conducive to the close fit between the stainless steel plate and the carbon steel plate and promotes the diffusion of atoms across the interface.

[0013] Furthermore, in step (2), the sealing welding process is performed by argon arc welding.

[0014] Furthermore, in step (3), the evacuation treatment is performed to a vacuum degree of less than 0.001 Pa, thereby ensuring an interface vacuum environment and reducing the formation of oxide inclusions.

[0015] Furthermore, in step (4), the process parameters of the hot isostatic pressing treatment are: introducing argon gas with a purity of not less than 99.999% into the hot isostatic pressing furnace for pressurization, and starting the heating temperature rising program, the insulation temperature is 920-1180°C, the pressure intensity is 120-160MPa, and the insulation time is 3-6h, so that the contact area between the stainless steel and the carbon steel can fully undergo element diffusion and atomic bonding.

[0016] Furthermore, in step (4), the cooling parameters are: cooling to 200-300°C at a cooling rate of 3-10°C / min; the heating treatment parameters are: heating temperature of 1100-1200°C, insulation for 2-3h; the hot rolling treatment parameters are: hot rolling temperature of 830-1050°C, rolling reduction rate of 47-65%, water cooling to 500-550°C after rolling and then air cooling to room temperature; the carbon steel and stainless steel microstructure properties of the composite plate are improved by hot rolling controlled rolling and controlled cooling.

[0017] Principle of the invention: The solid-state composite process of stainless steel and carbon steel needs to be achieved through huge plastic deformation and atomic diffusion reaction at the contact interface between the two. The present invention uses high-intensity isostatic pressure and high-temperature environment to cause creep and diffusion at the interface to be composited, avoiding the destruction of vacuum conditions at the interface during the huge plastic deformation process or relying on huge deformation external forces, and can obtain a clean and uniform composite interface. The hot isostatically pressed composite plate is then hot-rolled, which further promotes the interface bonding strength between stainless steel and carbon steel, regulates the organizational properties of stainless steel and carbon steel, and also expands the finished thickness range of the composite plate.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: (1) By utilizing high temperature and high isostatic pressure, a dense metallurgical bond can be obtained between carbon steel plates with a wide range of thickness and significant performance differences and stainless steel plates; (2) A high-strength metallurgical bonded composite plate intermediate billet is prepared by hot isostatic pressing, which reduces the control requirements of the hot rolling process on the rolling temperature and rolling reduction rate; (3) Compared with the large plastic deformation preparation process of the composite plate billet, the hot isostatic pressing process does not have external force impact, which prevents the interface oxidation and bonding performance degradation caused by vacuum failure of the composite interface; (4) The composite plate intermediate billet is prepared by hot isostatic pressing, and the thickness and matrix structure of the composite plate are adjusted by hot rolling, so that composite plate products with various thickness specifications and excellent performance can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of surface treatment and combination of stainless steel and carbon steel to obtain composite slab in Example 1;

[0020] Figure 2 The metallographic microstructure of the interface area of ​​the 316L / Q370qE layered composite plate prepared in Example 1;

[0021] Figure 3 The metallographic microstructure of the interface area of ​​the 316L / Q370qE layered composite plate prepared in Example 2;

[0022] Figure 4 The metallographic microstructure of the interface area of ​​the 316L / Q370qE layered composite plate prepared in Example 3;

[0023] Figure 5 The metallographic microstructure of the interface area of ​​the 316L / Q370qE layered composite plate prepared in Comparative Example 1;

[0024] Figure 6 This is the metallographic microstructure diagram of the interface area of ​​the 316L / Q370qE layered composite plate prepared in Comparative Example 2. DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with specific embodiments and drawings.

[0026] Example 1: The stainless steel layered composite plate provided in this example comprises a 10 mm thick hot-rolled 316L stainless steel plate and a 48 mm thick hot-rolled normalized Q370qE carbon steel plate. The specific preparation method is as follows:

[0027] (1) Use a sawing machine to cut the stainless steel plate and carbon steel plate into 180mm×140mm blanks, and use a grinder to grind the surface to be composited. After grinding, the surface roughness reaches Ra0.8. Mill a semicircular exhaust hole groove with a diameter of 8mm at the end of the stainless steel plate and the carbon steel plate near the surface to be composited. Figure 1 As shown;

[0028] (2) Scrub the grinding surfaces of stainless steel and carbon steel with acetone and ethanol, then use a high-pressure air gun to blow away impurities on the grinding surfaces, and after drying, bond the grinding surfaces together;

[0029] (3) The exhaust pipe with an outer diameter of 8 mm is butt-jointed with the exhaust hole groove and then spot-welded. The contact interface of the stacked stainless steel plate and the carbon steel plate is sealed and welded around by argon arc welding to ensure that the contact surface of the slab can only be connected to the outside world through the exhaust pipe;

[0030] (4) Use a vacuum pump to extract the air inside the composite slab from the vent hole to make the vacuum inside the slab reach 0.001Pa, then use hydraulic pliers to flatten the middle part of the exhaust pipe and bend it, and then weld the pipe mouth to seal it;

[0031] (5) placing the composite slab on a layered shelf, fixing it with a clamp, and hoisting the entire shelf into a hot isostatic pressing furnace;

[0032] (6) Filling the furnace with argon gas with a purity of not less than 99.999% to make the pressure strength in the furnace reach 120 MPa, while raising the temperature to 1180°C, and then maintaining the temperature and pressure for 3 hours;

[0033] (7) Cooling to 200°C at a rate of 10°C / min, removing the intermediate blank of the composite plate after pressure relief, and continuing to cool to room temperature in air;

[0034] (8) placing the intermediate billet of the composite plate in a heating furnace and heating it to 1200° C., keeping it at this temperature for 2 hours, and then hot rolling it, with the hot rolling start temperature being 1050° C., the final rolling temperature being 830° C., and the total rolling reduction being 65%. After rolling, the intermediate billet is cooled to 550° C. through a water curtain cooling roller and then air-cooled to room temperature;

[0035] (9) Straightening and cutting to size to obtain a stainless steel layered composite plate.

[0036] Example 2: The stainless steel layered composite plate provided in this example comprises a 3 mm thick hot-rolled 316L stainless steel plate and a 16 mm thick hot-rolled normalized Q370qE carbon steel plate, and the preparation method is as follows:

[0037] (1) Use a sawing machine to cut the stainless steel plate and the carbon steel plate into 180 mm × 140 mm blanks, and use a grinder to grind the surface to be composited. After grinding, the surface roughness reaches Ra 0.8. Mill a semicircular exhaust hole groove with a diameter of 3 mm at the end of the stainless steel plate and the carbon steel plate near the surface to be composited;

[0038] (2) Scrub the grinding surfaces of stainless steel and carbon steel with acetone and ethanol, then use a high-pressure air gun to blow away impurities on the grinding surfaces, and after drying, bond the grinding surfaces together;

[0039] (3) The exhaust pipe with an outer diameter of 8 mm is butt-jointed with the exhaust hole groove and then spot-welded. The contact interface of the stacked stainless steel plate and the carbon steel plate is sealed and welded around by argon arc welding to ensure that the contact surface of the slab can only be connected to the outside world through the exhaust pipe;

[0040] (4) Use a vacuum pump to extract the air inside the composite slab from the vent hole to make the vacuum inside the slab reach 0.0005 Pa, then use hydraulic pliers to flatten the middle part of the exhaust pipe and bend it, and then weld the pipe mouth to seal it;

[0041] (5) placing the composite slab on a layered shelf, fixing it with a clamp, and hoisting the entire shelf into a hot isostatic pressing furnace;

[0042] (6) Filling the furnace with argon gas with a purity of not less than 99.999% to make the pressure strength in the furnace reach 160 MPa, while raising the temperature to 920°C, and then maintaining the temperature and pressure for 6 hours;

[0043] (7) Cool to 300°C at a rate of 3°C / min, remove the workpiece after decompression and continue cooling to room temperature in air;

[0044] (8) placing the intermediate billet of the composite plate in a heating furnace and heating it to 1100° C., keeping it at this temperature for 2.5 hours, and then hot rolling it, with the hot rolling start temperature being 1020° C., the final rolling temperature being 860° C., and the total rolling reduction being 47%. After rolling, the intermediate billet of the composite plate is cooled to 550° C. through a water curtain cooling roller and then air-cooled to room temperature;

[0045] (9) Straightening and cutting to size to obtain a stainless steel layered composite plate.

[0046] Example 3: The stainless steel layered composite plate provided in this example comprises a 6 mm thick hot-rolled 316L stainless steel plate and a 35 mm thick hot-rolled normalized Q370qE carbon steel plate. The steps of the preparation method are as follows:

[0047] (1) Use a sawing machine to cut the stainless steel plate and the carbon steel plate into 180 mm × 140 mm blanks, and use a grinder to grind the surface to be composited. After grinding, the surface roughness reaches Ra 1.6. Mill a semicircular exhaust hole groove with a diameter of 3 mm at the end of the stainless steel plate and the carbon steel plate near the surface to be composited;

[0048] (2) Scrub the grinding surfaces of stainless steel and carbon steel with acetone and ethanol, then use a high-pressure air gun to blow away impurities on the grinding surfaces, and after drying, bond the grinding surfaces together;

[0049] (3) The exhaust pipe with an outer diameter of 8 mm is butt-jointed with the exhaust hole groove and then spot-welded. The contact interface of the stacked stainless steel plate and the carbon steel plate is sealed and welded around by argon arc welding to ensure that the contact surface of the slab can only be connected to the outside world through the exhaust pipe;

[0050] (4) Use a vacuum pump to extract the air inside the composite slab from the vent hole to make the vacuum inside the slab reach 0.001Pa, then use hydraulic pliers to flatten the middle part of the exhaust pipe and bend it, and then weld the pipe mouth to seal it;

[0051] (5) placing the composite slab on a layered shelf, fixing it with a clamp, and hoisting the entire shelf into a hot isostatic pressing furnace;

[0052] (6) Filling the furnace with argon gas with a purity of not less than 99.999% to make the pressure strength in the furnace reach 140 MPa, while raising the temperature to 1050°C, and then maintaining the temperature and pressure for 4 hours;

[0053] (7) Cool to 300°C at a rate of 5°C / min, remove the workpiece after decompression and continue cooling to room temperature in air;

[0054] (8) placing the intermediate billet of the composite plate in a heating furnace and heating it to 1150° C., keeping it at this temperature for 3 hours, and then hot rolling it, with the hot rolling start temperature of 1000° C., the final rolling temperature of 840° C., and the total rolling reduction rate of 50%. After rolling, the intermediate billet is cooled to 500° C. through a water curtain cooling roller and then air-cooled to room temperature;

[0055] (9) Straightening and cutting to size to obtain a stainless steel layered composite plate.

[0056] Comparative Example 1: The stainless steel layered composite plate provided in this comparative example, the raw materials include a hot-rolled 316L stainless steel plate with a thickness of 19 mm and a hot-rolled normalized Q370qE carbon steel plate with a thickness of 120 mm, and the specific preparation method is as follows:

[0057] (1) The stainless steel plate raw material is cut into two pieces with a size of 300 mm × 200 mm by a sawing machine, and the carbon steel plate raw material is cut into two pieces with a size of 350 mm × 240 mm by a sawing machine;

[0058] (2) The surfaces of the stainless steel and carbon steel plates to be composited are ground using a grinder to a surface roughness of Ra0.8, and a semicircular exhaust hole with a diameter of 8 mm is milled at the ends of the steel plates near the grinding surface. The surfaces are cleaned with propanol and ethanol and dried;

[0059] (3) Apply a 1.5 mm thick anti-adhesive release agent on the surface of one of the stainless steel pieces and dry it, stack and symmetrically assemble the blanks in the order of carbon steel / stainless steel / anti-adhesive release agent / stainless steel / carbon steel, butt-mount and spot-weld a 16 mm outer diameter exhaust steel pipe at the exhaust hole position, and install sealing steel strips around the outer periphery of the stainless steel so that the stainless steel is sealed inside the composite blank;

[0060] (4) Argon arc welding is used to weld the edges of the four layers of stacked steel plates to the contact positions of the sealing steel bars and the exhaust pipe. The gap inside the composite slab can only communicate with the outside world through the exhaust pipe;

[0061] (5) Use a vacuum pump to extract the air inside the slab to make the vacuum degree reach 0.001Pa. After the air is extracted, the middle part of the exhaust pipe is flattened and bent by hydraulic pliers, and then the pipe mouth is welded and sealed;

[0062] (6) The composite slab is heated to 1200°C in a heating furnace for 8 hours of heating and holding time;

[0063] (7) After being discharged from the furnace, the steel is hot rolled on a rolling mill for 9 passes, with a starting rolling temperature of 1100°C, a final rolling temperature of 880°C, and a total rolling reduction of 87%;

[0064] (8) After rolling, it is cooled to 550°C through a water curtain cooling roller and then air-cooled to room temperature;

[0065] (9) Cut the original welding area at the edge of the composite plate, separate it into two composite plates along the separator, and straighten the plate shape on a straightening machine to obtain a stainless steel layered composite plate.

[0066] Comparative Example 2 is different from Example 1 in that the heating and hot rolling treatment in step (8) are not included, and only hot isostatic pressing treatment is used.

[0067] The stainless steel layered composite plates prepared in Examples 1 to 3 and Comparative Examples 1 to 2 were sampled and characterized, and the metallographic microstructures were as follows: Figure 2-Figure 6 shown.

[0068] according to Figure 2-Figure 4 It can be seen that in the layered composite plate obtained in the embodiment of the present invention, a transition layer composite interface with obvious organizational characteristics is formed between the stainless steel and the carbon steel, the stainless steel matrix does not form an obvious grain boundary carbide precipitation phase, and is composed of flat austenite, and the carbon steel matrix organization is acicular ferrite and a small amount of blocky ferrite.

[0069] Figure 5 It shows that the hot-rolled composite plate has no obvious composite interface transition layer, but there are a small amount of flat black inclusions on the interface, and there are obvious grain boundary precipitation phases in the stainless steel layer.

[0070] Figure 6 It shows that the interface of the hot isostatic pressed composite plate is clean, flat and densely bonded, but the carbon steel and stainless steel have coarse grain structures and uneven grain sizes.

[0071] The bonding strength of the composite plate interface was analyzed by interface tensile shear test, and the mechanical properties and corrosion resistance of the composite plate were analyzed by tensile test, V-notch impact test and intergranular corrosion test. The specific test results are shown in Table 1.

[0072] Table 1 Mechanical properties and corrosion resistance of stainless steel laminated plates prepared by different methods

[0073]

[0074] As shown in Table 1 above, the stainless steel composite plate obtained by hot isostatic pressing alone has higher interface bonding strength and tensile elongation than that obtained by hot rolling alone, but the yield strength, tensile strength and low-temperature impact performance of carbon steel are relatively low due to the coarsening of the grain structure. The hot isostatic pressed composite plate is further hot-rolled, and the composite interface is more compact, the stainless steel and carbon steel matrix structures are refined, the bonding strength of the composite interface is further improved, the yield strength and tensile strength of the composite plate are significantly improved, especially the low-temperature impact performance of carbon steel is greatly improved. The results show that hot isostatic pressing can promote the solid-state bonding of stainless steel and carbon steel by utilizing high-temperature creep and diffusion, and further hot rolling can regulate the stainless steel and carbon steel matrix structures of the composite plate, thereby obtaining a stainless steel composite plate with improved interface and matrix properties.

[0075] In summary, the stainless steel layered composite plate prepared by the combined method of hot isostatic pressing and hot rolling in the present invention forms a transition layer interface structure, which is dense, uniform, and free of oxide inclusions. The interface tensile shear strength is significantly higher than that of the hot-rolled composite plate. The composite plate has good tensile properties, low-temperature impact properties, and intergranular corrosion resistance.

Claims

1. A method for preparing a stainless steel layered composite plate, characterized in that: The following steps are involved: (1) Take a stainless steel plate and a carbon steel plate of equal size, grind the surfaces to be composited, and then respectively open exhaust grooves at the edges of the stainless steel plate and the carbon steel plate at opposite positions at the same end, and the opposite exhaust grooves form exhaust holes. After completion, the stainless steel plate and the carbon steel plate are laminated to form an initial layered plate; (2) The initial layered plate is sealed and welded around, leaving only the exhaust hole connected to the outside world; (3) exhausting the initial layered plate through the exhaust holes, and sealing the exhaust holes after the exhaust is completed to obtain a layered composite plate blank; (4) The layered composite plate is subjected to hot isostatic pressing, and after the pressing is completed, it is unloaded and cooled, and then taken out of the furnace and air-cooled to room temperature, and then heated and hot-rolled, and finally straightened to obtain a stainless steel layered composite plate.

2. The preparation method according to claim 1, characterized in that: In step (1), the stainless steel plate is hot-rolled 316L with a thickness of 3-10 mm.

3. The preparation method according to claim 1, characterized in that: In step (1), the carbon steel plate is hot-rolled normalized Q370qE with a thickness of 16-48 mm.

4. The preparation method according to claim 1, characterized in that: In step (1), the grinding process is: using a grinder to grind until the surface roughness of the raw material plate reaches Ra0.8-1.

6.

5. The preparation method according to claim 1, characterized in that: In step (2), the sealing welding process is performed by argon arc welding.

6. The preparation method according to claim 1, characterized in that: In step (3), the vacuum treatment is performed to a vacuum degree less than 0.001Pa.

7. The preparation method according to claim 1, characterized in that: In step (4), the process parameters of the hot isostatic pressing treatment are: introducing argon gas with a purity of not less than 99.999% into the hot isostatic pressing furnace for pressurization, and starting the heating temperature rising program, the insulation temperature is 920-1180°C, the pressure intensity is 120-160MPa, and the insulation time is 3-6h.

8. The preparation method according to claim 1, characterized in that: In step (4), the cooling parameters are: cooling to 200-300°C at a cooling rate of 3-10°C / min.

9. The preparation method according to claim 1, characterized in that: In step (4), the parameters of the heating treatment are: heating temperature is 1100-1200°C, and insulation time is 2-3h.

10. The preparation method according to claim 1, characterized in that: In step (4), the parameters of the hot rolling treatment are: hot rolling temperature is 830-1050°C, rolling reduction ratio is 47-65%, and after rolling, the steel is water-cooled to 500-550°C and then air-cooled to room temperature.

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