Method for avoiding intermetallic compound formation at interface of titanium-steel clad plate

Abstract

The application discloses a method for avoiding intermetallic compound generation at the interface of a titanium-steel composite plate, which comprises the following steps: S1, decarburization annealing is performed on a steel plate so that a decarburization layer is formed on the surface of the steel plate to be compounded; S2, the surfaces to be compounded of the steel plate and a titanium plate are attached and the periphery is welded to form a first group of blanks; and S3, the first group of blanks is heat rolled after being kept at 800-880 DEG C, and then a titanium-steel composite plate without TiC, FeTi and Fe2Ti intermetallic compounds at the interface is obtained. The method can avoid intermetallic compound generation at the interface of the titanium-steel composite plate without adding an intermediate layer metal, and has the advantages of simple process, low production cost and easy industrial popularization.

Description

Technical Field

[0001] This invention relates to the field of metal layered composite material preparation technology, and specifically to a method for avoiding the formation of intermetallic compounds at the interface of titanium-steel composite plates. Background Technology

[0002] Titanium / steel composite plates, formed by layering titanium and steel plates, possess not only the excellent corrosion resistance of titanium but also the high strength and low cost of steel, making them widely used in the petroleum, chemical, and shipbuilding industries. The main methods for preparing titanium-steel composite plates are explosive bonding and hot rolling bonding. However, these methods result in the formation of intermetallic compounds such as TiC, FeTi, and Fe2Ti at the interface, leading to a decrease in interfacial bonding strength.

[0003] To prevent the formation of intermetallic compounds at the titanium-steel interface, an intermediate metal layer is typically added to inhibit atomic diffusion between titanium and steel. This intermediate metal must not only effectively block the diffusion of Ti, Fe, and C atoms, but also not react with titanium or steel to form intermetallic compounds, or the formed compounds should cause minimal damage to the interface. Currently, common intermediate metals include DT4 pure iron, IF steel, niobium, molybdenum, nickel, silver, copper, and vanadium. Niobium, molybdenum, and vanadium are completely miscible with titanium and do not form intermetallic compounds, while copper, nickel, and silver do not form intermetallic compounds with steel. DT4 pure iron and IF steel are not only inexpensive but also effectively block the diffusion of C atoms. While the addition of an intermediate metal can prevent the formation of TiC, FeTi, or Fe2Ti at the titanium / steel interface and improve the interfacial bonding quality, it also introduces new problems. The addition of an intermediate metal increases raw material and production costs and promotes relative sliding at the titanium-steel interface, which is detrimental to plate shape control. Furthermore, the addition of an intermediate metal can introduce new brittle phases or pores at the interface, making the interface situation more complex. Summary of the Invention

[0004] The main objective of this invention is to provide a method for avoiding the formation of intermetallic compounds at the interface of titanium-steel composite plates, thereby solving the problems of increased material and cost, difficulty in plate shape control, and introduction of new brittle phases or pores at the interface that exist in the prior art method of preparing titanium-steel composite plates by adding an intermediate metal layer.

[0005] According to one aspect of the present invention, a method for avoiding the formation of intermetallic compounds at the interface of titanium-steel composite plates is provided, comprising:

[0006] S1, decarburize and anneal the steel plate to form a decarburized layer on the surface of the steel plate to be composited;

[0007] S2, the surfaces of the steel plate and titanium plate to be composited are bonded together and welded around the perimeter to form the first set of blanks;

[0008] S3, the first billet is held at 800-880℃ and then hot-rolled to obtain a titanium-steel composite plate without TiC, FeTi and Fe2Ti intermetallic compounds at the interface.

[0009] According to one embodiment of the present invention, in step S1, the thickness of the decarburized layer is 100-300 μm.

[0010] According to one embodiment of the present invention, in step S1, decarburization annealing is performed in a heating furnace at a temperature of 800–950°C for 5–20 min. The furnace atmosphere is a mixture of wet H2 and N2, wherein the volume percentage of H2 is 15–35% and the dew point of the mixture is 40–80°C.

[0011] According to one embodiment of the present invention, in step S1, during decarburization annealing, the surface of the steel plate to be laminated is exposed, and the surface opposite to the surface to be laminated is covered.

[0012] According to one embodiment of the present invention, before step S1, the method further includes: stacking two steel plates of the same size on top of each other and welding them together around the perimeter to form a second set of billets; in step S1, the second set of billets is subjected to decarburization annealing.

[0013] According to one embodiment of the present invention, between step S1 and step S2, the method further includes: pickling to remove the oxide scale on the surface of the second set of billets, then separating the second set of billets into two steel plates, and polishing the surfaces of the steel plates and titanium plates to be laminated.

[0014] According to one embodiment of the present invention, in step S2, the surfaces of the steel plate and the titanium plate to be laminated are bonded together, and a release agent is applied to the surface of the titanium plate opposite to the surface to be laminated and an additional steel plate is covered thereon. Then, the steel plate, the titanium plate and the additional steel plate are welded together around their perimeters to form the first set of blanks.

[0015] According to one embodiment of the present invention, in step S3, the heat preservation time is 60 to 240 minutes, the reduction per pass during hot rolling is 15 to 25%, and the total reduction is more than 80%.

[0016] According to one embodiment of the present invention, in step S3, the additional steel plate is separated from the titanium plate after hot rolling, thereby obtaining the titanium-steel composite plate.

[0017] According to one embodiment of the present invention, the interfacial bonding strength of the titanium-steel composite plate is greater than or equal to 280 MPa.

[0018] In the method for avoiding the formation of intermetallic compounds at the interface of titanium-steel composite plates according to an embodiment of the present invention, a decarburized layer is generated on the surface of the steel plate by decarburizing annealing. This decarburized layer blocks the diffusion of carbon elements at the titanium-steel interface, thus preventing the formation of TiC at the interface. Simultaneously, the hot rolling temperature is controlled below the β-Ti phase transformation temperature (882°C) to prevent the formation of FeTi and Fe2Ti at the titanium-steel interface. The formation of intermetallic compounds at the titanium-steel composite plate interface can be avoided without adding an intermediate layer metal, thus avoiding a series of problems caused by adding an intermediate layer metal. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples.

[0020] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0021] This invention proposes a method to avoid the formation of intermetallic compounds at the interface of titanium-steel composite plates, comprising the following steps:

[0022] S1, decarburize and anneal the steel plate to form a decarburized layer on the surface of the steel plate to be composited;

[0023] S2, the surfaces of the steel plate and titanium plate to be composited are bonded together and welded around the perimeter to form the first set of blanks;

[0024] S3, the first billet is held at 800-880℃ and then hot-rolled to obtain a titanium-steel composite plate without TiC, FeTi and Fe2Ti intermetallic compounds at the interface.

[0025] The inventors of this application recognized that FeTi and Fe2Ti are formed at temperatures exceeding the β-Ti phase transformation temperature (882°C). Controlling the processing temperature below 882°C can prevent their formation. However, TiC has a wider formation temperature range, making it impossible to completely prevent its formation. This invention further avoids TiC formation by forming a decarburized layer. In the embodiments of this invention, the steel plate is decarburized and annealed, causing a decarburized layer to form on the surface. This decarburized layer blocks the diffusion of carbon elements at the titanium-steel interface, preventing TiC formation at the interface. Simultaneously, the hot rolling temperature is controlled below the β-Ti phase transformation temperature (882°C) to prevent the formation of FeTi and Fe2Ti at the titanium-steel interface. The final result is a titanium-steel composite plate without intermetallic compounds at the interface. This invention solves the problem of intermetallic compounds at the titanium-steel composite plate interface without adding an intermediate layer metal, avoiding a series of problems caused by adding an intermediate layer metal. It has the advantages of simple process, low production cost, and easy industrialization.

[0026] In some embodiments, in step S1, the thickness of the decarburized layer is 100–300 μm. Such a micron-level thickness promotes the plastic flow of the interfacial metal without causing relative sliding at the interface, and eliminates interfacial defects and improves the interfacial bonding quality without adversely affecting the plate shape.

[0027] In some embodiments, in step S1, decarburization annealing is performed in a heating furnace at a temperature of 800–950°C for 5–20 minutes. The furnace atmosphere is a humid mixture of H2 and N2, wherein the volume percentage of H2 is 15–35%, and the dew point of the mixture is 40–80°C. By setting these parameters, a decarburized layer of the desired thickness can be obtained.

[0028] In some embodiments, during decarburization annealing in step S1, the surface of the steel plate to be laminated is exposed, while the surface opposite to the surface to be laminated is covered. This allows a decarburized layer to be formed only on the surface of the steel plate to be laminated, preventing the formation of a decarburized layer on the opposite surface and thus avoiding impact on the steel plate's performance.

[0029] In some embodiments, prior to step S1, the method further includes: stacking two steel plates of the same size vertically and welding them together around their perimeter (e.g., fixing them with spot welding with sealing strips around the perimeter of the steel plates) to form a second set of blanks; in step S1, the second set of blanks is subjected to decarburization annealing. This method allows for the simple formation of a decarburized layer only on the surface of the steel plates to be laminated.

[0030] In some embodiments, between steps S1 and S2, the method further includes: pickling to remove the oxide scale from the surface of the second set of billets, then separating the second set of billets into two steel plates, and grinding the surfaces of the steel plates and titanium plates to be laminated (e.g., using abrasive tools such as grinding wheels, sanding belts, or grinding wheels for mechanical grinding). This avoids the influence of oxide scale on subsequent lamination, and grinding facilitates a tight fit between the surfaces to be laminated.

[0031] In some embodiments, in step S2, the surfaces of the steel plate and titanium plate to be laminated are bonded together, and a release agent is applied to the surface of the titanium plate opposite to the surface to be laminated, and an additional steel plate is covered thereon. Then, the steel plate, titanium plate, and additional steel plate are welded together around their perimeters (e.g., the perimeter of the billet is sealed using vacuum electron beam welding with sealing strips in a vacuum environment) to form the first set of billets. By symmetrically stacking the billets in the order of additional steel plate-titanium plate-steel plate in this manner, a first set of billets with a symmetrical structure is obtained. This ensures uniform deformation of the sheet material during subsequent hot rolling, which is beneficial for improving the performance of the final product.

[0032] In some embodiments, in step S3, the holding time is 60 to 240 minutes, and multiple hot rolling passes are performed, with a reduction of 15 to 25% per pass and a total reduction of more than 80%.

[0033] In some embodiments, in step S3, after hot rolling, the head, tail and both sides of the billet are cut off to separate the additional steel plate from the titanium plate, thereby obtaining the titanium-steel composite plate.

[0034] In some embodiments, the interfacial bonding strength of the titanium-steel composite plate is greater than or equal to 280 MPa.

[0035] In summary, this invention utilizes the surface decarburization characteristic of carbon steel during high-temperature heat treatment to generate a pure iron layer on the steel plate surface. This eliminates the need for an intermediate metal layer, thus solving the problem of intermetallic compounds at the interface of titanium-steel composite plates, resulting in low production costs. Furthermore, the thickness of the pure iron layer generated on the carbon steel surface is controllable and can be flexibly adjusted according to the needs of rolling composite processes. The process is simple and suitable for industrial application. In addition, the pure iron layer generated on the carbon steel surface is at the micron level, which promotes plastic flow of the interfacial metals without causing relative sliding at the interface. This eliminates interfacial defects, improves interfacial bonding quality, and does not adversely affect the plate shape.

[0036] The following description is based on specific embodiments.

[0037] Example 1

[0038] The cladding material is TA2 pure titanium with an initial thickness of 10.0 mm, and the base material is Q235 low carbon steel with an initial thickness of 110.0 mm.

[0039] Step 1: First, stack two steel plates of the same size one on top of the other, and spot weld the four edges of the steel plates to secure the assembly. Then, place the assembly in a heating furnace for decarburization annealing at a temperature of 950℃ for 20 minutes. The furnace atmosphere is a humid mixture of H2 and N2, with H2 comprising 35% by volume and a dew point of 80℃. The decarburized layer thickness on the surface of the steel plate after decarburization annealing is 300μm.

[0040] Step 2: Pickling removes the oxide scale from the surface of the billet. Then, the billet is separated into two steel plates. The decarburized surface of the steel plate is the surface to be laminated. The surfaces to be laminated on both the titanium plate and the steel plate are mechanically polished using grinding wheels, abrasive belts, or grinding wheels. The surfaces to be laminated on the titanium plate and the steel plate are then bonded together. A release agent is then applied to the outer surface of the titanium plate, and a steel plate of the same size is placed on top to obtain a symmetrical composite billet.

[0041] Step 3: In a vacuum environment, seal the four sides of the assembled billet with vacuum electron beam welding using sealing strips.

[0042] Step 4: Place the assembled billet in a heating furnace and hold at 880℃ for 240 minutes.

[0043] Step 5: The heated billet is hot rolled in multiple passes, with the reduction per pass controlled at 24% and the total reduction controlled at 92%.

[0044] Step 6: Cut off the head, tail, and both sides of the billet to separate the steel plate from the titanium / steel composite plate, thus obtaining the finished titanium-steel composite plate. The interface of the titanium-steel composite plate does not contain TiC, FeTi, or Fe2Ti intermetallic compounds, and the interfacial bonding strength is 310 MPa.

[0045] Example 2

[0046] The cladding material is TA1 pure titanium with an initial titanium plate thickness of 3.0 mm, and the base material is Q235 low carbon steel with an initial steel plate thickness of 18.0 mm.

[0047] Step 1: First, stack two steel plates of the same size one on top of the other, and spot weld the four edges of the steel plates to secure the assembly. Then, place the assembly in a heating furnace for decarburization annealing. The furnace temperature is 800℃, the holding time is 5 minutes, and the furnace atmosphere is a humid mixture of H2 and N2, where the volume percentage of H2 is 15% and the dew point of the mixture is 40℃. The decarburized layer thickness on the surface of the steel plate after decarburization annealing is 100μm.

[0048] Step 2: Pickling removes the oxide scale from the surface of the billet. Then, the billet is separated into two steel plates. The decarburized surface of the steel plate is the surface to be laminated. The surfaces to be laminated on both the titanium plate and the steel plate are mechanically polished using grinding wheels, abrasive belts, or grinding wheels. The surfaces to be laminated on the titanium plate and the steel plate are then bonded together. A release agent is then applied to the outer surface of the titanium plate, and a steel plate of the same size is placed on top to obtain a symmetrical composite billet.

[0049] Step 3: In a vacuum environment, seal the four sides of the assembled billet with vacuum electron beam welding using sealing strips.

[0050] Step 4: Place the assembled billet in a heating furnace and hold it at 800℃ for 60 minutes.

[0051] Step 5: The heated billet is hot rolled in multiple passes, with the reduction per pass controlled at 15% and the total reduction controlled at 82%.

[0052] Step 6: Cut off the head, tail, and both sides of the billet to separate the steel plate from the titanium / steel composite plate, thus obtaining the finished titanium-steel composite plate. The interface of the titanium-steel composite plate does not contain TiC, FeTi, or Fe2Ti intermetallic compounds, and the interfacial bonding strength is 285 MPa.

[0053] Example 3

[0054] The cladding material is TA2 pure titanium with an initial titanium plate thickness of 6.0 mm, and the base material is Q345 low carbon steel with an initial steel plate thickness of 50.0 mm.

[0055] Step 1: First, stack two steel plates of the same size one on top of the other, and spot weld the four edges of the steel plates to secure the assembly. Then, place the assembly in a heating furnace for decarburization annealing at a temperature of 850℃ for 10 minutes. The furnace atmosphere is a humid mixture of H2 and N2, with H2 comprising 25% by volume and a dew point of 60℃. The decarburized layer thickness on the surface of the steel plate after decarburization annealing is 220μm.

[0056] Step 2: Pickling removes the oxide scale from the surface of the billet. Then, the billet is separated into two steel plates. The decarburized surface of the steel plate is the surface to be laminated. The surfaces to be laminated on both the titanium plate and the steel plate are mechanically polished using grinding wheels, abrasive belts, or grinding wheels. The surfaces to be laminated on the titanium plate and the steel plate are then bonded together. A release agent is then applied to the outer surface of the titanium plate, and a steel plate of the same size is placed on top to obtain a symmetrical composite billet.

[0057] Step 3: In a vacuum environment, seal the four sides of the assembled billet with vacuum electron beam welding using sealing strips.

[0058] Step 4: Place the assembled billet in a heating furnace and hold it at 860℃ for 120 minutes.

[0059] Step 5: The heated billet is hot rolled in multiple passes, with the reduction per pass controlled at 20% and the total reduction controlled at 88%.

[0060] Step 6: Cut off the head, tail, and both sides of the billet to separate the steel plate from the titanium / steel composite plate, thus obtaining the finished titanium-steel composite plate. The interface of the titanium-steel composite plate does not contain TiC, FeTi, or Fe2Ti intermetallic compounds, and the interfacial bonding strength is 296 MPa.

[0061] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for avoiding the formation of intermetallic compounds at the interface of titanium-steel composite plates, characterized in that, include: S1, decarburize and anneal the steel plate to form a decarburized layer on the surface of the steel plate to be composited; S2, the surfaces of the steel plate and titanium plate to be composited are bonded together and welded around the perimeter to form the first set of blanks; S3, after holding the first billet at 800-880℃, hot-roll it to obtain a titanium-steel composite plate without TiC, FeTi and Fe2Ti intermetallic compounds at the interface. In step S1, the thickness of the decarburized layer is 100–300 μm; In step S1, decarburization annealing is carried out in a heating furnace at a temperature of 800–950°C for 5–20 minutes. The furnace atmosphere is a mixture of wet H2 and N2, wherein the volume percentage of H2 is 15–35% and the dew point of the mixture is 40–80°C. In step S2, the surfaces of the steel plate and titanium plate to be laminated are bonded together, and a release agent is applied to the surface of the titanium plate opposite to the surface to be laminated and an additional steel plate is covered. Then, the steel plate, titanium plate and additional steel plate are welded together to form the first set of blanks. In step S3, the holding time is 60-240 min, the reduction per pass during hot rolling is 15-25%, and the total reduction is over 80%.

2. The method according to claim 1, characterized in that, In step S1, during decarburization annealing, the surface of the steel plate to be laminated is exposed, while the surface opposite to the surface to be laminated is covered.

3. The method according to claim 2, characterized in that, Before step S1, the method further includes: stacking two steel plates of the same size on top of each other and welding them together around the perimeter to form a second set of billets; in step S1, the second set of billets is decarburized and annealed.

4. The method according to claim 3, characterized in that, Between steps S1 and S2, the method further includes: pickling to remove the oxide scale from the surface of the second set of billets, then separating the second set of billets into two steel plates, and polishing the surfaces of the steel plates and titanium plates to be laminated.

5. The method according to claim 1, characterized in that, In step S3, the additional steel plate is separated from the titanium plate after hot rolling to obtain the titanium-steel composite plate.

6. The method according to claim 1, characterized in that, The interfacial bonding strength of the titanium-steel composite plate is greater than or equal to 280 MPa.