Titanium-steel composite steel plate for ship body and production method of titanium-steel composite steel plate

Abstract

A production method of a titanium-steel clad steel plate for a hull comprises a base material steel plate and a clad material titanium plate, the base material steel plate is hull steel and comprises the following chemical components in percentage by mass: 0.06%-0.010% of C, 0.15%-0.50% of Si, 0.90%-1.10% of Mn, less than or equal to 0.008% of P, less than or equal to 0.002% of S, 0.02%-0.06% of Alt, 0.015%-0.030% of Nb, 0.60%-0.75% of Cr, 0.008%-0.015% of Ti, 0.50%-0.80% of Ni and 0.40%-0.60% of Cu; and the balance of Fe and inevitable impurities. And the cladding material titanium plate is an industrial pure titanium plate. A rectangular groove matched with a covering material is formed in the surface of a base material, a titanium-titanium binding surface is coated with a glass lubricant or a MoS separant after the covering material is embedded, and the periphery is welded and sealed; according to the preparation method, composite forming is achieved through surface treatment, blank assembly, vacuum seal welding, multi-pass rolling and heat treatment. And the product performance can meet the requirements of extremely low ship and ocean platform structures on the corrosion-resistant and high-strength composite board.

Description

Technical Field

[0001] This invention relates to the field of composite metal forming technology, and specifically to a method for producing titanium-steel composite steel plates for ship hulls. Background Technology

[0002] With the increasing frequency of oil and gas resource development in extremely cold regions such as the Arctic, the polar marine environment is characterized by low temperature, high salinity, high dissolved oxygen content, and extensive sea ice coverage. Therefore, materials for the waterline components of special vessels and marine engineering equipment in extremely cold regions need to possess excellent resistance to marine corrosion and low-temperature impact. Titanium, as an emerging material, has excellent corrosion resistance, making it an ideal material for manufacturing equipment for corrosive environments. However, pure titanium plates are too expensive and have relatively low strength and stiffness. Therefore, marine titanium-steel composite plates, prepared by combining titanium plates as a cladding with marine steel plates, have a better application prospect.

[0003] Currently, there are four main methods for producing titanium-steel composite plates: explosive bonding, diffusion bonding, explosive bonding-rolling, and rolling bonding. The first two processes produce composite plates with smaller dimensions, sometimes failing to meet user requirements. Due to the commissioning of high-capacity rolling mills, these methods are only used in certain specialized fields and are showing a trend towards obsolescence. The latter two methods can produce large-size titanium-steel composite plates, but the explosive welding-rolling method involves complex processes, many factors affecting the bonding strength of the composite plate, and also consumes a lot of energy, pollutes the environment, and has a relatively low yield; therefore, it is trending towards being replaced by the direct rolling method.

[0004] Chinese patent CN105080997A discloses "A method for preparing a titanium-steel composite plate without an interlayer," Chinese patent CN104624644A discloses "A method for producing titanium-steel composite plates," and Chinese patent CN105107841A discloses "A method for preparing titanium-steel composite plates." All three methods employ direct titanium-steel composite rolling technology to prepare the titanium-steel composite plates. The base material is low-alloy structural steel such as Q345B, which has good ductility but low strength, and no interlayer is added. Through the selection of billet composition and covering agent, as well as rolling temperature control, problems such as weld cracking and oxidation during the rolling process are avoided, allowing metallurgical bonding to occur at the titanium-steel interface. However, in these technical solutions, the surface quality of the titanium-steel composite plate billet is poor, and defects such as lack of bonding between titanium and steel are easily observed. Furthermore, the mechanical properties of the prepared titanium-steel composite plate are not mentioned. Currently, there is no stable manufacturing process in the industry that can produce high-quality titanium-steel composite plates suitable for low-temperature environments. There is an urgent need for a technical solution that balances "performance compliance", "cost controllability", and "easy industrialization". Summary of the Invention

[0005] The purpose of this invention is to provide a method for producing titanium-steel composite steel plates for ship hulls. The titanium-steel composite plates produced by this method have high strength and toughness matching and performance uniformity, as well as good interfacial bonding performance: yield strength ≥420MPa, tensile strength 530~590MPa, elongation after fracture ≥22%; impact energy at -60℃ ≥120J, titanium-steel interfacial bonding strength ≥280MPa, and seawater corrosion resistance of the cladding ≤0.01mm / year, which can better meet the service requirements of ships and offshore platforms in extremely cold regions.

[0006] The technical solution of the present invention is as follows: A method for producing titanium-steel composite steel plates for ship hulls, wherein the titanium-steel composite steel plates comprise a base steel plate and a cladding titanium plate. The base steel plate is ship hull steel, and its chemical composition by mass percentage is: C = 0.06%–0.010%, Si = 0.15%–0.50%, Mn = 0.90%–1.10%, P ≤ 0.008%, S ≤ 0.002%, Alt = 0.02%–0.06%, Nb = 0.015%–0.030%, Cr = 0.60%–0.75%, Ti = 0.008%–0.015%, Ni = 0.50%–0.80%, Cu = 0.40%–0.60%; the remainder being Fe and unavoidable impurities. The cladding material is industrially pure titanium TA2 or TA1. Key process steps include: (1) Billet preparation: The dimensions of the base steel plate and the cladding titanium plate in the composite slab are determined according to the actual target thickness. The thickness of the composite slab is determined to be 5 to 7 times the thickness of the composite plate of the product. The base steel plate and the cladding titanium plate are successively surface-ground to a surface roughness Ra≤1.6μm.

[0007] (2) Assembly of the blank: A rectangular groove is opened on the upper surface of the base steel plate. The length, width and depth of the rectangular groove are adapted to the length, width and thickness of the cladding titanium plate. The cladding titanium plate is embedded in the rectangular groove and the gap between the cladding titanium plate and the groove wall is ≤0.5mm. The titanium-titanium bonding surface of the cladding titanium plate is coated with a release agent. The release agent is glass lubricant coating or MoS2, and the coating thickness is 5-10μm.

[0008] (3) Welding and sealing: After symmetrically stacking the above blanks, the edges of the rectangular grooves of the titanium cladding plate and the base steel plate are sealed by tungsten inert gas welding. The argon arc welding current is 170±10A and the welding voltage is 14±3V. After sealing the edges, the sample is vacuumed through the reserved evacuation hole to evacuate the interior of the composite blank for 2±0.1h, and the vacuum degree reaches 10. -5 Torr then inserts the cylindrical plug into the vent hole; the cylinder is then welded to the steel plate using an electron beam, with a welding current and voltage of 20±5mA and 60±5kV, respectively.

[0009] (4) Rolling treatment: The vacuum-sealed billet structure is placed in a continuous heating furnace and heated to 850-950℃ and held for 1.5±0.1h; then it is sent to a four-roll mill for multi-pass rolling with a total reduction of 75%-86.7%, the difference between the initial rolling temperature and the heating temperature is not more than 10℃, and the final rolling temperature is not less than 800℃; after rolling, it is naturally cooled to room temperature to obtain the rolled titanium-steel composite plate.

[0010] (5) Heat treatment: Put the titanium steel composite plate into a continuous heating furnace, heat it to 600-640℃, hold it for 20-50 minutes, and after air cooling, cut the edges and separate the sheets to obtain a marine titanium steel composite plate with good strength and toughness.

[0011] Further, in step (1) blank preparation: after milling, the verticality deviation of the rectangular groove wall of the base material steel plate is ≤0.1mm / m, and the straightness deviation of the side of the titanium plate is ≤0.05mm / m.

[0012] Further, step (3) welding and sealing: after vacuum treatment, the oxygen content inside the preform structure is ≤50ppm.

[0013] Further, step (4) rolling process: the pass allocation of multi-pass rolling meets the following requirements: rolling is carried out in 6 to 9 passes, wherein the reduction rate of the first pass is controlled within 10%, the reduction rate of the second to third passes is controlled between 18% and 35%, and the reduction rate of subsequent passes is reduced in turn.

[0014] Further, step (4) rolling treatment: after rolling, the interface reaction products of the titanium-steel composite plate are composed of β-Ti and a small amount of TiC, with a thickness ≤4μm, an interface bonding strength ≥280MPa, a surface flatness of the cladding titanium plate ≤0.3mm / m, and a yield strength of the base steel plate ≥420MPa.

[0015] Further, step (5) heat treatment: after heat treatment, the mechanical properties of the marine composite plate meet the requirements of titanium-steel interface bonding strength ≥280MPa, weld pass rate 100%, cladding separation rate reduced to 0, composite steel plate yield strength not less than 420MPa, tensile strength not less than 530MPa, and low temperature impact performance at -60℃ not less than 120J.

[0016] This invention is based on the concept of "structural design-process synergy," and the design principles of the material design and preparation methods are as follows: 1) Material Selection and Design: The principle of alloy composition design for titanium-steel composite plates is mainly to reduce the thickness of the brittle TiC phase at the bonding interface by controlling the chemical composition of the base material, thereby improving the bonding strength of titanium / steel. Specifically, there are two measures: ① Reduce the C content of the base material to reduce the formation of the brittle TiC phase at the bonding interface due to C diffusion, while also considering the requirements for strength and toughness. The C content is controlled at 0.06-0.010%; ② Add appropriate amounts of solid C elements, such as Ti, Nb, and Cr, to the base material. These elements combine with C to form MC, preventing free C from diffusing to the titanium-steel interface and causing embrittlement. While considering corrosion resistance and other properties, Cr is controlled at 0.60%-0.75%, and Nb and Ti are added appropriately, with Nb=0.015-0.030% and Ti=0.008-0.015%. The cladding material is selected as TA2 / TA1 industrial pure titanium, which has a seawater corrosion resistance of ≤0.01mm / year and good plasticity (elongation ≥25%), making it suitable for rolling deformation.

[0017] 2) Billet preparation: The thickness of the composite slab is determined to be 5-7 times the thickness of the composite plate of the product; the base steel plate and the cladding titanium plate are successively subjected to surface grinding (surface roughness Ra≤1.6μm) and surface blowing to remove rust (Fe2O3) on the surface of the base material and oxide film (TiO2) on the surface of the cladding titanium plate, so as to avoid the oxide layer affecting the interface bonding; hot air blowing is used to prevent secondary corrosion and surface moisture evaporation.

[0018] 3) Billet preparation: The substrate surface is designed with a rectangular groove embedded structure. Compared with traditional lamination, the rectangular groove can achieve the dual function of "positioning and limiting" of the cladding material. The gap ≤0.5mm ensures uniform interface pressure during rolling and avoids local non-bonding. Glass lubricant (high temperature resistant 850-950℃) or MoS2 (good lubricity) is applied with a coating thickness of 5-10μm to prevent titanium-titanium adhesion without affecting the titanium-steel interface bonding (the release agent can be extruded with deformation during rolling).

[0019] 4) Welding sealing: A double sealing method is used, combining tungsten inert gas welding for repair and electron beam welding for hole sealing, to ensure a defect-free weld; vacuum is applied to 10... -5 Torr (oxygen content ≤50ppm) completely isolates the interface from air, preventing oxidation during heating.

[0020] 5) Multi-pass rolling and heat treatment: The heating temperature is selected at 850-950℃, below the β-phase transformation point of titanium, to avoid titanium embrittlement, and the thickness of the titanium-steel interface reaction is controlled to be ≤3.5μm; the holding time is 1.5h to ensure uniform temperature between the substrate and the cladding; the total reduction rate is 75%-86% to ensure sufficient diffusion and bonding at the interface; rolling is carried out in multiple passes, with the reduction rate decreasing to avoid excessive deformation in a single pass leading to cracking; the final rolling temperature is 800-840℃ to ensure the austenitic state of the steel and the grain refinement effect of the substrate, thereby improving the ductility and toughness; tempering heat treatment is controlled at 600~640℃, with a holding time of 20~50min to further reduce the proportion of hard phase structure in the substrate, while improving the stress state of the bonding surface and enhancing the bonding effect.

[0021] The beneficial effects of this invention are as follows: The marine titanium-steel composite plate produced by the method of this invention has high strength and toughness matching and performance uniformity, as well as good interfacial bonding performance. The mechanical properties are as follows: yield strength ≥ 420 MPa, tensile strength 530~590 MPa, elongation after fracture ≥ 22%; impact energy at -60℃ ≥ 120 J; titanium-steel interfacial bonding strength ≥ 280 MPa, a 40% improvement compared to traditional processes; 100% weld pass rate; 0% titanium layer separation rate; seawater corrosion resistance of the cladding ≤ 0.01 mm / year. It can better meet the service requirements of ships and offshore platforms in extremely cold regions, filling the gap in 420 MPa-grade marine titanium-steel composite plates. Furthermore, the process has high repeatability and is suitable for industrial mass production. Compared with the "explosive bonding + heat treatment" process, the production cost is reduced by about 30%, and the production cycle is shortened by nearly 50%. Attached Figure Description

[0022] Figure 1 This is a sectional view of the billet structure.

[0023] Figure 2 Metallographic image of the steel produced in Example 1.

[0024] Figure 3 Metallographic image of the steel produced in Example 2. Detailed Implementation Example 1

[0025] A method for producing titanium-steel composite steel plates for ship hulls involves preparing a marine titanium-steel composite plate with a base material thickness of 8 mm and a cladding material thickness of 2 mm. The chemical composition weight percentages of the base material and cladding steel are shown in Table 1. The method includes the following key process steps: (1) Billet preparation: The thickness of the composite slab is determined to be 60 mm for the base plate and 10 mm for the cladding titanium plate. The base steel plate and the cladding titanium plate are successively subjected to surface grinding (surface roughness Ra≤1.6μm) and surface purging to remove visible particles and foreign matter.

[0026] (2) Assembly of the blank: A rectangular groove is opened on the upper surface of the base steel plate. The depth of the rectangular groove is 8mm, and the width and length are adapted to the length and width of the clad titanium blank to ensure that it is fully embedded in the rectangular groove. The gap between the clad titanium plate and the wall of the rectangular groove is 0.5mm. The titanium-titanium bonding surface of the clad titanium plate (the surface in contact with the bottom surface of the rectangular groove) is coated with glass lubricant coating with a coating thickness of 5μm.

[0027] (3) Welding and sealing: After symmetrically stacking the above blanks, the edges of the rectangular grooves of the base steel plate and the cladding titanium blanks are sealed by tungsten inert gas (TIG) welding. The TIG welding current is 172A and the welding voltage is 14.5V. After sealing the edges, the sample is evacuated through the reserved evacuation holes to evacuate the interior of the composite blank for 2 hours, achieving a vacuum level of 10. -5 Torr. Then insert the cylindrical plug into the vent hole. Use an electron beam to weld the cylinder to the steel plate to seal it, with a welding current of 21mA and a voltage of 61kV.

[0028] (4) Rolling control: The vacuum-sealed billet structure is placed in a continuous heating furnace and heated to 920℃ and held for 1.5h; then it is sent to a four-roll mill for 8 passes of rolling, with single pass reduction rates of 8%, 25%, 31%, 30%, 28%, 24%, 16%, and 8%, and a total reduction rate of 86.7%. The initial rolling temperature is 917℃ and the final rolling temperature is 804℃. After rolling, it is naturally cooled to room temperature to obtain a rolled titanium-steel composite plate with a titanium-steel interface reaction product thickness of 1.2μm.

[0029] (5) Heat treatment control: Put the titanium steel composite plate into a continuous heating furnace, heat it to 640℃, hold it for 45 minutes, and after air cooling, cut the edges and separate the sheets to obtain a titanium steel composite plate with a thickness of 10mm. The properties of the finished steel plate are shown in Table 2. Example 2

[0030] A method for producing titanium-steel composite steel plates for ship hulls involves preparing a 20mm thick base material and a 5mm thick cladding layer. The chemical composition (weight percentage) of the base material and cladding steel is shown in Table 1. The method includes the following key process steps: (1) Blank preparation: The thickness of the composite slab is determined to be 150 mm for the base plate and 25 mm for the cladding titanium plate. The base steel plate and the cladding titanium plate are successively ground and bleached to remove visible particles and foreign matter.

[0031] (2) Assembly of the blank: A rectangular groove is opened on the upper surface of the base steel plate. The depth of the rectangular groove is 23mm, and the width and length are adapted to the length and width of the clad titanium blank to ensure that it is fully embedded in the rectangular groove. The gap between the clad titanium plate and the wall of the rectangular groove is 0.5mm. The titanium-titanium bonding surface of the clad titanium plate (the surface in contact with the bottom surface of the rectangular groove) is coated with MoS2 lubricant coating with a coating thickness of 8μm.

[0032] (3) Welding and sealing: After symmetrically stacking the above blanks, the edges of the rectangular grooves of the base steel plate and the cladding titanium blanks are sealed by tungsten inert gas (TIG) welding. The TIG welding current is 168A and the welding voltage is 13.8V. After sealing the edges, the sample is evacuated through the reserved evacuation holes to create a vacuum inside the composite blank for 2.2 hours, achieving a vacuum level of 10. -5 Torr. Then insert the cylindrical plug into the vent hole. Use an electron beam to weld the cylinder to the steel plate to seal it, with a welding current of 19mA and a voltage of 59KV.

[0033] (4) Rolling control: The vacuum-sealed billet structure is placed in a continuous heating furnace and heated to 900℃ and held for 1.5h; then it is sent to a four-roll mill for 9 passes of rolling, with single pass reduction rates of 8%, 26%, 25%, 24%, 21%, 18%, 16%, 14%, and 9%, respectively, and a total reduction rate of 83%. The initial rolling temperature is 898℃ and the final rolling temperature is 811℃. After rolling, it is naturally cooled to room temperature to obtain a rolled titanium-steel composite plate with a titanium-steel interface reaction product thickness of 3.2μm.

[0034] (5) Heat treatment control: Put the titanium steel composite plate into a continuous heating furnace, heat it to 620℃, keep it at that temperature for 50 minutes, and then air cool it after taking it out of the furnace. Cut the edges and separate the sheets to obtain a titanium steel composite plate with a thickness of 25mm. The properties of the finished steel plate are shown in Table 2.

[0035] Table 1. Chemical composition of substrates in the examples, by weight percentage (wt.%) .

[0036] Table 2. Test results of mechanical properties of the composite steel plates produced in the examples. .

Claims

1. A method for producing titanium-steel composite steel plates for ship hulls, characterized in that: The titanium-steel composite steel plate comprises a base steel plate and a cladding titanium plate. The base steel plate is hull steel, and its chemical composition by mass percentage is: C = 0.06%–0.010%, Si = 0.15%–0.50%, Mn = 0.90%–1.10%, P ≤ 0.008%, S ≤ 0.002%, Alt = 0.02%–0.06%, Nb = 0.015%–0.030%, Cr = 0.60%–0.75%, Ti = 0.008%–0.015%, Ni = 0.50%–0.80%, Cu = 0.40%–0.60%. The remainder consists of Fe and unavoidable impurities; The cladding material is made of industrial pure titanium TA2 or TA1; Key process steps include: (1) Billet preparation: The dimensions of the base steel plate and the cladding titanium plate in the composite slab are determined according to the actual target thickness. The thickness of the composite slab is determined to be 5 to 7 times the thickness of the product composite plate. The base steel plate and the cladding titanium plate are successively surface-ground to a surface roughness Ra≤1.6μm. (2) Assembly of the blank: A rectangular groove is opened on the upper surface of the base steel plate. The length, width and depth of the rectangular groove are adapted to the length, width and thickness of the cladding titanium plate. The cladding titanium plate is embedded in the rectangular groove and the gap between the cladding titanium plate and the groove wall is ≤0.5mm. The titanium-titanium bonding surface of the cladding titanium plate is coated with a release agent. The release agent is glass lubricant coating or MoS2, and the coating thickness is 5~10μm. (3) Welding and sealing: After symmetrically stacking the above blanks, the edges of the rectangular grooves of the titanium cladding plate and the base steel plate are sealed by tungsten inert gas welding. The argon arc welding current is 170±10A and the welding voltage is 14±3V. After sealing the edges, the sample is vacuumed through the reserved evacuation hole to evacuate the interior of the composite blank for 2±0.1h, and the vacuum degree reaches 10. -5 Torr then inserted the cylindrical plug into the vent hole; the cylinder was then welded to the steel plate using an electron beam, with a welding current and voltage of 20±5mA and 60±5kV, respectively. (4) Rolling treatment: The vacuum-sealed billet structure is placed in a continuous heating furnace and heated to 850-950℃ and held for 1.5±0.1h; then it is sent to a four-roll mill for multi-pass rolling, with a total reduction of 75%-86.7%, the difference between the initial rolling temperature and the heating temperature does not exceed 10℃, and the final rolling temperature is not lower than 800℃; after rolling, it is naturally cooled to room temperature to obtain the rolled titanium-steel composite plate. (5) Heat treatment: Put the titanium steel composite plate into a continuous heating furnace, heat it to 600-640℃, keep it at that temperature for 20-50 minutes, and then air cool it after taking it out of the furnace. Then cut the edges and separate the sheets to obtain a marine titanium steel composite plate with good strength and toughness.

2. The method for producing a titanium-steel composite steel plate for ship hulls according to claim 1, characterized in that... Step (1) Blank preparation: After milling, the verticality deviation of the rectangular groove wall of the base material steel plate is ≤0.1mm / m, and the straightness deviation of the side of the titanium plate is ≤0.05mm / m.

3. The method for producing a titanium-steel composite steel plate for ship hulls according to claim 1, characterized in that... Step (3) Welding and sealing: After vacuum treatment, the oxygen content inside the preform structure is ≤50ppm.

4. The method for producing a titanium-steel composite steel plate for ship hulls according to claim 1, characterized in that... Step (4) Rolling treatment: The pass allocation of multi-pass rolling meets the following requirements: rolling is carried out in 6 to 9 passes, with the reduction rate of the first pass controlled within 10%, the reduction rate of the second and third passes controlled between 18% and 35%, and the reduction rate of subsequent passes decreasing sequentially.

5. The method for producing a titanium-steel composite steel plate for ship hulls according to claim 1, characterized in that... Step (4) Rolling treatment: After rolling, the interfacial reaction products of the titanium-steel composite plate are composed of β-Ti and a small amount of TiC, with a thickness ≤4μm, an interfacial bonding strength ≥280MPa, a surface flatness of the titanium cladding plate ≤0.3mm / m, and a yield strength of the base steel plate ≥420MPa.

6. A method for producing a titanium-steel composite steel plate for ship hulls according to claim 1, characterized in that... Step (5) Heat treatment: After heat treatment, the mechanical properties of the marine composite plate meet the requirements of titanium-steel interface bonding strength ≥280MPa, weld pass rate 100%, cladding separation rate reduced to 0, composite steel plate yield strength not less than 420MPa, tensile strength not less than 530MPa, and low temperature impact performance at -60℃ not less than 120J.

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