Method for preparing large-size titanium alloy seamless cylinder part through combination of stack forging and rolling

Abstract

The invention discloses a method for preparing a large-size titanium alloy seamless cylinder part by combining stack forging and rolling, and belongs to the technical field of metal stack forging and rolling forming. The method comprises the following steps: 1, preparing a rolled blank by adopting a metal stack forging technology, and detecting the actual temperature of a phase transformation point T beta; the rolled blank prepared in the first step is subjected to diameter expanding rolling through a rolling mill; performing performance heat treatment on the large-size cylinder part subjected to expanding rolling in the step 2; performing bulging treatment on the large-size cylinder part subjected to heat treatment in the step 3; the inner surface and the outer surface of the large-size cylinder piece subjected to bulging in the fourth step are machined, so that the wall thickness, the diameter and the surface quality of the cylinder piece meet the technical requirements; and the size of the large-size cylinder machined in the step 5 is detected, machining is finished if the large-size cylinder is qualified, and the step 5 is executed again if the large-size cylinder is unqualified until the large-size cylinder is qualified. According to the method, the limitation that large-size seamless barrel parts cannot be produced according to existing titanium alloy cast ingot specifications is broken through, and meanwhile the defect that large-size titanium alloy barrel parts are produced through welding and free forging is overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of metal stack forging and rolling forming, and in particular relates to a method for preparing a large-size titanium alloy seamless cylinder by combining stack forging and rolling. Background Art

[0002] Titanium alloy cylinders are divided into seam cylinders and seamless cylinders. For large-size seam cylinders, there are two production processes: one is to use plate for coil welding, and the other is to stack and weld multiple low rings. Due to the presence of welds, welded products will inevitably reduce the service life, safety and reliability of parts, and thus do not meet the technical requirements and use requirements of special-purpose products such as aerospace, marine equipment and nuclear power. In addition, the welding operation is complicated, which will increase the product manufacturing cost and increase the product production cycle.

[0003] The traditional production process of large titanium alloy seamless cylinders is generally a free forging process, and the specific process is material smelting → blanking forging → punching → horse frame expansion → heat treatment → machining. The main production equipment is a free forging press. This type of production equipment consumes a lot of energy, and the products in the forging process need to be repeatedly reheated. In addition, due to the irregularity of the forged products, the processing reserve margin is large, resulting in low product processing efficiency and high manufacturing process costs, which cannot meet the needs of batch and low-cost production. In addition, due to the narrow processing temperature range of titanium alloys, low thermal conductivity, and difficulty in deformation, the traditional method of producing large-size cylinder parts is extremely technically difficult. Summary of the invention

[0004] The present invention aims at the above-mentioned problems, makes up for the shortcomings of the prior art, and provides a method for preparing large-sized titanium alloy seamless cylinders by combining stack forging and rolling; the present invention breaks the limitation that the current titanium alloy ingot specifications cannot produce large-sized seamless cylinders, and at the same time improves the disadvantages of welding and free forging in producing large-sized titanium alloy cylinders.

[0005] To achieve the above purpose, the present invention adopts the following technical solution.

[0006] The present invention provides a method for preparing a large-size titanium alloy seamless cylinder by combining stack forging and rolling, characterized in that the method comprises the following steps: Step 1: Prepare the rolled billet using metal stacking technology and detect the actual temperature of the phase transition point Tβ; Step 2: using a rolling mill to expand the diameter of the rolled billet prepared in step 1; Step 3: Performing a performance heat treatment on the large-size tube completed by the diameter expansion rolling in step 2; Step 4: Perform bulging treatment on the large-sized cylinder after heat treatment in step 3; Step 5: Process the inner and outer surfaces of the large-sized cylinder after bulging in step 4, so that the wall thickness, diameter and surface quality of the cylinder meet the technical requirements; Step 6: Check the size of the large-size cylinder after processing in step 5. If it is qualified, the processing is terminated. If it is not qualified, repeat step 5 until it is qualified.

[0007] Furthermore, the step 1 is: calculating the weight of the required slab according to the specifications of the finished tube, using a forging machine and a rolling mill to forge the titanium alloy ingot into plates of the same thickness, using a planer and a CNC lathe to remove the scale on the surface of each plate and process holes in the plate, and finally using an organic solvent to remove oil and impurities on the surface of the plate, stacking all the plates, and then loading them as a whole into a box consistent with the material of the plate, vacuum sealing the box, and then heating and insulating the box, upsetting and pressure-maintaining welding, and finally unpacking and returning to the furnace, high-temperature diffusion, taking out forging, expanding the hole and stretching to the required size, and after completion, detecting the actual temperature of its phase change point Tβ.

[0008] Furthermore, the step 2 is: heating the billet obtained in step 1 in an environment of 20°C~50°C below the phase transformation point Tβ temperature, calculating the heating time of the billet according to a heating rate of 1 mm / min, and then placing it on a rolling mill for diameter expansion rolling, with a final rolling temperature ≥750°C. During the rolling process, detecting the temperature of the ring billet, when the temperature of the ring billet is lower than the final rolling temperature of 750°C, stopping the rolling, and returning to the heating furnace for supplementary heating, with the supplementary heating temperature being 20°C~50°C below the phase transformation point Tβ temperature, and calculating the heating time of the billet according to a heating rate of 1 mm / min.

[0009] Furthermore, the step 3 is: heat treating the large-sized tube completed by the expansion rolling in step 2, the heat treatment temperature depends on the final required performance of the tube, and the insulation time is t=0.8D~0.8D+300min, where D is the smaller value of the billet diameter and the wall thickness, in mm.

[0010] Furthermore, the step 4 is: using a bulging machine to bulge the large-sized cylinder after the heat treatment in step 3. Due to the large specifications of the cylinder and the limitations of the specifications of existing equipment, a segmented bulging method is adopted, that is, first bulging half of the height of the entire cylinder, and then bulging the other half of the height.

[0011] Furthermore, the step 5 is: using a CNC lathe to process the surface and thickness of the large-sized cylinder after bulging in step 4, so that the wall thickness, diameter and surface quality of the cylinder meet the technical requirements.

[0012] Furthermore, the step 6 is: using a thickness gauge and an inner diameter ruler to perform finished product inspection on the size of the large-sized cylinder processed in step 5.

[0013] Beneficial effects of the present invention.

[0014] Compared with the traditional process, the present invention utilizes a process method that combines stack forging and rolling, breaking the limitation that large-sized titanium alloy seamless cylinders cannot be prepared with existing titanium alloy ingot specifications, solving the problem that large-sized titanium alloy cylinders cannot be formed in one piece, and improving the production efficiency and material utilization rate of titanium alloy cylinders. The produced titanium alloy seamless cylinders have the advantages of good performance, low cost and good safety performance, and can almost meet the large-sized cylinders of various specifications required in the fields of aerospace, energy and chemical industry, and deep-sea equipment.

[0015] During the ring rolling process of the tube, according to the product specifications and the real-time rolling temperature, a reheating program is added to return the billet to the target temperature, ensuring that the surface and core temperatures of the billet are consistent, thereby ensuring the uniformity of the structure, performance, size and surface quality of the finished tube.

[0016] In order to solve the problems of poor roundness, cylindricity and wall thickness uniformity of ring-rolled tubes and increase the processing volume of subsequent machining processes, the bulging process is added, which can effectively solve the above-mentioned problems of tubes after rolling, greatly reduce the processing volume of machining processes, and improve material utilization. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to make the technical problems, technical solutions and beneficial effects solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] Figure 1 It is a process flow chart of the present invention.

[0019] Figure 2 The invention discloses a process route diagram for preparing rolled billets by metal stack forging.

[0020] Figure 3 It is the rolling process curve diagram of the present invention. DETAILED DESCRIPTION

[0021] As shown in the accompanying drawings, this embodiment provides a method for preparing a large-size titanium alloy seamless cylinder by combining stack forging and rolling. Taking the preparation of a TC4 titanium alloy seamless cylinder with an outer diameter of 12000 mm, a wall thickness of 80 mm and a height of 3000 mm as an example, the processing method includes the following steps: Step 1: The weight of the required slab is calculated to be 3 tons according to the specifications of the finished tube. According to the conventional slab specifications, a total of 18 TC4 titanium alloy slabs with specifications of 1715x1715x210mm are required. The 3-ton TC4 titanium alloy ingot is forged by a forging press, and then rolled into 1715x1715x230mm TC4 slabs by a rolling mill. The surface oxide scale of each slab is removed by a planer, and then a hole with a diameter of 600mm is processed in the middle of the sheet by a CNC lathe. Then, alcohol or acetone is used to remove surface oil stains and impurities and other pollutants. Then, the 18 TC4 slabs are stacked and then loaded into a box consistent with the sheet material. The box is vacuum-sealed with a vacuum degree of no more than 3x10 -3 Pa, and then heat the box to 960℃. After the temperature is uniform, keep it warm for 390min, take out the box for upsetting, and use a forging press to cold-press and press-weld the stacked slabs along the height direction of the slabs. The reduction is 20%. Finally, unpack and return to the furnace for high-temperature diffusion. Heat to 1000℃, keep warm for 300min, take out forging, expand the hole and draw to an outer diameter of 2800mm, an inner diameter of 2000mm, and a wall thickness of 400mm. After completion, the actual temperature of the phase change point Tβ is detected to be 980℃.

[0022] Step 2: After the oxide scale and cracks on the surface of the ring blank obtained in step 1 are polished clean, heat and keep warm at 960℃ for 400min~430min, take out the ring blank and put it on the roller of the ring rolling machine, adjust the equipment, start diameter expansion rolling, monitor the surface temperature of the blank, and when the temperature is below 750℃, return to the furnace to make up the temperature, the temperature is 960℃, and the time is controlled within 90min. The thermal conductivity of titanium alloy is small, and the temperature difference between the core and the surface of the blank is large. When the surface temperature of titanium alloy is lower than the minimum allowable rolling temperature, a large number of cracks are very likely to appear on the surface. In order to reduce the generation of surface cracks, in step 2, use a temperature measuring gun to detect the surface temperature of the blank during rolling. When it is lower than the minimum allowable rolling temperature, return to the furnace to make up the temperature in time, reduce defects, and improve quality.

[0023] Step 3: The large-size tube completed by the expansion rolling in step 2 is placed in a heat treatment furnace for performance heat treatment, heated to 750°C with the furnace, and kept warm for 120 minutes before being taken out of the furnace.

[0024] Step 4: The large-sized tube that has been heat treated in step 3 is immediately placed on the bulging machine, and the residual heat of the heat treatment is used to bulge half of the height of the tube, and then the other half is bulged after completion. This can further control the shape, surface quality and wall thickness of the tube, greatly reduce the processing volume of the machining process, and improve material utilization.

[0025] Step 5: Use a CNC lathe to process the surface and thickness of the large-sized cylinder after bulging in step 4, so that the wall thickness, diameter and surface quality of the cylinder meet the technical requirements.

[0026] Step 6: Use a thickness gauge and an inner diameter ruler to inspect the size of the large-sized cylinder processed in step 5. If it is qualified, the processing is completed. If it is not qualified, repeat step 5 until it is qualified.

[0027] It can be understood that the above specific description of the present invention is only used to illustrate the present invention and is not limited to the technical solutions described in the embodiments of the present invention. Those skilled in the art should understand that the present invention can still be modified or replaced by equivalents to achieve the same technical effects; as long as the use requirements are met, they are within the protection scope of the present invention.

Claims

1. A method for preparing large-size titanium alloy seamless cylinders by combining stack forging and rolling, characterized in that: The method comprises the following steps: Step 1: Prepare the rolled billet using metal stacking technology and detect the actual temperature of the phase transition point Tβ; Step 2: using a rolling mill to expand the diameter of the rolled billet prepared in step 1; Step 3: Performing a performance heat treatment on the large-size tube completed by the diameter expansion rolling in step 2; Step 4: Perform bulging treatment on the large-sized cylinder after heat treatment in step 3; Step 5: Process the inner and outer surfaces of the large-sized cylinder after bulging in step 4, so that the wall thickness, diameter and surface quality of the cylinder meet the technical requirements; Step 6: Check the size of the large-size cylinder after processing in step 5. If it is qualified, the processing is terminated. If it is not qualified, repeat step 5 until it is qualified.

2. The method for preparing large-size titanium alloy seamless cylinder by combining stack forging and rolling according to claim 1, characterized in that: The step 1 is as follows: the weight of the required slab is calculated according to the specifications of the finished tube, the titanium alloy ingot is forged into a plate of the same thickness by a forging press and a rolling mill, the oxide scale on the surface of each plate is removed by a planer and a CNC lathe, and holes are processed on the plate, and finally, the oil and impurities on the surface of the plate are removed by an organic solvent, all the plates are stacked, and then the whole is loaded into a box consistent with the material of the plate, the box is vacuum-sealed, and then the box is heated and insulated, upsetting and pressure-maintaining welding is performed, and finally the box is unpacked and returned to the furnace, high-temperature diffusion is performed, the plate is taken out for forging, the hole is expanded and drawn to the required size, and after completion, the actual temperature of the phase change point Tβ is detected.

3. The method for preparing large-size titanium alloy seamless cylinder by combining stack forging and rolling according to claim 1, characterized in that: The step 2 is: heating the billet obtained in step 1 in an environment 20°C to 50°C below the phase transformation point Tβ temperature, the heating time is calculated according to a heating speed of 1 mm / min, and then placing the billet on a rolling mill for diameter expansion rolling, the final rolling temperature is ≥750°C, during the rolling process, the temperature of the ring billet is detected, when the temperature of the ring billet is less than the final rolling temperature of 750°C, the rolling is stopped, and the billet is returned to the heating furnace for supplementary heating, the supplementary heating temperature is 20°C to 50°C below the phase transformation point Tβ temperature, and the heating time is calculated according to a heating speed of 1 mm / min.

4. The method for preparing large-size titanium alloy seamless cylinder by combining stack forging and rolling according to claim 1, characterized in that: The step 3 is: heat treating the large-sized tube completed by the expansion rolling in step 2, the heat treatment temperature depends on the final required performance of the tube, and the holding time is t=0.8D~0.8D+300min, where D is the smaller value of the billet diameter and the wall thickness, in mm.

5. The method for preparing large-size titanium alloy seamless cylinder by combining stack forging and rolling according to claim 1, characterized in that: The step 4 is: using a bulging machine to bulge the large-sized cylinder after the heat treatment in step 3. Due to the large specifications of the cylinder and the limitations of the specifications of existing equipment, a segmented bulging method is adopted, that is, first bulging half of the height of the entire cylinder, and then bulging the other half of the height.

6. The method for preparing large-size titanium alloy seamless cylinder by combining stack forging and rolling according to claim 1, characterized in that: The step 5 is: using a CNC lathe to process the surface and thickness of the large-sized cylinder after bulging in step 4, so that the wall thickness, diameter and surface quality of the cylinder meet the technical requirements.

7. The method for preparing large-size titanium alloy seamless cylinder by combining stack forging and rolling according to claim 1, characterized in that: The step 6 is: using a thickness gauge and an inner diameter ruler to perform finished product inspection on the size of the large-size cylinder processed in step 5.

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