Method for forming low-cost titanium alloy bottomed cylindrical part

Abstract

The invention provides a forming method of a novel low-cost titanium alloy material bottomed cylindrical rotary body part, which is a plastic forming method. Comprising the following steps that (1) a novel low-cost titanium alloy bar blank is subjected to die forging to form a preformed blank; (2) preheating the core mold before spinning; (3) the prefabricated blank is heated to the spinning temperature in a heating furnace or directly on a core mold to be subjected to spinning forming, and a lubricating agent is evenly smeared before spinning; (4) carrying out spinning forming on a spinning machine; (5) discharging and cooling after spinning forming; and (6) after spinning, a preformed part needs to be machined. According to the hot spinning forming method for the engine shell type part, the hot spinning forming process is adopted for replacing a bar machining process, the material utilization rate is increased, the manufacturing cost is reduced, the material performance is secondarily strengthened through the hot spinning process, the performance requirement for light weight of an engine shell is met, and the product quality is improved. And the produced economic benefits and social benefits are huge.

Description

Technical Field

[0001] The present invention relates to a forming method for a rotary body part, and in particular to a forming method for a low-cost titanium alloy bottomed cylindrical part. Background Art

[0002] The bottomed cylindrical part is a kind of engine housing part, which is generally made of structural steel. Without changing the structure, replacing the steel material with a titanium alloy material can achieve the lightweight of the housing under the condition of equal strength, thereby improving the mass ratio of the engine and enhancing the overall performance.

[0003] The titanium alloy material is a high-strength, high-ductility and low-cost titanium alloy material independently developed in China. Its material properties are superior to TC11 and the cost is reduced by more than 10%, but its room-temperature plasticity is poor. For the forming of this kind of titanium alloy bottomed cylindrical part, the present invention adopts a hot spinning forming method. By making full use of the good plasticity of this titanium alloy material at high temperature and adopting the hot spinning forming method, not only can the dimensional accuracy of the workpiece be improved, but also the surface of the workpiece can be strengthened and the performance can be enhanced. The hot power spinning forming method for the low-cost titanium alloy bottomed cylindrical part can reduce the machining process and the manufacturing cost, and can meet the requirements of high-performance and low-cost manufacturing of titanium alloy rotary body parts. Summary of the Invention

[0004] The present invention provides a forming method for a thin-walled cylindrical rotary body part with a bottom seal, the material of which is a high-strength, high-ductility and low-cost titanium alloy independently developed in China. It is a plastic forming method. The hot spinning forming process route for the low-cost titanium alloy bottomed cylindrical part is: bar stock - die forging - heat treatment - three-pass hot spinning - trimming - inspection.

[0005] The technical solutions adopted by the present invention include the following steps: (1) The bar stock blank of the bottomed cylindrical part is preformed by die forging. The outer diameter of the preform is Φ203mm, the inner diameter is Φ167mm, the inner hole depth is 253mm, the total length is 260mm, and the wall thickness is 18mm.

[0006] (2) Before spinning, the core die is preheated to 600 - 800°C.

[0007] (3) The forging blank is heated to 800 - 1000°C in a heating furnace or directly on the core die for spinning forming. Before spinning, a lubricant is evenly applied to the core die and the forging blank.

[0008] (4) The spinning process is carried out on a numerically controlled three-roller power spinning machine, and the three-pass power hot spinning process is adopted for spinning forming. The specific parameters are as follows: During the spinning process of the core mold and the spinning wheels, cooling water is passed through for cooling. During the spinning process, supplementary heating is carried out to ensure that the temperature of the bottomed cylindrical workpiece forging blank is between 800 and 1000 °C for spinning plastic forming. The fillet radii of the front, middle, and rear spinning wheels are all r = 8 mm, and the forming angle α of the front spinning wheel 前 = 25°, the forming angle α of the middle spinning wheel 中 = 30°, the forming angle α of the rear spinning wheel 后 = 35°, the withdrawal angle α of the front, middle, and rear spinning wheels is 5°. The stagger distance between the front spinning wheel and the middle spinning wheel is 5 mm, and the stagger distance between the middle spinning wheel and the rear spinning wheel is 5 mm. The spindle speeds for the two passes are n = 100 and 120 r / min respectively, the longitudinal feed rate f of the spinning wheel is 60 and 144 mm / min, the reduction per pass is 5 mm and 5 mm. Using these hot spinning process parameters, affected by the springback amount, after hot spinning, the outer diameter size of the workpiece is Φ183 - Φ185 mm, the inner diameter size is Φ167 mm, the workpiece length is 520 - 550 mm, and the wall thickness is 8 - 8.5 mm.

[0009] (5)Hot spinning forming for the third pass, the spinning wheels remain unchanged. The stagger distance between the front spinning wheel and the middle spinning wheel is 3 mm, and the stagger distance between the middle spinning wheel and the rear spinning wheel is 3 mm. The spindle speeds are n = 60, 80, and 100 r / min respectively, the longitudinal feed rate f of the spinning wheel is 40, 60, and 80 mm / min, and the reduction of the spinning wheel is 0.5 - 1 mm. Different reductions are selected according to the different wall thicknesses of the workpiece. After cold spinning, the outer diameter size of the workpiece is Φ182 mm, the inner diameter size is Φ167 mm, the wall thickness is 7.5 ± 0.1 mm, and the workpiece length is 530 - 560 mm.

[0010] (6)Trimming after hot spinning, the workpiece length is 492 mm.

[0011] Advantages and beneficial effects of the present invention: The present invention explores a hot spinning forming method for bottomed cylindrical parts made of a specific new type of low-cost titanium alloy material, which can save raw materials, reduce manufacturing costs, double-strengthen the material properties through the hot spinning process, meet the accuracy and performance requirements of the workpiece, expand the application range of this new type of low-cost titanium alloy material, and generate huge economic and social benefits.

[0012] The innovation points are as follows: (1)Spinning process: Hot spinning forming is carried out on the forging blank of the low-cost titanium alloy bottomed cylindrical part. The optimal spinning process parameters are selected to make the wall thickness difference of the workpiece processed by the plastic forming method without chips for the forged preform reach an accuracy of ±0.1 mm for the bottomed cylindrical part, maximizing the material utilization rate and reducing production costs.

[0013] (2) Reasonably design the hot spinning temperature parameters: Titanium alloy materials have a high yield ratio and a low normal temperature elongation rate of only about 10%, making forming difficult. However, the elongation rate of titanium alloy reaches 50% - 75% or more at around 700 - 900 °C, and plastic forming is easy. Therefore, titanium alloy materials are mostly hot spun. This newly developed low-cost titanium alloy material has a small deformation resistance at high temperatures and is easy to hot spin form. However, too high a temperature will cause grain coarsening and a reduction in performance after deformation. Therefore, the temperature control range for spinning deformation is narrow and precise control is required. Selecting the appropriate deformation temperature is crucial. The present invention reasonably designs the hot spinning temperature, including the preheating temperature of the mandrel, etc., and the temperature maintenance during the hot spinning process, which can not only ensure the dimensional accuracy of the wall thickness difference of the formed part, but also avoid defects such as cracking in the spun parts, ensure good metal fluidity during the hot spinning process, and improve the hot spinning quality.

[0014] (3) Selection of lubricant and lubrication method: Graphite water-based lubricant is evenly applied to the surface of the die and the workpiece during hot spinning, which plays a role in lubrication and anti-oxidation during the spinning process; reduces the deformation resistance, improves the die life, and obtains higher surface quality. Embodiment Example

[0015] It includes the following steps: The workpiece material is a newly developed low-cost titanium alloy, and the spinning equipment is a numerically controlled three-roller hot spinning machine.

[0016] (1) A bar blank of a newly developed low-cost titanium alloy with a bottomed cylindrical part is preformed by die forging. The outer diameter of the preform is Φ188mm, the inner diameter is Φ168mm, the inner hole depth is 371.5mm, and the wall thickness is 10mm.

[0017] (2) The mandrel is preheated to 600 - 800 °C before spinning.

[0018] (3) The preform is heated to 850 - 900 °C in a heating furnace or directly on the mandrel, and then spun formed. Lubricant is evenly applied to the mandrel and the forging blank before spinning.

[0019] (4) The spinning forming is carried out on a numerically controlled three-roller power spinning machine, and the multi-pass power hot spinning process is used for spinning forming. Cooling water is passed through the mandrel and the spinning wheels during the spinning process. During the spinning process, supplementary heating is carried out to ensure that the temperature of the forging blank of the bottomed cylindrical part is between 800 - 1000 °C for spinning plastic forming. The spindle speed n = 100r / min, the longitudinal feed rate f of the spinning wheel = 60mm / min, the fillet radii r of the front, middle, and rear spinning wheels = 10mm, the forming angle α of the front spinning wheel 前 = 25°, the forming angle α of the middle spinning wheel 中 = 30°, the forming angle α of the rear spinning wheel 后= 35°, the front, middle, and rear roller withdrawal angles α = 5°, the offset between the front roller and the middle roller is 5 mm, the offset between the middle roller and the rear roller is 5 mm. Using these process parameters, the outer diameter of the spun workpiece is Φ182 mm, the inner diameter is Φ168 mm, the workpiece length is 520 mm, and the wall thickness is 7 mm (5) Unload and cool after spin forming.

[0020] (6) The preformed bottomed cylindrical part after spinning needs machining.

[0021] All other process steps except hot spin forming are conventional machining methods. Example

[0022] It includes the following steps: (1) A newly developed titanium alloy bottomed cylindrical billet is preformed by die forging. The outer diameter of the preform is Φ188 mm, the inner diameter is Φ168 mm, the inner hole depth is 371.5 mm, and the wall thickness is 12 mm.

[0023] (2) The core die is preheated to 600 - 800 °C before spinning.

[0024] (3) The preform is heated to 850 - 900 °C in a heating furnace or directly on the core die for spin forming. Lubricant is evenly applied to the core die and the forging blank before spinning.

[0025] (4) Spin forming is carried out on a numerically controlled three - roller power spinning machine. The multi - pass power hot spin forming process is used for spin forming. Cooling water is passed through during the spin process of the core die and the rollers. During the spin process, supplementary heating is used to ensure that the temperature of the bottomed cylindrical forging blank is between 800 - 1000 °C for spin plastic forming. The spindle speed n = 120 r / min, the longitudinal feed rate of the rollers f = 144 mm / min, the fillet radius r of the front, middle, and rear rollers = 10 mm, the forming angle α of the front roller 前 = 25°, the forming angle α of the middle roller 中 = 30°, the forming angle α of the rear roller 后 = 35°, the front, middle, and rear roller withdrawal angles α = 5°, the offset between the front roller and the middle roller is 5 mm, the offset between the middle roller and the rear roller is 5 mm. Using these process parameters, the outer diameter of the spun workpiece is Φ182 mm, the inner diameter is Φ168 mm, the workpiece length is 550 mm, and the wall thickness is 7 mm (5) Unload and cool after spin forming.

[0026] (6) The preformed bottomed cylindrical part after spinning needs machining.

[0027] All other process steps except hot spin forming are conventional machining methods. Example

[0028] It includes the following steps: (1) A new type of titanium alloy bottomed cylindrical blank developed independently is forged into a preform. The outer diameter of the preform is Φ188mm, the inner diameter is Φ168mm, the inner hole depth is 371.5mm, and the wall thickness is 15mm.

[0029] (2) The core die is preheated to 600 - 800 °C before spinning.

[0030] (3) The preform is heated to 850 - 900 °C in a heating furnace or directly on the core die for spinning forming. Lubricant is evenly applied to the core die and the forging blank before spinning.

[0031] (4) The spinning forming is carried out on a numerically controlled three - roller power spinning machine, and the multi - pass power hot spinning process is used for spinning forming. Cooling water is passed through during the spinning process of the core die and the spinning wheels. During the spinning process, supplementary heating is used to ensure that the temperature of the bottomed cylindrical forging blank is between 800 - 1000 °C for spinning plastic forming. The spindle speed n = 240 r / min, the longitudinal feed rate f of the spinning wheel = 216 mm / min, the fillet radii r of the front, middle, and rear spinning wheels = 10 mm, the forming angle α of the front spinning wheel 前 = 25°, the forming angle α of the middle spinning wheel 中 = 30°, the forming angle α of the rear spinning wheel 后 = 35°, the withdrawal angle α of the front, middle, and rear spinning wheels = 5°, the stagger distance between the front spinning wheel and the middle spinning wheel is 5 mm, the stagger distance between the middle spinning wheel and the rear spinning wheel is 5 mm. Using these process parameters, the outer diameter dimension of the spun workpiece is Φ182mm, the inner diameter dimension is Φ168mm, the workpiece length is 600mm, and the wall thickness is 7mm. (5) After spinning forming, unloading and cooling are carried out.

[0032] (6) The pre - formed bottomed cylindrical part after spinning needs machining.

[0033] Except for the hot spinning forming, other process steps are conventional processing methods.

Claims

1. A forming method for a low-cost titanium alloy bottomed cylindrical part, characterized in that It includes the following steps.

2. (1) The bar blank of the bottomed cylindrical part is forged into a preform. The outer diameter of the preform is Φ203mm, the inner diameter is Φ167mm, the inner hole depth is 253mm, the total length is 260mm, and the wall thickness is 18mm.

3. (2) Preheat the core mold to 600 - 800 °C before spinning.

4. (3) Heat the forging blank in a heating furnace or directly on the core mold to 800 - 1000 °C, and perform spinning forming. Apply lubricant evenly to the core mold and the forging blank before spinning.

5. (4) The spinning process is carried out on a numerically controlled three-roller powerful spinning machine, and the spinning forming is carried out by using a three-pass powerful hot spinning process. The specific parameters are as follows: Cooling water is passed through the core mold and the spinning wheels during the spinning process. During the spinning process, supplementary heating is carried out to ensure that the temperature of the forging blank of the bottomed cylindrical part is between 800 - 1000 °C for spinning plastic forming. The fillet radius of the spinning wheels of the front, middle, and rear spinning wheels is r = 8 mm, and the forming angle α of the front spinning wheel 前 = 25°, the forming angle α of the middle spinning wheel 中 = 30°, the forming angle α of the rear spinning wheel 后 = 35°, the withdrawal angle α of the front, middle, and rear spinning wheels is 5°. The stagger distance between the front spinning wheel and the middle spinning wheel is 5 mm, and the stagger distance between the middle spinning wheel and the rear spinning wheel is 5 mm. The spindle speeds of the two passes are n = 100 and 120 r / min respectively, the longitudinal feed rate f of the spinning wheels is 60 and 144 mm / min respectively, and the reduction per pass is 5 mm and 5 mm. Using these hot spinning process parameters, affected by the springback amount, the outer diameter dimension of the workpiece after hot spinning is Φ183 - Φ185 mm, the inner diameter dimension is Φ167 mm, the workpiece length is 520 - 550 mm, and the wall thickness is 8 - 8.5 mm.

6. (5) For the third-pass hot spinning forming, the spinning wheels remain unchanged. The stagger distance between the front spinning wheel and the middle spinning wheel is 3 mm, and the stagger distance between the middle spinning wheel and the rear spinning wheel is 3 mm. The spindle speeds are n = 60, 80, and 100 r / min respectively, the longitudinal feed rate f of the spinning wheels is 40, 60, and 80 mm / min respectively, and the reduction of the spinning wheels is 0.5 - 1 mm. Select different reductions according to the different wall thicknesses of the workpiece. After cold spinning, the outer diameter dimension of the workpiece is Φ182 mm, the inner diameter dimension is Φ167 mm, the wall thickness is 7.5 ± 0.1 mm, and the workpiece length is 530 - 560 mm.

7. (6) Trim the edge after hot spinning, and the workpiece length is 492 mm. Except for the hot spinning forming, other process steps are all conventional processing methods.