Spinning process for wheel hub made of magnesium alloy

Description

Technical Field

[0001] The invention relates to the technical field of wheels, in particular to a spinning process of a magnesium alloy wheel hub.Background

[0002] Magnesium alloy is an alloy based on magnesium and other addition elements, with low density, high specific strength, large specific elastic modulus, good heat dissipation and shock elimination, the ability to bear impact load greater than that of aluminum alloy, and the corrosion resistance of organic matter and alkali, and is the lightest metal among practical metals with the specific gravity of magnesium being about 2 / 3 of that of aluminum and 1 / 4 of that of iron, so it is widely used in automobile, aviation and aerospace fields, especially in automobile field. For example, parts made of magnesium alloy can make automobiles lightweight. Nowadays, for increasingly high demand of lightweight automobiles, the application of aluminum alloy has encountered a bottleneck in the weight reduction effect of automobiles, so the application of magnesium alloy in automobiles is imperative. In recent years, the automobile industry has developed rapidly and changed greatly. Many countries all over the world have introduced the deadline of banning the sale of fuel vehicles. The large-scale application of electric vehicles has brought opportunities for the development of magnesium alloy auto parts.

[0003] Magnesium alloy wheel hub has won the favor of more and more users because of its beautiful appearance, safety and comfort. Because of its light weight and high manufacturing precision, magnesium alloy wheel hub has small deformation and small inertia resistance when rotating at high speed. Magnesium alloy wheel hub has the metal characteristics of absorbing vibration and rebound force. After machining by NC machine tools, it has high dimensional accuracy, high roundness, small yaw runout and good balance, which makes the automobile run smoothly and comfortably.

[0004] At present, the forging production method of magnesium alloy wheel hub usually adopts forging and extrusion process, the spoke part is usually obtained by forging process, and the wheel rim part is usually obtained by extrusion process.

[0005] It is well known that the properties of forging materials are closely related to forging process and sequence. In the spinning process of magnesium alloy, the selection of spinning process and sequence will have an important impact on the performance of magnesium alloy wheel hub. Because of the face-centered cubic structure of magnesium alloy materials, magnesium alloy materials show poor spinning properties. Even if the corresponding products can be forged by traditional forging and extrusion process, they often show poor material properties.

[0006] CN 107 363 474 A refers to a production process and system for magnesium alloy wheel hub. CN 110 331 320 A refers to a corrosion resistance and high temperature resistance magnesium alloy wheel hub and preparation method thereof.

[0007] TW 201 800 162 A refers to near net shape forged magnesium alloy wheels and method of manufacturing the same.Summary

[0008] The present disclosure provides a spinning process of a magnesium alloy wheel hub according to claim 1. Some features of optional or preferred embodiments are recited in the dependent claims.

[0009] In view of this, the invention aims to provide a spinning process of magnesium alloy wheel hub, which improve the spinning property of magnesium alloy material, and obtain magnesium alloy wheel hub with excellent mechanical properties.

[0010] The manufacturing method of the magnesium alloy wheel hub of the invention has the following advantages: In the invention, the magnesium alloy bar is heated to a preset temperature, so that the magnesium alloy bar is easier to deform and is not easy to generate forging cracks. The finally forged blank is treated with low temperature insulation first, then heated up and solid dissolved for more than 16 h, and then spun directly at the solid solution temperature of 390 ~< 420°C. Spinning is carried out in three times, the thinning (machining) amount is 25 ~< 36%, 14 ~< 22%, 6 ~< 12% respectively, the total thinning amount reaches 45 ~< 70%. The feed speed needs to be controlled at 120 ~< 190 mm / min, and the spindle speed is controlled at 280 ~< 350 r / min, so that the deformation process of magnesium alloy is more continuous, the spinning process is easier, and the magnesium alloy wheel hub with excellent performance is obtained, which greatly improves the spinning process and machining efficiency.

[0011] The magnesium alloy wheel hub obtained by the above method still has excellent mechanical properties, which meets the requirements of American wheel SAE J175 and SAE J328-2005, namely, 13-degree impact strength, radial fatigue and bending fatigue performance, and can also

[0012] The manufacturing method of the magnesium alloy wheel hub of the invention has the following advantages: In the invention, the magnesium alloy bar is heated to a preset temperature, so that the magnesium alloy bar is easier to deform and is not easy to generate forging cracks. The finally forged blank is treated with low temperature insulation first, then heated up and solid dissolved for more than 16 h, and then spun directly at the solid solution temperature of 390 ~< 420°C. Spinning is carried out in three times, the thinning (machining) amount is 25 ~< 36%, 14 ~< 22%, 6 ~< 12% respectively, the total thinning amount reaches 45 ~< 70%. The feed speed needs to be controlled at 120 ~< 190 mm / min, and the spindle speed is controlled at 280 ~< 350 r / min, so that the deformation process of magnesium alloy is more continuous, the spinning process is easier, and the magnesium alloy wheel hub with excellent performance is obtained, which greatly improves the spinning process and machining efficiency.

[0013] The magnesium alloy wheel hub obtained by the above method still has excellent mechanical properties, which meets the requirements of American wheel SAE J175 and SAE J328-2005, namely, 13-degree impact strength, radial fatigue and bending fatigue performance, and can also meet the requirements of national standards GB / T 5334-2005 and GB / T 15704-1995 for wheel strength and fatigue and industry standard QC / T 991-2015 for passenger car light alloy wheel 90-degree impact test method.Brief Description of the Drawings

[0014] Fig. 1 is a flow diagram of a spinning process of a magnesium alloy wheel hub of the present invention. Fig. 2 is a schematic diagram of bar of a magnesium alloy wheel hub in the spinning process of the present invention. Fig. 3 is a diagram of finally forged blank of a magnesium alloy wheel hub in the spinning process of the present invention. Fig. 4 is a cross-sectional view of hub of the manufacturing method of a magnesium alloy wheel deformation.

[0015] In the cutting process of magnesium alloy bar, the most suitable and economical bar length is selected by calculating the material length and material ratio of each magnesium alloy wheel hub in advance, and the bar is cut by a metal cutting machine; in the heating process of magnesium alloy bar to the temperature required for forging deformation, the magnesium alloy bar is heated to a certain temperature in a heating furnace and is kept the temperature for a period of time, wherein, the heating furnace can be an electromagnetic heating furnace and the like; the preset temperature is greater than or equal to 360°C, but it is not allowed to exceed 420°C; 400°C is the temperature at which magnesium alloy deformation is most easy and fracture is not easy, which ensures that there will be no crack in the subsequent forging process. Step 2. The magnesium alloy bar is initially forged and formed to obtain initially forged blank. The blank shown in FIG. 2 is initially forged and formed, and the forging down-pressing speed is control at 6-15 mm / s. The purpose of initial forging is to position, which ensure that the bar does not crack during forging.

[0016] Step 3. The bar is finally forged and formed to obtain hub blank with spoke basic structure, as shown in Fig. 3.

[0017] Step 4. The finally forged magnesium alloy blank is subjected to stress relief annealing at a holding temperature of 300-350°C and a holding time of 6-8 h. The purpose of stress relief annealing is to remove internal stress, release deformation energy storage or weaken deformation energy storage, and prevent abnormal grain growth during subsequent heating. Step 5. The finally forged magnesium alloy blank is solid dissolved and kept the temperature at 390-420°C, and the solid solution time is greater than or equal to 16 h. The purpose of solid solution is to solid solve the precipitated phases in AZ80 alloy and ZK60 alloy to the matrix, make the alloy elements uniformly distributed, reduce the composition segregation at the grain boundary, and make the grains more prone to recrystallization.

[0018] Step 6. The solid-dissolved blank is taken out and spun directly by using a spinning machine. Spinning is carried out in three times. The thinning (processing) amounts are 25-36%, 14-22%, 6-12% respectively and the total thinning amount reaches 45-70%. The feed speed needs to be controlled at 120-190 mm / min and the spindle speed is controlled at 280-350 r / min. The purpose of three-times spinning is that the selected AZ80 magnesium alloy and ZK60 magnesium alloy have poor shaping deformation, and the one-time processing capacity is too large, which will cause tension crack. The purpose of controlling spinning speed is to prevent the speed from being too slow, and the temperature drops too fast during spinning, which will lead to narrow processing interval, while the spinning speed is too fast, which will cause transverse tension crack. The wheel rim structure after spinning is shown in Fig. 7.

[0019] Step 7. Heating treatment is carried out. Aging treatment is carried out, with aging temperature of 140-170°C and aging time of 16-24h.

[0020] Step 8. According to the drawing and design requirements of magnesium alloy wheel hub, the magnesium alloy wheel hub meeting the requirements is processed by NC machining center machine tool, as shown in Fig. 4.

[0021] As shown in Figs. 5 and 7, the spinning wheel rim part has excellent microstructure and mechanical properties, with yield strength reaching 213 MPa, tensile strength reaching 329 MPa and elongation reaching 16%.

[0022] As shown in Fig. 5, it can be observed from the drawing that the microstructure of wheel rim is fine and uniform, showing complete recrystallization structure, with yield strength reaching 184 MPa, tensile strength reaching 291 MPa and elongation reaching 5%.

[0023] The traditional forging and extrusion process needs large tonnage forging equipment, which has high processing risk, large metal loss and high cost.

[0024] As shown in Figs. 6 and 7, it can be observed from the drawings that the wheel rim of the wheel obtained by the traditional extrusion process has incomplete recrystallization structure with uneven grain size, yield strength reaching 177 MPa, tensile strength reaching 296.5 MPa and elongation reaching 7.3%.

[0025] Various performance tests were carried out on the magnesium alloy motor vehicle hub of Example 1. In the test center of CITIC Dicastal Co., Ltd., 13-degree impact strength, radial fatigue, bending fatigue and other wheel strength and fatigue tests were carried out on the above wheels. The test shows that the wheel hub meets the requirements of American wheel SAE J175 and SAE J328-2005, that is, 13-degree impact strength, radial fatigue and bending fatigue performance, and can also meet the requirements of national standards GB / T 5334-2005, GB / T 15704-1995 wheel strength and fatigue performance and industry standard QC / T 991-2015 passenger car light alloy wheel 90-degree impact test method.

[0026] A 90-degree impact test was done on the magnesium alloy wheel hubs with traditional forging process and magnesium alloy wheel hubs with new spinning process according to the requirements of industry standard QC / T 991-2015. The results show that the deformation of inner wheel rim of magnesium alloy wheel hub after impact by traditional forging and extrusion process is 12 mm, which indicates the wheel rim strength, and the deformation of inner wheel rim of magnesium alloy wheel hub after impact by new spinning process is 6.7 mm. The impact resistance of magnesium alloy wheel hub produced by new spinning process is stronger. It can be inferred that if the same use requirements are met, the weight reduction space of magnesium alloy wheel hub produced by the new spinning process is larger.

[0027] The manufacturing method of the magnesium alloy wheel hub of the invention has the following advantages: In the invention, the magnesium alloy bar is heated to a preset temperature, so that the magnesium alloy bar is easier to deform and is not easy to generate forging cracks; the finally forged blank is solid dissolved for more than 16 h, and then is spun directly at the solid solution temperature of 400-420°C. Spinning is carried out in three times, the thinning (machining) amount is 25-36%, 14-22%, 6-12% respectively, the total thinning amount reaches 45-70%, the feed speed needs to be controlled at 120-190 mm / min, and the spindle speed is controlled at 280-350 r / min, so that the deformation process of magnesium alloy is more continuous, the spinning process is easier, and the magnesium alloy wheel hub with excellent performance is obtained, which greatly improves the spinning process and machining efficiency.

[0028] The magnesium alloy wheel hub obtained by the above method still has excellent mechanical properties, which meets the requirements of American wheel SAE J175 and SAE J328-2005, namely 13-degree impact strength, radial fatigue and bending fatigue performance, and can also meet the requirements of national standards GB / T 5334-2005 and GB / T 15704-1995 for wheel strength and fatigue and industry standard QC / T 991-2015 passenger car light alloy wheel 90-degree impact test method. The following table is the reliability test data table of impact and fatigue. Preparation process90-degree impact (wheel rim deformation )Radial fatigueBending fatigue (heavy load)Bending fatigue (light load)13-degree impactTraditional forging process12 mm2.8 million (limit)350,000 (limit)1.9 million (limit)QualifiedNew spinning process6.7 mm3.6 million (limit)500,000 (limit)6 million (limit)Qualified properties, which meets the requirements of American wheel SAE J175 and SAE J328-2005, namely 13-degree impact strength, radial fatigue and bending fatigue performance, and can also meet the requirements of national standards GB / T 5334-2005 and GB / T 15704-1995 for wheel strength and fatigue and industry standard QC / T 991-2015 passenger car light alloy wheel 90-degree impact test method. The following table is the reliability test data table of impact and fatigue. Preparation process90-degree impact (wheel rim deformation )Radial fatigueBending fatigue (heavy load)Bending fatigue (light load)13-degree impactTraditional forging process12 mm2.8 million (limit)350,000 (limit)1.9 million (limit)QualifiedNew spinning process6.7 mm3.6 million (limit)500,000 (limit)6 million (limit)Qualified

[0029] The scope of protection of the present application is defined by the appended claims.

Claims

1. A spinning process of a magnesium alloy wheel hub, wherein the spinning process comprises the following steps: Step 1, heating the magnesium alloy bar at 350~430°C and keeping the temperature for 20 minutes; Step 2, initially forging and forming on the bar under a forging press, wherein the forging down-pressing speed is 6~15 mm / s; Step 3, finally forging and forming on the bar under a forging press, wherein the forging down-pressing speed is 5~8 mm / s; wherein Step 4, stress relief annealing on the finally forged magnesium alloy blank; Step 5, solid dissolving on the annealed magnesium alloy blank, wherein the solid solution temperature in step 5 is 390~420°C and the holding time is equal to or more than 16 hours; Step 6, taking out the solid-dissolved blank and directly spinning by a spinning machine, wherein the spinning process in step 6 is carried out in three times, and the spinning thinning amounts are 25~36%, 14~22% and 6~12%, respectively, and the total thinning amount reaches 45~70%, and the spinning feed speed is 120~190 mm / min and the spindle speed is 280~350 r / min; Step 7, heating treatment and aging treatment; wherein the magnesium alloy comprises an AZ80 magnesium-aluminum-zinc alloy or a ZK60 magnesium-zinc-zirconium alloy.

2. The spinning process of a magnesium alloy wheel hub according to claim 1, wherein the forging press comprises a 6000-ton forging press.

3. The spinning process of the magnesium alloy wheel hub according to claim 1, wherein the stress relief annealing temperature in step 4 is 300~350°C and the holding time is 6~8 hours.

4. The spinning process of the magnesium alloy wheel hub according to claim 1, wherein the solid solution temperature in step 5 is 390~420°C and the holding time is 16~24 hours.

5. The spinning process of the magnesium alloy wheel hub according to claim 1, wherein the aging treatment temperature in step 7 is 140~170°C and the aging treatment time is 16~24 hours.

6. The spinning process of the magnesium alloy wheel hub according to claim 1, wherein the magnesium alloy wheel hub is manufactured by machining after aging treatment.