1 Introduction
Alloy wheels are light weight, low cost, the advantages of high strength and thermal conductivity of aluminum with a strong performance can be greatly extended auto, motorcycle tire service life, especially high-load truck tire life. (According to the European wheel manufacturers "ALCOA" company test data, aluminum alloy wheels may be extended up to 20% tire life).
2 issues raised
In recent years, with the international market wheel manufacturers continue to improve the production process, Europe and the United States with a strong spin the wheel industry to gradually replace the conventional aluminum alloy wheel hub production process, the domestic industry is also moving the wheel of advanced production technology, the development of aluminum alloy wheels . The following is typical of a company need custom-made wheel hub (Figure 1). 6061 alloy wheel aluminum materials, (equivalent to domestic grades LD30).
3 wheel metal spinning processing equipment
PT30501CNC wheel horizontal metal spinning machine, metal spinning workpiece diameter φ100 ~ φ1000mm, roller vertical travel 1900mm, the maximum metal spinning force of 30 tons. These machine parameters shows that the station metal spinning wheel metal spinning machine to meet the process requirements.
4 alloy wheels metal spinning program
4.1 Hub Material 6061 alloy aluminum metal spinning performance analysis
6061 aluminum alloy is Cu-Mg-Si-Mn series aluminum alloy, its chemical composition is as follows:
Cu-0.15% ~ 0.4%, Mg-0.45% ~ 0.9%, Si-0.4% ~ 0.8%, Mn-0.15%; the kinds of materials in solution and aging state of the mechanical properties of indicators:
σb ≥ 320Mpa, δ5 ≥ 12%, ψb ≥ 25%, HB ≥ 120.
Therefore, the 6061 aluminum alloy in the solution and aging state of the spin index will be - a single-pass thinning rate limit:
φmax = ψb / (0.17 ψb) × 100% = 0.25 / (0.17 0.25) × 100% = 60%.
This indicator shows the value of it can spin rotation than high strength steel can be of some difference, metal spinning process, where necessary, adequate heating, the workpiece heating temperature 310 ℃ ~ 350 ℃. In addition, to improve the rotation of aluminum alloy can be appropriately adding some mineral elements - antimony and strontium (0.02%).
4.2 Project Choice metal spinning wheel
Symmetrical dish like this wheel, metal spinning can be used to take the general form of metal spinning plates or split-type cast (forged) piece of rough for two powerful metal spinning process methods. Split metal spinning disc-shaped slab is split round by using hierarchical process, so rough was hack in the central two decile, after, and then molding molding can metal spinning round progressive; power metal spinning process is rough cast aluminum billet or forging a number of passes of strong spin molding, metal spinning wheel surface to size requirements, power metal spinning process produced by the weight wheel forged wheel reduces the weight of about 25%, because the strong spin process can spin out of the system variable section thickness, to meet the requirements of strength index of the wheel under the premise of wheel thickness can be properly thinned.
As I plant PT30501CNC machine into a 75 ° vertical and horizontal angle to the ball screw, when the programming track roller moves only along the radial parts, machine tool during the actual campaign took part in the axial displacement of the roller, making the process of metal spinning process split round the outer edge of the axial end by a certain pressure, it's backlash ball screw drive directly on the machine tool parts, precision of the machine tool service life and, therefore, this structure is not conducive to split-style metal spinning wheel. Based on the above analysis, we chose metal spinning process for forming such a symmetrical dish aluminum wheels.
4.3 Hub power metal spinning process routes
Precision forging strong spin rough first pass
The second pass strong spin transfer molding machine plus wheels CNC workshop finished.
5. Technology program implementation
5.1 Equipment Design
metal spinning core mold material selection, surface finish Ra0.4 ~ Ra0.8um; forming roller preform angle °, radius mm, material selection, heat treatment and hardness.
5.2 metal spinning blank design
Using solid modeling software (Solidworks, MastCAM, etc.) draw metal spinning wheel parts modeling, and the metal demand volume. Calculation based on volume invariance metal spinning forging blank.
5.3 Process of implementation of the effect of strongly swirling
The first pass metal spinning process parameters: S = 0r/min, feed ratio F = 0mm / r, the second-pass power metal spinning process parameters: S = 0r/min, F = 0mm / r.
Beginning of the trial process, with R15 forming wheels spin forming two times stronger, in the test process from the accumulation of skin, crack defects. Subsequently, the Rmm round shape round to R, and increases the metal spinning core module on the transition radius, from the skin, crack was to eliminate defects. We believe that this accumulation was mainly due to defect from the skin forming metal spinning wheel radius is smaller and no pre-formed corner, metal spinning the metal by the force of smaller, part of the deformation of metal unable to participate, together with the workpiece surface complex , poor flow of material deformation; blank at the bottom of Rmm arc rupture was mainly due to metal spinning tires rough and die radius Rmm in the area is too small, leading to stress concentration during deformation is more severe, and where the maximum rate of material deformation , reaching about 65% more than the 6061 aluminum alloy (LD30) of the spin reduction rate of 60% limit, resulting in severe hardening phenomenon.
The test analysis indicated that the initial metal spinning blank, there are some tire metal spinning mold design. metal spinning blank piece of metal volume should be required to meet the prerequisite conditions, the appropriate reduced the thickness of metal metal spinning parts (that is, ensuring the same volume of metal billets under the premise of increasing height, reducing the billet diameter) to This lower reduction rate of metal spinning, metal spinning reduced hardening problem; metal spinning mode transition radius of the surface of fetal type generally small, and the processing of surface finish does not meet the design requirements of Ra0.8mm. According to the results on metal spinning in front of and quality of analysis, we test parts on the back of the metal spinning process to make the appropriate adjustments to the program, changed three times to two times metal spinning, forming roller are used Rmm. Accumulation, from the skin defects were basically resolved, but the workpiece surface both inside and outside the big end there tearing. We believe that the phenomenon is due to the parts of material in two sub-metal spinning process are not fully up to punch in a universal rotary molding, metal was able to move the extension is due to the roller surface with a metal billet forward Mobile, materials generated within the tensile stress, compressive stress state and not. Tear for the workpiece, we will pre-forming roller angle from ° to °, metal spinning from the rough outside diameter φ427mm to φ421mm, and so to reduce the metal spinning deformation zone thickness, thinning reduced pass rate. Also on the metal spinning wheel trajectory was amended, and the material flow more smooth, breaking the workpiece has been resolved.
metal spinning wheel parts for the solution heat treatment, guaranteeing a more stable shape and size of aluminum wheel products, while improving the mechanical properties of wheel.
6. Conclusion
metal spinning process using strong program in PT30501CNC horizontal metal spinning wheel spin machine system 6061 aluminum alloy wheels is feasible, but must be designed to create a reasonable metal spinning mandrel and roller, and select the reasonable metal spinning process parameters to solve the problem arising in the process of metal spinning wheel accumulation of defects such as peeling and cracking.