Introduction and Comparative Performance of Commonly Used Metal Spin Forming Materials

　　Common CNC Spin Forming Metal Materials
　　Many metal materials can be used for CNC spin forming, such as aluminum, iron, copper, stainless steel, titanium, molybdenum, etc. We choose metal blanks and metal tubes as the raw materials for spin forming. Blanks are generally laser-cut from specification plates, which are divided into hot-rolled and cold-rolled plates. Cold-rolled plates have higher hardness than hot-rolled plates, but better spin forming performance, because hot-rolled plates have tiny pores inside before cold rolling, which are prone to cracking during spin forming. Tubes include extruded tubes and welded tubes, both of which can be used as spin forming blanks. The precision of extruded tubes after spin forming is higher than that of welded tubes. We need to understand the material properties of different spin-formed metals, and the spin forming performance of different materials will be introduced below.
　　By comparing the above spin forming materials, we find that the spin forming performance of aluminum, pure copper, and iron is better than that of stainless steel, titanium, and brass, mainly because of their better ductility. All materials will undergo work hardening and grain refinement during cold spin forming, and the strength of the blank after spin forming will be much better than other processing methods under the same wall thickness. The greater the material rebound performance, the lower the precision of the formed material. The lower the material hardness, the better the surface quality of the spin-formed product.
　　① Hardness: Aluminum (excluding aluminum alloy) < Pure copper < Brass < Iron < Titanium < Stainless steel
　　The higher the hardness, the greater the spinning pressure required, and the faster the wear of the spinning die and spinning roller.
　　② Ductility: Aluminum (excluding aluminum alloy) > Red copper > Iron > Stainless steel > Brass > Titanium
　　The worse the ductility, the easier it is for the metal to crack during spin forming.
　　③ Tensile strength: Aluminum (excluding aluminum alloy) < Pure copper < Brass < Iron < Stainless steel < Titanium
　　If the tensile strength is high, the spinning pressure required is greater.
　　④ Internal pressure: Aluminum (excluding aluminum alloy) < Pure copper < Brass < Iron < Stainless steel < Titanium
　　Internal pressure will cause the material to rebound, which will affect the precision, so the precision of stainless steel and titanium is difficult to control.
　　Commonly Used Die Materials for Spin Forming
　　45# steel and CR12 steel are commonly used as spin forming die materials.
　　45# steel is commonly used for aluminum spin forming. 45# steel has low hardness, is easy to process, and has low material cost. Because spin forming aluminum requires a relatively slow die speed, 45# steel can generally meet the requirements. The service life of 45# steel for spin forming aluminum is 5 years. If the inner wall surface of the product requires a bright surface, because the inner wall surface quality of the product is related to the surface quality of the die, CR12 steel should be selected as the die material. This material has high hardness and better wear resistance after heat treatment, and can reach a mirror finish after fine machining and polishing.
　　CR12 steel dies are required for iron and stainless steel spin forming, because iron and stainless steel have high hardness and cause greater wear on the dies. 45# steel is easily worn, resulting in reduced die size and die scrap. The service life of CR12 dies for processing iron and stainless steel is 10 years.
　　Commonly Used Materials for Spin Forming Rollers
　　Commonly used materials for spin forming rollers include CR12 steel, high-speed steel, and tungsten steel.
　　After heat treatment, CR12 steel rollers have a relatively long service life when processing aluminum products. However, stainless steel and iron have high hardness, and the processing temperature is high. Long-term use of CR12 will cause serious scratches on the surface of the roller, which will in turn scratch the surface of the formed product, or the wear rate will be too fast, affecting the gap between the roller and the die, causing production instability. Using high-speed steel improves the hardness, wear resistance, and high-temperature resistance of the roller, but the toughness of high-speed steel is insufficient after heat treatment, and it is easy to chip when subjected to large forces. Spin forming rollers can also use CR12 with a tungsten steel coating on the surface to increase the hardness and wear resistance of the roller surface. When the surface of aluminum parts needs to be polished during spin forming, tungsten steel can be used as the material for the polishing surface.