Blank Sheet Precautions
Date: Mar,12 2020 View:
Blank Sheet Precautions
1. Precautions for aluminum and its alloys during forming
(1) The surface of aluminum is easy to be scratched. Pay full attention to the corner radius and feeding speed of the roller.
(2) In principle, it is advised not to use a blank back pressure roller, and it is best to use a rubber roller or a plastic roller when needed.
(3) Promote the use of hard plastic rollers.
(4) Alumina powder and peeling are easy to occur during the forming of aluminum plate. Care should be taken to choose the shape of roller, such as taking a slightly larger roller radius.
(5) If the anisotropy of the blank is large during shear forming as well as the outer edges are not uniform, the outer edges can be trimmed with a spare edger while forming to reduce the tendency of fracture.
(6) In multi-path shear forming, the surface roughness obtained by unidirectional shear forming is smaller than obtained by reciprocating shear forming.
(7) Hard surface alloy rollers can also be used to achieve good surface roughness, and alumina powder is not easy to adhere to the rollers.
(8) When using the forward path to make the thickness too thin, you can use the return path spinning to make the thickness thicker.
(9) For the cutting of the flange part, if a board axe-shaped cutter (refer to the figure below) is used, it will cut well and quickly, and the amount of tool can reach 1mm / r. Pay attention to the handling of chips and consider safety.
2. Precautions for brass and copper during forming
(1) Brass is prone to work hardening, so it is necessary to perform intermediate stress relief annealing during forming.
(2) When forming brass parts, you can also spin-form while heating
(3) The path arrangement of shear forming should be minimized.
(4) Brass thin-walled parts are easy to break, so special attention should be paid to the determination of the path.
(5) When the cylindrical part is beaded in the axial direction, the curled surface is prone to peel, so use a suitable shape of roller
(6) Annealing is required before spinning copper pipe and the deformation rate should be paid attention to.
(7) When the copper plate is subjected to shear forming, the counter pressure roller should be a rubber roller.
3. Precautions for mild steel during forming
(1) The test proves that the purity of the material composition and the size of the crystal grains have a significant effect on the spinning ability of the material. For example, the higher the oxygen content in carbon steel, that is, the more impurities such as oxides (sulfur dioxide, phosphorus oxide, etc.), the worse the spinning ability and the easier to crack during spinning.
(2) Q235A steel plate is one of the most commonly used materials for shear forming parts. However, this type of steel plate purchased from the market, although the steel grade is the same, has a large difference in spinning ability, and some cannot even be cold-spun. This is not only related to the metallographic structure and heat treatment of the steel plate when it leaves the factory, but also related to the harmful oxide impurity content, so the spinning ability varies greatly.
(3) Low carbon steels, such as 08F, No. 10 steel and Q235A, have superior spinning ability, but take care to prevent instability during spinning. When the carbon content is less than 0.06%, coarse crystals may also appear, and the ultimate deformation rate is reduced. Medium carbon steel is rotatable, but has high strength, poor plasticity and a narrow range of process parameters. In addition, the spinning ability of open hearth steel is superior to that of converter steel.
(4) In the carbon steel materials, most of the low-carbon steels and low-alloy steels with good plasticity can be spin-formed at room temperature with a large amount of deformation, and some must be hot-spun under heating.
(5) The shear forming test of the conical part of the thin steel plate blank shows that the instability and wrinkling of the flange during the spinning of the workpiece is related to the yield point of the material.
4. Precautions for stainless steel during forming
(1) In the case of multi-path shear forming and spinning, if it is used for round drawing, it is easy to break, so unidirectional deep drawing should be performed.
(2) When the stainless steel slab is subjected to multi-path deep-drawing and spinning, it is difficult to form due to severe work hardening, high resistance to deformation, and a serious tendency of workpiece surface adhesion. Austenitic stainless steel has superior spinning ability in the solid solution state. For example, 1Cr18Ni9 steel in 18-8 stainless steel has a higher nickel content and a lower carbon content, which is easy to spin-form. The situation is better when its carbon content is controlled below 0.03%. However, the spinning ability of martensitic stainless steel 2Cr13 and ferritic-martensitic stainless steel 1Cr13, Cr17Ni2, etc. is poor. It is necessary to strictly control the composition, heat treatment specifications and spinning specifications of these materials to avoid spinning cracks. The spinning ability of Cr17Ni2 in ferritic-martensitic steel is worse than that of 1Cr13.
(3) When drafting the technical solution of stainless steel workpieces, it should be studied in advance whether the structural shape of the workpiece can be changed to make it suitable for shear forming.
(4) When the stainless steel cylindrical parts are thinned and spun, the wall thickness reduction rate in one path should be as close as 30%. It will be difficult to increase it further.
(5) When using stamped preforms, consider whether or not heat treatment is performed to relieve stress before spinning according to the degree of work hardening experienced by this preform.
(6) During continuous forming, the temperature rise caused by the deformation heat of the core mold and rollers is likely to cause the change of the set gap. Therefore, it is necessary to use water-soluble coolant for cooling.
(7) Roller wear is serious, so it is generally suitable to use hard alloy roller.
(8) In order to facilitate the dressing of worn-out rollers or manufacture new rollers, it is best to save the processing template of the rounded portion of the roller that can be formed smoothly from the beginning.
