Types and technical requirements of metal drawing process:
I. Types of metal drawing processes
(1) cylinder stretching: flange cylinder stretching. The flange and the bottom are straight, the cylinder is axisymmetric, the deformation is uniform on the same circumference, and the blank on the flange is drawn and deformed.
(2) Elliptical stretching: the blank on the flange is stretched and deformed, but the deformation amount and deformation ratio change accordingly. The greater the curvature, the greater the deformation of the blank; The smaller the curvature, the smaller the deformation of the blank.
(3) Rectangular drawing: a low rectangular part formed by one-time drawing. During stretching, the tensile resistance at the fillet of flange deformation zone is greater than that at the straight edge, and the deformation degree at the fillet is greater than that at the straight edge.
(4) Mountain-shaped stretching: the side wall is suspended during the process, and the die is attached after the forming. In the forming process, the deformation characteristics of different parts of the sidewall are not exactly the same.
(5) Yamagata stretching: The blank deformation of Yamagata cover plate is not a simple stretching deformation, but a composite forming in which stretching and bulging deformation coexist.
(6) Semi-spherical drawing with flange: When the spherical part is drawn, the blank part is in contact with the spherical top of the punch, and most of the rest is suspended.
(7) Flange stretching: shallow stretching the stretched flange part. Its stress and strain are similar to compression flanging.
(8) Edge stretching: Angular re-stretching of the flange requires good deformation of the material.
(9) Deep drawing: It can only be completed after more than two times of drawing. Wide flange drawing parts are drawn to the required flange diameter in the first drawing, and the flange diameter remains unchanged in subsequent drawings.
(10) Tapered drawing: Deep tapered parts are prone to local excessive thinning or even fracture due to the large degree of deep deformation, and need to be gradually formed through multiple transitions.
(1 1) Rectangular deep drawing: The deformation of high rectangular parts formed by multiple deep drawing is not only different from that of deep cylindrical parts, but also very different from that of low box parts.
(12) Curved surface forming: a stamping forming method with non-straight wall and non-flat bottom curved surface shape, in which the outer flange part of the metal plate blank is reduced and the inner flange part is extended.
(13) ladder diagram: redraw the initial diagram to form the ladder bottom. The deep part is deformed at the initial stage of drawing, and the shallow part is deformed at the later stage of drawing.
(14) Reverse painting: Reverse painting is a kind of redrawing. The reverse stretching method can increase the radial tensile stress and achieve good anti-wrinkle effect. It can also improve the tensile coefficient of re-stretching.
(15) Thinning drawing: Different from ordinary drawing, Thinning drawing mainly changes the wall thickness of the drawn part during drawing.
(16) panel stretching: the surface shape of the panel is complex. In the process of deep drawing, the deformation of blank is complex, and its forming nature is not simple deep drawing, but compound forming with both deep drawing and bulging.
Second, the metal wire drawing process scheme
(1) According to the drawings of the workpiece, analyze the shape characteristics, size, accuracy requirements, raw material size, mechanical properties of the workpiece, and combine the available equipment, batch number and other factors. Good drawing process should ensure less material consumption, fewer processes and less equipment occupation.
(2) Calculation of main process parameters Through the analysis of stamping process, the characteristics and difficulties of the process are found out, and various possible drawing process schemes are put forward according to the actual situation, including the nature, quantity, sequence and combination of the process. Sometimes there may be several feasible technological schemes for the same workpiece. Usually, each scheme has its own advantages and disadvantages, so it is necessary to comprehensively analyze and compare and determine the best scheme.
(3) Process parameters refer to the data on which the process plan is made, such as various forming coefficients (drawing coefficient, bulging coefficient, etc.). ), parts development size and various stresses. There are two ways to calculate. Firstly, the process parameters can be accurately calculated, such as the material utilization rate of parts layout and the workpiece area. Second, the process parameters can only be approximately calculated, such as the general bending or deep drawing forming force, the unfolding size of complex parts blank and so on. These process parameters are generally roughly calculated according to empirical formulas or charts, and some of them need to be adjusted through experiments.
(4) Selection of stretching equipment According to the nature of the process to be completed and the stress and energy characteristics of various equipment, the main factors such as the required deformation force and size are comprehensively considered, and the type and tonnage of equipment are reasonably selected in combination with the existing equipment.
Third, the selection method of stretching oil products
(1) Because silicon steel sheet is a relatively easy-to-stretch material, low-viscosity stamping oil will be selected on the premise of preventing scratches, so as to facilitate the cleaning of finished workpieces.
(2) When selecting drawing oil for carbon steel plate, the better viscosity should be determined according to the process difficulty and degreasing conditions.
(3) Due to chemical reaction with chlorine additives, attention should be paid to the problem of white rust in chlorine drawing oil when selecting drawing oil for galvanized steel sheet, and the problem of rust can be avoided by using sulfur drawing oil.
(4) Stainless steel is easy to harden, so drawing oil with high oil film strength and good sintering resistance is needed. Generally, drawing oil containing sulfur and chlorine compound additives is used to ensure extreme pressure performance and avoid burr and fracture of the workpiece.