RU2635990C2 - Method to form part of semispherical shape from hard-deformable titanium alloy bt6-c in one die - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: preliminary drawing of a blank from sheet into conical cup with use of a cone clamp is carried out. A weakening annealing of the blank is carried out to finishing drawing of the blank in a single die is performed. Forming of flat sheet blanks at different thicknesses into conical cup is performed in the die with heating and specific taper angle of the die and the clamp.

EFFECT: reduced thinning in the process and improved quality of the parts.

2 dwg

Description

The invention relates to the field of metal forming, and in particular to a method of stamping a hemispherical part from a hard-to-deform titanium alloy in one die, in particular from a VT6-C titanium alloy.

The existing technologies for producing hemispherical shaped parts involve two main technological processes: volumetric stamping followed by machining of the workpiece to the required thickness and sheet stamping with preheating of the workpiece in the furnace.

A known method of sheet stamping, which consists in forming a heated flat billet from a sheet in several dies for several transitions with a flat clip. Hardening in the process of stamping is characteristic of titanium alloys and this necessitates the drawing of parts in several transitions, which entails the manufacture of die tooling for each stamping transition (V.P. Romanovsky. Handbook of cold stamping. - L.: Mechanical Engineering, 1979, p. 208). When stamping according to well-known schemes, thinning in the bottom of the stamped hemisphere reaches more than 20% of the initial thickness, which leads to the need to choose the initial thickness of the workpiece that is 1.8 ÷ 2 times greater than the thickness of the finished part.

The disadvantage of these methods is the inability to provide the maximum allowable degree of thinning of hemispherical parts from VT6-C alloy.

As a result of a patent search, no information sources were found containing information about the method of stamping a hemispherical part from VT6-C titanium alloy in one stamp.

The technical result to which this invention is directed is to reduce the amount of thinning of a hemispherical part, which does not allow the destruction of the part during the drawing process, at the optimum drawing ratio.

This technical result is achieved using a method of stamping a hemispherical part from a hard-deformed titanium alloy VT6-C in one stamp. The method includes preliminary drawing of a heated flat sheet billet into a conical cup with a cone clamp in a conical matrix heated to 220 ± 10 ° C, softening the annealing of the resulting cup, and final drawing of the conical cup with a cold punch in the heated matrix into a hemispherical part. In this case, a matrix and a clamp are used with taper angles determined by the formula:

где

Where

Dzag. - diameter of the initial billet, mm;

Ddet. - diameter of the part, mm;

- коэффициент вытяжки для сплава ВТ6-С,

- drawing ratio for alloy VT6-S,

dk is the maximum diameter of the conical cup.

Stamping is carried out in a conical matrix and the same clamp (V.P. Romanovsky. Handbook of cold stamping. - L .: Engineering, 1979, p. 122). In the case of the use of a cone clamp, the angle of coverage of the billet with a radius of curvature of the edge of the matrix is reduced, which leads to a decrease in the meridional (tensile) stresses, a decrease in the drawing force, and, consequently, a decrease in the amount of thinning of the bottom of the hemisphere. To reduce the amount of thinning, stamping is carried out with a cold punch in a heated matrix, which also does not allow the metal to be thinned in the touch zone of the punch, and the heated workpiece is covered with a cold punch. Thinning in the bottom of the stamped part with this stamping method is not more than 8%, which allows the use of blanks with an initial thickness of 8-10% more than the final thickness of the part after machining and, therefore, use less expensive blanks.

The invention is illustrated by drawings.

In FIG. 1 shows a sequence diagram of the shaping of a part, indicating the designation of stamping parameters; in FIG. 2 is a diagram of a stamp with an indication of its structural elements.

Empirically, the maximum allowable drawing coefficient m (m = 1.12) was obtained for the VT6-C alloy when drawing a heated flat sheet billet into a conical cup with a cone clamp in a heated conical matrix. The heating temperature of the matrix to prevent rapid cooling of the part during shaping is determined empirically and is 220 ± 10 ° C.

At a higher drawing coefficient for the indicated stamping conditions, the part was destroyed. Proceeding from this, the optimum taper angle of the matrix and the clamp for stamping a part from a VT6-C titanium alloy of a hemispherical shape in one stamp is determined using the experimentally derived maximum allowable drawing coefficient m = 1.12.

The method is as follows.

A flat sheet billet is mounted on a matrix 1 with a heating temperature of 220 ± 10 ° C. The clamp 2 forms the workpiece into a conical cup and presses it against the conical surface of the matrix with effort. Due to the optimum angle β of the conical surface of the clamp, the possibility of folding at the beginning of forming the conical cup, when the workpiece is molded in a free state, is excluded. When lowering the punch 3, the conical cup is constricted to the hemispherical part, while in the initial stage of drawing, the part flange is under clip (a), and at the final stage, when the diameter of the edge of the part flange becomes less than d _pressure. , the hood is made without pressure (b). The parameter determining the possibility of drawing at the final stage without pressing is the limit value of the drawing coefficient (or the degree of deformation) in the case of drawing without pressing in a stamp with a conical matrix. In our invention, this is ensured by the drawing coefficient m = 1.12 and the angle of conicity of the matrix and pressure, depending on this value. The drawing process is carried out in several transitions in one stamp.

In the annealed state, VT6-C titanium alloy is one of the most difficult to deform titanium alloys. Considering that the microstructure of the VT6-C alloy is a plastic-needle α-phase, separated by a layer of β-phase (α + β) to obtain the greatest ductility and stampability, it is necessary that the heating temperature of the workpiece before forming is 90 ° C lower than the start of transformation structures α + β in beta.

Example

For our specific case, introduced into production, when stamping a hemispherical part ∅ 367 mm from a sheet blank ∅ 620 mm, 8 mm thick and ∅ 628 mm from a sheet blank ∅ 980 mm, 11 mm thick, we obtain the taper angle of the die and clamp β = 46 °, which was used and successfully implemented at the enterprise. The allowance for machining with a thickness of 8 mm is 1.2 mm per side when machining the inner and outer surfaces, and with a thickness of 11 mm - 1.3 mm.

As a result of the application of this method, the present invention allowed to significantly reduce the amount of thinning in the process of forming up to 8%, as well as to abandon expensive purchased blanks-stampings, reduce the complexity of machining due to a small allowance for machining.

Claims (6)

A method of stamping a hemispherical part from a VT6-C hard-to-deform titanium alloy in one stamp, comprising pre-drawing a heated flat sheet billet into a conical cup with a cone clamp in a conical matrix heated to 220 ± 10 ° C, softening the annealing of the resulting cup, and final drawing of the conical cup with cold a punch in a heated matrix into a hemispherical part, using a matrix and a clamp with taper angles determined by the formula:

Where Dzag. - diameter of the initial billet, mm; Ddet. - diameter of the part, mm;

- drawing coefficient for alloy VT6-C; dk is the maximum diameter of the conical cup.

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