CN101406911A - Technique for stretching workpiece with flange - Google Patents

Abstract

The invention relates to a stretching process with a flange workpiece. Firstly, a workpiece blank is stretched into a semifinished product of a straight cylindrical piece according to the prior process; the diameter of the semifinished product is 5 to 8 mm larger than the diameter of a flange after subtracting two times of the radius of a circular angle of the bottom of a cylinder; secondly, the semifinished product is put to a mould of a finished product; and when a convex stretching mould and a side pressing ring act on the semifinished product, pressure is applied on the wall of the semifinished product cylinder through annular pressure till a finished product is obtained. In the stretching process with the flange workpiece, the function of the pressure applied on the wall of the semifinished product cylinder through the annular pressure ring is to reduce the axial tensile stress of the cylinder wall of a stretching piece, improve the degree of stretching and deformation and reduce the times of stretching; and as the stretching can be molded only through two times, the stretching process reduces the working procedure of stretching, saves machining cost, needs small number of moulds and has short production period.

Description

A kind of drawing process of flanged pin workpiece

Technical field

The present invention relates to the stretch forming process in the panel beating, especially a kind of drawing process of flanged pin workpiece.

Background technology

Traditional drawing process of flanged pin spare, particularly wide flange piece is: when stretching first flange portion is formed into workpiece size, remains unchanged substantially in subsequent handling flange part, highly reach dimensional requirement by reducing the cylindrical member radial dimension, increasing.The shortcoming of this traditional drawing process is: big for the flange width size, and the flange piece that the barrel height is big with respect to the barrel radial dimension, drawing numbers is more, and die needed quantity is many, and the production cycle is long, and cost is very high.

Summary of the invention

Purpose of the present invention just provides a kind of drawing process that reduces stretching process, saves the flanged pin workpiece of processing cost.

The drawing process of flanged pin workpiece of the present invention is: at first being drawn into straight cylindrical member semi-finished product by traditional handicraft with the workpiece hair is bad, the semi-finished product diameter range is than the big 5-8mm of lip diameter after the twice of a radius of corner at the bottom of the semi-finished product diameter deducts tin; Secondly, again semi-finished product are put into the finished product mould, when stretching convex die and blank holder are to the semi-finished product effect, are exerted pressure by double finished product barrel of annular pressure circle, until finished product.

In the drawing and forming of flanged pin workpiece, the wrinkling and drawing crack of material is the main cause that influence stretches and carries out smoothly, has only when material not produce wrinkling or drawing crack, and stretching could be carried out smoothly.Usually, to blank holder apply certain pressure can prevent wrinkling, but in traditional drawing and forming, the main cause that produces drawing crack is that the stretcher strain degree is big, makes that suffered axial tension stress is greater than effective tensile strength of critical section on the tensioning member barrel.Among the present invention double finished product barrel of annular pressure circle applied pressure by material transfer to the stretching barrel, make the suffered tension of barrel reduce, as long as applied pressure size (this power can be calculated by following formula (C)) is suitable, just can make the effective tensile strength of the suffered tension of barrel, prevent that material from carried out stretching by drawing crack smoothly less than critical section.Therefore, the effect of double finished product barrel of annular pressure circle applied pressure is the axial tension stress that reduces the tensioning member barrel, improves the stretcher strain degree, reduces drawing numbers, reduces cost.

The theory analysis of the drawing process of flanged pin workpiece of the present invention is:

F1 is the tensile force that stretching convex die produces; F2 is the pressure-pad-force that blank holder produces; F3 is the axial force that double finished product barrel applies, and below sets forth the effect of power F3:

In the tradition stretch forming process is that power F3 is not provided, and when not having this power of F3 (traditional drawing process belongs to this situation), the suffered axial tension stress of middle barrel is:

$\mathrm{\σ}=({\mathrm{\σ}}_{1\max }+{\mathrm{\σ}}_M)e^{\mathrm{\μ}\·\frac{\mathrm{\π}}{2}}+\frac{{\mathrm{\σ}}_s/2}{2\frac{r_2}{t}+1}---\left(a\right)$

Wherein: ${\mathrm{\&sigma;}}_{1\max }=1.1{\mathrm{\&sigma;}}_s\ln \frac{R_t}{R}+\frac{1/2{\mathrm{\&sigma;}}_s}{\frac{2r_1}{t}+1},$ The latter walks around the required additional stress of fillet r1 for material in the formula; ${\mathrm{\&sigma;}}_M=\frac{\mathrm{\&mu;}{\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="A20081013623800061.png"\; state="\{\{state\}\}">F</figure-callout>}}_2}{\mathrm{\&pi;}(R+t+r_2)t},$ It is the frictional force that causes of pressure-pad-force F2 and the additional stress that produces;

μ: the coefficient of sliding friction of part and blank holder and part and die;

σ _s: the yield stress intensity of part;

T: the thickness of part;

F ₂: the pressure-pad-force that blank holder produces;

R _t: half-finished radius;

R: the radius of finished product;

r ₁: radius of corner at the bottom of the semi-finished product;

r ₂: finished product mould die profile radius;

If the σ among the formula a＞[σ] (wherein: $\left[\mathrm{\&sigma;}\right]=1.1{\mathrm{\&sigma;}}_s^{\&prime;}-\frac{1/2{\mathrm{\&sigma;}}_s^{\&prime;}}{\frac{2r}{t}+1},$ (r is a part base angle radius of corner, σ _s' YIELD STRENGTH when not stretching, σ _sBe YIELD STRENGTH after the flow harden that stretches for the first time)), then material is just by drawing crack ([σ] is effective tensile strength of critical section).The drawing coefficient of tradition drawing process is decision thus mainly.

When applying this power of F3, the suffered axial tension stress of A point (barrel) is among Fig. 1:

${\mathrm{\&sigma;}}^{\&prime;}=({{\mathrm{\&sigma;}}_{1\max }}^{\&prime;}+{\mathrm{\&sigma;}}_M)e^{\mathrm{\&mu;}\&CenterDot;\frac{\mathrm{\&pi;}}{2}}+\frac{{\mathrm{\&sigma;}}_s/2}{2\frac{r_2}{t}+1}---\left(b\right)$

Wherein: ${{\mathrm{\&sigma;}}_{1\max }}^{\&prime;}=1.1{\mathrm{\&sigma;}}_s\ln \frac{R_t}{R}+\frac{1/2{\mathrm{\&sigma;}}_s}{\frac{2r_1}{t}+1}-{\mathrm{\&sigma;}}_{\mathrm{ex}}$

${\mathrm{\&sigma;}}_{\mathrm{ex}}=\frac{{\mathrm{<figure-callout\; id="3"\; label="F"\; filenames="A20081013623800061.png"\; state="\{\{state\}\}">F</figure-callout>}}_3}{2\mathrm{\&pi;}{R}_{t}t};$ It is the stress of the effect generation of F3;

${\mathrm{\&sigma;}}_M=\frac{\mathrm{\&mu;}{\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="A20081013623800061.png"\; state="\{\{state\}\}">F</figure-callout>}}_2}{\mathrm{\&pi;}(R+t+r_2)t}$

From formula a and formula b as can be seen:

$\mathrm{\&sigma;}-{\mathrm{\&sigma;}}^{\&prime;}={{\mathrm{\&sigma;}}_{\mathrm{ex}}}^{\mathrm{\&mu;g}\frac{\mathrm{\&pi;}}{2}}$

That is to say, little before the suffered axial tension stress ratio of A point improves among Fig. 4 after improving Owing to can control F ₃Size, promptly can control σ _ExSize, therefore can make σ '＜[σ], can calculate thus:

${\mathrm{<figure-callout\; id="3"\; label="F"\; filenames="A20081013623800061.png"\; state="\{\{state\}\}">F</figure-callout>}}_3>2\mathrm{\&pi;}{R}_{t}t[1.1{\mathrm{\&sigma;}}_s\ln \frac{R_t}{R}+\frac{1/2{\mathrm{\&sigma;}}_s}{\frac{2r_1}{t}+1}+\frac{\mathrm{\&mu;}{\mathrm{<figure-callout\; id="2"\; label="F"\; filenames="A20081013623800061.png"\; state="\{\{state\}\}">F</figure-callout>}}_2}{\mathrm{\&pi;}(R+t+r_2)t}-\left(\right[\mathrm{\&sigma;}]-\frac{{\mathrm{\&sigma;}}_s/2}{2{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="A20081013623800061.png"\; state="\{\{state\}\}">r</figure-callout>}}_2/t+1})e^{-\mathrm{\&mu;g\&pi;}/2}]---\left(c\right)$

Material can be by drawing crack, and stretching can be carried out smoothly.Can reach a conclusion by above: the stretching after the improvement only need twice promptly plastic.

The drawing process of flanged pin workpiece of the present invention and since stretch only need twice promptly plastic, can reduce stretching process, save processing cost, die needed quantity is few, and is with short production cycle.

Description of drawings

Fig. 1 is structure and structure stress figure in the technology of the present invention.

The specific embodiment

A kind of drawing process of flanged pin workpiece is: the hair that at first with diameter of work is 102mm badly is drawn into the straight tubular semi-finished product that diameter is 72mm by traditional handicraft; Secondly, again semi-finished product are put into finished product mould 4, in stretching convex die 3 and 2 pairs of semi-finished product effects of blank holder, (get YIELD STRENGTH 200Mpa when not stretching by 1 pair half finished product barrel of annular pressure circle, 18000 newton that exert pressure, YIELD STRENGTH 240Mpa after the flow harden stretches for the first time), until finished product, lip diameter 64mm, barrel diameter 30mm, the flanged pin workpiece of high 62mm.

Claims (2)

1, a kind of drawing process of flanged pin workpiece, it is characterized in that: it may further comprise the steps: at first being drawn into straight cylindrical member semi-finished product by traditional handicraft with the workpiece hair is bad, the semi-finished product diameter range is than the big 5-8mm of lip diameter after the twice of a radius of corner at the bottom of the semi-finished product diameter deducts tin; Secondly, again semi-finished product are put into finished product mould (4), when stretching convex die (3) and blank holder (2) are to the semi-finished product effect, are exerted pressure (F3) by annular pressure circle (1) double finished product barrel, until finished product.

2, the drawing process of a kind of flanged pin workpiece as claimed in claim 1 is characterized in that: describedly exert pressure (F3) by annular pressure circle (1) double finished product barrel, should satisfy:

$F_3>2\mathrm{\&pi;}{R}_{t}t[{1.1\mathrm{\&sigma;}}_s\ln \frac{R_t}{R}+\frac{1/2{\mathrm{\&sigma;}}_s}{\frac{{2r}_1}{t}+1}+\frac{{\mathrm{\&mu;F}}_2}{\mathrm{\&pi;}(R+t+r_2)t}-\left(\right[\mathrm{\&sigma;}]-\frac{{\mathrm{\&sigma;}}_s/2}{{2r}_2/t+1})e^{-\mathrm{\&mu;g\&pi;}/2}]$

μ: the coefficient of sliding friction of part and blank holder and part and die;

σ _s: the yield stress intensity of part;

T: the thickness of part;

F ₂: the pressure-pad-force that blank holder produces;

R _i: half-finished radius;

R: the radius of finished product;

r ₁: radius of corner at the bottom of the semi-finished product;

r ₂: finished product mould die profile radius;

$\left[\mathrm{\&sigma;}\right]=1.1{\mathrm{\&sigma;}}_s^{\&prime;}-\frac{1/2{\mathrm{\&sigma;}}_s^{\&prime;}}{\frac{2r}{t}+1}$ (r is a part base angle radius of corner).

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