RU2115498C1 - Tool for extruding rods - Google Patents

Abstract

FIELD: plastic metal working, namely, rod extrusion. SUBSTANCE: invention allows to eliminate difference of metal yielding rates along crosss section of blank at the end period of extrusion process. Uniform metal yield is achieved due to equal conicity angles of pressure pad and die of extrusion tool. Conicity angles are determined by value α = α_f-β, where α- cone apex angle, angular degrees; α_f- angle of natural yield 777 of metal heated up to extrusion temperature, angular degrees; β = 2^°-30^°= (2-30) degrees. Stepped annular turnings are made on cone of pressure pad. Pitch and depth values of turnings increase from apex to base of cone and they are equal one to another. EFFECT: improved design. 2 cl, 2 dwg

Description

 The invention relates to the processing of metals by pressure and can be used in the process of pressing bars.

 A known classical method of pressing solid products by extruding a metal washer heated to a pressing temperature with a press washer and placed in the container of the workpiece through the die point Perlin I. et al. Theory of metal pressing. -M.: Metallurgy, 1975 [1]. At the same time, at the final stage of pressing in the body of the pressed product, a central press tension is formed, sometimes deeply penetrating into the body of the press product and violating its continuity. The source of central press tension is the increase in the axial component of the velocity of the metal from the periphery to the axis as a result of a decrease in the volume of the pressed metal with a significant approximation of the press washer to the crimping part of the plastic zone [1, p. 81 and 87]. Before the press washer is inserted into the squeezing part of the plastic zone, its volume practically does not decrease. As much metal is introduced into it as is withdrawn into the press product [1, p. 83].

 Since the press section, in which there is press tension, has to be cut off and sent for recycling, the yield and productivity of the pressing process are reduced.

From existing practice it is known:
1. The shape of the channel of the matrix influences the formation of central press tension: the smaller the angle of inclination of this channel (taking into account the part that is formed by its elastic zone), the smaller the gradient of the increase in the axial component of the metal flow velocity and the limiting distance between the press washer and the matrix, at which the formation of press tension begins [1, p. 87].

 2. Significantly decreases the central Prussy tension when pressing the workpiece with an unheated internal axial zone, especially with heavy lubrication of the container and the matrix. At the same time, the lag of the peripheral layers from the central ones slows down [1, p. 88]. However, the uniformity of the structure of the molded product may be impaired.

 3. Changing the shape of the press washer does not have a noticeable effect on the size of the press tension, since it has little effect on the unevenness of deformation [1, p. 88].

 4. The formation and increase in the size of press tension is promoted by large friction forces on the surface of the container and small on the surface of the press washer. The former contribute to the twist of the peripheral layers adjacent to the press washer, while the latter delay such movement. Container lubrication, which reduces lateral friction, reduces the size of the press tension.

 On the surface of the press washers make a toothed notch that prevents the metal from sliding on the press washer] 1, p. 87 - 88]. In addition, pressing “with a jacket” contributes to the reduction of pressure load [1, p. 96 - 97]. However, this increases the deterioration of the container and the amount of metal going to waste.

 Known use in pressing conical and plane-conical matrices [1, p. 72, 388], SU, 668735, class. In 21 С 25/00, 06/25/79 - [2], however, it was noted that the value of elastic deformation when using such matrices, all other things being equal, is greater than that of a matrix with a sharp edge.

 The joint use of a conical matrix and a conical press washer (press stamp) is known. So in the tool for the manufacture of hollow products SU, 608580, class. At 21 С 25/00, 05/30/78 - [3], in order to increase the yield by reducing the pressure, the conical working surface of the press stamp head in the area adjacent to the piercing needle was made stepwise. However, such a tool is not very effective for pressing rods.

 The aim of the invention is to reduce the magnitude of the pressure and increase the yield in the manufacture of rods.

This goal is achieved by the fact that in the known tool for pressing bars containing a container placed inside its press washer with a working surface in the form of a truncated cone, on which stepped annular grooves are made, and a matrix with a conical inlet installed at the outlet of the container, the following design changes
- on the working end of the press washer, a finely toothed notch is made, which prevents the sliding of the flowing metal over the press washer;
- stepped annular grooves are made with a step and depth, increasing from the top to the base of the cone;
- the taper angle of the press washer is equal to the taper angle of the matrix;
- the angle at the top of the cone of the press washer and the matrix is determined by the value:
α = α _t. - β,
where α _t is the angle of the natural flow of the metal heated to the pressing temperature, angular degrees,
β = 2 ^° - 30 ^° .

In addition, the step of each step is equal to its depth and is determined by the ratio:
h _n = b _n = (D - d) / 2N tg 0,5α - (1 - kn),
Where
h _n is the step of the step, mm;
b _n - step depth, mm;
D is the diameter of the base of the cone of the press washer, mm;
d is the diameter of the top of the cone of the press washer, mm;
N is the total number of steps;
n is the sequence number of the step;
α is the angle at the apex of the cone;
k = 0.05 - 0.4 - is determined empirically.

 The execution on the working surface of the press washer of annular grooves and fine-cut notches, contributing to the reduction of pressures, is known from sources - 3 and 1, p. 87 - 88.

However, only stepwise execution of annular grooves with a step and depth increasing from the top of the cone of the press washer to its base, the choice of the angle at the top of the cones of the press washer and matrix within α = α _t. - β, the performance of the parameters of stepwise grooves in accordance with the formula:
b _n = h _n = (D - d) / 2N tg 0,5α - (1 - kn)
allow, as shown by industrial tests, either to almost completely eliminate the pressing weight from the pressed product, or to reduce it by more than 50%, depending on the geometric dimensions of the workpiece and the finished product.

 At the same time, the previously concluded conclusion is refuted that "changing the shape of the press washer does not have a noticeable effect on the size of the press tension".

 Based on the foregoing, we can conclude that the proposed technical solution is not obvious.

 In FIG. 1 shows a General view of the proposed tool for pressing rods; in FIG. 2 - image of a structural element (press washers).

In the container of the press 1 there is a press washer 2, with a stamp 3 connected to a horizontal press (not shown). At the output of the container 1, a matrix 4 is fixed with a tapered lead 5 and a point d ₁ . On the working cone 6 of the press washer 2, stepwise annular grooves 7 of variable pitch from h ₁ to h _N and depths from b ₁ to b _{N are made} . In the presented example, the step and depth of each individual groove are equal to each other:
b ₁ = h ₁ ; b _n = h _n ; b _N = h _N , which simplifies the manufacture of the profile of the press washer on universal turning equipment, makes it possible to quickly master the process of converting an existing press tool into a tool of the proposed design.

The step and the depth of the steps increase from the top of the cone 6 to its base: h _N > h _n > h ₁ ; b _N > b _n > b ₁ . Changing the geometrical dimensions of the grooves makes it possible to carry out the process of equalizing the outflow velocity of the peripheral and central layers of the metal at the final stage of pressing without violating the continuity of the central part of the rods.

The dimensions of the grooves are determined by the ratio:
b _n = h _n = (D - d) / 2N tg 0,5α - (1 - kn),
Where
b _{n is the} depth of the nth groove, mm;
h _{n is the} step of the nth groove, mm;
N is the number of steps;
n is the sequence number of the step;
D is the outer diameter of the press washer, mm;
D is the diameter at the top of the cone of the press washer, mm;
α is the angle at the apex of the cone.

 The coefficient k lies in the range 0.05 - 0.4 and is determined empirically. A fine toothed notch 8 is applied to the working end of the cone 6, for example, in the form of scallops 3.0 mm high, which improves the adhesion of the press washer to the end of the pressed workpiece (not shown).

 The angles at the apex of the cone 6 and at the entrance of the matrix 4 are the same and equal to α.

 A similar implementation of the tool allows you to keep at the end of the pressing the flowing mass of metal in a fixed position.

Pressing the bar using the proposed tool is carried out in the usual way. A workpiece heated to the pressing temperature is placed in the container between the die and the press washer (not shown). Then, under the action of force P, the press washer 2, acting on the workpiece, moves in the direction of the force P, squeezing the workpiece metal into the point d _{1 of the} matrix 4. To reduce the friction forces, a lubricant is applied on the inner surface of the container 1 and matrix 4, for example: colloidal graphite water according to TU 113-08-48-62-90, while the same lubricant is applied to the surface of the working cone 6 and to the end 8 of the press washer 2. Lubrication of the working surfaces of the press washer facilitates the separation of the pressure switch (not shown) from press washers when disassembling the tool e closure pressing process.

 Using the proposed tool and method, rods ⌀30 mm, ⌀41 mm, ⌀114 mm were made from zirconium alloys Zr-2.5Nb, Zr-1,0Nb, Zr-1,3Sn-1,0Nb-0,5Fe, from copper alloy M1 and titanium alloy VT-1,0.

 In this case, the angles of the natural flow of the pressed alloys were previously determined experimentally. For this, blanks were made up of two half-cylinders with a coordinate grid along the diametrical plane of the connector. Then the billet was heated to the pressing temperature and squeezed into a bar. The angles of the natural flow of the pressed alloys were determined by mesh distortions. L. Prozorov Pressing steel and refractory alloys. -M.: Engineering, 1969. - [4].

So for zirconium alloys Zr - 1.0Nb, Zr - 2.5Nb, Zr - 1.3Sn - 1.0Nb - 0.5Fe - α _t. = 107 - 122 ^° . For copper alloy M1 - α _m = 97 - 115 ^°, for titanium alloy BT-1,0 -α _t = 110 - 125 ^°. .

Angle β = 2 ^° , when used as a lubricant for a pressing tool, a colloidal graphite aqueous preparation according to TU 113-08-48-62-90 and a copper coating, in the form of a lubricating layer, on billets of zirconium alloys and VT-1 titanium alloy .

The coefficient k was determined empirically, as the ratio (σ _B1 / σ _B2 ) or (P ₁ / P ₂ ) at various pressing temperatures (for zirconium alloys T = 580 - 780 ^o C, copper alloy M1 - T = 500 - 650 ^o C , titanium alloy VT-1 T = 650 - 800 ^o C), where σ _B1 is the tensile strength of the workpiece metal heated to extrusion temperature, MPa; σ _B2 - tensile strength at room temperature of the metal of the workpiece, MPa; P ₁ - the pressing force of the workpiece, MPa; P ₂ - maximum press force, MPa.

The k value of the alloy, for example Zr-1.0Nb, when pressing ⌀30 mm rods from a ⌀109 mm billet, is 0.08. The parameters of the press washer were: b ₁ = h ₁ = 1.094, N = 16, the height of the combs on the basis of the working cone of the press washer 2.0 mm The parameters of the press washer for pressing ⌀114 mm rods from the ⌀298 mm billet of Zr-1,0Nb alloy were: k = 0.09, b ₁ = h ₁ = 1.433, N = 32, scallops height on the base 3.0 mm . Similarly, the parameters of the press washers were calculated for pressing rods of other sizes.

 When pressing bars ⌀20 ÷ 50 mm using press washers according to the proposed method, there was an almost complete absence of press tension. At the ends of the rods there were prints from a notch on the end surface of the press washer or corrugated traces of metal detachment from the press washer not exceeding 30 mm. For comparison, according to the existing technology for zirconium alloys, when conical dies and press washers are used, which have smooth conical and end surfaces, a section with a press tension of at least 300 mm is cut from bars of ⌀20 ÷ 50 mm. When pressing rods ⌀81 ÷ 114 mm, using the proposed method and tool, the magnitude of the pressing tension decreased by more than 50%, compared with the existing pressing technology.

 At the same time, the yield of the product during the pressing of the rods according to the proposed method increased by 3 - 6%, which made it possible to change the initial dimensions of the workpiece for pressing. For example, according to the existing method for pressing bars of ⌀25 mm from Zr-2.5Nb alloy, a workpiece of ⌀109 × 232 mm is used, and according to the proposed method, a workpiece of ⌀109 × 222 mm is sufficient to obtain a bar of the same length.

 At present, Chepetsk Mechanical Plant OJSC is conducting industrial tests of the proposed tool in the mass production of bars.

Claims (2)

1. Tool for pressing rods, containing a container, a press washer placed inside it with a truncated cone working surface, on which stepped annular grooves are made, and a matrix with a tapered inlet installed at the container outlet, characterized in that the press has a working end - the washers are made with a finely serrated notch, the taper angle of the press washer is equal to the taper angle of the matrix, the stepped annular grooves are made with a step and depth increasing from the top to the base of the cone, and the angle at its top it is not determined by
α = α _t -β,
where α _t is the angle of the natural flow of the metal heated to the pressing temperature, angular degrees;
β = 2-30 ^o ;
α is the angle at the apex of the cone, angular degrees. 2. The tool according to claim 1, characterized in that the step of each step is equal to its depth and is determined by the ratio
_{h n = b n = (Dd} ) / 2Ntg0,5α- ( 1-k _{· n),}
where h _n is the step of the step, mm;
b _n - step depth, mm;
D is the diameter of the base of the cone of the press washer, mm;
d is the diameter at the top of the cone of the press washer, mm;
N is the total number of steps;
n is the sequence number of the step;
k = 0.05 - 0.4.