GB2092930A - Metalworking tool with insert - Google Patents

Abstract

The tool is used for both hot and cold metalworking operations, mainly of copper and aluminium alloys. An insert (1) is fitted into an enclosing metal frame comprising a filler ring (2), a retainer ring (3) and a case (4). The inner wall of the case (4) comprises three steps (6, 8, 5) into which the retainer ring (3) is fitted. There is an air space (7) between the retainer ring (3) and the filler ring (2). The radially inner external surface (9) of the filler ring (2) is a conical surface widening towards the retainer ring (3). The insert (1) is fitted to this conical surface (9) and is supported by the retainer ring (3). Expediently, the insert (1) is supported by the retainer ring (3) by inserting a soft metal ring. <IMAGE>

Description

SPECIFICATION Tool insert for the metalworking of metals, mainly of copper- and aluminium alloys The invention relates to a tool with insert for cold and hot metalworking of metals, mainly of copperand aluminium alloys, where an insert made of a material different from that of the clamp frame is fitted in the clamp frame made of metal.

For hot extrusion of metals, mainly of copper- and aluminium alloys a tool of that type has already been known /See: West Germany patent application No. P 2900909.4/ the life time of which is considerably longer and besides, it results in higher productivity, better tool economy and products with bettersur- face quality than the solid tools used earlier or the ones with insert prestressed by conventional shrink- age fit.

At the same time, apart from its advantages, the above-described tool has several disadvantages which prevent it from reaching the maximum possible life time and the inserts from being replaced quickly and simply. As the tool has a clamping such that at the temperature of cold metalworking it is not prestressed hence, of course, it cannot be used for such operation.The disadvantages of the abovementioned tool with insert, as compared to the solution according to the invention, can be well seen in the drawing, where, for the sake of better understanding, the shaft-section of the earlier tool with insert is shown on the left of the Figures /Figures la and 2a/ while that of the tool with insert according to the invention, on the right of the Figures/Figures ib and 2b/./With regard to the symmetrical formation of the tool only half shaftsections are shown/. Essentially, both Figures in the drawing show the same tool part, but while in Figure 1 the constituents of the two tools are provided with reference numbers, Figure 2 shows in the first place the force and torque conditions on the two tools.

In Figure 2a it can be seen that at the temperature of hot metalworking the inner surface of cone 9' of the enclosing case 4' of greater heat expansion expands in such a manner that it becomes unfavourably distorted for the insert 1'/the rate of the distortion A is at least 0.01-0.02 mm/, hence the critical diameter dofthe insert 1' will not be prestressed.

At the same time a torque, producing tensile stress on the section of the resultant arm reforming the cross-section, is brought about on the resultant arm re by the resultant force Fe, which derives from the load P0 exerted on the surface of the insert 1' by the formed metal, distributing uniformly, and which is correlated with a circular ring and exerts an effect, due to the surface regularity, from the symmetry axis approximately in a distance amounting to two-thirds of the radius.

As the line of action of the resultant force Fe is out of the center of gravity C of the given cross-section /if the static torque of some cross-section round two axes perpendicular to each other equals to zero, then these axes are termed axes of center of gravity and their point of intersection is called center of gravity: see V. I. Feodosev Soprotivlenie Materialov, Chapter III/,force Pe brings about further torque M1 on the arm r1, and this torque also brings about tensile stress exerting an effect perpendicularly to the cross-section; thus is brought about the stress 5t of direction t, under the influence of which the insert may split, shown in Figure 2a.

In case of continuous metalworking a stable state may set in between the insert and the case in spite of the radial haircracks and the tool can be operated till longitudinal scratches caused by the hair cracks will appear on the surface of the product. When the tool is used for a short while but several times the balance between the cracked insert and the case cannot set in as the latter regains its original shape on each cooling down and on re-heating the insert may lose its stability and may disintegrate or it may result in nicked produced of poor quality.

In Figure 2a, a further disadvantage can be seen.

The part of insert out of the line of action of the resultant force Pe and exposed to stress from all directions, can be considered as a rigid solid. Where the bearing of the insert 1' along the surface of cone 9' ceases, the part of insert from the cylinder-jacket F towards the symmetry axis is exposed only to unidirectional stress /exerting effect in the direction of the resultant force P,I. As, due to the air space 7', the critical part of the insert is not supported opposite to the direction of the force Fe, the insert 1' is used on the cylinder-jacket F for shearing action.

The material of the insert 1' is generally rigid /e.g.

Al203/thus its shearing strength is smaller considerably than its bearing strength /T S 0.1-0.5 BZ, where 5z is the stress exerting effect in the direction of the axis z/. Under unfavourable operational circumstances /e.g. the metal to be worked is not warm enough/, due to the greater loads, the insert may deteriorate early.

The third disadvantage of the afore-mentioned method of enclosing presents itself when, due to the occurrence of one of the first two cases, the insert 1' is to be replaced. The inserts are fixed, the ring fastener 11' /Figure 1/can be removed only by chipping. Consequently, the replacement of the inserts is laborious and time-consuming, and not more than only a few /2 to 3/ replacements can be realized.

In case of tools for cold metalworking the inserts have been enclosed up till now in a conventional manner, by shrinkage fit. The disadvantage of this method of enclosing can be found in that it requires extremely precise preparatory works and, although the necessary rate of the prestress can be calculated in a theoretical way, the measurement of the actual value of prestress has not been solved yet. The replacement of the inserts is very intricate and the interchangeability is not ensured.

The invention is based on the recognition that with a tool with insert, preferably provided with an insert of material Al2O3, maximum life time can be reached both in the case of hot and certain cold metalworking operations, if the insert is enclosed in a novel way.

In case of the known enclosing the insert 1 ' fits conically into the case 4' in such a manner that the half cone angle narrowing towards the air space 7' is largerthan the self-closing angle of the fitting surfaces, i.e. 10 to 45 , expediently 12.5 to 150, and there is an air space 7' between the case 4' and the insert 1' under the lower surface of the insert 1', and the insert is fixed in the case by a ring fastener 11'; while, according to the invention /Figures 1b and 2b/ the insert 1 fits into a clamping frame made of metal, which is constituted by a filler ring 2, a retainer ring 3 and a case 4. The inner wall of the case 4 is a stepped surface of cylinder consisting of three steps, where the threaded diameter of the lower part 5 is the largest and the diameter of the upper part 6 is the smallest.The retainer ring 3 fits into the lower part 5 by a screw-joint, while the filler ring 2 fits into the middle and upper parts 8 and 6 by a clearance fit.

There is an air space 7 between the retainer ring 3 and the filler ring 2, the radially inner external surface 9 of the filler ring 2 is formed as a surface of cone widening towards the retainer ring 3, where the half cone angle a is 10 to 45 , preferably 12.5 to 150, and the shape of the insert 1 being supported by the retainer ring 3 is formed to fit to this conical surface 9.

It is important that the insert 1 should be supported perfectly by the retainer ring 3. Any unevenness of surface may be compensated by inserting a soft metal /e.g. copper/ ring of a thickness of 0.2 to 0.5 mm the melting point of which is higher than the metalworking temperature of the metal to be worked.

With the thus enclosed tool with insert, preferably with a ceramic insert /A1203/ the necessary prestress is brought about by the extrusion process itself in the case of hot extrusion, while, in the case of cold metalworking it can be adjusted to the theoretically calculated value on assembly, by means of holes 10 formed in the retainer ring 3 and the enclosing case 4 and by a press with adequate pressing force.

In Figure 2b it can be seen that the insert 1 becomes prestressed even in spite of the distortion caused by the heat expansion A of the filler ring 2, partly because the torques arising neutralize one another, and partly because the insert is exposed to stress from all directions, thus the pressure stresses coming into being in the insert 1 neutralize the remaining tensile stresses. Shearing phenomenon cannot occur as the insert is exposed to stress from all directions /Figure 2b/. The replacement of the inserts can be performed easily and quickly by the releasing of the threaded fits.

The tools with insert according to the invention keeping the advantages of the tools with Al203 insert known already - have a life time some 1.2 to 1.8 times longer than that of the earlier tools, ensure more economical utilisation of tool, higher productivity and products of better quality. The replace ment of the deteriorated inserts is simple, reliable and interchangeability is ensured /min. 6 inserts/ till the steel parts lose their temper. The tool according to the invention makes both cold and hot metalwork ing of the metals and other materials possible through introducing a modern enclosing, choosing the outer dimensions properly and forming, as required, the profile of the insert performing formation.

Claims (4)

1. Tool with insert for the metalworking of metals, advantageously of copper and aluminium alloys, comprising an insert which is fitted into a metallic clamp frame, the material of the insert being different from that of the clamp frame, and wherein the clamp frame is constituted by a filler ring, a retainer ring and an enclosing case, the inner wall of the case is cylindrical and is formed with three steps of which the lowermost one is threaded and has the greatest diameter while the uppermost one has the smallest diameter, the retainer ring being fitted into the said lowermost step by a screw fit, while the filler ring is fitted into the middle and uppermost steps; and wherein there is an air space between the retainer ring and the filler ring, and the radially inner external surface of the filler ring is formed as a conical surface widening towards the retainer rng with a half-cone angle of 10 to 450, and the insert supported by the retainer ring is formed to fit to said conical surface.

2. Atool according to claim 1 wherein said half-cone angle is 12.5 to 150.

3. A tool with insert as claimed in claim 1 or 2 wherein the insert is supported by the retainer ring by inserting a soft metal ring of a thickness of 0.2 to 0.5 mm the melting point of which is higher than the metalworking temperature of the metal to be worked.

4. A tool with insert substantially as herein described with reference to and as shown in Figures 1b and 2b of the accompanying drawing.