SU971575A2 - Method for making wire from sintered tungsten-based materials - Google Patents

Description

The invention relates to the field. powder metallurgy, in particular, to the method of making wire from sintered materials, mainly refractory metals, for example tungsten.

A known method for manufacturing tungsten products includes hydrostatic pressing of cylindrical billets, their sintering, heating and rolling in four-roll calibers with intermediate heating and turning to edge 1.

The disadvantage of this method is the uneven crimping of the workpiece.

According to the main auth .. sv. 763471, a method of manufacturing a wire of sintered tungsten-based materials is known, which includes pressing a billet, sintering it, rolling a square billet onto a rib at a speed of 0.5-1.0 m / s, crimping 20-40% per pass in four-roll gauges, oval to rolls with a smooth barrel, and turning between the passageway and at an angle of 45 ° ,. rotational forging and drawing 2.

In this case, the first stage of pressure treatment of brittle billet

is carried out under favorable rolling conditions with four-side crimping, when there are no stretching surges resulting in defects on the rods, and the ductility of the rod increases. Therefore, during subsequent rotational forging and drawing rods with increased ductility, spillage and breakages are significantly reduced, and the quality of rods and wire is improved. Replacing hand forging by rolling significantly reduces the laboriousness of making bars, labor productivity increases by 5-6 times.

The disadvantage of the known method is the considerable unevenness of the distribution of the reduction across the width of the smooth rolls during the rolling of the square billet. In the first pass to the rib. Irregularity, crimping of the workpiece across the width of the rolls leads to additional tensile stresses, which are the cause of defects on the rods, especially from doped alloys of refractory metals, for example, tungsten alloys of type VT, VI and VL.

The aim of the invention is to improve the uniformity of rolling across the width of the roll, the quality of the products. In order to achieve the goal, a method has been proposed for fabricating a wire of sintered tungsten-based materials according to ed. St. No. 763471, characterized in that before rolling the billet in a four-roll caliber, it is subjected to deformation in a six-roll caliber with compression of 15-20%. Cylindrical blanks obtained by hydrostatic pressing have a uniform density distribution along the length and cross section. In addition, the maximum compression of a round billet in a six-caliber caliber is 2 times less than the maximum compression of a square billet per edge in a square caliber. All this significantly (almost 2 times) reduces the unevenness of the workpiece compression across the width of the rolls, eliminating the occurrence of additional tensile stresses and defects on the rods. In the final stages of processing, this leads to an improvement in quality (increased plasticity, heat resistance) and an increase in yield by eliminating delamination and dragging. The proposed method is carried out as follows. After hydrostatic pressing of a cylindrical, for example, tungsten billet and its sintering, it is heated in a furnace with a protective atmosphere to 1450150 ° C. The heated billet is rolled with a six-sided crimp, in a caliber, formed with six smooth rollers. Then the hexagonal bar is rolled in a four-roll gauge with a uniform compression on the two rolls on the edges and on the ribs on two rolls. This, compared to rolling a square to an edge, also reduces the unevenness of the distribution of compression across the width of two opposite rolls, and the width of the two other rolls makes the distribution of compression almost uniform. Thus, in the second pass, the likelihood of defects on the bars is reduced. The resulting square bar with rounded corners, after turning over to angle 45, is rolled onto an edge in subsequent passes, then subjected to rotary forging to a rod with a diameter of 3 mm and drawing. An example implementation of the proposed method. On a universal laboratory mill equipped with interchangeable cassettes with four-roll and six-roll calibers, tungsten blanks of the B-PM grade with a diameter of 30 mm, made by gland pressing and subsequent sintering, are rolled. The blanks are heated to 1450t50 C and rolled in six-roll and four-roll calibers. The rolling parameters, the degree of uneven distribution of the reduction across the width of the rolls are given in the table. In the table, LPP is the maximum compression of the workpiece from the side of one roll; dNs - the average compression of the workpiece from one roll. The average compression is determined from the condition that square and hexagonal billets are pressed into the square and hexagonal gages, respectively, crimped along the edges and equal in area to the round billet.

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Claims (2)

A roll caliber.65 reduces the possibility of an occurrence of 23.0 mm, 5.9715 additional tensile stresses, and provides an improvement in the quality and yield of bars, especially from alloyed, refractory metal alloys. The introduction of the proposed method provides 5-year annual economic effect in excess of 150 thousand rubles. Invention v-wt wyjia nauot cicnwn A method of manufacturing a wire of 10 sintered materials based on tungsten by the author. St. No. 763471, about tl and the fact that, in order to increase the uniformity of rolling across the width of the roll and the quality of the products, before rolling the billet in a four-roll caliber, it is subjected to deformation in a yustivalkovy caliber with a reduction of 15-20%. Sources of information taken into account in the examination of A. Vydrya and others. Research rolling of tungsten rods. powder metallurgists, 5, 1978, p. thirty. 2. USSR author's certificate I 763471, cl. B 22 F 3/20, 1978.