SU933259A1 - Sintered work rolling method - Google Patents

Description

(5) METHOD FOR ROLLING SINTERED BLINDS

one

The invention relates to powder metallurgy,

 The known method of rolling low-ductility of sintered billets, including heating and multiple deformation on an edge at a speed of 0.5-1.5 m / s and compression per pass in four-roll calibers with a canting between passes on S ° l J.

The main disadvantages of this method are significant metal loss during rolling. In the first passes, when the sintered billet has the least plasticity, cracks are formed at the rear, and especially the front, ends. These subsequent cracks often result in segregation of the ends of the blanks and scrap. Cracking at the ends contributes to the shock application of the load to the front and rear ends of the workpiece when it is caught by the rolls and ejected from the rolls. Strikes rolls on the front and rear

the ends of the workpiece are reduced if the reduction in the reduction in the first passages to 20%, but not completely eliminated, so the cracks on the ends and the separation of the ends of the workpieces are not eliminated.

There is also known a method of rolling sintered billets of hard-to-deform materials, including the formation at the ends of the billet

10 at a distance of 1-1.2 slope lengths 1: 7-1: 3.5. feeding the billet into a caliber with inclines against non-driving rolls and repeated hot deformation of 8 four-roll caliber

15 with compression 2.

The method provides reliable gripping of the workpiece with rollers, however, it also does not allow to significantly reduce metal losses.

20

The closest to the proposed technical essence and the achieved result is the method of rolling sintered billets, including the repeated hot deformation of the sintered billet with the front and rear end sections of conical shape in four-roll gauges / 3j. The ends of the blanks for eliminating sintering defects (this applies to blanks sintered in welding machines) are also processed. Rolling blanks with conical ends and machined ends practically does not lead to the appearance of cracks on the ends and subsequent stratification. However, a significant disadvantage of this method is significant (up to 20 and more) metal losses during the machining of the ends and the formation of cones at the ends of the blanks. The most significant losses (more than 20) occur when rolling short (up to 150 mm) cylindrical sintered billets with a diameter of 50-90 mm obtained by hydrostatic pressing. Under industrial conditions, since the rear end of the workpiece is more susceptible to cracking, a cone is formed only at the rear end of the workpiece. At the same time, metal loss is reduced to 10-15, but still remains fairly high. The purpose of the invention is to reduce metal losses. This goal is achieved by the fact that in the rolling method of sintered billets, mainly from tungsten-based alloys, including repeated hot deformation of the sintered billet with a front conical section in four-roll calibers, before rolling the billet, in the first two passes from the side of its rear end surface, the cylindrical billet and the deformation of the joints of the billets are carried out with compression of the ends. The essence of the method is based on the fact that the sintered workpieces compressed at the ends form a workpiece of increased length with a conical front end, the ends of the first and subsequent workpieces are rolled without impact, and therefore the ends of the connected workpieces are not subject to cracking. For better joining, the ends of the blanks can be (processed. Metal losses in this rolling method are reduced to 5-10. Rolling in this method must be carried out no less than in two passes, since after the first pass, the edges of the workpiece remain undeformed and therefore are subject to cracking. Fig. 1 shows a billet with a cone at the front end; Fig. 2 is a diagram of rolling two round sintered billets in a joined state on the ends; Fig. 3 is a diagram of rolling three square billets in a joined but not end Example: Rolling were subjected to three batches of tungsten B-PM billet with a diameter of 30 mm, obtained by hydrostatic pressing. The rolling was carried out in three passes up to a square of 20 mm in a mill with Mehtrekhvalkovyh calibers formed 180-mm drive cylindrical rollers. there were no cones on the front end. The second batch of blanks had cones on the front and rear ends and a third of the batch of blanks had cones only on the front end of a part of the blanks. The test results are shown in the table. 1 20 Cracks at the ends and 25% of the workpieces are uncovered 240 3 Cracks and no openings 3iO 3 No, no openings, there are cracks on the back end of the last workpiece

Claims (1)

Claim Method for rolling sintered billets, mainly from tungsten-based alloys, including repeated hot deformation of a sintered billet with a front conical section in four-roll calibers, characterized in that, in order to reduce metal losses, before rolling the billet in the first two passes from its rear end surface put an additional cylindrical billet and the deformation of the joints of the blanks lead with the compression of the ends.