RU2417857C1 - Method of deformation processing of metal rod-like workpiece - Google Patents

Abstract

FIELD: process engineering. ^ SUBSTANCE: invention relates to metal forming, particularly, to deformation processing of long rods. Proposed method comprises feeding workpiece into working channel formed between rotary disk and stationary limiting base. Working channel outlet direction is changed with help of support part arranged in annular groove. Disk rotation allows workpiece motion in working channel toward its outlet. At the same time, continuous equal-channel angular pressing without varying notably the workpiece cross section. Continuous equal-channel angular pressing of workpiece is carried out step-by-step. At each step, working channel cross section is gradually decreased. Prior to each next step, workpiece is subjected to forming strain deformation. Deformation temperature is lower than recrystallisation temperature of processed material. ^ EFFECT: higher mechanical properties of processed material due to intensive reduction of its structure. ^ 5 cl, 1 tbl, 1 ex

Description

The invention relates to a deformation processing of metals with a change in their physico-mechanical properties, in particular to a deformation processing of long workpieces in the form of a bar. It can be used in mechanical engineering, aircraft engine manufacturing, in medicine in the manufacture of semi-finished products.

Known methods of processing metals in order to improve their properties, in particular to obtain an ultrafine-grained structure, providing improved physical and mechanical characteristics. For example, a method of deforming workpieces in intersecting vertical and horizontal channels (see V. M. Segal, V. I. Kopylov, V. I. Reznikov, “Processes of plastic structure formation of metals.” - Minsk: Navuka and tehnika), 1994, p. 26) allows you to harden the metal during processing by achieving a high intensity of the accumulated shear strain.

A known method of producing ultrafine titanium billets (RF patent No. 2175685, IPC C22F 1/18, B21J 5/00, publ. 10.11.2001.), Which includes plastic deformation in intersecting vertical and horizontal channels with back pressure in the latter, and plastic deformation is carried out with a decrease in temperature in the range 500-250 ° C, with an accumulated logarithmic degree of deformation of e≥4, then thermomechanical treatment is carried out by alternating cold deformation with a degree of 30-90% with intermediate and final annealing.

However, the known methods do not allow to process long workpieces in the form of rods and have low productivity.

A known method of continuous equal-channel angular pressing of long workpieces, implemented in a device containing a driving impeller with a caliber, a pad with an insert and an emphasis made with working surfaces forming a pressing channel, the height of which is adjustable (RF patent No. 2345861, IPC B21J 5/06, published on February 10, 2009)

There is also a method of continuous equal-channel angular pressing of metals (US No. 7152448, IPC В21С 3/00, publ. 12/26/2006), which includes the supply of a solid metal billet in the form of a rod at one end of the passage channel formed between the circumferential groove of the rotating disk and motionless bounding base surrounding the rotating disk, advancement of the workpiece due to friction and rotation of the disk in the direction of the outlet made in the bounding basis with the possibility of making equal-channel angular pre popping (ECAP). This method is adopted as a prototype.

This method provides intensive shear deformation by the ECAP method of long rods, which leads to the formation of an ultrafine-grained structure in them, leading to an increase in physical and mechanical characteristics.

However, the known method, as well as the previous one, does not provide a further increase in mechanical properties at a level of accumulated strain e≥4 due to the attenuation of the process of grinding the structure and stabilization of the dislocation density.

The objective of the invention is to increase the mechanical properties of the material of the workpiece due to more intensive grinding of the structure upon reaching the desired cross section of the workpiece.

The problem is solved by the method of deformation processing of a metal billet in the form of a bar, including feeding the billet into a working channel formed between a rotating disk with a continuous circumferential groove and a stationary bounding base surrounding part of the length of the annular groove, and at the output of the working channel they provide a change in its direction through the support part installed in the annular groove, and by rotating the disk, the workpiece is advanced along the working channel in the direction of its outlet yes, while performing continuous equal-channel angular pressing (the circuit name accepted in the technique is “ECAP-Conform”) without significant change in the cross section of the workpiece, in which, unlike the prototype, the said angular pressing of the workpiece is carried out in stages, with a sequential decrease in the cross section of the working channel by each stage, and the workpiece before each subsequent stage of equal-channel angular pressing "Conform" is subjected to forming plastic deformation at a temperature below e temperature recrystallization of the processed material

According to the invention, inter-stage forming plastic deformation can be carried out by rolling, or drawing, or forging.

According to the invention, the number of cycles of equal channel angular pressing of each processing step is ≥1.

The proposed invention allows the use of various methods of plastic deformation, a combination of which provides subsequent hardening of the workpiece material due to additional deformation, leading to further refinement of the structure.

The inter-stage forming plastic deformation (MPPD) at a temperature lower than the recrystallization temperature helps prevent a decrease in the mechanical properties of the material achieved as a result of ECAP, provides additional refinement of the structure, and an increase in the dislocation density. At the same time, the required geometry of the cross section of the bar for the next stage of ECAP is achieved.

However, MPPD by rolling or drawing, or forging, is a quasimonotonic treatment, which leads to high anisotropy of the mechanical properties due to the formation of sharp textures and a large coefficient of anisotropy of the shape of the grains. This adversely affects the ductility of the material. And the next stage of ECAP, realizing a nonmonotonic process, provides the isotropic structure of the bar material and, accordingly, higher plastic characteristics.

The method is as follows.

The metal billet in the form of a rod is subjected to continuous equal-channel angular pressing by feeding it to the input of the working channel formed between a rotating disk with a continuous circumferential groove and a stationary bounding base surrounding the rotating disk and covering part of the length of the groove. The other end of the working channel, remote from its entrance, is blocked by the support part from the side of the circumferential groove and has an outlet through the bounding base. The cross section of the outlet is mainly equal to the cross section of the working channel, so that the cross section of the deformable workpiece remains unchanged. By rotating the disk and the friction forces arising between the groove and the workpiece, the workpiece is advanced through the working channel towards the outlet, while performing continuous conformal angular pressing of "Conform". To achieve the required degree of deformation, the processing is carried out in one or more of one cycle of Conform. Thus, the first stage of pressing is carried out, as a result of which the preliminary structure of the workpiece is ground to an ultrafine state. Subsequent plastic deformation by rolling, or forging, or drawing is carried out in order to further refine the structure and reduce the cross section of the workpiece for the next stage of ECAP with a smaller cross section of the working channel. The second and subsequent stages of pressing are carried out similarly to the first stage described above. Moreover, the choice of the type of intermediate plastic deformation carried out between the stages of ECAP depends on the technical and economic feasibility, and the choice of processing modes depends on the properties of the metal material being processed.

Example

The starting material was a hot-rolled bar of technically pure titanium Gr4 with a diameter of 12 mm with an average grain size of 50 μm and a tensile strength of 750 MPa. At the first stage of processing, the bar was subjected to two cycles of continuous equal-channel angular pressing according to the conform pattern on a snap with a square cross section of the working channel 11 × 11 mm. As a result, a bar of square section 11 × 11 mm was obtained, which received a total deformation of e = 1.5. Then, by drawing, its cross section was reduced to a diameter of 10 mm, as a result of which the bar received additional deformation e = 0.7. At the second stage, a bar with a diameter of 10 mm was subjected to two cycles of equal-channel angular pressing according to the conform pattern on a snap with a square cross section of the working channel of 9 × 9 mm, and the accumulated strain was e = 1.5. The processing modes of a phased ECAP with an intermediate forming drawing and the obtained mechanical properties are shown in the table.

For comparison, a bar with a diameter of 10 mm was made from the same material by the ECAP method according to the “Conform” scheme with the number of cycles equal to 4 (see table).

Processing Modes and Achieved Performance Stage 1 ECAP-K ⌀ 12 → 11 × 11 mm Drawing by a square 11 × 11 → ⌀ 10 mm Stage 2 ECAP-K ⌀ 10 → 9 × 9 mm ECAP-K 4 cycles ⌀ 10 → 9 × 9 mm Tensile strength, MPa 850 910 1100 950 Plasticity, δ% fifteen 13 12 12 Temperature ° C 140 140 140 140 True accumulated deformation, e 1,5 0.7 1,5 3 The average grain size, nm 510 330 220 270

The data presented in the table show that multi-stage processing according to the proposed method leads to higher strength values while maintaining ductility due to the formation of a finer structure and a larger proportion of high-angle grain boundaries.

Thus, the proposed invention improves the mechanical properties of the processed material due to more intensive grinding of the structure upon reaching the desired cross section of the workpiece.

Claims (5)

1. The method of deformation processing of a metal billet in the form of a rod, comprising feeding the billet into a working channel formed between a rotating disk with a continuous circumferential groove and a stationary bounding base surrounding part of the length of the annular groove, and at the output of the working channel they provide a change in its direction by means of a support part, installed in the annular groove, and by rotating the disk, the workpiece is advanced along the working channel in the direction of its exit and continuous equal-channel angular pressing without significant change in the cross section of the workpiece, characterized in that the continuous equal-channel angular pressing of the workpiece is carried out in stages, with a sequential decrease in the cross section of the working channel at each stage, and the workpiece is subjected to a plastic forming deformation at each temperature before each subsequent stage of continuous equal-channel angular pressing at temperature below the temperature of recrystallization of the processed material. 2. The method according to claim 1, characterized in that the inter-stage forming plastic deformation is carried out by rolling. 3. The method according to claim 1, characterized in that the inter-stage forming plastic deformation is carried out by drawing. 4. The method according to claim 1, characterized in that the inter-stage forming plastic deformation is carried out by forging. 5. The method according to claim 1, characterized in that the number of cycles of equal channel angular pressing of each processing step is ≥1.