RU2752056C1 - Method for strengthening weld joints - Google Patents

Abstract

FIELD: welding.

SUBSTANCE: invention relates to strengthening of weld joints. Mechanical deformation treatment of the weld joints is performed with an impact tool by means of static-pulse treatment with shock deformation waves creating plastic indentations on the weld joint. The uniformity of overlapping of the plastic indentations on the weld joint is adjusted by the coefficient of overlapping of plastic indentations K=1-S/(δf60), wherein K = 0.4 to 0.6; δ is the size of the plastic indentation measured in the direction of feeding, mm; S is the feeding rate of the workpiece relative to the tool, mm/min; f is the impact frequency, Hz.

EFFECT: bullet resistance of the weld joints is increased as a result.

1 cl, 2 dwg

Description

The invention relates to military equipment and can be used in the manufacture of body armor, in particular, in armored vehicles and armored structures of all types of troops.

Currently, metallic materials remain the most common armor material. In the manufacture of armored vehicles and armored structures, welding of armor plates is often used. As a result, welded seams are formed that have a significantly lower hardness than the base metal and, therefore, are inferior in bullet resistance to welded armor plates.

Known combat vehicle, which contains a body welded from armor plates, made in it with hatch openings with edging around the perimeter and protective screens [RF Patent No. 2289777. Fighting machine. Bul. No. 35, 2006]. Its disadvantage is the low bullet resistance of the body welds.

There is a known method of static-pulse processing by surface plastic deformation (SPD) of metallic materials, in which a hardened structure of the material is formed under the action of shock waves of deformation, as a result of which a set of plastic imprints with a certain size, overlap and multiplicity of application is formed on the hardened surface [Kirichek A. V., Soloviev D.L., Lazutkin A.G. Technology and equipment for static-impulse treatment by surface plastic deformation. Technologist's library. M .: Mashinostroenie, 2004.288 p .; Patent No. 2098259 RF, MKI V24V 39/00. Method of static-impulse treatment by surface plastic deformation / A.G. Lazutkin, A.V. Kirichek, D.L. Soloviev. Bull. No. 34, 1997]. When using static-impulse processing, a hardened surface layer can be obtained, up to 8-10 mm in depth and 35-45 HRC hardness. The method has successfully proved itself for hardening machine parts, however, it was not used to strengthen the welded seams of armored steels.

There is a known method of strengthening treatment of welded joints, which consists in mechanical processing of welded joints with a percussion pneumatic tool with the formation of holes on the surface of welded joints [Patent No. 2364489 RF. Method for hardening treatment of welded joints. Bul. No. 23, 2009]. For hardening, pneumatic hammers with an impact energy of 6-22.5 J were used and a tool in the form of a pneumatic chisel with a tip radius of 2-3 mm or a multi-ribbed hardener made in the form of a bundle of spring wire of round or flat section, the working ends of the wires are rounded off with a radius of 0.8- 2.5 mm. The disadvantage of this method is the shallow depth of hardening. The method is intended to increase the fatigue strength of welded joints of frame structure elements, in particular, diesel locomotive bogie frames, but was not used to increase the bullet resistance of armor.

The aim of the proposed invention is to improve the bullet resistance of welded seams of metal armor structures.

To achieve this goal, a technology for strengthening welded joints by static-impulse processing is proposed, which creates a work-hardened surface layer by shock waves of deformation.

The mechanism of wave strain hardening by static-impulse processing is as follows. For hardening, a pulse generator is used, which provides the energy and frequency of impacts, respectively, 50-200 J and 7-40 Hz, the main elements of which are the striker 1 and the waveguide 2 (see Fig. 1). When hardening, the firing pin 1 strikes the waveguide 2 statically compressed to the surface to be hardened through the tool - the rod roller 4, as a result, plane acoustic waves are generated in the impact system, which are characterized by the law of the change of forces in time, the maximum value of the forces, the time of action of the forces (duration of the deformation wave) and the energy of the deformation wave. These characteristics depend on the geometry of the colliding striker 1 and waveguide 2, the properties of their materials and the impact speed. The shock wave of deformation is determined by a sequence of pulses, and the duration of each of them is equal to the period of the wave. The shape of the shock pulse (change in force over time) entering the deformation zone, i.e. the area of contact of the tool - the rod roller, with the hardened material, will determine the efficiency of dynamic loading. Preliminary static compression of the waveguide 2 contributes to the most complete use of the pulsed load for plastic deformation of the hardened material. During hardening, the shape of shock pulses is maximally adapted to the properties of the material and loading conditions, which increases the efficiency of the process, expands the technological capabilities of processing, making it possible to create a deep hardened layer. The technology of static-impulse processing by shock waves of deformation allows you to accurately control the uniformity of hardening, creating both uniformly and heterogeneously hardened structure.

Usually, butt welding is used to connect the armor plates 3. FIG. 1 shows a diagram of the wave strain hardening of the welded seam of butt-welded armor plates with a V-shaped bevel of the edges. Hardening by static-impulse processing by deformation shock waves is carried out when the tool is fed along the weld. For hardening, a tool is used - a rod roller 4, the width of which exceeds the width of the welded seam 5 by at least 3 times, providing hardening not only of the welded seam 5 over the entire width, but also of the heat-affected zone. Strengthening of the welded seam 5 can be carried out both on one and on both sides.

When using multilayer welding for connection of armor plates 3, strengthening by static-pulse processing by shock waves of deformation is carried out layer by layer for one or several layers.

To obtain better characteristics of the welded seam 5 (increasing the density, reducing structural defects and its porosity), the uncooled material of the welded seam 5, which is at a temperature above 100 ° C, but below the recrystallization temperature, can be hardened by static-pulse processing by shock waves of deformation.

As a result of the application of static-pulse processing by shock waves of deformation of the welded seam 5 and the near-weld zone, the hardness increases, primarily of the material of the welded seam 5, and the material is hardened to a depth comparable to the thickness of the parts being welded, which increases its bullet resistance (Fig. 1 shows part of the weld after wave strain hardening 6).

Description of drawings.

FIG. 1 is a diagram of the wave strain hardening of butt-welded armor plates with a V-shaped bevel of the edges.

1 - striker;

2 - waveguide;

3 - armor plates;

4 - rod roller;

5 - welded seam;

6 - part of the weld after wave strain hardening;

A - energy of shock waves of deformation, f - frequency of impacts, P _st - preliminary static compression of the waveguide; S is the feed rate of the workpiece from the armor plates being welded relative to the tool to ensure its feed along the weld.

FIG. 2 is a diagram of the seam cleaning by machining after welding the armor plates.

Example.

Sheets of 2P armor steel were subjected to wave strain hardening at temperatures above 100 ° C, but below the recrystallization temperature. Two 6.5 mm thick plates were butt welded with a V-bevel. After welding, the welded seam was machined to remove an allowance of 0.5-1.0 mm (see Fig. 2). For hardening, rod rollers with a diameter of 10 mm and a width of 40 mm were used. Loading by a deformation wave was carried out with an energy of A = 150 J. The uniformity was regulated by changing the coefficient of overlapping of plastic indentations K = 1-S / (δf60), where δ is the indentation size measured in the feed direction, mm, S is the feed rate of the workpiece from the welded armor plates relative to the tool, mm / min; f is the frequency of impacts, Hz. The values of the coefficient of overlap of plastic imprints were selected from the range K = 0.4-0.6.

The samples obtained were used to study the microhardness and bullet resistance of welded joints without hardening and after wave strain hardening.

To study the microhardness, the samples were cut across the weld, i.e. across the direction of application of the action by the deformation wave, and then thin sections were made from them. The measurement was carried out over the depth of the hardened surface layer. The results of microhardness measurements showed the gradient nature of its change along the weld seam depth. It was found that on the surface of the weld the degree of hardening reached 50%, and the microhardness was 5500 MPa, while the microhardness of the unreinforced weld was 3660 MPa. The depth of the hardened layer reached 3 ... 6.5 mm.

Tests for bullet resistance of hardened and unreinforced welds were carried out with PS bullets (TUS), ind. 57-N-231 caliber 7.62 × 39 mm, firing distance 5-10 m, to reduce the speed of the bullet in the range of 450-540 m / s, powder was poured. As a result of the tests carried out for bullet resistance, the penetration of unreinforced and non-penetration of hardened welds was established.

Sources of information

1. RF patent No. 2289777. Fighting machine. Bul. No. 35, 2006.

2. Kirichek A.V., Soloviev D.L., Lazutkin A.G. Technology and equipment for static-impulse treatment by surface plastic deformation. Technologist's library. M .: Mashinostroenie, 2004.288 p.

3. Patent No. 2098259 RF, MKI V24V 39/00. Method of static-impulse treatment by surface plastic deformation / A.G. Lazutkin, A.V. Kirichek, D.L. Soloviev. Bull. No. 34, 1997.

4. Patent No. 2364489 RF. Method for hardening treatment of welded joints. Bul. No. 23, 2009.

Claims (1)

A method of strengthening welded seams, including mechanical deformation processing of welded seams with an impact tool by means of static-pulse processing by shock waves of deformation with the creation of plastic imprints on the welded seam, characterized in that the uniformity of overlapping of plastic indentations on the welded seam is controlled by the coefficient of overlapping plastic indentations K = 1- S / (δf60), where K = 0.4-0.6; δ is the size of the plastic indentation measured in the feed direction, mm; S is the feed rate of the workpiece relative to the tool, mm / min; f is the frequency of impacts, Hz.

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