SU1632673A1 - Plate-like electrode for built-up welding - Google Patents

Abstract

The invention relates to mechanical engineering, and can be used to restore and strengthen parts. The purpose of the invention is to obtain a constant penetration depth of the base metal along the length of the deposited layer by means of a uniform heat input to the product. The plate electrode consists of a metal plate with a bent end for fixing the conductor. On the lower surface of the metal plate there is a layer of non-conducting substance associated with the surface of the plate, which, when the plate is melted, is partially or completely removed into the slag. The angle between the bottom surface of the non-conducting substance layer and the surface of the metal plate gradually decreases towards the current-carrying end. A metal plate at a distance not exceeding the length of the weld pool from the bent current-carrying end may have an enlarged cross-section. 1 hp f-ly, 3 ill. S

Description

The invention relates to mechanical engineering and can be used to restore and strengthen parts.

The aim of the invention is to obtain a constant penetration depth of the base metal along the length of the weld surface by uniform heat input into the product.

FIG. 1 shows a plate electrode; in fig. 2 - the same, with a section enlarged near the current-carrying end; in fig. 3 - the same, top view.

The plate electrode consists of a metal plate 1 (Fig. 1 and 2) with an end bent to attach the current lead. On the bottom surface of the plate 1 there is a layer 2 of an electrically non-conductive substance associated with the surface of the plate 1 by adhesive forces or chemical interaction forces. The composition of the substance of layer 2 may be similar to the flux used in welding and surfacing of this class of metal. Then, when the plate 1 is melted, the substance of the layer 2 is completely or almost completely removed into the slag. Layer 2 of an electrically non-conductive substance may contain a metal of the same as plate 1, or of a composition other than it in the form of grit or powder. When the plate is melted, then 1 part of the substance of the layer 2 melted by the arc passes into the weld layer. A layer 3 of a substance like a flux can also be applied to the upper surface of the plate 1 (Fig. 1). The plate electrode may have three (Fig. 1) or four (Fig. 2) working areas. In the initial section A, the angle between the metal plate 1 and the lower surface of the layer 2 (or the surface of the part) gradually decreases from a; to “2- In the middle section B, the angle between the metal plate 1 and the bottom surface of layer 2 is practically

ABOUT

WITH

0

one

00

permanently - a.2. The end section B has an enlarged cross section as compared with the rest of the plate 1 (FIG. 2). Section G is a conductive end. To ensure reliable electrical contact between the sheets, the electrode in section B is welded by spot or seam welding.

The cladding is carried out as follows.

After laying the electrode on the surface, filling it with a flux, pressing it with a load and igniting the arc, the plate 1 melts and the layer 2 of the substance 2 under the plate 1 and layer 3 melts above the plate 1. If there is no coating, layer 3 is filled with flux on plate 1. In the initial section A, the largest angle a between plate 1 and the surface of the part and, consequently, the greatest arc pressure on the part metal is observed at the beginning of the deposited layer. The shortest arc length and the largest current are also observed at the beginning of the process. In this case, the cold metal of the part is quickly heated and smelted to the required depth. Moreover, due to the relatively low deposition rate, the metal of the part has time to warm up before the arc. In order to obtain a uniform heating and constant penetration depth, the current is gradually reduced (the arc length increases) and the arc pressure decreases (the angle a decreases). At a certain distance depending on the deposition mode from the beginning, a quasistationary thermal state is reached, but due to a decrease in the length of the electrode when the plate 1 melts, the resistance of the electrode on the outflow decreases, and the current increases at a constant arc length. To compensate for the decrease in resistance of the plate 1, a linear increase in the arc length in section B is provided, which is proportional to the decrease in resistance. At the same time, the average current along the length of the deposited layer does not change. The depth of penetration of the base metal and the heat input into it are almost constant.

In the case of surfacing at high currents in the crater zone, a large difference in the thickness of the deposited layer is formed. In addition, due to the large temperature gradient in this zone, significant thermal deformations occur, leading to a high level of residual stresses. Due to the high cooling rates of the base metal in the zone of the arc breakage, the formation of quenching structures is possible.

The use of an electrode with an increased cross section over the crater zone (Fig. 2) allows to eliminate the listed adverse factors. In this case, the current and the amount of the melted filler metal increase in section B (Fig. 2), and the deposition rate decreases.

When this occurs, the crater is filled and the base metal is heated.

It was established experimentally that when an enlarged section of a metal plate is made at a distance equal to the weld pool, the maximum penetration depth of the base metal in the crater zone exceeds the thickness average over the layer thickness by no more than 0.5 mm, which is not

more fluctuations in the depth of penetration along the length of the weld.

When performing an enlarged section of the plate at a distance greater than the length of the weld pool, a local increase in the penetration depth is observed in the region

near the crater, which causes a large dilution of the deposited metal with the main metal and the deterioration of the mechanical properties of the metal of the deposited layer. For example, in the case where the length of the thickened part on

Q 10 mm exceeds the length of the weld pool, the depth of penetration in the zone adjacent to the crater is 1.0-1.5 mm greater than the average length of the layer. In addition, there is a local thickening of the deposited layer, which requires the use of

5 mechanical processing layer.

Example With the help of an electrode of the proposed construction (Fig. 2), the friction wedges of the oscillation absorbers of freight cars were deposited. The worn surface was restored in three passes.

0 with overlapping under a layer of flux AN-348A. Power supply from transformer TSD-1000-4. Electrode dimensions, mm: length 135; width -45: thickness 4. Material - steel Art. Z. A layer of a substance containing 70% of iron powder PZH-2C and 30% flux AN-348 AM, mixed with liquid glass, was applied on the bottom surface of the electrode. Made electrodes were dried in an oven at 100-300 ° C. The angle at section A (Fig. 1)

0 varied from 45 to 1.2 ° over a length of 40 mm. The thickness of the layer on the bottom surface of the plate in the zone of the deposition end is 4.5 ± 0.5 mm.

Surfacing mode: idle voltage

& 71 stroke; arc voltage 17–21 V;

current 700 + 50 A; surfacing speed 2.9 m / h.

The formation of the deposited layer is satisfactory. The depth of penetration on the length of the weld varies not more than 0.25 mm and is 0.75 mm. On a batch of 10 parts, no cessation of the process and significant defects in layer formation were observed.

The use of a plate electrode of the proposed design allows for a uniform heat input to the part and the penetration of the base metal. During surfacing of moderately alloyed steels, the formation of cracks in the initial and final portions of the surfacing is prevented.

Claims (1)

Invention Formula 1 A lamellar electrode for surfacing, made of a metal plate with a bent end for fastening the current lead, on the surface of which there is a layer of an electrically non-conducting substance, characterized in that, in order to obtain a constant penetration depth of the base metal along the weld layer, uniform heat input into the product, the plate is made curved with an angle between the surface of the layer of non-conductive substance and the surface of the metal plate, decreasing in the direction of the current supplying end 2. Electrode according to claim 1, characterized in that the portion of the metal plate adjacent to the bent current lead end is made with an enlarged cross section. 3 / Fig 2 3 / Fig /