DD150566A1 - METHOD FOR ELECTROSHELK WELDING - Google Patents

Abstract

The invention relates to the ES welding of plated and / or unalloyed metal sheets by means of a two- or multi-layer technology. The goal is to reduce time and costs. The method should be designed so that, while avoiding after-treatment in the weld compound, a Schattzgut equivalent to the plating in the corrosion behavior is achieved on the plating side. According to the invention, in the welding of clad sheets, a forming shoe is used, on the cladding side to limit the molten bath, so that after the welding of the base material there is sufficient space for introducing the high-alloyed cladding material, the area of the forming shoe reaching into the joint shall be one at least 4 mm smaller width compared to the joint possesses. When welding the plating side, the forming shoe is designed to ensure a sufficient plating thickness and the width of the overlay for plating high alloyed, preferably ferritic-austenitic steels, at least 1.5 times the plating thickness.

Description

Process for electroslag welding

Field of application of the invention

The invention relates to a Verfanren for electroslag welding, preferably of plated and / or unalloyed sheets by means of a two- or multi-layer technology, in particular for use in pressure vessels, apparatus, containers and any thick-walled components,

Characteristic of the known technical solutions

It is known that in particular thick-walled sheets, forgings or castings made of unalloyed, low-alloyed or high-alloyed steel can be joined by means of welding according to the state of the art according to rules and regulations. In this case, usually in a welding sequence of the entire weld cross section is detected, the area of the sheet thickness and dependent on her and the applied technology weld seam width (single wire, Mehrdrahi> j band welding, etc.) is determined, The resulting large melt baths lead to a strong dendritic oriented coarse-grained microstructure with low toughness properties When higher toughness requirements are placed on such an electro-welded joint, the joint must be heat-treated, normally normalizing unalloyed steels, air quenching low alloy steels and austenitizing annealing for high alloy steels.

According to EOPaton, Kiev "Electro-slag welding" is a method for a partial electroslag welding is known for repair welds on thick-walled steel or steel castings with preferably irregular breakage, in which the connection by introducing successively welded weld seam volume with itself Branding is made. This method requires a lot of preparation and welding work, and is therefore useful only for special repair work.

Object of the invention

The invention enables the electro-slag welding of plated and / or unalloyed metal sheets while reducing the time and expense, and thus to expand the scope of ES welding.

The essence of the invention

The invention is therefore an object of the invention to develop a process for electroslag welding of clad and / or unalloyed sheets with a two- or multi-layer technology, which is to be designed so that while avoiding after-treatment in the welded connection plattierungsseitlg one of the plating in Corrosion behavior equivalent weld metal is obtained.

Following on from the prior art and the disadvantages described there, it would have been obvious to a person skilled in the art to carry out the welding of clad steels by means of the conventional ES welding technologies in the following two variants

- ES welding of the total cross-section using a filler material matched to the base material

- ES welding of the overall cross-section using a high-alloy (alloyed) filler material matched to the cladding material, taking into account the mixing with molten parent material

The first variant has the disadvantage that the weld metal of the plating is inferior in corrosion resistance (corresponds to the corrosion behavior of an unalloyed or low-alloyed weld metal) and must therefore be protected against corrosion by welding a strip of high-alloyed material or by a high-alloy hardfacing »Es had to be found that in the execution of the second variant, the bond plane between the ferritic base material and the austenitic weld metal due to the greatly different thermal expansion of both materials is extremely susceptible to cracking, so that crack-free welding can not be guaranteed. Surprisingly, it has now been found that the above-described disadvantages can be avoided that according to the invention when ES-welding clad sheets plating side to limit the molten bath in the joint to be filled a form shoe is used, which is designed so that after welding of the base material sufficient Hardly for the introduction of high alloy cladding is present. In order for a stable welding process is ensured, and the forming shoe is not jammed during introduction of the material material welding material, the reaching into the joint area of the form shoe must have a width at least 4 mm smaller than the joint.

When welding the plating side, the forming shoe is designed so that a sufficient plating thickness is formed. Upon introduction of the plating layer, heat post-treatment (improvement of the mechanical and technological properties) of the previously produced material-side welded joint is effected at the same time. The width of the covering must be selected according to the load situation. So is at specifically high corrosion attacks

Claddings of high-alloy steels, preferably ferritic-austenitic steels, to carry out an overlapping width of at least 1.5 × plating thickness, in order thereby to prolong the corrosion path along the heat-affected zone.

The welding process itself is carried out with a filler material adapted to the plating material. Thus, with ferritic-austenitic cladding and stress corrosion cracking hazard, an additional material should be selected which has a sufficiently high cf ferrite content in the weld metal to counteract such an attack.

When ES welding of thick-walled unplated sheets, the same effect is achieved when the weld area is divided into a plurality of cross-sections by correspondingly shaped shoes. These cross-sections are to be filled in a single order so that the highest-stressed area is welded first and, consequently, several heat effects obtained during welding of the following areas. Thus, the primary structure in the split weld seam is finer-grained by the smaller weld puddles and, on the other hand, the strength and toughness properties in the most stressed area of the weld joint are improved by heat exposure of the subsequently welded ply or plies.

Execution play

The invention will be explained in more detail below using an exemplary embodiment. In the accompanying drawings show:

4: the ES welding of a clad sheet

The clad plates to be joined are prepared by means of a plasma cutting cut and brought into the required position for ES welding. As a backup of the base material side a conventional copper shoe 1 is used. To weld the base material, a suitably metallurgically matched additional material of type 10 Mn 4 is used. Plating side is to limit the molten bath 2, a forming shoe 3 is arranged, which is designed so that after welding of the base material sufficient space for introducing the high-alloyed Plattierungsschweißgutes is present. To ensure a stable welding process, the area of the forming shoe 3 extending into the joint has a width 4 mm smaller than the joint. The filler material used is an austenitic filler material of £ 25p Nb adjusted to the plating sv / ks tof f.

Figs. 3 and 4 show the welding of the plating layer, at the same time a YVärmenachbehandlung (improvement of the mechanical and technological properties) of the previously prepared base material side welded joint is effected during their introduction. The form shoe 4 is to be designed during welding of the plating side so that a sufficient plating thickness 5 is achieved. The width of the cover 6 is to be selected according to the claim case. Thus, in the case of specific high corrosion attacks from claddings of high-alloy, preferably ferritic-austenitic steels, an overlay 6 of at least 1.5 x plating thickness is to be carried out in order to lengthen the corrosion path along the heat-affected zone. The welding process

itself is made with a filler material adapted to the cladding material. Thus, in the case of ferritic-austenitic plating and stress corrosion cracking risk, an additional material should be selected which has a sufficiently high cf ferrite content in the weld metal to counteract such an attack.

Claims (2)

invention claim 1. A process for electroslag welding, preferably of plated and / or unalloyed metal sheets by means of a two- or multi-layer technology, in particular for use in pressure vessels, apparatus, containers and any thick-walled components, characterized in that in the Bs welding clad sheets plated on the side Limiting the molten bath (2) in the joint to be filled a form shoe (3) is used, which is designed so that after welding of the base material sufficient space for introducing the high-alloy plating material is present in that the reaching into the joint area of the Shoe (3) has a width at least 4 mm smaller than the joint, wherein the forming shoe (4) is designed during welding of the plating side so that a sufficient plating thickness (5) is ensured and the width of the cover (6) in platings high-alloyed , preferably ferritic-austen of at least 1.5 times the plating thickness, 2. Method for electroslag welding, preferably of plated and / or unalloyed metal sheets by means of a two or multi-layer technology according to item 1, characterized by the fact that, in the case of thick-walled unplated sheets, the weld seam area is divided into a plurality of cross-sections by correspondingly shaped forming shoes arranged in such an order filled by first welding the most stressed area · For this 2 ropes drawings