SU1473924A1 - Method of producing fluid-tight butt or fillet welds - Google Patents

Abstract

The invention relates to welding, in particular to the production of hermetic butt and corner joints in various parts of the engineering industry. The purpose of the invention is to prevent the formation of through defects. The method involves evacuation during welding. Welding of the joints is carried out in two or more passes, and vacuuming is carried out in the process of welding the second and subsequent passes on the reverse side of the joint. When welding the second pass, vacuuming is carried out to a pressure of 96 to 98 kPa, and subsequent passes to a pressure of no more than 60 kPa. The method also provides for evacuation to a pressure of not more than 60 kPa on the back side of the joint when the weld surface is melted after all the passages have been completed, which is performed by an arc under a flux or in a protective gas with a meltable or non-consumable electrode. 2 hp f-ly.

Description

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The invention relates to arc welding of structures operating under pressure or in a vacuum, and can be used in all areas of national economy, mainly in the oil and gas and chemical industries.

The aim of the invention is to obtain hermetic welded joints by eliminating the formation of through defects in the seams.

Example 1. It is necessary to butt-weld a hermetic ring joint in the manufacture of a product with a closed cavity, for example, a cylinder for storing liquefied gas. The cylinder diameter is 60 cm, the wall thickness is 1.7 cm. Welding is unilateral from the outside of the product, under the flux, with a melting electrode. The seams are made in three passes. For the first pass, which provides the initial connection of edges, no vacuuming is applied. In the second pass, which fills the edge cutting and melts about 50% of the first pass metal, in the internal cavity of the product through the nozzle, using a vacuum pump and regulating equipment, reduce the pressure to a value of 96 to 98 kPa. The third, closing, passage is welded after the pressure in the internal cavity decreases to a value of no more than 60 kPa. Example 2. It is necessary to weld a sealed ring joint with a diameter of 142 cm and a wall thickness of 2.2 cm. Welding double-sided under flux and in a protective gas in four passes. The first passage is welded in shielding gas without vacuum from the outside of the joint. Local vacuum chambers are used for the remaining passages. When welding the second pass, which is performed on the outside of the ring joint in shielding gas and melts about 50% of the first pass metal, the vacuum chambers are set on the inside surface of the joint.

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in the chamber, the switch is lowered to 96-bar closing and the internal is submerged under the flux with amer no more than 60 kPa, the remaining passage of the first pass melting with a seam, and with its vacuum chambers installing an external interface.

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Example 3. It is necessary to weld a hermetic butt joint between two steel sheets of small (0.5 cm) thickness. The seams are welded in two flux passes on both sides of the joint. The first pass is performed without evacuation. The product is rotated 180 ° and the second pass is welded, simultaneously providing pressure reduction to 96-98 kPa from the back side of the joint using local vacuum chambers. Then, depending on the working conditions of the product on the same side of the joint or after re-rotating the product through 180 °, the surface of the seam is melted by the plasma arc at a pressure in the vacuum chamber not exceeding 60 kPa.

The use of the invention provides cost savings by reducing the transfer of products to lower quality due to the presence of leakages, reducing the amount of work to eliminate

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such defects, as well as reducing the loss of gaseous or liquid products during storage and transportation.

Claims (3)

1. A method of producing hermetic welded butt or corner joints, which provide for evacuation during the welding process from the root side, characterized in that, in order to prevent the formation of through-defects, the joints are welded in several passes and the evacuation is performed during the second and subsequent welding. when welding the second pass, vacuuming is carried out to a pressure of 96-98 kPa, and subsequent passes to a pressure of no more than 60 kPa. 2. A method according to claim 1, characterized in that in the case of two-pass welding, evacuation is carried out when the weld surface is melted after the second pass welding, and the evacuation is performed to a pressure of not more than 60 kPa. 3. A method according to claim 2, characterized in that the melting of the surface of the seams is performed by an arc under a flux or in a protective gas with a melting or non-consumable electrode.