SU1538946A2 - Method of joining enamelled tubes - Google Patents

Abstract

The invention relates to welding, in particular to methods for joining enamelled pipes, which can be used in the oil, gas, chemical and other industries of the industry. The purpose of the invention is to improve the quality of the enamel coating in the area of the weld. Enamelled pipes, after applying to the ends of the enamel slip to be welded and drying, are collected for welding and heated to the softening temperature of the enamel at a speed of 200-1200 degrees / min and in this form they are made. After welding, the joint zone is additionally calcined at the reflow temperature of the enamel and cooled slowly.

Description

The invention relates to welding, in particular to methods for joining enamelled pipes, can be used in the oil, gas, chemical and other industries of the industry and is complementary to the main author. St. No. 1353549.

The aim of the invention is to improve the quality of the enamel coating in the weld area.

The method is carried out as follows.

Before assembling for welding pipes with internal enamel coating, a layer of enamel slip is applied and forced drying is performed. The pipes prepared in this way are collected between each other, after which the ends of the pipes are heated to the temperature of the beginning of softening of the enamel at a speed of 200-1200 degrees / min and in this form the pipes are welded. After welding, the joint zone is fired at the melting temperature of the enamel and slowly cooled at a speed of 6-30 degrees / s.

The most optimal rate of temperature rise during heating of pipe ends before welding is in the range of 200-1200 degrees / min. At heating rates above 1200 degrees / min, enamel chips are possible. Heating rates Below 200 deg / min are irrational, as they lead to an increase in the duration of the pipe joints.

Example. Testing of the method was carried out on tubular samples with a diameter of 76 mm, a wall thickness of 3.5 mm with an internal enamel coating grade 47/149. An enamel enamel slip 47/149 was applied to the inner surface of the samples on top of the enamel coating at a distance of 10 mm from the ends. Drying the slip was done by heating the outer surface of the pipe ends with a gas burner to 140 ° C. The heating temperature of the outer surface of the pipe

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controlled by thermocouple. After the drying of the slurry, the samples were docked in pairs. The joint area was heated outside by a gas burner, while the temperature of the pipe ends was gradually raised to 500 ° C. The temperature rise rate was changed; the heating intensity varied from 200 to 1400 deg / min. After heating the pipe ends to 500 ° C, the samples were welded using electric arc welding. After this zone

seals the mechanical properties and strength of the welded joint.

Claims (1)

Invention Formula Method of joining enamelled pipes according to ed. St. No. 1353549, characterized in that, in order to improve the quality of the enamel coating in the weld area, the ends are heated before welding  the junction was burned with a gas burner at 10 pipes to a softening start temperature of 840 ° C and cooled slowly, insulating the oil at a speed of 200-1200 degrees / min, the area of the junction with asbestos cloth. Part of the samples were connected without heating the ends before the weld. The rate of temperature rise when the ends of pipes are heated before welding to 500 ° C, degrees / min The presence of defects in the enamel coating in the area of the seam koi After cooling the samples to room temperature, the samples were cut along and examined for defects visually and with the help of an LCD-1 flaw detector. The results of the experiments are shown in the table. As follows from the results of experiments, given in the table, this method when heating rates of pipe ends before welding 200-1200 ° C makes it possible to eliminate coating defects in the weld area. With an increase in the heating rate of more than 1200 ° C (experiment No. 8), the formation of defects as a result of chipped enamel is possible. Heating rates below 200 ° C are impractical because of the unjustified increase in the duration of the pipe joining process. In addition, the preheating of the ends is coarse before welding at the same time seals the mechanical properties and strength of the welded joint. Invention Formula Method of joining enamelled pipes according to ed. St. No. 1353549, characterized in that, in order to improve the quality of the enamel coating in the weld area, the ends are heated before welding tort, no The rate of temperature rise when the ends of pipes are heated before welding to 500 ° C, degrees / min The presence of defects in the enamel coating in the area of the seam there is No No No No No No Yes