SU1673334A1 - Method for welding fixed pipe butts - Google Patents

Abstract

The invention relates to electric-arc fusion welding, in particular, to automatic welding of non-rotary joints of pipelines with flux-cored wire with forced formation of a weld, and can be used in all branches of mechanical engineering. The purpose of the invention is to improve the quality of the welded joint and to simplify the welding technique by adjusting the thermal power of the arc depending on the spatial position. Welding of non-rotating pipe joints with flux-cored wire with forced formation of a weld is led from the bottom up from the ceiling position to the lower pulsating current. Here, the pause current I _p is between 0.6 and 0.8 pulse current I _and . Welding pipe sections with a central angle α, where 0 ≤ α ≤ ϕ / 4 and 3/4 ϕ ≤ α ≤ ϕ is carried out with a smooth change in the pause time T _p in accordance with the dependence T _n = m ₀ CoSL, where T ₀ is the initial time pause, set for the ceiling position and equal to 0.2 - 0.4 TC, where TC is the pulse cycle time. Welding a pipe section with a central angle β, where ϕ / 4 ≤ β ≤ 3/4 ϕ, is carried out with a fixed pause duration T _n = T ₀ COS ² ϕ / 4. 1 tab. 2 Il.

Description

The invention relates to electric arc welding by fusion, in particular, to automatic welding of non-rotary joints of pipelines with cored wire with forced formation of a weld.

The purpose of the invention is to improve the quality of the welded joint, to simplify the welding technique by adjusting the heat power of the arc depending on the spatial position of the weld.

Fig, 1 shows a diagram of the welding joint; FIG. 2 is a diagram of a change in the parameters of a pulse cycle during welding of a non-turn joint.

The proposed welding method is implemented as follows.

Before welding, a joint marking is made, fixing the lowest point 1 of the pipe surface, where al, pipe sections 2, 3, corresponding to the central angles. ravnymZ / 4l and IO a l / 4, and the highest point 4 on the surface of the pipe a 0.

Manual arc welding of the root seam is performed. Then, the automatic welding machine is installed in the overhead position. The welding modes, including the amplitude and time parameters of the pulse cycle, are set: lu, p.Tc. T t. Then begin

sk j so

GO 00

welding process, which is carried out with a smooth decrease in the pause time.

When the machine reaches the mark 2 on the pipe surface (7 3/4 l), the regulation of the pause time (tn) is stopped. At the junction between marks 2 and 3, the welding process is carried out with constant parameters of the pulse cycle. When the automatic welding machine reaches the mark 3 (yy-l / 4), they gradually increase the pause time to the value t () in the lower position (a - O).

The welding of the second half period of the pipe is carried out according to a similar scheme.

Experimental verification of the method was carried out when welding pipes with a diameter of 1220x12 mm. As a current source, Kemppi PS 5000 inverter rectifiers with the C 100P prefix were used to adjust the pulse cycle parameter and the VDU-506 rectifier with a prefix for pulse generation.

Welding modes in the testing process are given in table 1.

In options 1-4, the value of the pause current (1P) was changed. In options 5 8 - pause time (tn). Option 10 welding was conducted with an arbitrary change in the pause time.

The parameters of welding modes for options 1,2,5 and 6 were set within the limits regulated by the claimed method. In option 1, the pause current is ln 0.6 1c; in option 2 in 0.8 In. In option 5 t0-tn 0.2 TC; in variant b 0.4 Tu. The quality of the butt welded in options 1,2, 5 and 6 is satisfactory.

When assigning mode parameters whose values exceed the limits regulated by the method, a decrease in welding quality is noted. Thus, when welding according to option 3 (In 0.5 lu), non-fusion is formed, according to option 4 (ln 0.9 1i), burn-throughs are formed in the overhead position. When tcrtn -0.1 TC is reached (option 7), burn-throughs are observed in the overhead position and unsatisfactory formation of the seam in the down position due to the random spreading of the weld pool metal.

When a pause is reached, 6Tn (option 8), the welding

baths in the ceiling position, formed by non-fusion along the edges

Comparative tests of welding conditions in which the pause time ee-s depending on the spatial position in accordance with the dependence

g

tn to cos a (option 9) and arbitrarily (option 10) showed that with an arbitrary change in pause time, it is not possible to get rid of defects such as burn-throughs in the flow position and non-fusions at different parts of the seam perimeter.

Thus, the proposed method provides improved quality of the welded

5 th joint while simplifying the welding technique. The welder's labor time is improved by eliminating the operation of stripping the seam from inside the pipe.

Claims (1)

Formula of invention The method of welding non-rotary pipe joints with flux-cored wire with forced formation of a weld, in which welding of each half of the joint is 5 upwards from the ceiling to the lower position, characterized in that, in order to improve the quality of the welded joint and simplify the welding technique by 0 depending on its spatial position, butt welding is carried out with a pulsating current with a pause current of 0.6–0.8 pulse current, the pause time in the overhead position is set to 0.2–0.4 cycle times, while in the welded sections the seams with central angles from l to 3/4 l yot l ds 5/4 l and opposite to them from 7/4 to 2 l and from 1/4 l to 0, the pause time varies along 0 dependencies about tn to COS (I. where tn is the pause time, s; to - pause time in the overhead position, s; 5 (I is the current value of the central angle of the welded section. And welding of the section with the central angle from 3/4 l to 1/4 and the opposite angle from 5/4 l to 7/4 l is carried out at the pause time. 0 equal to 1/2 the pause time in the overhead position. JCd., T4  WITH u u 1.4. LLLP n a pptpppppll n a V4. #