1 Overview

With the rapid development of the social economy, China's oil and gas long-distance pipeline construction is more and more, the pipeline construction topography, environment, climate vary, the diameter of the pipeline is getting larger and larger, the grade of pipeline steel is getting higher and higher, long The welding process and welding quality requirements of the pipeline are also increasing. So far, the main welding processes of long-distance pipelines have various schemes: under-welding of cellulose electrode and bottom-welding of iron powder low-hydrogen welding rod, covering surface; under-welding of cellulose electrode and self-protecting medicine Semi-automatic welding filling and capping of cored wire; low-splash solid wire welding and gas-preserving welding base and semi-automatic welding filling and capping of self-shielded flux-cored wire; low-splash metal powder cored wire gas shielded welding base and self-shielded flux cored wire semi-automatic Solder fill, cover and all-position automatic welding machine for bottoming and filling and covering. Among them, electrode arc welding root welding + self-protecting flux cored wire semi-automatic welding filling, cover surface and low splash solid core/metal powder core wire welding semi-automatic welding root welding + self-protecting flux cored wire semi-automatic welding filling, covering surface is currently domestic application The most mature, the most used process in the construction unit.

At present, there are many multifunctional welding machines for manual cellulose and self-protecting flux core welding in the pipeline market, but the low-splash solid/metal powder core welding wire combined with manual welding, self-protecting flux core welding and integrated welding machine is still blank in China. When the construction unit adopts the above process, two welding power sources must be configured. In order to simplify the field equipment configuration and reduce equipment investment, the DC-500IIIa pipeline multi-function welding machine (see Figure 1) has been specially developed to meet the welding requirements of cellulose electrode, self-shielded flux core welding and argon arc welding. The low-splash welding of the cored wire/metal powder cored wire can provide a cost-effective and economical pipeline multi-function power supply for the on-site construction team.

2. System composition and principle

The DC-500IIIa power system is divided into three parts: the inverter part, the output current chopping part and the waveform control part, as shown in Figure 2.

(1) Main circuit of power supply The main circuit adopts the improved phase shift resonant circuit of Shandong Aotai, as shown in Figure 3.

The main loop inverter effectively solves the soft switching work in the full load range of the welder, greatly improves the reliability of the welder inverter, and lays a solid foundation for the reliable operation of the entire welding system.

(2) The scheme of output chopping part When low-splash gas shielded welding, in the initial stage of short circuit and late stage of short circuit, in order to reduce the splash, the welding current should be rapidly reduced from several hundred amperes to several tens of amperes in several tens of microseconds. There are two options: the primary side inverter control scheme; the secondary side series chopping scheme, we use the latter. The current and voltage waveforms output by the series chopping method are shown in Fig. 5.

It can be seen from Fig. 5 that after chopper is used, the current drop rate is increased, the spatter rate is significantly reduced, the welding stability is high, and an excellent welding effect is obtained.

(3) The scheme of the control part adopts the combination of software and hardware to accurately detect the moments of the droplet transfer, so that the detection accuracy rate reaches 99%; the current is rapidly reduced before the splash is generated, so that the droplets smoothly transition and the splash is reduced. , effectively reducing welding defects.

3. Welding procedure qualification

Our company cooperates with the Education and Training Center of the Fifth Engineering Company of China Petroleum Pipeline Bureau to comprehensively develop DC-500IIIa welding parameters for the long-distance construction of the site and conduct relevant process evaluation.

The test tube is made of X80 steel, the size is f1016mm×17.5mm, the matching gap is 1.5~3mm, the blunt edge is 1~1.5mm, and the groove form is shown in Figure 6. The bottoming and filling cover welding parameters are shown in Table 1 and Table 2.

After repeated trials and tests by senior technicians and first-line welders of the welding company and the pipeline company, several tests and process evaluations were carried out according to the parameters of Tables 1 and 2. It is concluded that the DC-500IIIa pipeline multi-function welder successfully realized the entire pipeline. The position of solid wire is efficient root welding and self-welding to fill the cover surface, and the welding quality and welding consistency are very high. At present, the pass rate of one flaw detection reaches 98%.

4. Reliability design and testing of welding machine

As we all know, the construction environment of the pipeline welding machine is very bad, and the construction intensity is very large, which may reach 10~12h every day. Once the equipment fails, it will cause a large area of ​​work in the assembly line, causing great losses to the users. We know this. Therefore, the reliability was fully considered at the beginning of the design, and the comprehensive reliability test was carried out in accordance with the relevant national standards before the device was put into the market, and finally passed. The relevant environmental test equipment of our company is shown in Figure 7.

5. Welding equipment and process promotion and application

The equipment has been produced and sold more than 100 sets, and has been successfully applied to the construction of large-scale pipelines such as China-Myanmar Line, Zhonggui Line and West-East Gas Transmission Line. Most of them use low-splash gas protection semi-automatic root welding + core self-protection welding filling cover. The qualified rate of X-ray flaw detection reaches 98%, and the weld bead is well formed. Because the improved core self-shielding welding process is simple and easy to master, it is well received by the welder. Therefore, this equipment has a good application in the field of pipe welding. prospect.

The main application cases are as follows:

(1) The material of 1 pipe of China-Myanmar Line and Zhonggui Line is X80, and the specification is f1016mm×15.3mm. The two weldings are made of low-splash gas-shielded welding. The welding consumables are Jintai JM-58, f1.2m m and 100% CO2 gas. 3 self-protection welding using JC-30 self-protecting flux cored wire produced by Jinqiao, f2mm. 4 The groove shape is V-shaped and composite V-shaped, the blunt edge is (1.2±0.4) mm, and the counterpart clearance is 2.0-3.5 mm. The field application is shown in Figure 8.

(2) The material of the third line of the West-East Gas Pipeline is X80, and the specification is f 1219mm×18.4mm. The two weldings are made of low-splash gas-shielded welding. The welding consumables are Jintai JM-58, f 1.2mm, 100% CO2 gas protection. 3 self-protection welding using Fabshield 81N1 self-protecting flux cored wire produced by Herbert, f2mm. 4 The groove type double V compound groove, the blunt edge is 1.0~1.5mm, and the counterpart gap is 2.0~3.5mm. The effect of the self-protective welding cover of the multi-function welder core is shown in Fig. 9.

6. Conclusion

Our company DC-500IIIa multi-function pipe welding machine has been successfully applied in batches to the China-Myanmar line, the Zhonggui line and the West-East gas transmission line, making up for the defects of similar equipment, filling the domestic gap and providing the long-distance pipeline construction technicians. A cost-effective and economical pipeline multi-function welding power source will make greater contributions to China's pipeline construction in the future.

[Shandong Aotai Electric Co., Ltd. (Jinan 250101) Li Haitao Zhang Guangxian Fifth Engineering Company of China Petroleum Pipeline Bureau (Renqiu, Hebei 062552) Chen Qiangwu Security]

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