Application of welding technology in the machine tool industry

Foreword

The machine tool industry is an important part of the machinery industry, the "master craftsman" of the machinery industry, and the basic industry of the national economy. Machine tool products are machines that make all machines, and their working accuracy is generally higher than the precision of the machine parts being machined. To this end, the technical level and service level of machine tool products play a decisive role in the improvement of production technology and economic benefits of machinery industry products.

Due to the particularity of the machine tool, the particularity of the machine structure is determined. Casting structures have dominated the machine tool structure for decades. The casting process has always been the dominant process for machine tool products. After the 1980s, with the increasing introduction of machine tool products, the structure of machine tools has increasingly adopted welded structures. development trend. The welding process has also become an important basic process in the machine tool manufacturing industry, and has evolved from a single processing technology to an emerging comprehensive project including raw material pretreatment, cutting blanking, forming welding, post-weld inspection and post-weld treatment. technology. It has completely changed the situation that the casting structure has been “unified in the world” in the past few decades, and machine tool manufacturing is inseparable from welding.

1 Development of welding technology in the machine tool industry

The development of welding technology in the machine tool industry has evolved with the development of the welding structure of machine tool products. The leading products of China's machine tool industry mainly include metal cutting machine tools, forging machinery products, foundry machinery products, woodworking machine tools, tool products, abrasive tools and machine tool accessories. Among them, metal cutting machine tools, forging machinery and casting machinery products are the main fields of welding technology application in the machine tool industry. From the technical level of machine tool product development, the development of welding technology in the machine tool industry is roughly divided into three stages.

1.1 Welding technology as an auxiliary process stage

This phase was from the 1950s to the early 1970s. At this stage, in the development of machine tool products, it is mainly to copy the stage of foreign machine tool products. At that time, the metal cutting machine was successfully copied by the type 1Д63 lathe, 2A125 vertical drilling machine, 6H82 universal milling machine, 1617 horizontal lathe and 262 horizontal boring machine, which accounted for 70% of the total number of 204 kinds of machine tools. Forging machinery mainly developed open presses, closed single point presses of 315 tons or less, air hammers, double disc friction presses of 300 tons or less, shearing machines, four-column universal hydraulic presses, thread rolling machines and automatic forging presses, etc. General purpose forging machinery products with large demand.

At this stage, the structure of the machine tool products is basically all of the cast blank structure, so the welding technology at this stage only serves as an auxiliary process for the product. The focus of the welding is the defect welding of the cast structural parts and the fuel tank and electric box cover of the product. Some small non-main parts such as shells. The main welding method is manual arc welding, or oxyacetylene gas welding, which is controlled by the workers themselves. There are no formal welding technicians and process measures, and there is no special welding workshop. In larger companies, welding is combined with other foundry or product assembly workshops with limited production area.

1.2 Initial application stage of welding technology

This phase, from the 1970s to the early 1980s, was the initial application phase of welding technology. At this stage, based on the imitation of machine tools in the 1950s, the research and development of high-precision precision machine tools began. In the field of metal cutting machine tools, only in the 1970s, the second automobile factory was provided with a high level of 7664 machine tools, which met more than 98% of the machine tools required by the second automobile factory; in the forging machinery, In order to equip the second automobile plant, 115 kinds of 510 general-purpose forging machines and some production lines were developed and manufactured. At the same time, at this stage, the professional fixed-point factories have mastered 257 kinds of forging machinery.

In this stage, with the advancement of the overall welding technology, some enterprises have begun to adopt welded structures in the structure of their own designed machine tools, such as the base of the 800-ton mechanical press products of Jinan No. 2 Machine Tool Plant, the beam and other large-scale. Parts and gas cylinder parts; Qiqihar No. 2 Machine Tool Plant, the J81-1250 trimming press developed and designed in 1973 used welded parts for the first time. The main structural parts were base, column and head, and the maximum welded parts weighed 25 tons; From 1978 to 1979, the plant was welded on the bed of the Z41-30 nut cold heading machine and the high pressure vessel parts of the TA88-200 cold extrusion machine. The adoption of these welded structures has contributed to the development of welding technology in the machine tool industry.

Since the late 1970s, conditional enterprises have organized the establishment of independent welding workshops, increased workshop lifting equipment and improved welding techniques. For example, Jinan No. 2 Machine Tool Plant established a welding workshop in 1975. At that time, the workshop area was 5,275 square meters, and the maximum lifting capacity was 50 tons. The welding process also developed from simple manual arc welding to submerged arc welding and electroslag welding. Semi-automatic cutting blanking and radiographic inspection methods. This shows that the application of welding technology in the machine tool industry has entered the comprehensive engineering technology field from the beginning, laying the foundation for the technical introduction of the third-stage machine tool products.

1.3 The leading process stage of welding technology

At this stage, the introduction of technology began in the early 1980s. At this stage, the machine tool industry promoted the rapid development of high-end advanced machine tools by introducing advanced foreign design and manufacturing technologies. For example, in the field of metal cutting machine tools, Beijing No. 1 Machine Tool Plant cooperated with Hitachi Seiki Co., Ltd. to produce K-type milling machine, and successfully developed a new series of CNC milling machines. At the same time, it cooperated with the Federal Republic of Germany WALDRICH COBURG. CNC gantry milling machine; Jinan No. 1 Machine Tool Plant cooperated with Yamazaki Iron Works of Japan to produce Mazak horizontal lathe, Jinan No. 2 Machine Tool Plant cooperated with French BMO Company to develop 4×10m large gantry beam mobile five-face machining center and Φ200 Large-scale CNC floor milling and boring machine and 2.4×13m large gantry mobile five-face machining center; Wuhan Heavy Machine Tool Plant and Federal Republic of Germany. With the cooperation of the company, the company has produced a high-end machine tool with a world-class vertical lathe with a diameter of 1.4 to 2.5 m and a floor milling and boring machine with a diameter of Φ260 mm or more. In terms of forging machinery, Jinan No. 2 Machine Tool Plant took the lead in introducing the complete design, manufacturing and testing technology of eight series of 35 varieties of heavy-duty and super-heavy mechanical presses of American VERSON All-steel Machinery Press Company. The introduction, absorption and digestion stages of heavy forging equipment. Subsequently, in 1981, Huangshi Forging Machine Tool Plant introduced the drawings and manufacturing techniques of the Belgian hydraulic shearing machine and bending machine series. In 1986, Qiqihar No. 2 Machine Tool Plant introduced the mechanical press manufacturing technology of Komatsu Group of Japan. In 1991, Shanghai Forging Machine Tool Plant cooperated with SCHULER of Germany to provide 14 600-ton closed-type four-point multi-link mechanical presses for Shanghai Volkswagen. In 1992, Qiqihar No. 2 Machine Tool Plant cooperated with Alfte of Germany to introduce multi-link press manufacturing technology, and so on. Through the introduction, digestion and absorption, the design capability and manufacturing level of China's heavy-duty and ultra-heavy forging equipment have been rapidly improved, and they have basically reached and reached the international advanced level. At present, the domestic forging industry has developed more than 440 kinds of forging equipment. The heavy machinery press has been developed, the single machine capacity has reached 3,000 tons, the hydraulic bending machine has a single machine capacity of 4,000 tons, and has the ability to develop and manufacture single machine. The ability of over 4,500 tons of super heavy mechanical presses and large multi-station presses.

The introduction of technology has promoted the application of welded structures in the machine tool industry. For example, in Jinan No. 2 Machine Tool Plant, the mechanical press products designed by 1981, the welded structural parts only accounted for 14%, the welding structure of the planer products was less than 1%, and the proportion of welded structural parts introduced into the press products in 1981 reached 44.3%. The proportion of welded structure of mechanical press products with self-digested design after the introduction of technology reached 67.1%. The welded structure of the imported CNC machine tools has also reached 60%. Tianjin Forging Machine Tool Plant, the number of welded structural products used in 1975 was only 8 kinds, less than 47%. In 1991, it broke through 44 species, accounting for more than 66% of the total number of varieties.

The application of the welding structure of machine tool products has changed the situation of the former casting machine system structure, and the welding technology has gradually developed into the leading technology of the machine tool industry, which is mainly reflected in the following aspects:

(1) Some key enterprises have established welding workshops or metal structure factories with a certain scale, and established a complete welding management system. Absorbed and digested the welding process standards of imported products, implemented national professional standards, and formulated corporate standards.

(2) Improve the welding process, from a single processing technology to a set of emerging comprehensive engineering technology from raw material pretreatment, cutting blanking, forming, welding, post-weld inspection and post-weld treatment.

(3) CNC precision cutting and computer programming nesting technology has been applied, and the traditional manual cutting and blanking has been changed, the machining has been reduced, and the “cutting and cutting” and “cutting by welding” have been realized.

(4) Promote the application of advanced and efficient new technologies such as CO ₂ gas and argon-rich gas shielded or submerged arc welding. The welding workload has exceeded 50% in the backbone enterprises, and individual enterprises have reached more than 80%.

(5) X-ray flaw detection and ultrasonic non-destructive flaw detection are commonly used to stabilize the intrinsic quality of the weld.

(6) The new vibration aging process has been promoted to achieve the purpose of reducing and homogenizing the residual stress of the welded structure, reducing the deformation of the welded parts and stabilizing the accuracy.

(7) The welding technicians and welders have been continuously strengthened and embarked on formal management. Most enterprises have implemented welders to hold certificates. In addition, during the “Eighth Five-Year Plan” period, a welding model factory with industry-representative significance was established, which promoted the development of welding technology in the machine tool industry.

2 Application of welding technology in the machine tool industry

The application of welding technology in the machine tool industry has been developed with the introduction of foreign product technology. At the same time, the development of domestic welding technology has also promoted the application of welding technology in the machine tool industry. At present, the main welding techniques used in the machine tool industry have the following aspects:

2.1 Steel plate pretreatment technology application

The steel plate pretreatment production line of the machine tool industry was started in 1993 by Jinan No. 2 Machine Tool Plant. It started on the basis of the shipbuilding industry, heavy machinery industry and mining industry. The pretreatment production line is jointly developed and manufactured by the plant and Qingdao No. 3 Foundry Machinery Factory. The main process flow is: steel plate leveling, preheating, shot blasting, automatic painting and drying, with a total length of 60 meters. The main technical parameters are: steel plate leveling thickness 8 ~ 40mm, leveling width 3m; pretreatment steel plate thickness 8 ~ 160mm, effective width 3m; processing structure maximum specification is 1500 (width) × 800 (height); pretreatment speed is 0 ~ 4m / min; annual processing capacity of 40,000 tons / year; using PC automatic control and manual control two ways. The steel plate pretreatment production line solves the bad factors such as rust and scale of raw materials, and improves the quality of CNC cutting blanking and the appearance quality of machine tools.

2.2 CNC cutting technology application

In 1982, the second CNC machine tool factory began to apply the domestic CNC cutting machine to the cutting and blanking of steel plate parts. In 1988, the computer automatic programming nesting technology was applied to increase the utilization rate of steel plate from 70% to 74%; 1992 In the year, Jinan No. 1 Machine Tool Plant introduced the US plasma CNC cutting machine and laser CNC cutting machine, and started the application of CNC plasma and laser cutting in the machine tool industry, so that the cutting precision of thin steel plate with thickness of 0.5~8mm reached 0.5~1mm. During the “Seventh Five-Year Plan” period, Jinan No. 2 Machine Tool Plant developed and researched the precision cutting technology of thick steel plate CNC, which made the thickness of CNC precision cutting of thick steel plate reach 275mm. The project won the first prize of the “Seventh Five-Year” process achievements of the machine tool industry of the Ministry of Machinery. In 1993, Jinan No. 2 Machine Tool Plant increased the cutting thickness of CNC plasma carbon steel in the machine tool industry from 8mm to 25mm by introducing CNC underwater oxygen plasma cutting machine, which reduced the cutting deformation of medium and heavy plates and improved the cutting of medium and thick steel plate parts. Precision and cutting quality.

2.3 Application of high efficiency welding technology such as gas shielded welding

With the introduction of foreign technology, in 1981, Jinan No. 2 Machine Tool Plant first applied Φ1.6 solid CO2 gas shielded welding technology to replace the Φ2.4 core argon-rich gas shielded welding process of American VERSON All Steel Machinery Press Company. The welding process of the large welded parts of the press was tackled and succeeded. The project won the third prize of the Ministry of Machinery Science and Technology Progress. In 1986, Qiqihar No. 2 Machine Tool Plant applied Φ1.2 solid core argon-rich gas shielded welding technology to solve the welding problem of large welded parts of presses, and used the argon-arc copper surfacing technology to weld copper on the surface of pistons, cylinders and other workpieces. Layer surfacing, which is a success in replacing the traditional copper sleeves in China. In 1992, Jinan No. 1 Machine Tool Plant applied Φ0.8 solid CO2 gas shielded welding for the first time on the thin-plate cover structural parts of machine tools. During the “Seventh Five-Year Plan” period, Jinan No. 2 Machine Tool Plant also applied CO2 gas shielded welding to the long welding of the tensioning bolts of the press. The project won the second prize of the “Seventh Five-Year” technological achievements of the machine tool industry of the Ministry of Machinery. At present, high-efficiency welding techniques such as gas shielded welding have been widely used in machine tool beds, gears, eccentric bodies, rocker shafts, cylinder blocks, pipe flanges and casings that are not processed after welding, and have become machine tool industries. One of the main processes of welding.

2.4 Vibration aging technology application:

The new vibration aging process is a new process technology developed in the 1960s. It has the advantages of strong applicability, energy conservation, environmental pollution reduction, shortened production cycle and improved production efficiency. Jinan No. 2 Machine Tool Plant began to apply this process to the welded parts of imported products in 1981, and achieved good results. Huangshi Forging Machine Tool Plant conducted in-depth research and application on the vibration aging process during the “Seventh Five-Year Plan” period, and won the second prize of the “Seventh Five-Year” process achievements of the machine tool industry of the Ministry of Machinery. At present, the process has been widely used in the machine tool industry.

2.5 Application of welding automation and mechanization technology

In addition to CO ₂ semi-automatic welding, the welding automation of the machine tool industry is mainly embodied in the application of submerged arc automatic welding, mainly used in the seam welding of steel plates and the barrel welding of pressure vessels. Jinan No.2 Machine Tool Plant introduced the automatic submerged arc welding equipment for domestic cross-operating frame purchased in 1988 by introducing the automatic seam tracking system and welding power source in the United States in 1993, and realized the pressure vessel cylinder and the head without the thickness of 18mm. The double-sided automatic tracking submerged arc welding of the beveling butt joint has achieved full success. The mechanization of welding is mainly the application of welding positioner. In 1981, Jinan No. 2 Machine Tool Plant started the application research of the positioner on the welding gear of the introduced product, but it was not promoted. Only the positioner was modified. Automatic cutting equipment for gear webs. After 1988, the welding positioner was applied in Shanghai Forging Machine Tool Plant, Yingkou Forging Machine Tool Plant and Huangshi Forging Machine Tool Plant, which improved the degree of welding mechanization. In addition, in 1998, Jinan Second Machine Tool Group Co., Ltd. successfully applied the positioner to the welding of 40GrMo high alloy gears in cooperation with Komatsu Japan.

2.6 Propane energy efficient and environmentally friendly cutting gas application

Liquefied cutting gas such as propane is an energy-efficient and environment-friendly gas promoted by the national “Eighth Five-Year Plan” and “Ninth Five-Year Plan”. In 1993, Jinan No.2 Machine Tool Group Co., Ltd. began to study the industrial application of propane liquefied gas. After a large number of comparative tests, in 1998, C ₃ series liquefied gas was used to replace acetylene gas, which greatly reduced production cost and improved production safety. Sex and cutting quality, coupled with a new gas cutting nozzle, improves production efficiency.

2.7 Application of non-destructive testing technology

The application of non-destructive testing technology in the machine tool industry begins with the main welds of machine tool parts. For example, in 1975, Jinan No. 2 Machine Tool Plant established a radiographic inspection room while establishing a welding workshop. In 1989, the pressure vessel quality assurance system was established and improved according to national standards, and the GB150 "Steel Pressure Vessel" standard and JB4730 "Pressure Vessel Non-destructive Testing" standard were fully implemented.

In the early 1990s, the machine tool industry began to apply ultrasonic flaw detection technology to 20% sampling of the main welds of the main structural parts of machine tools, and implemented the national standard GB11345-89 "Manual ultrasonic flaw detection method for steel welds and classification of flaw detection results". The main parts of the welds to be inspected include the press base of the press base, the beam and the slider; the weld of the column and the slide rail; the bushing weld of the beam; the base, the beam, the upper and lower facing welds of the table and All splice plate welds and gear welds around the gear.

2 . 8 application of centralized gas supply technology

The gas supply method of CO ₂ gas has also received attention in the welding production of the machine tool industry. At present, many domestic manufacturers basically use single-bottle single-machine gas supply. This gas supply method not only limits the expansion of production scale, but also has a great impact on welding production management and welding quality. The concentrated gas supply of CO ₂ gas improves the welding production efficiency, and also increases the purity of CO ₂ gas by 0.4-0.6%, and the moisture content of gas by 0.25%, which ensures the welding quality and is also obtained in the welding production of the machine tool industry. application. For example, in 1992, Jinan Second Machine Tool Group Co., Ltd. built a CO ₂ gas centralized gas supply device while establishing a new metal structure plant. The total working pressure of the device is 0.15MPa, and the capacity of the intermediate storage cylinder is 2m ³ . It can continuously supply gas to more than 120 CO ₂ welders in the whole plant. At that time, the annual welding production capacity was 12,000 tons. By 2002, the annual welding production capacity was 15,000 tons. Demand.

3 Application prospects of new welding technology in machine tool industry

With the rapid development of welding technology and machine tool technology, the new welding technology has a broad prospect in the machine tool industry. The welding structure of the machine tool industry is also seeking to explore new technologies and materials in the field of applied welding.

3 . 1 application of flux cored wire in CNC machine tools

The flux-cored wire has the joint protection effect of gas and slag, and the weld seam is beautiful in appearance and less in spatter. The iron-containing flux cored wire has high deposition efficiency and has many advantages over solid core gas shielded welding.

Metal cutting machine tools, especially CNC metal cutting machines, have high precision requirements and beautiful appearance. For this reason, it is required that the welded structure has a small size, smooth and beautiful appearance. The use of flux cored wire has great advantages. Jinan Second Machine Tool Group Co., Ltd. has explored the application of flux-cored wire in recent years, such as Japan Sanling Heavy Industry Co., Ltd. and Japan Benjian Co., Ltd., using Φ1.6 flux cored wire CO ₂ gas shielded welding, welding production The horizontal hobbing machine body and the CNC gantry milling and boring machine bed, the column of the CNC floor milling boring machine, the welding quality is better than the solid core CO ₂ gas shielded welding, which has been approved by the Japanese experts and successfully passed the Japanese quality inspection and acceptance.

3 . 2 Filament gas shielded welding application

In recent years, the trend of Φ0.8 filament gas shielded welding in the machine tool industry has become stronger and stronger. With the technological advancement of machine tools, the appearance and quality requirements of machine tools are getting higher and higher. In the past, the thin-plate cover parts of the machine tool products using manual arc welding have basically failed to meet the requirements of the appearance quality of existing machine tools, especially CNC machine tools. Now they are looking for exploration, using laser cutting, Φ0.8 filament gas shielded welding. Jinan No. 1 Machine Tool Group Co., Ltd. has applied laser cutting and Φ0.8 filament CO ₂ gas shielded welding since the beginning of 1990 to weld machine tool casing parts. The appearance quality meets the high level requirements of CNC machine tools.

3 . 3 Welding mechanization and automation application plan

The realization of welding mechanization and automation is an important way to apply new welding technology in the machine tool industry. The welding structure of machine tool products is mostly complicated box structure. In the current welding production, the whole assembly and overall welding process are adopted, and it is difficult to realize automatic welding. If the assembly and welding of the welding structure of the machine tool product are combined into one process, with mechanical chemical equipment and positioner, automatic welding is completely feasible.

3 . 3 . 1 welding gear automation welding program

The transmission gears of heavy forging equipment products mainly consist of a web, a ring gear and an eccentric axle. The ring gear material of the welding gear is 45 ^# or 40CrMo material, which needs to be preheated before welding, and must be insulated after welding. The automatic welding can be carried out by using a positioner. The ring gear and the web are pre-assembled and fixed on the positioner. Then, the positioner is continuously rotated, the workpiece is preheated to 200-350 °C by a flame preheater, and the positioner is automatically adjusted to an angular position of 45°, and automatic tracking is performed for automatic tracking welding and fillet welding. The height of the seam fillet meets the design weld size requirements. At the same time, the inner ring welds are also automatically welded.

Automated welding of such parts will significantly improve work efficiency, reduce labor intensity, and reduce auxiliary work hours such as preheating in the furnace and post-weld insulation. At the same time, the quality of the welding is also guaranteed.

3 . 3 . 2 automatic welding scheme for box parts

The welding structure of machine tools is mostly complicated box structure, and many reinforcing ribs are arranged inside the structure, which makes automatic welding more difficult. If the box-shaped parts are modified from the design and welded on one side of the welding and turning machine, automatic welding is completely feasible. For example, the column of the mechanical press first clamps the bottom plate on the assembly platform of the large welding and turning machine, and then assembles the tension bolt support plate, various reinforcing ribs and the like. The cross-weld automatic welder is used to weld and tighten the fillet welds in the bolt support plate. The gantry type automatic welding machine is used to weld all kinds of ribbed fillet welds and outer surface welds. The assembly and welding work can be completed at one time, which will reduce the back-to-back assembly process of the two parts and improve the welding productivity.

4 Conclusion

The development of welding technology in the machine tool industry has evolved with the development of machine tool product technology. After the 1980s, the introduction of product technology in the machine tool industry played a decisive role in the development of welding technology in the machine tool industry. With the increasing application of welding structures for machine tools, the situation of casting structures in the past few decades has been completely changed. It has become the general development trend of machine tool manufacturing by welding casting, welding forging and welding. Machine tool manufacturing is inseparable from welding.

At present, the development of welding technology in the machine tool industry is also developing in an efficient and automatic direction. The application of new welding technology in the machine tool industry has broad prospects. It is the responsibility of each of our welding workers to vigorously promote the application of new and advanced welding processes and methods. We hope that new welding technology will be promoted in the machine tool industry as soon as possible and can be widely applied.

*Jiang Yijun, Director of the Machine Tool Professional Committee of the Welding Association, Deputy Chief Engineer of Jinan Second Machine Tool Group Co., Ltd.