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Due to the particularity of the machine tool products, the particularity of the machine structure is determined. For decades, casting structures have always dominated the structure of machine tools. The casting process has always been the dominant process for machine tool products. After the 1980s, with the continuous increase in the introduction of machine tool products, the product structure of machine tools has increasingly adopted welded structures. To replace cast by welding, to replace forging by welding, cutting by welding has become an integral part of the machine tool manufacturing industry. 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 into a new comprehensive project including raw material pretreatment, cutting blanking, forming welding, post-weld inspection and post-weld treatment. technology. Completely changed the past decades of casting structure "unified world" situation, machine tool manufacturing can not be separated from welding.
1. The development of welding technology in the machine tool industry
The development of welding technology in the machine tool industry has developed with the development of the application of welding structures for machine tools. 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, grinding tools and machine tool accessories. Among them, metal cutting machine tools, forging machinery and foundry machinery products are the main fields of application of welding technology 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 stage was from the 1950s to the early 1970s. This stage is mainly in the stage of machine tool product development. At that time, the success of the metal cutting machine tools were 1 1 63 type lathes, 2A125 vertical drilling machines, 6H82 universal milling machines, 1617 horizontal lathes, and 262 horizontal boring machines, which accounted for about 70% of the total 204 types of machine tools at that time. Forging machinery mainly imitates the development of open type presses, closed single point presses under 315 tons, air hammers, double disc friction presses under 300 tons, shears, four-post universal hydraulic presses, and thread rolling machines and automatic forging presses, etc. Larger demand for general purpose forging machinery products.
The structure of the machine tool products at this stage is basically all of the casting blank structure. Therefore, the welding technology at this stage is only used as an auxiliary process means to service the product. The welding is focused on the defect welding repair of the structural components and the fuel tank and the electric box cover of the product. Shell and other small non-main parts. The main welding method is manual arc welding, or oxyacetylene gas welding, which is controlled by the workers themselves. There are no formal welding professional technicians and technological measures, and there is no special welding shop. Individual large-scale enterprises, welding and other casting workshops or product assembly workshop together, the production area is limited.
1.2 Preliminary application of welding technology
This stage, from the 1970s to the early 1980s, was the initial application of welding technology. At this stage, machine tool products began their research and development of high-precision precision machine tools on the basis of imitation in the 1950s. In the field of metal cutting machine tools, only 7760 machines with a higher level were provided to the second automobile factory in the 1970s, which satisfied more than 98% of the required machine tool equipment for the second automobile factory. Forging machinery, In order to equip the Second Automobile Factory, 115 kinds of general purpose forging machines and some production lines were developed and researched. At the same time, at this stage, the designated factories of various specialties have mastered 257 types of forging machinery.
In this stage, with the advancement of the overall welding technology, some companies started to adopt welded structures in the self-designed machine tool product structure, such as large bases and crossbeams for mechanical presses with a capacity of more than 800 tons at Jinan No. 2 Machine Tool Works. Parts and gas reservoir parts; Qiqihar No. 2 Machine Tool Plant, J81-1250 trimming press developed and designed in 1973 was used for the first time with welded parts. The main structural parts were the base, the column and the nose. The maximum weight of the welded parts was 25 tons; From 1978 to 1979, the plant adopted a welded structure on the high pressure vessel part of the TA88-200 cold press machine bed of the Z41-30 nut cold heading machine. The adoption of these welding structures has promoted the development of welding technology in the machine tool industry.
From the late 1970s onwards, qualified companies began to organize the establishment of an independent welding shop, increased workshop lifting equipment and improved the welding process. For example, Jinan No. 2 Machine Tool Plant established a welding shop in 1975. The workshop area was 5,275 square meters and the maximum lifting capacity was 50 tons. The welding process was also developed from simple manual arc welding to submerged arc welding and electroslag welding. Semi-automatic cutting and ray inspection inspection methods. This illustrates the application of welding technology in the machine tool industry. From the very beginning, it entered a comprehensive engineering technology field, which laid the foundation for the technology introduction of the third stage machine tool products.
1.3 Leading process stage of welding technology
At this stage, technology has been introduced since the early 1980s. At this stage, the machine tool industry has 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 Precision Machinery Co., Ltd. of Japan to produce K-type milling machines, and successfully developed a new series of CNC milling machines, and also co-produced with the Federal Republic of Germany Valdrich Coburg. CNC Gantry Milling Machine; Jinan No. 1 Machine Tool Plant cooperated with Yamazaki Iron Works of Japan to produce Mazak horizontal lathes; Jinan No. 2 Machine Tool Plant cooperated with BMO of France to develop a 4×10m large-sized gantry beam movable five-face machining center and Φ200 Large-scale CNC floor-type milling and boring machine and 2.4×13m large-sized gantry movable five-face machining center; Wuhan Heavy Machine Tool Factory cooperated with the German company Hess-Flolip Company to produce the international standard machining vertical diameter of 1.4-2.5 meters. Lathes, heavy-duty machine tools such as floor-drilling and boring machines with a Φ260mm or more boring bar diameter. In terms of forging machinery, Jinan No.2 Machine Tool Plant took the lead in introducing a complete set of technology for the design, manufacture, and testing of 8 series and 35 types of heavy-duty and super-heavy mechanical presses from the American VERSON all-steel mechanical press company. The introduction, absorption and digestion of heavy forging equipment. Subsequently, in 1981, the Huangshi Forging Machine Tool Plant introduced drawings and manufacturing technology for the series of hydraulic shears and bending machines from Belgium. In 1986 Qiqihar No.2 Machine Tool Plant introduced the mechanical press manufacturing technology of Japan Komatsu Group. In 1991, Shanghai Forging Machine Tool Factory cooperated with German SCHULER to provide 14 sets of 600-ton closed four-point multi-linkage mechanical presses for Shanghai Volkswagen Automotive Plant. In 1992, Qiqihar No. 2 Machine Tool Factory also cooperated with German Alft 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 super heavy-duty forging equipment have been rapidly improved, and have basically reached and reached the international advanced level. At present, the domestic forging and pressing industry has developed more than 440 forging and pressing equipments that have been developed. The developed heavy-duty mechanical presses have a stand-alone capacity of 3,000 tons. The hydraulic bending machine has a stand-alone capacity of 4,000 tons and has the ability to develop and manufacture stand-alone machines. The capacity of over 4500 tons ultra-heavy mechanical presses and large multi-station presses.
The introduction of technology has promoted the application of welding structures in the machine tool industry. For example, Jinan No. 2 Machine Tool Plant, a mechanical press product designed by itself before 1981, only 14% of welded structural members and less than 1% of welded product of planer products. In 1981, the proportion of welded structural parts introduced into presses reached 44.3%. After the introduction of the technology, the proportion of the welded structure of the mechanical press product itself has reached a maximum of 67.1%. The welding structure of its imported CNC machine tools also reached 60%. Tianjin Forging Press General Plant, the number of welded structural products used in 1975 was only 8 species, less than 47%. In 1991, it broke through 44 species, accounting for more than 66% of the total number of varieties.
The application of welding structure of machine tool products has changed the situation in the past where the casting blanks were unified in the world of machine tools. The welding technology has gradually developed into a leading process in 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 set corporate standards.
(2) The welding process has been perfected, enabling it to develop from a single processing technology into a comprehensive set of emerging comprehensive engineering technologies from raw material pretreatment, cutting and blanking, forming, welding, post-weld testing and post-weld treatment.
(3) CNC precision cutting and computer programming nesting technology has been applied, and has changed the traditional manual cutting and blanking, reduced the mechanical processing, and achieved the "cut generation plane", "to weld cutting."
(4) Promote the use of advanced and efficient new processes such as CO2 gas and argon-enriched gas shielded arc welding or submerged arc welding. The amount of welding work has broken through more than 50% in key enterprises, and individual companies have reached more than 80%.
(5) X-ray detection and ultrasonic non-destructive testing are commonly used to stabilize the intrinsic quality of the weld.
(6) The new process of vibration aging was promoted, and the purpose of reducing and homogenizing the residual stress of the welded structure was achieved. The deformation of the welded part was reduced, and the accuracy was stabilized.
(7) Welding technicians and welders have gotten stronger and embarked on regular management. Most of the companies have employed welders to hold certificates. In addition, during the “Eighth Five-Year Plan†period, we established a welding model factory site that is representative of the industry and played an important role in promoting the development of welding technology in the machine tool industry.
Application of Automatic Welding Technology in Machine Tool Industry
The machine tool industry is an important part of the machinery industry. It is the "master craftsman" of the machinery industry and the basic industry of the national economy. The machine tool product is the machine that manufactures all the machines. Their working accuracy is generally higher than the precision of the machine parts being machined. For this reason, the technical level and service level of machine tool products play a decisive role in improving the production technology and economic efficiency of mechanical industry products.
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