Welcome to Megmeet!
Overview of Construction Machinery
1. Construction machinery is a strategic pillar industry of one country. As China enters the process of rapid economic development and rapid urbanization, construction machinery has entered a stage of great development and has played an important role in China's modernization. With the development of China in recent years, China has become the world's largest engineering machinery processing and manufacturing country by its construction machinery industry. China's engineering machinery processing and manufacturing enterprises have also entered the stage of developing core technologies and healthy and sustainable development from the stage of initial low-tech and extensive development. The mechanical welding process in engineering machinery processing is an important core technology. In order to improve its core competitiveness, engineering machinery processing and manufacturing enterprises have begun to pay attention to the development of its mechanical welding process. Advances in engineering machinery welding processes can improve the production efficiency of mechanical welding, improve the quality and stability of mechanical products, and reduce production costs.
2. Construction machinery is the general term for construction machinery used in engineering construction. The title of this industry is basically the same in countries of the world, in which it is called construction machinery and equipment in the United States and the United Kingdom, it is called construction machinery and device in Germany, it is called construction and road construction machinery in Russia, it is called building machinery in Japan. Some products are also called building machinery in China, and they are collectively referred to as engineering machinery in mechanical system by the State Council when it compiles the industry approval document, which has continued to the present.
3. Range of products of this industry in countries is roughly the same. Compared with other countries, China's construction machinery also includes railway line engineering machinery, forklifts and industrial handling vehicles, decoration machinery, elevators, pneumatic tools and other industries. It is widely used in architecture, water conservancy, electric power, roads, mines, ports, national defense and other engineering fields, and has a lot of types. It is mainly used in defense construction engineering, transportation construction, energy industry construction and production, mining and other raw material industry construction and production, construction of agriculture and forestry as well as water conservancy, industrial and civil construction, urban construction, environmental protection and other fields.
Construction machinery classification:
The range of products of China's construction machinery industry is mainly from the large categories of general equipment manufacturing industry and special equipment manufacturing industry. In 1979, the State Development Planning Commission and the First Ministry of Machinery Industry compiled the “7th Five-year” development plan for the development of China's construction machinery industry. The product range covers 18 major categories of engineering machinery industry, and these 18 major categories of construction machinery have been confirmed by all the national machinery industry plans following the “7th Five-year” development plan. Their product range has continued to this day. These 18 categories of products include:
(1) Excavation machinery such as single bucket excavator (also divided into crawler excavator and tire excavator), multi-bucket excavator (also divided into bucket wheel excavator and chain bucket excavator), multi-bucket trencher (also can be divided into bucket wheel trencher and chain bucket trencher), rolling excavator, mill-cut excavator, tunnel heading machine (including shield machinery), etc.
(2) Earthmoving machinery, such as bulldozers (which can be divided into tire bulldozers and crawler bulldozers) and scrapers (also can be divided into crawler self-propelled scrapers, tire self-propelled scrapers and towed scrapers), loader (can be divided into tire loaders and crawler loaders), graders (also can be divided into self-propelled graders and towed graders), transport vehicles (also can be divided into single-axis transport vehicles and double-axle traction transport vehicles), flatbed trucks and dump trucks.
(3) Engineering hoisting machinery such as tower cranes, self-propelled cranes, mast cranes, grab cranes, etc.
(4) Industrial vehicles
(5) Compaction machineries such as tire roller, smooth wheel roller, compactor, tamper, etc.
(6) Piling machineries such as drilling machine, diesel pile driver, vibratory pile driver, breaking hammer, etc.
(7) Concrete machineries such as concrete mixer, concrete mixing plant, concrete mixing building, concrete pump, concrete mixing truck, concrete sprayer, concrete vibrator, steel bar processing machinery, etc.
(8) Steel bar and pre-stressed machineries
(9) Decoration machineries
(10) Rock drilling machineries such as rock drilling jumbo, pneumatic rock drill, electric rock drill, diesel rock drill, burrow rock drills, etc.
(11) Road machineries such as temper mill, ballast cleaner, etc.
(12) Railway track machineries
(13) Driving machineries
(14) Municipal engineering and sanitation machineries
(15) Military engineering machineries
(16) Elevators and lifts
(17) Special parts for construction machineries
(18) Other special construction machineries such as bridge erecting machine, pneumatic tool (air tool), etc.
Distribution of China's engineering machinery industry:
90% of China's engineering machinery industry is concentrated in East China and Hunan, Sichuan, Guangxi and other regions. The main supporting enterprises in production and coordination are also developed centering on these regions. Specifically, it includes: the engineering machinery industry group in Xuzhou with XCMG as the core; the engineering machinery industry group in Changsha, Hunan led by Zoomlion, Sany Group, Sunward Intelligent; the engineering machinery industry group in Shandong with a cluster of Shandong Shantui Construction Machinery, SDLG, Fangyuan Group, Komatsu, Dayu Group in Jining, Linyi and Qingzhou; the engineering machinery industry group in the Yangtze River Delta represented by Anhui Heli Company, Hitachi Construction Machinery (China), Changlin Company, Hangcha Group, Komatsu (Changlin), Hyundai, Lonking, Shanghai Huajian, and other well-known enterprises. In recent years, Sany Group, Yuchai, Liugong and other enterprises have successively settled in the Yangtze River Delta to set up plants or merge enterprises, making the Yangtze River Delta region an important cluster and product distribution center of China's engineering machinery industry. In addition, the Chengdu, Xinjin and Zhangzhou industrial clusters in Sichuan, Liuzhou and Yulin industrial clusters in Guangxi, Xiamen, Jinjiang, Quanzhou industrial clusters, Beijing-Tianjin-Hebei industrial cluster, Shenyang and Fushun industrial cluster bases, etc. are also the regions with a vigorous growth in China's engineering machinery industry.
Private economies and small and medium-sized enterprises have achieved a rapid development. During the “11th Five-Year Plan” period, a group of private enterprises represented by Sany Heavy Industry, Lonking, Sunward Intelligent Machinery, South Highway Machinery and the restructured Hangcha Group, North Traffic, Nanyang Roady, Fushun Yongmao, etc. gave full play to their advantages of flexible mechanism, small social burden, and strong independent decision-making ability, and they were good at seizing development opportunities, making full use of social resources. They have developed into mainstay of the industry. In the industry of parts, private enterprises represented by Jiangsu Hengli, Fangyuan Slewing Bearing, Sykes, etc. have emerged vigorously, taking on the key tasks of some key parts, and have already achieved initial results.
Current situation of welding in construction machinery
As one of the four major process technologies, the welding process plays an increasingly important role in the development of human society, and especially for construction machinery industry with steel as the absolute main material, it is an indispensable power. At present, construction machinery is moving towards large-scale, specialized and intelligent development. The physical and appearance quality of welded structural parts have increasingly become a mark of the most important process technology level of construction machinery.
1. Construction machinery welded structural parts and their characteristics
The welded structural parts are very important in the construction machinery products, generally accounting for 50% to 70% of the weight of the entire mechanical equipment. The quality of the mechanically welded structural parts is directly related to the quality, performance and stability of the entire mechanical equipment. The welded structural parts of construction machinery mainly include the frame type structural parts, turntable type structural parts and ledge type structural parts. The design and manufacturing capabilities of welded structural parts have become the key researching contents of construction machinery manufacturing enterprises, which are also an important composition to improve the quality and level of welding. With the intensification of competition among construction machinery processing industry, at present, the specialization, intelligence and automation have become the main development directions of construction machinery processing and manufacturing, which also has higher requirements for construction machinery welded structural parts. Construction machinery welding parts mainly feature the following:
① Large-size and many thick-plate welding welds. In order to improve the performance of large-scale construction machinery and equipment, there are many large-scale and thick-plate welding welds in construction machinery (such as the length of the single-piece plate of crane is up to 15m, the maximum thickness of plate is up to 80～lOO mm), which requires higher quality of weld formation;
② Increase of high strength welded structural parts and thin plates, the use of high strength steel is very helpful to reduce the weight of construction machinery equipment and improve the performance of construction machinery equipment, but these materials feature poor welding performance, which put forward higher requirements to stability and reliability of welding process and welding equipment.(such as the yield strength of the plate applied to the crane has reached 1300M Pa, and the material required for 1400 MP or even higher strength will be used in the future)
③ As construction machinery equipment is gradually applied to more industries and fields and mostly heavy-duty equipment, the strength of welds is required to be higher, such as flat I-shape butt weld seam, symmetrical double groove 1:3 weld seam, T-shape weld seam and single groove welds.
④ Bilateral welding requires the workpiece to be displaced to improve the weld strength. Bilateral welding is adopted for most key welds to increase the strength. In order to ensure the weld quality and control the welding deformation, the welding process requires the workpiece to be frequently turned over and displaced.
⑤ Welding of truss type weld is complex, truss structure is an important boom type structure in the construction machinery industry, with many welds, complicated position and shape. The welding of such welds is an automated welding problem necessary to be solved.
2. Welding process
① At present, the welding equipment required by the construction machinery industry is mainly DC manual arc welder, CO2 welder and submerged arc welder. Automatic and semi-automatic CO2+Ar mixed gas shielded welding is commonly used in China's construction machinery industry. Thin wire gas shielded welding is mainly used for the thin plate parts, diameter of the welding wire is φ0.8～φ1.0mm, mark of the main welding wire is H08Mn2SiA, the application field is the cab, engine cover and other covering parts; for welding of the medium and thick plate, argon-rich mixed gas welding is adopted for more than 90% of this welding, the welding wire is generally φ 1.2mm, while the φ 1.6mm welding wire tends to be gradually reduced due to the higher rigidity and inconvenience in use; submerged arc welding is used for minority of structural parts with wall thickness in 40mm or above, such as road roller steel wheel, loading machine rims etc.
② IGBT inverter welder with low energy consumption has formed a general trend of popularization. After the actual test, the inverter welder saves the energy of 8kW•h/ disk than the non-inverter welder. There is a large inventory of non - inverter welders in the construction machinery industry. If this welder is applied in the industry, it can save 60 million kW•h per year for China.
③ The domestic digital welding power source has just begun to be popularized, accounting for less than 5%. While the proportion of digital welding power source used abroad is 25%-30%. The advantage of digital power source is that it can realize intelligent control and centralized control, solidify welding parameters and improve the stability and consistency of welding quality.
3. Development tendency of welding technology of construction machinery in China
① Digital welder control
All-digital control technology greatly enhances the control precision of welders.
② Intelligent welding control
The welding automation equipment is adopted with intelligent control technologies such as laser, vision, sensing, detection, image processing and computer, which make it possible to automatically adjust the welding track and process parameters under various complex and varying welding conditions, so as to achieve high quality and high efficiency intelligent welding control. The welding expert system equipped allows the operator to input welding process conditions such as welding material, thickness and groove form for the automatic generation of welding technology
③ Networked system integration
The digital integrated management of welding process, quality and production management is achieved through the network. The computer technology and remote communication are used to realize offline programming, remote monitoring, diagnosis and maintenance.
④ Welding automation and welding robot
With the improvement and application of welding automation, the application of the welding robot, positioner, special welding machine, installed and welded integrated positioner is becoming more and more wide. It can realize flexible production easy to control, improve welding efficiency, effectively reduce the labor intensity of workers, improve the quality of weld seam and effectively ensure the stability and consistency of welding quality.