I. Overview
At present, under the circumstance of the global economic downturn, China's economy has developed rapidly, and the rapid development of railway transportation equipment represented by motor vehicles is even more exciting. Railway trucks have also made great progress in the development of high-speed and heavy-duty. The reason is that a large number of advanced new technologies have been adopted. This proves again that science and technology are the primary productive forces.
In terms of truck heavy load, China is currently ranked first in the world. Since 2006, the new standard for heavy-duty trucks has been raised from 60t to 70t, and the special cargo for trucks has been weighed 80t. The company has developed a special steel ore truck with a load of 100t. The existing trucks have been upgraded at a speed of 120km/h. Completed the upgrading of China's railway wagons. In the past, the axle load of railway wagons in China has been below 21t for a long time. Since 2006, the axle load of general-purpose trucks has increased to 23t, and the axle load of heavy-duty trucks has increased to 25t. At present, the development project of the 30t axle heavy truck has started.
With the increase of axle weight, load and speed, higher requirements are placed on key components such as bolsters, side frames and couplers on important parts such as truck bogies and hooks, which are required to ensure load and speed requirements. To ensure the security of use. On the one hand, in the design of castings, new models, such as bolsters and side frames, are transferred from K2 and K4 to K5 and K6, and the couplers are from 13 to 16, 17 with increased size and wall thickness. Use high grade materials: from ordinary carbon steel to B grade steel, then to B+ grade steel, C grade steel, E grade steel, etc. The new material is low alloy steel, which can improve the strength and fatigue resistance of castings; The use of new casting technology has improved the quality of castings and provided guarantees for high speed and heavy loads of trucks. In recent years, these new casting technologies have involved molding, core making, core lowering, refining, falling sand, heat treatment, enhanced shot blasting and casting inspection.
Second, the application of new technologies
Modeling technique
China's railway freight car bolsters, side frames, couplers and other steel castings use tidal sand sand casting, air punching, ester hardened water glass sand molding, CO2 hardening water glass sand modeling, furan resin sand molding and V method modeling The production line with a higher degree of mechanization has improved the production efficiency and the quality of the molding has been greatly improved compared with the vibration molding machine widely used. Cast iron wedges are widely used in iron-coated sand. Due to the improvement of the quality of the molding, the dimensional accuracy of the casting is obviously improved, and the traditional defects which are most easily formed by castings over the years, the sand holes are greatly reduced, and the quality of the castings is obviously improved.
2. Core technology
The bolster and side frame core mainly adopt ester hardened water glass sand process, CO2 hardened water glass sand process, triethylamine process, Pep-set phenolic resin sand process, furan resin self-hardening sand process, polyacrylic acid resin sand process, etc. . The bolster, side frame and coupler adopt the integral core making process. The main methods are: the whole core making process of the compacted extrusion, the squeeze core forming process in the box, the overall core shooting process of the cold core box, the shell core shooting process, and the upper and lower sides. The overall core bonding process, as well as the integrated core shooting process of the coupler.
At present, in order to complete the bolster and side frame integral core shooting core, China has developed a core shooting machine with a maximum weight of 250kg, which is in good condition.
The development of the key components of the key components of railway wagons, such as bolsters and side frames, symbolizes that the core technology of China Railway Freight Car Cast Steel products has reached the world's leading level. The new core technology makes the inner core of the casting cavity change from 6 to 12 pieces into a whole piece. The bolster, side frame and the inner cavity of the casting part of the casting are formed by the integral core, which can eliminate the steps, flashes, etc. brought by the traditional process. Casting defects improve the quality of the inner cavity of the bolster, side frame and coupler.
3. Intelligent core technology
The lower core process is an important process to ensure the quality of the bolster and side frame products. For a long time, the artificial core is used in the manufacturing process of the bolster and the side frame. Not only the stability of the lifting equipment can not meet the production requirements of high-quality products, but also the human factors such as the skill of the operator are highly dependent, so the process quality fluctuates greatly. Transforming the original artificial core into the core core of the whole core manipulator is beneficial to comprehensively improve the manufacturing level of the bolster and side frame, improve the control level of the production process and product quality, and is an important improvement to the core technology of the bolster and side frame. . The intelligent manipulator (industrial robot) body adopts six-axis rotary joint design. The three-dimensional laser scanning positioning of the robot can accurately measure the translation, tilting and rotation angle of the positioning sand core and the sand box in the X, Y and Z directions. ±0.45mm, system repeat positioning accuracy ± 0.15mm. Process flow: the lower core robot waits for the sand core and the sand box to reach the station → the vision system locates the sand core and the sand box → the robot grabs the sand core into the sand box → the robot notification system outputs the good core sand box → robot Going back to the original position, the core cycle ends.
4. Refining technology
With the improvement of the mechanical properties of casting materials, the original carbon steel was replaced by low-alloy steel. For example, the railway truck bolster and side frame materials were successively improved from ZG230-450 to B-grade steel and B+ steel. The material of the coupler was Carbon steel is upgraded to grade C steel and grade E steel. Due to the improvement of material requirements, the requirements for smelting equipment are higher, the electric arc furnace is used for casting steel melting, and the electric furnace is used for cast iron, so that the melting quality of cast steel and cast iron is greatly improved. The use of new technologies such as LF furnace refining technology and refining technology outside the molten steel furnace further improves the quality of the molten steel and enables the content (mass fraction) of the steel grade S to reach a double zero level. Furnace feeding argon steel refining is a refining process outside the furnace. After tapping, the aluminum wire or Si-Ca-Ba core wire is fed into the molten steel bag with permeable brick for deoxidation. The argon gas is blown into the molten steel through the ceramic permeable brick to purify the molten steel. Since the permeable brick is installed at the bottom of the ladle, the argon gas is blown to agitate the molten steel, and a small and dispersed argon bubble is formed. The argon bubble floats to cause the agitation of the molten steel, so that the fine inclusions dispersed in the molten steel can collide and accumulate to form a low-melting-point large particle inclusion and adsorb on the surface of the bubble, thereby increasing the floating speed of the inclusion and purifying. The refining process outside the molten steel furnace can effectively reduce the gas content and inclusions in the steel, improve the shape of the inclusions, and improve the intrinsic quality of the casting. This technology has been widely used in the production of steel parts such as couplers and bolsters and side frames.
5. Falling sand
Since the 1950s, CO2 hardened water glass sand has been widely used in China's railway freight car cast steel manufacturing industry due to its simple process, low price and low pollution level. By the mid-1960s, water explosion and water bath processes were successively adopted, which solved the problem of difficulty in clearing sand with water glass. CO2 hardened water glass sand has been widely used. However, cast steel parts are prone to capillary crack defects under as-cast and chill conditions, and water pollution problems are becoming increasingly prominent.
With the increase in the requirements for high-speed heavy-duty railways, in the late 1990s, important steel castings for railway wagons began to adopt the dry sand-dropping process, which has been widely used. The use of dry falling sand significantly reduces the occurrence of cracks and reduces the hidden dangers for the safety of railway wagons.
6. Heat treatment
The truck cast steel bolster and side frame are B+ grade steel, which adopts normal heat treatment process, and the coupler is E-grade steel, which adopts quenching and tempering heat treatment process. In order to improve the consistency of heat treatment quality of castings, the coupler has adopted a continuous heat treatment process, and the bolster and side frame have also been promoted using a continuous heat treatment process.
7. Shot blasting treatment
The bolster and side frame are strongly shot blasting, which improves the surface quality of the casting and forms compressive stress on the surface of the casting to improve the surface strength of the casting and improve the fatigue resistance of the casting.
8. Casting inspection
In order to ensure the safety of railway trucks at high speed and heavy load, higher requirements are imposed on casting inspection technology. On the one hand, it is proposed to test the casting products, such as the iron standard TB/T3105-2005 "railway truck cast steel bolster, side frame magnetic particle inspection" implemented on July 1, 2005, and the transport truck [2007] No. 310 document in 2007. Requires "Technical Conditions for Radiographic Inspection of Railway Freight Car Bolster and Side Frame", "Technical Conditions for Ultrasonic Flaw Detection of Railway Freight Car Casting Steel Bolster and Side Frame", "Regulations for Fluorescent Magnetic Particle Testing of Railway Freight Car Casting Steel Bolster and Side Frame", "Technical conditions for ultrasonic measuring thickness of cast steel truck bolster and side frame". New detection techniques such as magnetic particle inspection, fluorescent magnetic particle inspection, radiographic inspection, ultrasonic inspection and ultrasonic thickness measurement have been used in railway freight car castings. In addition, in the past two years, the three-coordinate detection of the geometrical tolerance of the casting has been added, and the DR-real-time imaging and CT detection techniques have been applied to the casting entity. On the other hand, rapid and advanced detection techniques such as direct reading spectrometers, rapid analyzers before the furnace, and quantitative metallographic analyzers are commonly used in the production of castings. The use of new casting inspection technology guarantees reliable casting quality.
9. Casting Technology Management
There are many casting production processes, and the factors affecting quality are more complicated, and the quality control of the production process is particularly important. To this end, the Railway Freight Car Bolster and Side Frame Production Plant implemented the “Management Points for the Production Technology of the Bolster and Side Frame Casting†issued by the competent department of the Ministry of Railways. Its main contents include: casting process design and review, process verification, process document management, process execution and inspection, raw material management, tooling and equipment management, measurement instrumentation and inspection equipment management, staff training, modeling process Control, control of the smelting process, control of the casting process, control of the heat treatment process, control of the flaw detection process, and 22 quality records, and require one-card system for castings, ie one piece of quality for each bolster and side frame Guarantee card.
Third, the conclusion
The application of new casting technology is an important force to promote the high speed and heavy load of railway freight cars. These new technologies have now become the industry standard for the production of railway freight car castings. With the rapid development of the national economy, the requirements for railway freight car castings continue to increase, and newer casting technologies will be widely used.
At present, under the circumstance of the global economic downturn, China's economy has developed rapidly, and the rapid development of railway transportation equipment represented by motor vehicles is even more exciting. Railway trucks have also made great progress in the development of high-speed and heavy-duty. The reason is that a large number of advanced new technologies have been adopted. This proves again that science and technology are the primary productive forces.
In terms of truck heavy load, China is currently ranked first in the world. Since 2006, the new standard for heavy-duty trucks has been raised from 60t to 70t, and the special cargo for trucks has been weighed 80t. The company has developed a special steel ore truck with a load of 100t. The existing trucks have been upgraded at a speed of 120km/h. Completed the upgrading of China's railway wagons. In the past, the axle load of railway wagons in China has been below 21t for a long time. Since 2006, the axle load of general-purpose trucks has increased to 23t, and the axle load of heavy-duty trucks has increased to 25t. At present, the development project of the 30t axle heavy truck has started.
With the increase of axle weight, load and speed, higher requirements are placed on key components such as bolsters, side frames and couplers on important parts such as truck bogies and hooks, which are required to ensure load and speed requirements. To ensure the security of use. On the one hand, in the design of castings, new models, such as bolsters and side frames, are transferred from K2 and K4 to K5 and K6, and the couplers are from 13 to 16, 17 with increased size and wall thickness. Use high grade materials: from ordinary carbon steel to B grade steel, then to B+ grade steel, C grade steel, E grade steel, etc. The new material is low alloy steel, which can improve the strength and fatigue resistance of castings; The use of new casting technology has improved the quality of castings and provided guarantees for high speed and heavy loads of trucks. In recent years, these new casting technologies have involved molding, core making, core lowering, refining, falling sand, heat treatment, enhanced shot blasting and casting inspection.
Second, the application of new technologies
Modeling technique
China's railway freight car bolsters, side frames, couplers and other steel castings use tidal sand sand casting, air punching, ester hardened water glass sand molding, CO2 hardening water glass sand modeling, furan resin sand molding and V method modeling The production line with a higher degree of mechanization has improved the production efficiency and the quality of the molding has been greatly improved compared with the vibration molding machine widely used. Cast iron wedges are widely used in iron-coated sand. Due to the improvement of the quality of the molding, the dimensional accuracy of the casting is obviously improved, and the traditional defects which are most easily formed by castings over the years, the sand holes are greatly reduced, and the quality of the castings is obviously improved.
2. Core technology
The bolster and side frame core mainly adopt ester hardened water glass sand process, CO2 hardened water glass sand process, triethylamine process, Pep-set phenolic resin sand process, furan resin self-hardening sand process, polyacrylic acid resin sand process, etc. . The bolster, side frame and coupler adopt the integral core making process. The main methods are: the whole core making process of the compacted extrusion, the squeeze core forming process in the box, the overall core shooting process of the cold core box, the shell core shooting process, and the upper and lower sides. The overall core bonding process, as well as the integrated core shooting process of the coupler.
At present, in order to complete the bolster and side frame integral core shooting core, China has developed a core shooting machine with a maximum weight of 250kg, which is in good condition.
The development of the key components of the key components of railway wagons, such as bolsters and side frames, symbolizes that the core technology of China Railway Freight Car Cast Steel products has reached the world's leading level. The new core technology makes the inner core of the casting cavity change from 6 to 12 pieces into a whole piece. The bolster, side frame and the inner cavity of the casting part of the casting are formed by the integral core, which can eliminate the steps, flashes, etc. brought by the traditional process. Casting defects improve the quality of the inner cavity of the bolster, side frame and coupler.
3. Intelligent core technology
The lower core process is an important process to ensure the quality of the bolster and side frame products. For a long time, the artificial core is used in the manufacturing process of the bolster and the side frame. Not only the stability of the lifting equipment can not meet the production requirements of high-quality products, but also the human factors such as the skill of the operator are highly dependent, so the process quality fluctuates greatly. Transforming the original artificial core into the core core of the whole core manipulator is beneficial to comprehensively improve the manufacturing level of the bolster and side frame, improve the control level of the production process and product quality, and is an important improvement to the core technology of the bolster and side frame. . The intelligent manipulator (industrial robot) body adopts six-axis rotary joint design. The three-dimensional laser scanning positioning of the robot can accurately measure the translation, tilting and rotation angle of the positioning sand core and the sand box in the X, Y and Z directions. ±0.45mm, system repeat positioning accuracy ± 0.15mm. Process flow: the lower core robot waits for the sand core and the sand box to reach the station → the vision system locates the sand core and the sand box → the robot grabs the sand core into the sand box → the robot notification system outputs the good core sand box → robot Going back to the original position, the core cycle ends.
4. Refining technology
With the improvement of the mechanical properties of casting materials, the original carbon steel was replaced by low-alloy steel. For example, the railway truck bolster and side frame materials were successively improved from ZG230-450 to B-grade steel and B+ steel. The material of the coupler was Carbon steel is upgraded to grade C steel and grade E steel. Due to the improvement of material requirements, the requirements for smelting equipment are higher, the electric arc furnace is used for casting steel melting, and the electric furnace is used for cast iron, so that the melting quality of cast steel and cast iron is greatly improved. The use of new technologies such as LF furnace refining technology and refining technology outside the molten steel furnace further improves the quality of the molten steel and enables the content (mass fraction) of the steel grade S to reach a double zero level. Furnace feeding argon steel refining is a refining process outside the furnace. After tapping, the aluminum wire or Si-Ca-Ba core wire is fed into the molten steel bag with permeable brick for deoxidation. The argon gas is blown into the molten steel through the ceramic permeable brick to purify the molten steel. Since the permeable brick is installed at the bottom of the ladle, the argon gas is blown to agitate the molten steel, and a small and dispersed argon bubble is formed. The argon bubble floats to cause the agitation of the molten steel, so that the fine inclusions dispersed in the molten steel can collide and accumulate to form a low-melting-point large particle inclusion and adsorb on the surface of the bubble, thereby increasing the floating speed of the inclusion and purifying. The refining process outside the molten steel furnace can effectively reduce the gas content and inclusions in the steel, improve the shape of the inclusions, and improve the intrinsic quality of the casting. This technology has been widely used in the production of steel parts such as couplers and bolsters and side frames.
5. Falling sand
Since the 1950s, CO2 hardened water glass sand has been widely used in China's railway freight car cast steel manufacturing industry due to its simple process, low price and low pollution level. By the mid-1960s, water explosion and water bath processes were successively adopted, which solved the problem of difficulty in clearing sand with water glass. CO2 hardened water glass sand has been widely used. However, cast steel parts are prone to capillary crack defects under as-cast and chill conditions, and water pollution problems are becoming increasingly prominent.
With the increase in the requirements for high-speed heavy-duty railways, in the late 1990s, important steel castings for railway wagons began to adopt the dry sand-dropping process, which has been widely used. The use of dry falling sand significantly reduces the occurrence of cracks and reduces the hidden dangers for the safety of railway wagons.
6. Heat treatment
The truck cast steel bolster and side frame are B+ grade steel, which adopts normal heat treatment process, and the coupler is E-grade steel, which adopts quenching and tempering heat treatment process. In order to improve the consistency of heat treatment quality of castings, the coupler has adopted a continuous heat treatment process, and the bolster and side frame have also been promoted using a continuous heat treatment process.
7. Shot blasting treatment
The bolster and side frame are strongly shot blasting, which improves the surface quality of the casting and forms compressive stress on the surface of the casting to improve the surface strength of the casting and improve the fatigue resistance of the casting.
8. Casting inspection
In order to ensure the safety of railway trucks at high speed and heavy load, higher requirements are imposed on casting inspection technology. On the one hand, it is proposed to test the casting products, such as the iron standard TB/T3105-2005 "railway truck cast steel bolster, side frame magnetic particle inspection" implemented on July 1, 2005, and the transport truck [2007] No. 310 document in 2007. Requires "Technical Conditions for Radiographic Inspection of Railway Freight Car Bolster and Side Frame", "Technical Conditions for Ultrasonic Flaw Detection of Railway Freight Car Casting Steel Bolster and Side Frame", "Regulations for Fluorescent Magnetic Particle Testing of Railway Freight Car Casting Steel Bolster and Side Frame", "Technical conditions for ultrasonic measuring thickness of cast steel truck bolster and side frame". New detection techniques such as magnetic particle inspection, fluorescent magnetic particle inspection, radiographic inspection, ultrasonic inspection and ultrasonic thickness measurement have been used in railway freight car castings. In addition, in the past two years, the three-coordinate detection of the geometrical tolerance of the casting has been added, and the DR-real-time imaging and CT detection techniques have been applied to the casting entity. On the other hand, rapid and advanced detection techniques such as direct reading spectrometers, rapid analyzers before the furnace, and quantitative metallographic analyzers are commonly used in the production of castings. The use of new casting inspection technology guarantees reliable casting quality.
9. Casting Technology Management
There are many casting production processes, and the factors affecting quality are more complicated, and the quality control of the production process is particularly important. To this end, the Railway Freight Car Bolster and Side Frame Production Plant implemented the “Management Points for the Production Technology of the Bolster and Side Frame Casting†issued by the competent department of the Ministry of Railways. Its main contents include: casting process design and review, process verification, process document management, process execution and inspection, raw material management, tooling and equipment management, measurement instrumentation and inspection equipment management, staff training, modeling process Control, control of the smelting process, control of the casting process, control of the heat treatment process, control of the flaw detection process, and 22 quality records, and require one-card system for castings, ie one piece of quality for each bolster and side frame Guarantee card.
Third, the conclusion
The application of new casting technology is an important force to promote the high speed and heavy load of railway freight cars. These new technologies have now become the industry standard for the production of railway freight car castings. With the rapid development of the national economy, the requirements for railway freight car castings continue to increase, and newer casting technologies will be widely used.
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