The hot-expanded steel pipe is a steel pipe produced by a waste pipe finishing process that expands the diameter of the pipe—the hot-expanding process. The heat-expanded steel pipes usually mentioned are seamless steel pipes.There are many classification methods for heat-expanded steel pipes. According to the use, it can be divided into heat-expanded steel pipes for high-temperature equipment, heat-expanded steel pipes for low-temperature applications, heat-expanded steel pipes for pressure facilities, pipeline heat-expanded steel pipes, gas cylinder heat-expanded steel pipes, and structural heat-expanded steel pipes,heat-expanded steel pipe for fluid conveying and mechanical roller heat-expanded steel pipe, etc.According to the steel pipe material, it can be divided into carbon steel thermal expansion tube, low alloy thermal expansion tube, high alloy thermal expansion tube, stainless steel thermal expansion tube and titanium alloy steel thermal expansion tube. It is divided into cross-rolled hot-expanded steel pipe, drawn hot-expanded steel pipe, push-type hot-expanded steel pipe, etc.
Heat-expanded steel pipes have a wide range of uses and strong adaptability. In addition to being widely used in oil, water vapor and medium and low pressure flammable or non-flammable fluid pipelines, oil, natural gas and chemical industries. It is also used in power industries such as high and low temperature pressure vessels. It is used in pipes and pipes for urban construction and other structures.
Since the hot-expanded steel pipe is a seamless steel pipe obtained by thermally expanding the small and medium diameters into a large-diameter through the thermal expansion process, the general characteristics of the hot-expanded steel pipe are large diameter and thin wall. The hot-expanded steel pipe process originated from the secondary perforation. The traditional hot-expanded steel pipe production process mainly includes the diagonal rolling hot-diameter expansion process, the drawing-type hot-diameter expansion process, and the push-type hot-diameter expansion process.
Cross-rolling hot diameter expansion process
1. The hot-diameter expansion process of cross-rolling is a hot-diameter expansion process in which the rolled piece heated to an appropriate temperature is fed into the rolling mill in a spiral rotation, and rolled between the roll and the plug to expand the diameter of the steel pipe.
2. Features
①The torsional deformation and elongation coefficient are small, the energy consumption is small, and the angular velocity of the pipe is constant, and the torsion and shear stress are minimized. The cross-sectional area and length of the rolled piece remain basically unchanged before and after the diameter expansion, and the elongation is close to 1.
② The advancing speed is slow. Because the angle of the skew rolling mill is large and the angle of the silver is large and the bite angle is small, the transverse flow speed of the metal is large, the longitudinal flow speed is small, and the advancing speed of the pipe is slowed down.Sometimes it is possible to better ensure the stability of the expansion and the accuracy of the joint thickness by reducing the advancing speed of the expansion;
③The quality of pipe expansion is stable, and the mandrel is positioned by hydraulic small cabin, and the hydraulic small cabin can compensate for any change in length and dimension of the rolling mill due to the displacement of the head during rolling. In addition, the cross-rolling hot diameter expansion process can also improve the dimensional accuracy of the parent pipe, especially the uneven joint thickness of the parent pipe, and will not have adverse effects on the surface quality;
④ The production investment is large, the production equipment of the cross-rolling hot diameter expansion process is huge, the investment is high, and the production cost is also high. The diameter range of the pipe most suitable for the application of the skew rolling hot expansion process is 425-762mm.
The cross-rolling hot-diameter expansion process is considered to be one of the best processes for producing large-diameter, medium-thin-wall seamless steel pipes by heat engine
Drawing type thermal expansion process
The oblique drawing type thermal expansion process is to first expand a bell mouth at the end of the waste pipe, and the diameter of the surface expansion is about 100mm larger than the diameter after thermal expansion.This is beneficial for the inner and outer snap rings to clamp the pipe end during thermal expansion and perform water cooling.Then the mandrel rod is pulled by the chain and the plug is driven to pass through the inside of the waste pipe to realize the deformation process of expanding the diameter, reducing the wall and shortening the length.
The drawing type thermal expansion has low production cost, strong production flexibility and acceptable product quality.However, the accuracy of the outer diameter of the seamless pipe produced by this process is poor, the surface of the steel pipe is not smooth, the quality of the groove is poor, and the outer surface is seriously wavy.
Push-type thermal expansion process
1. The push-type thermal expansion process is to place the raw material pipe at the head displacement place in the intermediate frequency induction multi-circle heating furnace after local heating by the intermediate frequency induction, and then push the raw material pipe by the movement of the hydraulic cylinder piston.The raw material pipe is gradually pushed through the conical inner mold mandrel fixed on the fixing frame at the tail, so as to achieve the purpose of diameter expansion
2. Features
①Local heating. The push-type thermal expansion process uses an intermediate frequency induction coil to perform local heating only in the thermal expansion deformation area. The heating temperature is uniform and stable, and the heating is performed while advancing.
② With high elongation, there will be obvious intuitive changes in the process of thermal expansion and deformation, such as the expansion of the diameter of the steel pipe, the shortening of the length, and the thinning of the wall thickness.
③ The finished product rate is high, and the single-pass expansion ratio is large. Because the billet end is pushed, there is no need to prefabricate the bell mouth, so the finished product rate is high. The single-pass expansion ratio is large. Except for the production of extra-large-sized special steel pipes that require multi-pass expansion, other specifications generally use single-pass expansion.
④ Less investment, quick effect and flexible production organization. The varieties that can be produced are: fluid pipes, structural pipes, gas cylinder pipes, pipeline pipes, low and medium pressure boiler pipes, etc.
Heat-expanded steel pipes have a wide range of uses and strong adaptability. In addition to being widely used in oil, water vapor and medium and low pressure flammable or non-flammable fluid pipelines, oil, natural gas and chemical industries. It is also used in power industries such as high and low temperature pressure vessels. It is used in pipes and pipes for urban construction and other structures.
Since the hot-expanded steel pipe is a seamless steel pipe obtained by thermally expanding the small and medium diameters into a large-diameter through the thermal expansion process, the general characteristics of the hot-expanded steel pipe are large diameter and thin wall. The hot-expanded steel pipe process originated from the secondary perforation. The traditional hot-expanded steel pipe production process mainly includes the diagonal rolling hot-diameter expansion process, the drawing-type hot-diameter expansion process, and the push-type hot-diameter expansion process.
Cross-rolling hot diameter expansion process
1. The hot-diameter expansion process of cross-rolling is a hot-diameter expansion process in which the rolled piece heated to an appropriate temperature is fed into the rolling mill in a spiral rotation, and rolled between the roll and the plug to expand the diameter of the steel pipe.
2. Features
①The torsional deformation and elongation coefficient are small, the energy consumption is small, and the angular velocity of the pipe is constant, and the torsion and shear stress are minimized. The cross-sectional area and length of the rolled piece remain basically unchanged before and after the diameter expansion, and the elongation is close to 1.
② The advancing speed is slow. Because the angle of the skew rolling mill is large and the angle of the silver is large and the bite angle is small, the transverse flow speed of the metal is large, the longitudinal flow speed is small, and the advancing speed of the pipe is slowed down.Sometimes it is possible to better ensure the stability of the expansion and the accuracy of the joint thickness by reducing the advancing speed of the expansion;
③The quality of pipe expansion is stable, and the mandrel is positioned by hydraulic small cabin, and the hydraulic small cabin can compensate for any change in length and dimension of the rolling mill due to the displacement of the head during rolling. In addition, the cross-rolling hot diameter expansion process can also improve the dimensional accuracy of the parent pipe, especially the uneven joint thickness of the parent pipe, and will not have adverse effects on the surface quality;
④ The production investment is large, the production equipment of the cross-rolling hot diameter expansion process is huge, the investment is high, and the production cost is also high. The diameter range of the pipe most suitable for the application of the skew rolling hot expansion process is 425-762mm.
The cross-rolling hot-diameter expansion process is considered to be one of the best processes for producing large-diameter, medium-thin-wall seamless steel pipes by heat engine
Drawing type thermal expansion process
The oblique drawing type thermal expansion process is to first expand a bell mouth at the end of the waste pipe, and the diameter of the surface expansion is about 100mm larger than the diameter after thermal expansion.This is beneficial for the inner and outer snap rings to clamp the pipe end during thermal expansion and perform water cooling.Then the mandrel rod is pulled by the chain and the plug is driven to pass through the inside of the waste pipe to realize the deformation process of expanding the diameter, reducing the wall and shortening the length.
The drawing type thermal expansion has low production cost, strong production flexibility and acceptable product quality.However, the accuracy of the outer diameter of the seamless pipe produced by this process is poor, the surface of the steel pipe is not smooth, the quality of the groove is poor, and the outer surface is seriously wavy.
Push-type thermal expansion process
1. The push-type thermal expansion process is to place the raw material pipe at the head displacement place in the intermediate frequency induction multi-circle heating furnace after local heating by the intermediate frequency induction, and then push the raw material pipe by the movement of the hydraulic cylinder piston.The raw material pipe is gradually pushed through the conical inner mold mandrel fixed on the fixing frame at the tail, so as to achieve the purpose of diameter expansion
2. Features
①Local heating. The push-type thermal expansion process uses an intermediate frequency induction coil to perform local heating only in the thermal expansion deformation area. The heating temperature is uniform and stable, and the heating is performed while advancing.
② With high elongation, there will be obvious intuitive changes in the process of thermal expansion and deformation, such as the expansion of the diameter of the steel pipe, the shortening of the length, and the thinning of the wall thickness.
③ The finished product rate is high, and the single-pass expansion ratio is large. Because the billet end is pushed, there is no need to prefabricate the bell mouth, so the finished product rate is high. The single-pass expansion ratio is large. Except for the production of extra-large-sized special steel pipes that require multi-pass expansion, other specifications generally use single-pass expansion.
④ Less investment, quick effect and flexible production organization. The varieties that can be produced are: fluid pipes, structural pipes, gas cylinder pipes, pipeline pipes, low and medium pressure boiler pipes, etc.
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