Processing technology of stainless steel head by rotary extrusion
The mechanism of the process of processing stainless steel heads by rotary extrusion is “high-speed rotation”. In detail, this process uses high-speed rotating workpieces under the action of tools to make the process materials of the stainless steel heads that need to be processed pass itself well. The hot plasticity of the steel is deformed to form a stainless steel head that needs to be processed. The following not only analyzes the formation mechanism of stainless steel materials, the selection of tool materials and geometric parameters in the process of processing stainless steel heads by rotary extrusion, but also introduces the technology and characteristics of processing stainless steel heads by rotary extrusion.
Traditional stainless steel heads are usually processed by drawing die drawing or spin-extrusion, especially spin-extrusion. This processing technology has high molding performance, high toughness, and high hardness and deformation resistance. Severe hardening, cracking, wrinkling and other phenomena occur during processing; in addition, when the pressure-shaped head is first used and then butt-welded with the tube body, the quality of the processed product is easily affected by the welding quality. The products processed by the processing methods usually have large defects and cannot be satisfied by people. Therefore, from the perspective of improving product quality, improving product quality, and reducing costs, only the process of processing the head with the rotary extrusion method with the processing characteristics of simple operation and quick forming can completely solve this problem.
The process and characteristics of processing stainless steel heads by spinning
The process of processing stainless steel heads by rotary extrusion method is a method to make the processed workpiece partially deformed by the heat generated by the friction and extrusion between the tool and the workpiece during the processing, and there is no material fragmentation during the processing of the rotary extrusion method. When chips appear, the process of processing stainless steel heads by rotary extrusion is divided into three stages, which are described in detail below.
The first stage is the heat-giving stage. Once processing is carried out, the high-speed rotation of the lathe chuck will drive the workpiece to operate, and at the same time, the tool will also move in the axial and radial directions. However, in the process of processing stainless steel head by rotary extrusion method, the stainless steel tube end has a very large requirement for plastic deformation, which means that the tool mainly operates in the radial direction in this working area. The radial operation can increase the gap between the workpiece and the tool. Heat generated by friction and extrusion.
The second stage is the material softening stage. Under normal processing conditions, the thermal conductivity of ordinary stainless steel materials will be relatively low, which can only reach 28% of ordinary steel materials. The reason why the workpiece and the tool can produce a lot of friction in the area The frictional heat is caused by the severe friction between the workpiece under the action of the blunt radius of the tool and the flank surface, which causes the temperature of this friction area to rise sharply. Only when the surface temperature of the friction surface of the material is above the crystallization temperature can the plasticity of the material be maximized, and only by continuing to increase the radial force and axial force in the area where the material needs to be deformed can a certain degree of plastic deformation under the action of extrusion To reach the desired plastic state as soon as possible.
The third stage is also the final stage of the process of processing stainless steel heads by rotary extrusion, that is, the forming stage of the workpiece. Only when the material of the deformed part reaches a certain thermoplastic state can the forming of the workpiece be in a perfect state. At this time, the tool The radial force and axial force will be greatly reduced due to the softening of the material, which creates a good basic condition for the formation and feed of the tool, which can make the workpiece material in a thermoplastic state under the extrusion of the tool and follow the shape required by the drawing rapid prototyping.
In addition, the processed metal material will produce bite welding at the closing point at the moment of sealing, and finally form the head of the processed stainless steel pipe.
The forming mechanism of the process of processing stainless steel heads by spinning
The spinning process for processing stainless steel heads is based on a series of complex thermoplastic deformation processes of the processed metal materials under the action of force and force. The forming mechanism of the spinning process for processing stainless steel heads is analyzed below. .
In the preheating stage of the process of processing stainless steel heads by rotary extrusion, the color of the metal surface in the friction area will change due to the rapid increase in temperature when the tool and the workpiece produce extrusion and friction; In addition, the increase in the radial force of the tool will increase the friction. At this time, the material of the surface layer of the friction area will undergo a short period of work hardening and then enter the recovery stage and quickly reach the thermoplastic state. The extrusion of the tool will cause the material in the thermoplastic zone to gradually polymerize to the axis of the workpiece. According to the principle of constant volume, it can be concluded that the wall thickness of the deformed part of the workpiece is dynamically changing. When the deformation of the stainless steel pipe port reaches the maximum Time also means that the wall thickness of the workpiece will reach the thickest at this time, and the temperature will also reach the highest; finally, under the combined action of the high temperature and the friction and extrusion of the tool at the port of the stainless steel pipe, the fusion and adhesion of the pipe are greatly enhanced. The auxiliary function is to complete the sealing by the occurrence of bite welding at the closing of the port.
Changes in various properties in the process of processing stainless steel heads by spinning
In the process of processing stainless steel heads by rotary extrusion, the radial force will change with the progress of the processing process. Under normal circumstances, the change trend of the radial force is: before the processed workpiece material reaches the required softening requirements, The radial force will continue to increase; once the softening of the material reaches the required radial force, it will rapidly decrease, and the radial force will drop to zero when the workpiece is formed. According to the data of investigation and research, when keeping the working speed of the workpiece and the pressing friction force of the tool constant, the required radial force will increase when the wall thickness to be processed increases; in addition, with The radial force required to increase the diameter of stainless steel pipe fittings will also change to varying degrees.
In the process of processing stainless steel pipe fittings by rotary extrusion method, the temperature will also change with different developments. The effect of temperature when processing the head is equivalent to a local heat source acting on the pipe end of the stainless steel pipe fitting from the length direction. Seeing that the heat conduction mode of the heat source is carried out into the tube, and then a temperature field with the end of the stainless steel pipe fitting as the heat source is formed; in addition, due to the low thermal conductivity of the stainless steel material, it will appear in the length direction of the pipe fitting The larger temperature gradient makes the temperature at the point of action of the tool and the workpiece the highest, which in turn causes uneven heat distribution. Looking at it from another angle, the smaller value of the wall thickness of the processed workpiece makes the heat transfer speed reach the temperature of the heat source quickly and in time. The frictional heat transfer method in the process of processing stainless steel pipe fittings by the spinning method causes the frictional heat to increase at a rate greater than the rate of internal conduction and outward dissipation, so as to achieve the purpose of heat accumulation in the processing part.
Although the spin-extrusion process of processing stainless steel heads has the defect of poor thermal conductivity, the production practice of the stainless steel heads with smaller wall thicknesses fully reflects the feasibility of using the spin-extrusion process to process stainless steel heads. The superiority of the spin-extrusion process for processing stainless steel heads is reflected in the full use of ordinary machine tools and different special tooling, which fully reflects the high-speed, fast and efficient utilization of materials in the process of processing stainless steel heads by the spin-extrusion method; The use of spin-extrusion to process small-diameter U-shaped cylindrical parts get rid of the traditional processing technology. The stretch forming process has a lot of inconveniences for processing long stainless steel heads, which makes the spin-extrusion process stainless steel heads. Craft becomes the best choice. Therefore, the process of processing stainless steel heads by spin-extrusion requires further research and discussion.
Author: early Chang Wei, Xue steel
Source: Stainless Steel Head Manufacturer – Yaang Pipe Industry Co., Limited (www.metallicsteel.com)
(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)
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