A hot extrusion forming method for stainless steel rail

Abstract

The present invention relates to a hot extrusion forming method for a stainless steel rail, and the hot extrusion forming system includes machining equipment, heating equipment, lubrication equipment, hot extrusion equipment, cooling bed, heat treatment equipment and inspection equipment. The extrusion forming steps are: (1) Billet processing: sawing, lathe processing and outer surface polishing of forged smooth billet round steel; (2) Induction heating: heating the billet by multi-stage heating and temperature equalization; (3) Tool and die preparation: using an extrusion die with the same hole shape as the rail; (4) Lubrication: glass lubrication of the billet outer surface and the extrusion die; (5) Hot extrusion: hot extrusion forming the billet into a rail; (6) Cooling: air cooling the extruded rail; (7) Heat treatment: heat treatment of the rail; (8) Inspection: inspecting the surface quality, size, mechanics and physical and chemical properties of the rail. The present invention optimizes the production process by rationally integrating the production process, and the stainless steel rails produced meet the quality requirements, which is conducive to reducing production costs and increasing the economic benefits of the enterprise.

Description

Technical Field

[0001] The invention belongs to the technical field of hot extrusion forming technology and special-shaped material manufacturing technology, and relates to a hot extrusion forming method for a stainless steel rail. Background Art

[0002] Rails are the main components of railway tracks. Their function is to guide the wheels of locomotives and vehicles forward, and they are subjected to huge pressure from the wheels and transmitted to the sleepers. Rails must provide a continuous, smooth and least resistant rolling surface for the wheels. In electrified railways or automatic block sections, rails can also be used as track circuits. The cross-sectional shape of the rails adopts an I-shaped cross-section with the best bending resistance, consisting of three parts: the rail head, the rail waist and the rail bottom. In order to enable the rails to better withstand forces from all sides and ensure the necessary strength conditions, the rails should be of sufficient height, and their heads and bottoms should have sufficient area and height, and the waist and bottom should not be too thin.

[0003] The most commonly used forming method for rails is hot rolling, which is mainly used for the production of large quantities of rails. However, the method of producing rails by hot extrusion has not been reported in the literature. Since the hot extrusion forming method can be formed in one time and can ensure the surface quality, the organizational properties can be guaranteed after heat treatment. It is very simple to change the specifications during production, which is very suitable for the production of small batches of rails. However, this forming method also has many difficulties: problems in any link such as tooling design, heating process, lubrication effect, etc. will lead to the scrapping of the rails. Summary of the invention

[0004] The purpose of the present invention is to provide a hot extrusion forming method for stainless steel rails, optimize the rail production process, meet the quality requirements of the rails, reduce production costs, and increase the economic benefits of the enterprise.

[0005] The technical solution of the present invention is: a hot extrusion forming method of a stainless steel rail, which uses a hot extrusion forming system to perform extrusion forming, comprising the following steps:

[0006] ⑴ Billet processing: sawing, lathe processing and outer surface polishing of forged round steel billets are carried out according to the process requirements; after processing and polishing, the outer surface is smooth and defect-free, the roughness is ≤2.0μm, the cutting slope of the rear end face of sawing is ≤5mm, and the head of the billet after lathe processing is processed into a cone structure, with an R30mm inverted outer arc angle at the top, an outer diameter of φ350mm, and a length of 500-1100mm;

[0007] ⑵ Induction heating: The billet heating method is to use multi-stage heating and uniform temperature method

[0008] ⑶ Tool and die preparation: Use a rail extrusion die with the same hole shape as the rail. The hole shape of the rail extrusion die has a gradual guide arc line, and the die support and die center support of the die both have a hole shape of the rail;

[0009] (4) Lubrication: The outer surface of the blank and the extrusion die during the extrusion process are lubricated with glass. The hole type of the lubricating glass pad is a rail-shaped glass pad;

[0010] ⑸Hot extrusion: Use 375 series extrusion barrel and 63MN horizontal extruder to hot extrude the billet into rails;

[0011] (6) Cooling: air-cool the extruded rails on a cooling bed;

[0012] ⑺Heat treatment: Heat treatment is carried out on the rails. According to the different materials and performance requirements of the rails, appropriate heat treatment processes are selected for heat treatment.

[0013] ⑻Inspection: Inspect the surface quality, size, mechanical properties and physical and chemical properties of the rails.

[0014] The cone angle of the front end of the billet is 1:3 to 1:6. The temperature is measured based on the center temperature of the billet head in the segmented heating and temperature equalization method. The first segment: heat the temperature to 800°C at low power and average the temperature for 5 to 8 minutes; the second segment: heat to 1000°C at low power and average the temperature for 5 to 8 minutes; the third segment: heat to 1050°C at medium power and average the temperature for 4 to 6 minutes; the fourth segment: heat to 1100°C at medium power and average the temperature for 2 to 4 minutes; the fifth segment: quickly heat to 1120 to 1160°C at high power and quickly take out of the furnace; the extrusion process parameters are: extrusion ratio of 11.3, extrusion speed of 60 to 100 mm / S, and extrusion force theoretically calculated to be 50 to 58 MN.

[0015] The hot extrusion forming system of stainless steel rails includes machining equipment, heating equipment, lubrication equipment, hot extrusion equipment, cooling bed, heat treatment equipment and quality inspection equipment, which are arranged in sequence. The machining equipment includes lathes, cutting machines and polishing machines, the heating equipment is an electromagnetic induction heating furnace, and the quality inspection equipment includes surface quality equipment, specification and size inspection equipment, and mechanical and physical and chemical properties inspection equipment.

[0016] The hot extrusion equipment is a 63MN horizontal extruder. The horizontal extruder includes an extrusion barrel and an extrusion die. The extrusion barrel includes an extrusion barrel outer sleeve, an extrusion barrel middle liner and an extrusion barrel inner liner. The extrusion die includes a die support, a die support, a die seat, a die pad and a die back pad rail die. The rail hole of the rail extrusion die has a gradual flow guide arc. The die support and die support of the extrusion die both have rail-shaped rail hole shapes. The hole shape of the rail extrusion die is in the shape of a rail, and the edge of the hole shape has a gradual arc-shaped flow guide groove.

[0017] The present invention optimizes the rail production process by integrating the hot extrusion forming process of stainless steel rails. The produced stainless steel rails meet the quality requirements, which is conducive to reducing production costs and increasing the economic benefits of enterprises. Compared with the traditional hot rolling process, the hot extrusion process has many advantages such as no restrictions on billets, stable forming process, and flexible production methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the process of hot extrusion forming system for stainless steel rails.

[0019] Figure 2 It is the assembly drawing of the extrusion barrel and extrusion die of the extruder;

[0020] Figure 3 It is a schematic diagram of the hole type extrusion die structure;

[0021] Figure 4 for Figure 3 AA map;

[0022] Figure 5 It is a schematic diagram of processing the blank;

[0023] Figure 6 for Figure 1 Side cross-sectional view of .

[0024] Among them: 1-forged smooth round steel, 2-extrusion die, 3-rail hole type, 4-locating pin hole, 5-die center support, 6-die support, 8-extrusion cylinder outer jacket, 9-extrusion cylinder center liner, 10-extrusion cylinder inner liner, 11-die base, 12-die center pad, 13-die back pad, 14-processing equipment, 15-heating equipment, 16-lubrication equipment, 17-hot extrusion equipment, 18-cooling bed, 19-heat treatment equipment, 20-inspection equipment, 21-extrusion cylinder. DETAILED DESCRIPTION

[0025] The present invention is described in detail below with reference to the embodiments and drawings. The protection scope of the present invention is not limited to the embodiments, and any changes made by those skilled in the art within the scope defined by the claims also fall within the protection scope of the present invention.

[0026] The hot extrusion forming of the stainless steel rail of the present invention is carried out by using a hot extrusion forming system, such as Figure 1 As shown, the hot extrusion molding system includes machining equipment 14, heating equipment 15, lubrication equipment 16, hot extrusion equipment 17, cooling bed 18, heat treatment equipment 19 and inspection equipment 20. The machining equipment, induction heating equipment, lubrication equipment, hot extrusion equipment, cooling bed, heat treatment equipment and inspection equipment are arranged in sequence. The machining equipment includes a lathe, a cutting machine and a polishing machine, and the heating equipment is an electromagnetic induction heating furnace. The hot extrusion equipment is a 63MN horizontal extruder, such as Figure 2As shown, the extruder includes an extrusion barrel 21 and an extrusion die 2, the extrusion barrel includes an extrusion barrel outer sleeve 8, an extrusion barrel middle liner 9 and an extrusion barrel inner liner 10, and the extrusion die 2 includes a die support 5, a die support 6, a die base 11, a die pad 12 and a die back pad 13. Figure 3 , Figure 4 As shown, the die support 6 and the die center support 5 of the extrusion die 2 are both provided with a rail pass 3 in the shape of a rail. The process route of hot extrusion forming of stainless steel rails of the present invention is: blank processing → blank preheating → induction heating → tool and die preparation → lubrication → hot extrusion → cooling → heat treatment → inspection. The specific steps are as follows:

[0027] ⑴ Billet processing: The steel material is GB / T1220 06Cr19Ni10 forged round steel. According to the process requirements, the forged round steel is sawn, lathe-processed and polished. The outer surface is required to be smooth and defect-free after processing and polishing, with a roughness of ≤2.0μm, and the cutting slope of the rear end of sawing is ≤5mm; Figure 5 As shown, the head of the blank after lathe processing is processed into a cone structure, the taper of the cone is 1:4, the top is an R30mm inverted outer arc angle, the outer diameter is φ350mm, and the length is 640mm.

[0028] ⑵ Induction heating: In order to ensure the lubrication effect of the vertebral part of the blank during extrusion, glass powder is pre-coated on the vertebral part of the blank before heating. The segmented heating and temperature equalization method is adopted. The temperature measurement is based on the center temperature of the blank head. The first segment: heat the temperature to 800℃ with low power (300KW) and average the temperature for 5 to 8 minutes; the second segment: heat to 1000℃ with low power (300KW) and average the temperature for 5 to 8 minutes; the third segment: heat to 1050℃ with medium power (450KW) and average the temperature for 4 to 6 minutes; the fourth segment: heat to 1100℃ with medium power (450KW) and average the temperature for 2 to 4 minutes; the fifth segment: quickly heat to 1120~1160℃ with high power (600KW) and quickly take out of the furnace.

[0029] ⑶ Tool and die preparation: Use an extrusion die with the same hole shape as the rail. The hole shape of the rail die has a gradual guide arc, such as Figure 3 , 4 The die support 6 and the die support 5 of the extrusion die are provided with a rail-shaped rail hole 3, as shown Figure 5 As shown; the operator assembles the tooling into place, and after assembly the technician checks whether the tooling meets the rail extrusion requirements.

[0030] (4) Lubrication: The outer surface of the blank and the extrusion die during the extrusion process are lubricated with glass. The hole type of the lubricating glass pad is a rail-shaped glass pad;

[0031] ①Spread 844~7 types of glass powder on the lubrication table of the extruder;

[0032] ② Use HDK-5 glass powder to make glass pads, use the glass pads to make molds, and after the molds are pressed into shape, put them into a resistance furnace for drying at 150°C.

[0033] ⑸ Hot extrusion: Use 375 series extrusion barrel and 63MN horizontal extruder to hot extrude the billet into rails. The extrusion ratio is 11.3, the extrusion speed is 78mm / S, and the actual extrusion force is 54MN.

[0034] ⑹ Cooling: The extruded rails are air-cooled to room temperature on a cooling bed.

[0035] ⑺Heat treatment: Heat treatment of rails; heating temperature 1000℃, keep warm for 3 hours, and water cool after taking out of the furnace.

[0036] ⑻ Inspection: Inspection of the stainless steel rails produced through the above steps, including surface quality, size, mechanical properties and physical and chemical properties. All performance inspections are carried out by sampling at the upper track portion of the rails.

[0037] The chemical composition of the stainless steel rail produced by the present invention is shown in Table 1, and the mechanical property test results are shown in Table 2.

[0038] Table 1 Chemical composition test results

[0039]

[0040]

[0041] Table 2 Mechanical properties test results

[0042]

[0043] After inspection, the surface quality, dimensional accuracy, physical and chemical properties, mechanical properties and other indicators of the manufactured stainless steel rails all meet the design requirements.

Claims

1. A method for hot extrusion forming of a stainless steel rail, wherein the hot extrusion forming system is used for extrusion forming; the hot extrusion forming system comprises machining equipment (14), heating equipment (15), lubricating equipment (16), hot extrusion equipment (17), cooling bed (18), heat treatment equipment (19) and inspection equipment (20), wherein the machining equipment, heating equipment, lubricating equipment, hot extrusion equipment, cooling bed, heat treatment equipment and inspection equipment are arranged in sequence; the machining equipment comprises a lathe, a cutting machine and a polishing machine, and the heating equipment is an electromagnetic induction heating furnace; the hot extrusion equipment is a 63MN horizontal extruder, and the 63MN horizontal extruder comprises an extrusion barrel (21) and a rail extrusion die (2), wherein the extrusion barrel comprises an extrusion barrel outer sleeve (8), an extrusion barrel middle liner (9) and an extrusion barrel inner liner (10), and the rail extrusion die (2) comprises a die middle support (5) and a die support (6); wherein the method comprises: The hot extrusion molding method comprises the following steps: ⑴ Billet processing: sawing, lathing and outer surface polishing of forged round steel billets are performed according to the process requirements; after processing and polishing, the outer surface is smooth and defect-free, with a roughness of ≤2.0µm, and the cutting slope of the rear end face of sawing is ≤5mm. The head of the billet after lathing is processed into a cone structure, with an R30mm inverted outer arc angle at the top, an outer diameter of φ350mm, and a length of 500-1100mm; the taper of the cone structure is 1:3-1:6; (2) Induction heating: The billet heating method is to use a multi-stage heating and temperature equalization method for heating; the multi-stage heating and temperature equalization method is: the temperature measurement is based on the center temperature of the billet head, the first stage: heating the temperature to 800°C at low power, and the temperature is averaged for 5 to 8 minutes; the second stage: heating to 1000°C at low power, and the temperature is averaged for 5 to 8 minutes; the third stage: heating to 1050°C at medium power, and the temperature is averaged for 4 to 6 minutes; the fourth stage: heating to 1100°C at medium power, and the temperature is averaged for 2 to 4 minutes; the fifth stage: quickly heating to 1120-1160°C at high power, and quickly taking out of the furnace; (3) Tool and die preparation: using a rail extrusion die (2) having a hole profile identical to the shape of the rail, the hole profile of the rail extrusion die having a gradient flow guide arc, and the die support (6) and the die center support (5) of the rail extrusion die both having a hole profile in the shape of the rail; ⑷ Lubrication: Glass lubrication is performed on the outer surface of the blank and the rail extrusion die during the extrusion process; (5) Hot extrusion: using a 375 series extrusion barrel and a 63MN horizontal extruder to hot extrude the billet into a rail; the hot extrusion process parameters are: extrusion ratio of 11.3, extrusion speed of 60-100 mm / S, and extrusion pressure of 50-58 MN in theoretical calculation; (6) Cooling: air-cool the extruded rails on a cooling bed; ⑺Heat treatment: heat treatment of rails; ⑻Inspection: Inspect the surface quality, size, mechanical properties and physical and chemical properties of the rails.

2. The hot extrusion forming method of a stainless steel rail according to claim 1, characterized in that: The hole profile of the rail extrusion die (2) is in the shape of a rail, and the edge of the hole profile has a gradually changing arc-shaped flow guide groove.

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