Strong shearing extrusion forming method and device for annular cylindrical part

Abstract

The invention discloses a strong shearing extrusion forming method and device for annular and cylindrical parts, and belongs to the technical field of annular and cylindrical part extrusion forming. The method comprises the following steps that 1, a hollow blank and a hollow extrusion backing ring are heated; 2, a mold is assembled and preheated; 3, the hollow blank and the hollow extrusion backing ring which are heated in the step 1 are taken out, and hot shearing extrusion is conducted on the hollow blank; and 4, material heads and material tails are cut off, and finish machining is carried out after heat treatment to obtain the required size of a finished product. According to the method, hot shearing extrusion is adopted, strong shearing deformation is introduced in the wall thickness direction in the traditional hollow blank extrusion deformation process, the shearing-compression / stretching-shearing composite large plastic deformation effect is achieved, meanwhile, a thick and large solidified grain structure can be effectively refined and homogenized, the uniformity of wall thickness deformation can be improved, the extrusion force can be reduced, and the product quality is improved. And the multi-heating-number blank making process can be reduced, and the forming efficiency is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of extrusion forming of annular cylindrical parts, and relates to a strong shearing extrusion forming method and device for annular cylindrical parts. Background Art

[0002] Hollow products can be formed by extrusion forming technology. During the extrusion deformation process, the metal is under strong three-dimensional compressive stress in the deformation zone, the metal's plastic deformation ability is improved, and the grain structure is improved. The size of the extrusion force of the traditional positive extrusion deformation of annular cylindrical parts depends on the selection of process parameters such as material deformation resistance, deformation degree and friction factors. Therefore, it is limited by the extrusion equipment. Positive extrusion deformation is often used for the forming of pipes, profiles and small-diameter thin-walled annular cylindrical parts. However, for some annular cylindrical forgings made of difficult-to-deform alloy materials, the deformation resistance is large and it is difficult to achieve large forging ratio forming. Especially when extruding large-diameter or thick-walled annular cylindrical parts, the single-pass extrusion deformation is limited, and it is difficult to achieve one-time extrusion forming, which requires multiple extrusions.

[0003] During the extrusion deformation process, the difference in the cross-sectional dimensions of the billet and the extrusion before extrusion affects the distribution of the degree of deformation. The inner diameter of the cylindrical extrusion remains unchanged while the outer diameter decreases. After extrusion, the degree of deformation along the wall thickness direction is much greater on the outside than on the inside, and the deformation distribution along the wall thickness direction is uneven. The thicker the wall of the cylindrical extrusion, the worse the uniformity of the deformation distribution of the extrusion along the wall thickness direction after extrusion, resulting in more uneven distribution of the grain structure and performance of the extrusion. Therefore, even though the manufacture and commissioning of large extruders can provide sufficient extrusion loads for the extrusion of large cylindrical parts, the use of extrusion for cylindrical parts and the realization of the integration of "shape control / property control" of extruded products are still urgent issues to be solved. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to solve the technical problems of large deformation load, limited deformation amount, difficult control of macro deformation and microstructure uniformity in the traditional positive extrusion forming process of annular cylindrical forgings, and to provide a strong shear extrusion forming method and device for annular cylindrical parts. The prepared annular cylindrical forgings not only have uniform plastic deformation and fine grains, but also can realize short-process production of large annular cylindrical parts.

[0005] In order to solve the above technical problems, on the one hand, an embodiment of the present invention provides a strong shear extrusion forming method of a cylindrical part, comprising the following steps:

[0006] Step 1, heating the hollow blank and the hollow extrusion backing ring;

[0007] Step 2: Assemble the mold and preheat the mold;

[0008] Step 3, taking out the hollow billet and the hollow extrusion gasket ring heated in step 1, and performing hot shear extrusion on the hollow billet;

[0009] Step 4: Cut off the head and tail of the material, and then fine-process it to the required size of the finished product after heat treatment.

[0010] Preferably, step 1 specifically includes: using an annular furnace to heat the hollow billet and the hollow extrusion backing ring to an initial extrusion temperature of 1000-1230° C. and keep them warm for use in the next step.

[0011] Furthermore, the initial extrusion temperature is 1200°C.

[0012] Further, in step 1, the size of the hollow billet is based on the outer diameter D of the ring tube extrusion forging. 1 , inner diameter d 1 , wall thickness H, axial height B 1 Sure.

[0013] The outer diameter D of the extruded billet of the cylindrical parts 0 , inner diameter d 0 , wall thickness H, axial height B 0 , the change in outer diameter ΔD=D 0 ±D 1 , the change in inner diameter Δd = d 0 ±d 1 , where ΔD = Δd, This formula is used to calculate the initial cylindrical billet axial height B based on the size requirements of the ring cylinder extrusion forging. 0 The formula, where D 0 and d 0 Determined according to the wall thickness H, transition section length L, and cone angle α, 2% is a volume compensation, taking into account the small deformation area caused by the small constraint at the front end of the extruded billet because it is a free end. 0 Along the extrusion direction, i.e. the axial direction, due to the small deformation zone at the front end of the extrusion, a certain size increase of 2% is compensated in the initial axial direction. The actual size changes of the inner and outer diameters ΔD and Δd are consistent. The wall thickness of the cylindrical extrusion billet remains unchanged before and after the extrusion deformation. During the extrusion deformation process, uniform shear deformation occurs along the wall thickness direction.

[0014] Furthermore, the mold assembly described in step 2 specifically includes: assembling the core shaft, extrusion cylinder, core mold, die and die seat so that the extrusion forming channel is axisymmetric, and preheating the assembled mold at a preheating temperature of 350 to 450°C.

[0015] Furthermore, the preheating temperature is 400°C.

[0016] Preferably, step 3 is specifically as follows: quickly taking the hollow billet out of the heating furnace, then placing it into the extrusion channel, placing the extrusion gasket ring above the hollow billet, placing the extrusion punch device above the extrusion gasket ring, using a pressure device to apply force to the extrusion punch through punch pressure, and performing hot shear extrusion on the hollow billet.

[0017] In an embodiment of the present invention, the annular cylindrical part is a thick-walled cylindrical part or a large-diameter thick-walled cylindrical part.

[0018] On the other hand, an embodiment of the present invention further provides a strong shearing extrusion forming device for annular cylindrical parts, which adopts a shearing double-cone angle structure extrusion die, and the cone angle α is 30° to 75°.

[0019] Furthermore, the transition at the cone angle is a rounded arc transition, the curvature radius of the inner and outer arcs of the cone angle are different, and the transition section length L between the shear cone angles is taken as L = H·cscα. The constraint on the transition section length L in the mold and process is that the cylindrical extrusion part mainly undergoes double shear deformation during the extrusion process, reducing radial and circumferential compression or tensile deformation, so as to ensure the uniformity of the extrusion deformation of the cylindrical part and the filling property in the extrusion channel, and ensure the more precise control of the size and deformation of the extrusion part after extrusion.

[0020] Furthermore, the transition point at the cone angle is a rounded arc transition, and the curvature radius of the inner and outer arcs of the cone angle are different, wherein the radius of the inner and outer arcs at the first cone angle is r 1 and R 1 , the radius of the inner and outer arcs at the second cone angle is r 2 and R 2 .

[0021] Furthermore, the inner and outer arc radii at the first cone angle are r 1 ≤R 1 ≤H, the radius of the inner and outer arcs at the second cone angle is r 2 ≤R 2 ≤H, inner radius r at the first cone angle 1 ≤Inside of the second cone angle r 2 , which can improve the uniformity of the two shear deformations.

[0022] Furthermore, the shear double cone angle structure extrusion die is made of H13 hot working die steel or 4Cr5MoSiVi hot working die steel.

[0023] Furthermore, the hardness of the shear double cone angle structure extrusion die is 60HRC to 64HRC.

[0024] The above technical solution of the embodiment of the present invention has the following beneficial technical effects:

[0025] The invention proposes a ring-cylindrical part strong shear extrusion forming technology and device, which has the advantages of traditional forward extrusion and equal channel angular extrusion. Without substantially changing the wall thickness of the hollow billet, the double shear cone angle structure in the extrusion forming die is used to achieve shear-compression / stretching-shear composite large plastic deformation of the hollow billet, which can not only effectively refine and homogenize the coarse solidified grain structure, but also improve the uniformity of wall thickness deformation, reduce the extrusion force, and obtain a ring-cylindrical part with regular shape, uniform structure and properties and controllable shape and properties. Since the invention adopts a ring-cylindrical hollow steel billet for direct hot extrusion, it eliminates the process flow of multiple heating and multi-step hot forging, shortens the production cycle, improves the material utilization rate, and can reduce the production cost by more than 20%, which can meet the needs of nuclear power, thermal power, petrochemical and other process fields for hard-to-deform alloy ring-cylindrical parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the principle of shear extrusion of annular cylindrical parts with reduced diameter;

[0027] Figure 2 This is a schematic diagram of the principle of shear extrusion of annular cylindrical parts with expanding diameter;

[0028] Figure 3 It is a schematic diagram of a shear extrusion device for reducing the diameter of an annular cylindrical part;

[0029] Figure 4 It is a schematic diagram of a ring cylindrical part expansion shearing and extrusion device;

[0030] Figure 5 It is a schematic diagram of the cone angle structure in the corner deformation zone of the shear extrusion device for annular cylindrical parts;

[0031] Figure 6 It is a schematic diagram of the traditional forward extrusion simulation model and the deformation distribution after extrusion, where A is a schematic diagram of the traditional forward extrusion simulation model, and B is a cloud diagram of the equivalent strain distribution of the traditional forward extrusion simulation;

[0032] Figure 7 It is a schematic diagram of the strong shear extrusion simulation model and the deformation distribution after extrusion, where A is a schematic diagram of the strong shear extrusion simulation model, and B is a cloud diagram of the equivalent strain distribution of the strong shear extrusion simulation;

[0033] Figure 8 It is a schematic diagram comparing the strain distribution along the wall thickness and the extrusion load after the conventional forward extrusion and strong shear extrusion deformation, wherein A is a comparison diagram of the strain distribution along the wall thickness after the forward extrusion and strong shear extrusion deformation, and B is a comparison diagram of the extrusion load after the forward extrusion and strong shear extrusion deformation;

[0034] In the figure, 1-assembly mandrel, 2-extrusion cylinder, 3-extrusion gasket, 4-hollow blank, 5-core mold, 6-die, 7-die seat, 8-punch pressure plate, 9-punch pad, 10-hollow punch, 11-guide column, 12-guide column sleeve. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the description of well-known structures and technologies is omitted to avoid unnecessary confusion of the concept of the present invention.

[0036] In the strong shear extrusion forming technology for annular cylindrical parts, the inner diameter and outer diameter of the hollow billet are reduced or expanded at the same time in the extrusion channel, and the billet undergoes two symmetrical double shear deformations in opposite directions with the same degree of deformation. The billet undergoes slight compression or stretching deformation between the double shear deformations. After extrusion, the wall thickness of the hollow extruded part is the same as that of the billet.

[0037] The hollow billet can be a forged billet or a cast billet. The forged billet can be made by upsetting, drawing, punching and expanding, and the cast billet can be a hollow steel ingot prepared by electroslag remelting or a hollow cast billet prepared by electroslag liquid casting and refining.

[0038] Reference Figure 1 , Figure 2 The inner diameter and outer diameter of the hollow billet in the extrusion channel are reduced at the same time, the extrusion deformation is shear-shrinking extrusion, and the billet undergoes shear-compression-shear continuous deformation; the inner diameter and outer diameter of the hollow billet in the extrusion channel are expanded at the same time, the extrusion deformation is shear-expansion extrusion, and the billet undergoes shear-stretching-shear continuous deformation.

[0039] The size of the hollow billet is based on the outer diameter D of the ring tube extrusion forging. 1 , inner diameter d 1 , wall thickness H, axial height B 1 Determine the outer diameter D of the extruded billet of the cylindrical part 0 , inner diameter d 0 , wall thickness H, axial height B 0 , the change in outer diameter ΔD=D 0 ±D 1 , the change in inner diameter Δd = d 0 ±d 1 , where ΔD = Δd,

[0040] The strong shear deformation specifically refers to that the core shaft in the extrusion die is set as a cone angle structure, and its cone angle α is the same as the cone angle of the extrusion die, forming a shear double cone angle structure, and the billet undergoes approximately pure shear deformation in the shear double cone angle structure in the extrusion channel; the billet in the shear double cone angle structure passes through the shear deformation zone PDZ1, the shear transition zone PDLZ, and the shear deformation zone PDZ2 in sequence, and the billet undergoes symmetrical double shear deformation during extrusion.

[0041] The compression or tensile deformation of the blank between the double shear deformations refers to the circumferential deformation of the blank in which the diameter decreases or increases in the shear transition section. The circumferential deformation is much lower than the shear deformation. The length of the shear transition section L = H·cscα, and the inner and outer diameters before and after extrusion ΔD = Δd = 2H (sinα-cosα+1).

[0042] Example 1: Thick-walled cylindrical parts shrinking hot shear extrusion forming technology

[0043] The cylindrical extrusion part to be formed has an outer diameter of 1030mm, an inner diameter of 680mm, a thickness of 175mm and a height of 1000mm. The dimensions of the extruded billet are determined to be an outer diameter of 1428mm, an inner diameter of 1082mm, a height of 700mm and a thickness of 173mm. The cylindrical hollow billet is prepared by electroslag remelting method.

[0044] The extrusion die adopts a shear double cone angle structure extrusion die, the cone angle α is 60°, the distance L between the shear transition sections is 200mm, the die material is H13 hot working die steel or 4Cr5MoSiVi hot working die steel, and the hardness is 60HRC~64HRC.

[0045] like Figures 1 to 4 As shown, the cylindrical member hot shear extrusion method comprises the following steps:

[0046] S1, using a ring furnace to heat the hollow billet 4 and the hollow extrusion backing ring 3 to an initial extrusion temperature of 1200°C and keep them warm for later use;

[0047] S2, spraying glass lubricant on each forming surface corresponding to the extrusion forming channel, and then assembling the mandrel 1, the extrusion cylinder 2, the core mold 5, the die 6 and the die seat 7, so that the extrusion forming channel is in an axisymmetric state, and preheating the assembled mold at a preheating temperature of 350-450°C;

[0048] S3, quickly taking the hollow billet 4 out of the heating furnace, and then putting it into the extrusion channel, and placing the extrusion pad ring 3 above the hollow billet 4, placing the extrusion punch device 8-10 above the extrusion pad ring 3, using a pressure device to apply force to the extrusion punch 10 through the punch pressing plate 8, and performing hot shear extrusion on the hollow billet 4;

[0049] S4. After extrusion, the head and tail of the material are cut off, and after heat treatment, it is fine-processed to the required size of the finished product.

[0050] Example 2: Large-diameter thick-walled cylindrical parts are expanded by hot shearing extrusion

[0051] The cylindrical extrusion part to be formed has an outer diameter of 1830 mm, an inner diameter of 1480 mm, a thickness of 175 mm and a height of 770 mm. The dimensions of the extruded billet are determined to be an outer diameter of 1428 mm, an inner diameter of 1082 mm, a height of 1000 mm and a thickness of 173 mm. The cylindrical hollow billet is prepared by electroslag remelting method.

[0052] The extrusion die adopts a shear double cone angle structure extrusion die, the cone angle α is 60°, the distance L between the shear transition sections is 200mm, the die material is H13 hot working die steel or 4Cr5MoSiVi hot working die steel, and the hardness is 60HRC~64HRC.

[0053] The cone angle structure in the corner deformation zone of the ring-shaped cylindrical shear extrusion device is as follows Figure 5 shown.

[0054] The steps of the hot shear extrusion process of the cylindrical part are the same as those in Example 1 and will not be described in detail here.

[0055] Comparative Example 3 Comparison of traditional forward extrusion and shear extrusion forming technology solutions for cylindrical parts

[0056] After extrusion, the cylindrical part has an outer diameter of Φ90mm, an inner diameter of Φ60mm, and a height of 110mm. The following two methods are used for extrusion deformation, and the comparison is as follows:

[0057] Conventional forward extrusion: hollow billet size outer diameter Φ120mm, inner diameter Φ62mm, height 50mm, die half angle 45°, extrusion ratio 2.35, extrusion speed 10mm / s. When extruding pure lead material, the extrusion temperature is room temperature, graphite oil mixed lubricant, friction coefficient is 0.15.

[0058] Reduction shear extrusion: The hollow billet size is Φ120mm in outer diameter, Φ90mm in inner diameter, 90mm in height, the die cone angle is 45°, and the extrusion speed is 10mm / s. The extrusion temperature of pure lead material is room temperature, the graphite oil mixed lubricant, and the friction coefficient is 0.15.

[0059] The load curves of conventional forward extrusion and reduced diameter shear extrusion are as follows: Figure 8 Under the same extrusion stroke conditions, the extrusion load in the stable extrusion stage of conventional forward extrusion is about 380kN; the extrusion load in the stable extrusion stage of reduced diameter shear extrusion is about 260kN, which saves about 120kN of effort and reduces the load by about 32%.

[0060] The strain distribution under the two extrusion processes of conventional forward extrusion and reduced diameter shear extrusion is shown in the figure. Figure 6 As shown in the figure, the strain distribution along the wall thickness after extrusion is as follows Figure 7As shown in the figure. After the shrinkage shear extrusion, the strain distribution along the wall thickness direction is relatively uniform, and the average equivalent strain is 1.35; while during the forward extrusion process, the strain on the inside of the wall thickness direction is smaller than the strain on the outside, and the average equivalent strain is about 1.29. It can be seen that the uniformity of the strain distribution along the wall thickness direction after the shrinkage shear extrusion is higher than that of the forward extrusion, and the average strain value of the shrinkage shear extrusion is greater than that of the forward extrusion.

[0061] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, and do not constitute a limitation of the present invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or the equivalent forms of such scope and boundaries.

Claims

1. A strong shear extrusion forming method for annular cylindrical parts, characterized in that: The steps include: Step 1, heating the hollow blank and the hollow extrusion backing ring; Step 2: Assemble the mold and preheat the mold; Step 3, taking out the hollow billet and the hollow extrusion gasket ring heated in step 1, and performing hot shear extrusion on the hollow billet; Step 4: Cut off the head and tail of the material, and then fine-process it to the required size of the finished product after heat treatment.

2. The strong shear extrusion forming method of annular cylindrical parts according to claim 1 is characterized in that: Step 1 is specifically as follows: a hollow billet and a hollow extrusion backing ring are heated to an initial extrusion temperature of 1000-1230° C. using a ring furnace and kept warm for use in the next step.

3. The strong shear extrusion forming method of annular cylindrical parts according to claim 2 is characterized in that: The initial extrusion temperature is 1200°C.

4. The strong shear extrusion forming method of annular cylindrical parts according to claim 1 is characterized in that: In step 1, the size of the hollow billet is determined according to the outer diameter D1, inner diameter d1, wall thickness H, and axial height B1 of the annular tube extrusion forging.

5. The strong shear extrusion forming method of annular cylindrical parts according to claim 1 is characterized in that: The mold assembly described in step 2 specifically includes: assembling the core shaft (1), the extrusion cylinder (2), the core mold (5), the die (6) and the die seat (7) so that the extrusion forming channel is axially symmetrical, and preheating the assembled mold at a preheating temperature of 350 to 450°C.

6. The strong shear extrusion forming method of annular cylindrical parts according to claim 5, characterized in that: The preheating temperature is 400°C.

7. The strong shear extrusion forming method of annular cylindrical parts according to claim 1 is characterized in that: Step 3 specifically comprises: quickly taking the hollow billet (4) out of the heating furnace, and then placing it into the extrusion channel, and placing the extrusion gasket (3) above the hollow billet (4), placing the extrusion punch device (8-10) above the extrusion gasket (3), and using a pressure device to apply force to the extrusion punch (10) through the punch pressure plate (8), and performing hot shear extrusion on the hollow billet (4).

8. The strong shear extrusion forming method of annular cylindrical parts according to claim 1 is characterized in that: The annular cylindrical part is a thick-walled cylindrical part or a large-diameter thick-walled cylindrical part.

9. A strong shear extrusion forming device for annular cylindrical parts for implementing the method according to any one of claims 1 to 8, characterized in that: A shear double cone angle structure extrusion die is used, the cone angle α is 30° to 75°, and the transition section length L between the shear cone angles is L=H·cscα; the transition at the cone angle is a fillet arc, and the curvature radii of the inner and outer arcs of the cone angle are different, wherein the inner and outer arc radii at the first cone angle are r1 and R1, and the inner and outer arc radii at the second cone angle are r2 and R2; The inner and outer arc radii at the first cone angle are r1≤R1≤H, the inner and outer arc radii at the second cone angle are r2≤R2≤H, and the inner radius r1 at the first cone angle is ≤ the inner radius r2 at the second cone angle.

10. The strong shear extrusion forming device for annular cylindrical parts according to claim 9, characterized in that: The shear double cone angle structure extrusion die is made of H13 hot working die steel or 4Cr5MoSiVi hot working die steel with a hardness of 60HRC to 64HRC.

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