Tool and method for reducing extrusion force of seamless tube and bar

Abstract

The invention relates to a tool and method for reducing the extrusion force of a seamless tube and a bar, the tool is arranged at the front end of the extrusion direction of a target blank for extruding the seamless tube and the bar, and the deformation resistance of the tool 3 is lower than that of the target blank; the tool is of a hollow rotary body structure, the upper portion of the rotary body is of a chamfering structure, the lower portion of the rotary body is of a cylindrical structure, and the tool and a target blank are fixed together. According to the method, the tool with low deformation resistance is additionally arranged, the extrusion force when the tool is extruded is small, the extrusion force when the target blank is discharged out of the extrusion die is in the extrusion force reduction stage, at the moment, only the part, increased due to the large deformation resistance, of the extrusion force is increased, and the increased extrusion force is not increased when the target blank is just discharged out of the extrusion die; therefore, the extrusion force can be reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of extrusion molding, and in particular relates to a tool and a method for reducing the extrusion force of seamless pipes and bars. Background Art

[0002] When large-diameter seamless pipes and large-size bars are extruded, the extrusion pressure is the largest when the metal billet just leaves the extrusion die, and then gradually decreases. The change of extrusion pressure with extrusion stroke is shown in Figure 1 As shown in the figure, Pmax is the extrusion pressure when the metal billet just leaves the extrusion die. Due to the limitation of the extruder equipment capacity, for materials with high deformation resistance such as medium and high alloy steel, nickel-based alloy, stainless steel and titanium alloy, the maximum extrusion pressure during extrusion of some specifications of seamless pipes and bars exceeds the pressure limit of the equipment and cannot be extruded. Summary of the invention

[0003] The present invention provides a tool and method for reducing the extrusion pressure of seamless pipes and bars, and aims to solve the production problem that the extrusion pressure of some seamless pipes and bars exceeds the equipment capacity.

[0004] In order to solve the above technical problems, the present invention provides a tooling for reducing the extrusion force of seamless pipes and bars, characterized in that: it is arranged at the front end of the extrusion direction of the target billet for extruding seamless pipes and bars, the tooling is a hollow rotating body structure, the upper part of the rotating body is a chamfered structure for matching the inner cavity angle of the extrusion die, the lower part is a cylindrical structure, and there is a through hole in the center of the rotating body. The tooling is placed in the extrusion barrel together with the target billet, and the deformation resistance of the tooling is lower than that of the target billet.

[0005] A method for reducing the extrusion pressure of seamless pipes and bars, characterized in that: first, a tooling and a target billet are assembled together, and the tooling is located at the front end of the extrusion direction of the target billet, and after being loaded into a heating furnace and heated simultaneously, it is loaded into an extruder for extrusion; the extruder comprises an extrusion die 1, an extrusion barrel 2, and an extrusion pad 5; the tooling and the target billet are placed together in the extrusion barrel 2, the extrusion die 1 is fixed at the front end of the extrusion barrel 2, and the extrusion pad 5 enters the extrusion barrel 2 from the rear end to press the target billet; during extrusion, the tooling is first extruded out of the extrusion die, and the extruded length should be ≥500mm to ensure that the extrusion pressure can be effectively reduced.

[0006] Beneficial effects: The present invention solves the problem that some specifications of seamless pipes and bars cannot be extruded when they exceed the limit capacity of the equipment, and adds a tooling with a deformation resistance lower than the target billet at the front end of the extrusion direction of the target billet for extruding seamless pipes and bars. According to the theory of extrusion technology, the extrusion force is proportional to the deformation resistance of the material, that is, the greater the deformation resistance, the greater the extrusion force, and the extrusion force is the largest when it just comes out of the extrusion die. By adding a tooling with low deformation resistance, the extrusion force when extruding the tooling is smaller, and the extrusion pressure of the target billet when it comes out of the extrusion die is already in the stage of decreasing extrusion pressure. At this time, the extrusion pressure only increases due to the increase in deformation resistance, and the extrusion pressure that increases when it just comes out of the extrusion die no longer increases, so it can reduce the extrusion pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a graph showing the variation of extrusion pressure with extrusion stroke.

[0008] Figure 2 Schematic diagram of an extruded rod of the present invention.

[0009] Figure 3 Schematic diagram of an extruded seamless tube of the present invention.

[0010] Figure 4 A schematic diagram of another assembly of a tool and a blank according to the present invention.

[0011] Figure 5 A schematic diagram of another assembly of a tool and a blank according to the present invention. DETAILED DESCRIPTION

[0012] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below.

[0013] The present invention proposes a tool for reducing the extrusion force of seamless pipes and bars, which is arranged at the front end of the extrusion direction of the target billet for extruding seamless pipes and bars, and the deformation resistance of the tool 3 is lower than that of the target billet;

[0014] The tooling is a hollow rotating body structure, the upper part of the rotating body is a chamfered structure, the lower part is a cylindrical structure, and there is a through hole in the center of the rotating body with a diameter of 20mm-100mm.

[0015] The chamfer angle is preferably the same as the angle of the inner cavity of the extrusion die 1, generally 30-60 degrees. The horizontal side length of the end face chamfer is 50-200 mm.

[0016] When extruding seamless pipes, the diameter of the center hole of the tooling is 2-20mm larger than the target billet inner hole diameter.

[0017] The deviation between the diameter of the lower cylinder of the tooling of the present invention and the target blank diameter is ±10 mm, and the total height of the tooling is 60-400 mm.

[0018] The deformation resistance of the tooling material of the present invention at the same extrusion temperature is 50-85% of that of the target metal.

[0019] The target blank and the tooling described in the present invention are in mutual fit, and the tooling is located at the front end of the target blank in the extrusion direction, the coaxiality between the two is ≤2mm, and the connection method is welding connection at the circumferential edge interface of the two.

[0020] Another connection method of the target blank and tooling described in the present invention is mechanical matching positioning. This method is used in the case where the blank moves vertically. The target blank and the tooling are matched in a concave-convex form with a matching depth of 10-100mm, the concave and convex edges are chamfered at 30-60° or at right angles, and the end face diameter of the groove is 0.1-5mm larger than the end face diameter of the boss.

[0021] The weight of the tooling should ensure that the length of the seamless pipes and bars it extrude is ≥500mm.

[0022] The target blank and the tooling of the present invention are matched in concave and convex form. When the blank has a concave structure, the tooling has a convex structure; when the blank has a convex structure, the tooling has a concave structure.

[0023] During the production process, in order to prevent the tooling and the target blank from moving or falling apart during transportation after heating, welding can be performed on the circumferential edges where the two are in contact with each other; or a groove (or boss) can be machined at the bottom of the tooling and a boss (or groove) at the upper end of the target blank, and the two can cooperate with each other to prevent movement.

[0024] After the tooling and the target blank are assembled, they are loaded into the heating furnace for simultaneous heating. After heating, they are lubricated and then loaded into the extruder for extrusion. The length of the tooling extrusion should be ≥500mm to ensure that the extrusion pressure can be effectively reduced.

[0025] The present invention proposes a method for reducing the extrusion pressure of seamless pipes and bars. After the target blank and tooling are assembled, heating, lubrication and extrusion processes are performed together according to the product process. The specific steps are as follows:

[0026] S1, assembly tooling and target blank;

[0027] S2, heating: after the tooling and the target blank are assembled, they are loaded into a heating furnace and heated simultaneously;

[0028] S3. Remove oxide scale (if there is oxide scale)

[0029] S4, lubrication;

[0030] S5, loading into extruder for extrusion;

[0031] The extruder comprises an extrusion die 1, an extrusion barrel 2, and an extrusion pad 5; the tooling and the target billet are placed together in the extrusion barrel 2, the extrusion die 1 is fixed at the front end of the extrusion barrel 2, and the extrusion pad 5 enters the extrusion barrel 2 from the rear end to press the target billet.

[0032] If the target blank is a seamless tube, the mandrel 7 needs to be passed through the extrusion pad 5, the target blank 4, the tooling 3 and the extrusion die 1 in sequence to realize the forming of the seamless tube.

[0033] During extrusion, the tooling is first extruded out of the extrusion die, and the extruded length should be ≥500mm to ensure that the extrusion pressure can be effectively reduced.

[0034] The present invention is suitable for vertical extrusion or horizontal extrusion. Specific implementation 1:

[0036] The technology of the present invention is analyzed by finite element simulation software, the simulated tooling material is H13, the billet material is nickel-based alloy 718, and the extruded bar specification is 300mm. The tooling structure has the same outer diameter as the billet outer diameter, the total height of the tooling is 350mm, and the upper conical surface chamfer is C150.

[0037] By comparison, the maximum extrusion pressure of the nickel-based alloy 718 bar directly extruded without tooling is 3.7×108 N. The maximum extrusion pressure of the nickel-based alloy 718 bar extruded with tooling is 2.24×108 N. The extrusion pressure is reduced by 39% by using the technology of the present invention. Specific implementation 2:

[0039] The present invention is used to extrude a high temperature alloy bar with a specification of 300 mm. Figure 2 .

[0040] According to the results of hot compression test, 304 stainless steel at 1100℃ and strain rate 1s -1 Under the condition, the deformation resistance is 175MPa. A high temperature alloy is subjected to deformation at 1100℃ and strain rate 1s -1 The deformation resistance under the condition is 280MPa. The deformation resistance of a certain high temperature alloy is 1.6 times that of 304 stainless steel. 304 stainless steel is selected as the tooling material.

[0041] The upper end of the blank 4 is processed with a 45° chamfer, and the chamfer height is 25mm. The outer diameter of the tool 3 is the same as the diameter of the blank 3, and the total height is 350mm; the conical surface of the upper end of the tool 3 is a C150 chamfer. The groove depth of the lower end surface of the tool 3 that matches the blank 4 is 20mm, and the angle with the horizontal line is 30°. The diameter of the central through hole of the tool 4 is Φ40mm.

[0042] After the blank 4 and the tooling 3 are assembled by chamfering and grooving, they are painted with anti-oxidation paint and loaded into the heating furnace. After heating to 1100°C and insulation, the blank 4 and the tooling 3 are taken out at the same time and put into the lubrication device to spray lubricant. After spraying, the blank 4 and the tooling 3 are put into the extrusion barrel 2 of the extruder and pushed by the extrusion pad 5. The tooling 3 is first extruded out of the extrusion die 1, and then the blank 4 is extruded out of the die.

[0043] In this embodiment, the maximum extrusion pressure of the tooling 3 is 13,000 tons, and the maximum extrusion pressure of the blank 4 is 17,000 tons. According to the extrusion deformation theory, the extrusion force is proportional to the deformation resistance of the material. The maximum extrusion pressure of a normal high-temperature alloy rod should be 20,000 tons. Therefore, the extrusion pressure of a high-temperature alloy rod extruded out of the mold is reduced by about 18% using the present invention. Specific implementation 3:

[0045] The technology of the present invention is used to extrude a high-temperature alloy seamless pipe with an outer diameter of 500 mm and an inner diameter of 200 mm. See the schematic diagram. Figure 3 .

[0046] According to the results of hot compression test, 304 stainless steel at 1100℃ and strain rate 1s -1 Under the condition, the deformation resistance is 175MPa. A high temperature alloy is subjected to deformation at 1100℃ and strain rate 1s -1 The deformation resistance under the condition is 280MPa. The deformation resistance of a certain high temperature alloy is 1.6 times that of 304 stainless steel. 304 stainless steel is selected as the tooling material.

[0047] The upper end of the blank 4 is processed with a 30° chamfer. The outer diameter of the tool 3 is the same as the outer diameter of the blank 4; the inner diameter of the tool 3 is 10mm larger than the inner diameter of the blank 4, which is Φ210mm; the total height of the tool 3 is 350mm; the chamfer of the upper conical surface is C150; the blank 4 and the tool 3 are connected by welding to form a weld 5.

[0048] After the blank 4 and the tooling 3 are assembled, they are painted with anti-oxidation paint and loaded into the heating furnace. After heating to 1100°C and insulation, the blank 4 and the tooling 3 are taken out at the same time and put into the lubrication device to spray lubricant. After the spraying is completed, the blank 4 and the tooling 3 are put into the extruder and put into the extrusion barrel 2. The core rod 7 passes through the extrusion die 1, and the extrusion pad 6 pushes the blank 4 and the tooling 3 to extrude. The tooling 3 first extrude the annular gap formed by the extrusion die 1 and the core rod 7 to form a seamless pipe, and then the blank 4 is extruded into the annular gap between the extrusion die 1 and the core rod 7 to form a seamless pipe.

[0049] In this embodiment, the maximum extrusion pressure of the tooling 3 is 21,500 tons, and the maximum extrusion pressure of the blank 3 is 24,600 tons. According to the extrusion deformation theory, the extrusion force is proportional to the deformation resistance of the material. The normal extrusion pressure of a high-temperature alloy rod should be 34,400 tons. Therefore, the extrusion pressure of a high-temperature alloy seamless pipe extruded out of the mold is reduced by about 28% using the present invention. Specific implementation 4:

[0051] Figure 4 In the figure, the outer diameter of tool 1 is the same as that of blank 2; the chamfer of the upper end of tool 1 is 60° with the horizontal line, the horizontal side length is 100mm, the total height is 250mm, and the center hole diameter is 30mm; the bottom of tool 1 is a right-angle groove with a groove depth of 20mm and a groove edge thickness of 10mm. The upper end of blank 2 is a boss structure, the boss diameter is 2mm smaller than the diameter of the groove of tool 1, and the boss height is 23mm. Tool 1 and blank 2 are assembled and positioned through the concave-convex structure.

[0052] Figure 5 In the figure, the outer diameter of tool 1 is the same as that of blank 2; the chamfer of the upper end of tool 1 is 60° with the horizontal line, the horizontal side length is 50mm, the total height is 150mm, and the center hole diameter is 20mm; the bottom of tool 1 is a right-angled boss structure, the boss height is 20mm, and the diameter is 20mm smaller than the diameter of tool 1. The upper end of blank 2 is a groove-shaped structure, the groove diameter is 20mm smaller than the diameter of blank 2, and the groove depth is 23mm. Tool 1 and blank 2 are assembled and positioned by the concave-convex structure.

[0053] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A tool to reduce the extrusion force of seamless pipes and bars, Features: It is arranged at the front end of the extrusion direction of the target billet for extruding seamless pipes and bars. The tooling is a hollow rotating body structure. The upper part of the rotating body is a chamfered structure for matching the inner cavity angle of the extrusion die. The lower part is a cylindrical structure. There is a through hole in the center of the rotating body. The tooling is placed in the extrusion barrel together with the target billet. The deformation resistance of the tooling is lower than that of the target billet.

2. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: The through hole has a diameter of 20 mm to 100 mm.

3. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: The chamfer angle is 30-60 degrees.

4. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: The horizontal length of the end chamfer is 50 to 200 mm.

5. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: When extruding seamless pipes, the diameter of the center hole of the tooling is 2-20mm larger than the target billet inner hole diameter.

6. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: The deviation between the diameter of the lower cylinder of the tooling and the target billet diameter is ±10mm, and the total height of the tooling is 60 to 400mm.

7. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: The deformation resistance of the tooling material at the same extrusion temperature is 50-85% of the target billet metal.

8. A tool for reducing the extrusion force of seamless pipes and bars according to claim 1, Features: The positional relationship between the target blank and the tooling is that they fit each other, and the connection method is welding connection at the circumferential edge interface of the two, or a concave-convex form of connection; when a concave-convex form of connection is adopted, the matching depth is 10-100mm, the concave-convex edge chamfer is 30-60° or right angle, and the groove end face diameter is 0.1-5mm larger than the boss end face diameter.

9. A method for reducing the extrusion force of seamless pipes and bars, Features: First, assemble the tooling described in claim 1 and the target billet together, and the tooling is located at the front end of the extrusion direction of the target billet, load it into a heating furnace and heat it simultaneously, and then load it into an extruder for extrusion; the extruder includes an extrusion die 1, an extrusion barrel 2, and an extrusion pad 5; put the tooling and the target billet into the extrusion barrel 2 together, the extrusion die 1 is fixed at the front end of the extrusion barrel 2, and the extrusion pad 5 enters the extrusion barrel 2 from the rear end to press the target billet; during extrusion, the tooling is first extruded out of the extrusion die, and the extruded length should be ≥500mm to ensure that the extrusion force can be effectively reduced.

10. A method for reducing the extrusion pressure of seamless pipes and bars according to claim 9, Features: If the target blank is a seamless pipe, the mandrel 7 needs to be passed through the extrusion pad 5, the target blank 4, the tooling 3 and the extrusion die 1 in sequence to achieve the forming of the seamless pipe.

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