Multi-pass free forging punching forming method for deep blind hole of engine cylinder block

Abstract

The invention discloses a multi-pass free forging punching forming method for a deep blind hole of an engine cylinder block. Comprising the steps of jaw pressing, chamfering, pre-drawing, upsetting, wide anvil strong pressing square drawing, rolling drawing blanking, upsetting, step clamping blank making, blind hole pre-punching through a reducing punch for the first time, blind hole mechanical expanding through a second time, roll forging drawing, blind hole deep punching through a long punch for the third time, roll forging drawing, end face flattening and finishing, and a finished product is obtained. Through multi-pass and staged control over blind hole forming, blind hole pre-punching and mechanical blind hole expanding are achieved through a variable-diameter punch, blind hole deep punching is achieved through a long punch, the technologies of roll forging and drawing-out, end face flattening and the like are matched, the forming effect is guaranteed, staged shape control of all procedures can be achieved through multi-pass blind hole forming, parameter accurate control is facilitated, inner wall pulling shrinkage is restrained, and the quality of the product is improved. The phenomenon that the inner wall is greatly pulled and shrunk in a traditional punching mode is overcome, fiber streamline integrity and size reliability are guaranteed, the phenomenon that the bottom is extremely prone to being folded during traditional blind hole drawing-out forming is avoided, the forging efficiency is high, and the quality is more stable.

Description

Technical Field

[0001] The invention relates to the field of engine cylinder forging methods, in particular to a multi-pass free forging and punching method for deep blind holes in an engine cylinder. Background Art

[0002] As a core component of internal combustion engines, engine cylinders are facing increasing market demand and increasingly stringent technical requirements for cylinder blocks, driven by economic development and technological advancements in large-scale construction machinery, ships, and specialized power generation equipment. Due to the structural characteristics and specialized uses of cylinder blocks, the integrity of metal flow lines is crucial to the lifespan of the cylinder block while ensuring general performance.

[0003] Currently, the forging process for cylinder forgings typically uses a split forging process followed by welding after machining. For cylinder forgings with stringent performance requirements or where welding is not permitted, a process is typically employed in which a solid core or a small, shallow blind hole is forged first, and then the blind hole is machined to the part size. This process not only increases the weight of the forging but also wastes a significant amount of machining time, which does not meet the requirements for green development of castings and forgings.

[0004] With the development of forging technology, extrusion forming solutions have been gradually developed to achieve near-net-shape small-sized cylinder blind hole forgings. The blank allowance is smaller, the metal fiber streamline is more complete, and various performance indicators are excellent. However, for large-sized cylinder forgings, not only is the extrusion forming pressure high, exceeding the press load, but also the auxiliary tool manufacturing cost is increased due to the small batch size, and the disadvantages of extrusion forming are prominent. Moreover, when the cylinder blind hole is large, while meeting the punching conditions and ensuring the size, the traditional direct deep punching method of the blind hole is easy to destroy the integrity of the metal streamline due to the small inner wall aperture and large blank allowance. Summary of the invention

[0005] The purpose of the present invention is to provide a multi-pass free forging punching method for deep blind holes in an engine cylinder block, which controls the gross-to-net ratio, ensures the integrity of metal streamlines, and improves the comprehensive mechanical properties and service life.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a multi-pass free forging and punching method for forming deep blind holes in an engine cylinder block, wherein the diameter of the cylinder block is not less than 2000 mm, the diameter of the blind hole is not less than 1000 mm, and the depth of the blind hole is not less than 1500 mm, comprising the following steps: Step 1: Match the ingot shape according to the process weight of the cylinder body, and use the upper flat anvil and the lower V anvil to press the jaws, chamfer and pre-draw the blank; Step 2: upsetting the blank using the upper cover plate and the lower drain plate; Step 3: Use the WHF wide anvil strong pressing method to square the blank, and then round and lengthen it; Step 4: Flip the blank 90° axially for the first time, and upset it using the upper cover plate and the lower platform. Step 5: Flip the blank 90° axially for the second time, and perform stretching and step-block preform forging using the upper flat anvil and the lower V-shaped anvil. Step 6: Flip the blank 90° axially for the third time, and perform the first-pass pre-punching of the blind hole using a variable-diameter punch. The outer wall of the variable-diameter punch is successively a cylindrical surface section, a large-diameter conical surface section, and a small-diameter conical surface section along the axial direction. Define the cylinder diameter corresponding to the blind hole port as D, the small-end diameter of the small-diameter conical surface as d0, the large-end diameter of the small-diameter conical surface and the small-end diameter of the large-diameter conical surface as d1, the large-end diameter of the large-diameter conical surface and the diameter of the cylindrical surface as d2, the axial length of the small-diameter conical surface as H1, the axial length of the large-diameter conical surface as H2. The dimensions of the variable-diameter punch satisfy: D = (2.5 - 3)d0, d1 = (1.7 - 2)H1, d2 = (1.5 - 1.6)H2; When performing the first-pass pre-punching of the blind hole, punch with the end face of the small-diameter conical surface of the variable-diameter punch facing the cylinder, and the punching depth is the axial length H1 of the small-diameter conical surface. Step 7: After the first-pass pre-punching of the blind hole reaches the punching depth, continue with the second-pass mechanical blind hole expansion, and make the variable-diameter punch continue to punch into the cylinder until the large-diameter conical surface and part of the cylindrical surface of the variable-diameter punch both enter the inner side of the cylinder. Step 8: Flip the blank 90° axially for the fourth time, perform rolling and stretching using the upper and lower flat anvils, and then withdraw the variable-diameter punch from the blank. Step 9: According to the pre-expansion hole path of the variable-diameter punch, perform the third-pass deep punching of the blind hole using a long punch. Step 10: Flip the blank 90° axially for the fifth time, perform rolling and stretching using the upper flat anvil and the lower V-shaped anvil, and then withdraw the long punch from the blank. Step 11: Flip the blank 90° axially for the sixth time, perform end face leveling using the upper wide anvil and the lower platform, and finely machine each part, thus completing the punching forming of the deep blind hole of the cylinder.

[0007] Preferably, in Step 1, the single-side reduction amount of pre-stretching is not less than 60 mm.

[0008] Preferably, in Step 3, the reduction amount is controlled at 18% - 20%.

[0009] Preferably, the first-pass pre-punching of the blind hole and the second-pass mechanical blind hole expansion are carried out continuously, so that the variable-diameter punch moves to the punching depth of the second-pass mechanical blind hole expansion in one punching.

[0010] Preferably, in Step 10, the rolling deformation amount ≥ 10%.

[0011] According to the above technical solution, the beneficial effects of the present invention are as follows: The present invention controls the blind hole forming in multiple passes and in stages. A variable-diameter punch is used to pre-punch the blind hole and mechanically expand the blind hole, and a long punch is used to deep-punch the blind hole. In combination with processes such as rotary forging and end face flattening, the forming effect is ensured. The multi-pass blind hole forming can achieve stage-by-stage shape control of each process, which is conducive to precise parameter control.

[0012] The pre-punching of the blind hole and the mechanical expansion of the blind hole are carried out with a variable-diameter punch within a specific size range. The method of stamping the two conical surfaces successively can better meet the punching conditions and suppress the inner wall shrinkage. It overcomes the large inner wall shrinkage phenomenon of the traditional punching method, avoids the problems of large forming pressure and easy exceeding of the press clear distance in the direct deep punching scheme, can more precisely control the inner wall allowance, ensure the integrity of the fiber streamline and the dimensional reliability, and has high forging efficiency and more stable quality. The subsequent deep punching of the blind hole process can ensure the final size of the blind hole and avoid the bottom folding phenomenon that is extremely easy to occur during the traditional blind hole drawing and forming.

[0013] By adding the rotary forging and drawing process, the anisotropy caused by excessive deformation in a single direction can be controlled; the phenomenon of overall height reduction during blind hole forging can be offset to ensure the height dimension; the problem of outer circle deformation caused by blind hole forging can be suppressed to ensure the consistency of the outer circle dimension; as the forging temperature decreases, at this stage, through rotary forging and drawing and increasing the deformation amount, the grains are further refined, providing necessary conditions for subsequent heat treatment; and it is more conducive to withdrawing the punch to achieve continuous forging. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 is a schematic flow diagram of the present invention; Figure 2 is a schematic diagram of the dimensional structure of the variable-diameter punch. DETAILED DESCRIPTION OF THE INVENTION

[0015] Referring to the accompanying drawings, the detailed implementation is as follows: A multi-pass open-die punching and forming method for deep blind holes of an engine cylinder block, where the diameter of the cylinder block is not less than 2000 mm, the diameter of the blind hole is not less than 1000 mm, and the depth of the blind hole is not less than 1500 mm. Under the condition of meeting the punching conditions and ensuring the dimensions, due to the small inner wall hole diameter and large blank allowance of the traditional direct deep punching of the blind hole, it is easy to damage the integrity of the metal streamline. Therefore, a new process method is proposed, including the following steps, and the specific process is as Figure 1 shown.

[0016] Step 1: Match the ingot type according to the process weight of the cylinder block, and use the upper flat anvil and the lower V-shaped anvil to press the clamp mouth, chamfer, and pre-draw the blank. The pre-drawing single-side reduction amount is not less than 60 mm.

[0017] Step 2: Upset the blank using an upper cover plate and a lower leakage plate.

[0018] Step 3: Use the WHF wide anvil strong pressing method to perform square upsetting and then round upsetting and blanking on the blank, with the reduction in height controlled at 18% - 20%.

[0019] Step 4: Rotate the blank 90° axially for the first time, and upset it using an upper cover plate and a lower platform.

[0020] Step 5: Rotate the blank 90° axially for the second time, and perform drawing and shoulder forming blanking on the blank using an upper flat anvil and a lower V - shaped anvil.

[0021] Step 6: Rotate the blank 90° axially for the third time, and use a stepped punch to perform the first - pass pre - punching of a blind hole.

[0022] As Figure 2 shown, the outer wall of the stepped punch is successively a cylindrical surface, a large - diameter conical surface, and a small - diameter conical surface along the axial direction. Define the cylinder diameter corresponding to the blind - hole port as D, the small - end diameter of the small - diameter conical surface as d0, the large - end diameter of the small - diameter conical surface and the small - end diameter of the large - diameter conical surface as d1, the large - end diameter of the large - diameter conical surface and the diameter of the cylindrical surface as d2, the axial length of the small - diameter conical surface as H1, the axial length of the large - diameter conical surface as H2. The dimensions of the stepped punch satisfy: D = (2.5 - 3)d0, d1 = (1.7 - 2)H1, d2 = (1.5 - 1.6)H2.

[0023] When performing the first - pass pre - punching of the blind hole, use the end face of the small - diameter conical surface of the stepped punch to face the cylinder for stamping. The punching depth is the axial length H1 of the small - diameter conical surface, and the stepped punch moves into the cylinder to the boundary position between the large - diameter conical surface and the small - diameter conical surface.

[0024] Step 7: After the first - pass pre - punching of the blind hole reaches the punching depth, continue with the second - pass mechanical reaming of the blind hole, so that the stepped punch continues to stamp on the cylinder until the large - diameter conical surface and part of the cylindrical surface of the stepped punch both enter the inner side of the cylinder.

[0025] The first - pass pre - punching of the blind hole and the second - pass mechanical reaming of the blind hole can be carried out continuously, so that the stepped punch moves to the punching depth of the second - pass mechanical reaming of the blind hole in one stamping. In addition, the stepped punch can also make a short stop between the first pass and the second pass. The method of stamping the two conical surfaces successively can better meet the punching conditions and suppress the inner - wall shrinkage, overcome the large inner - wall shrinkage phenomenon of the traditional punching method, avoid the problems of large forming pressure and easy exceeding of the press clear - distance in the direct deep - drawing scheme, and can more precisely control the inner - wall allowance, ensuring the integrity of the fiber streamline and the dimensional reliability.

[0026] Step VIII: Flip the blank 90° axially for the fourth time, perform rotary forging and drawing out using upper and lower flat anvils, and then withdraw the reducing punch from the blank.

[0027] Step IX: According to the pre-expansion hole path of the reducing punch, perform the third deep drawing of the blind hole using a long punch to ensure the final size of the blind hole and avoid the bottom folding phenomenon that is prone to occur during the traditional blind hole drawing and forming.

[0028] Step X: Flip the blank 90° axially for the fifth time, perform rotary forging and drawing out using an upper flat anvil and a lower V-shaped anvil, with the rotary forging deformation amount ≥ 10%, and then withdraw the long punch from the blank.

[0029] The rotary forging and drawing out process can control the anisotropy caused by excessive deformation in a single direction, offset the phenomenon of overall height reduction during blind hole forging, ensure the height dimension, suppress the outer circle deformation problem caused by blind hole forging, and ensure the outer circle size consistency. As the forging temperature decreases, at this stage, by performing rotary forging and drawing out and increasing the deformation amount, the grains are further refined, providing necessary conditions for subsequent heat treatment.

[0030] Step XI: Flip the blank 90° axially for the sixth time, perform end face flattening using an upper wide anvil and a lower platform to repair the end face deformation problem generated during blind hole forging, ensure the end face flatness, and finely machine each part, thus completing the punching and forming of the deep blind hole of the cylinder block.

[0031] The cylinder block forgings forged by the method of this embodiment have a small ratio of rough to finished weight, good distribution of metal flow lines, and excellent various detection indexes.

Claims

1. A multi-pass open-die punching forming method for deep blind holes in an engine cylinder block, wherein the diameter of the cylinder block is not less than 2000 mm, the diameter of the blind hole is not less than 1000 mm, and the depth of the blind hole is not less than 1500 mm, characterized in that, It includes the following steps: Step 1: Match the ingot type according to the process weight of the cylinder block, and use an upper flat anvil and a lower V-shaped anvil to press the clamp mouth, chamfer, and pre-draw the billet; Step 2: Upset the billet using an upper cover plate and a lower leaky plate; Step 3: Use the WHF wide anvil strong pressing method to perform square-to-round and then roll and draw the billet for blanking; Step 4: Rotate the billet 90° axially for the first time, and use an upper cover plate and a lower platform to upset it; Step 5: Rotate the billet 90° axially for the second time, and use an upper flat anvil and a lower V-shaped anvil to draw and form a stepped blank; Step 6: Rotate the billet 90° axially for the third time, and use a variable-diameter punch to perform the first-pass pre-punching of a blind hole; The outer wall of the variable-diameter punch is successively a cylindrical surface section, a large-diameter conical surface section, and a small-diameter conical surface section along the axial direction. Define the diameter of the cylinder block corresponding to the blind hole port as D, the small-end diameter of the small-diameter conical surface as d0, the large-end diameter of the small-diameter conical surface and the small-end diameter of the large-diameter conical surface as d1, the large-end diameter of the large-diameter conical surface and the diameter of the cylindrical surface as d2, the axial length of the small-diameter conical surface as H1, the axial length of the large-diameter conical surface as H2, and the dimensions of the variable-diameter punch satisfy: D = (2.5 - 3)d0, d1 = (1.7 - 2)H1, d2 = (1.5 - 1.6)H2; During the first-pass pre-punching of the blind hole, use the end face of the small-diameter conical surface of the variable-diameter punch to face the cylinder block for stamping, and the punching depth is the axial length H1 of the small-diameter conical surface; Step 7: After the first-pass pre-punching of the blind hole reaches the punching depth, continue with the second-pass mechanical reaming of the blind hole, and let the variable-diameter punch continue to press the cylinder block until the large-diameter conical surface and part of the cylindrical surface of the variable-diameter punch both enter the inner side of the cylinder block; Step 8: Rotate the billet 90° axially for the fourth time, use upper and lower flat anvils to roll and draw, and then withdraw the variable-diameter punch from the billet; Step 9: According to the pre-expansion hole path of the variable-diameter punch, use a long punch to perform the third-pass deep punching of the blind hole; Step 10: Rotate the billet 90° axially for the fifth time, use an upper flat anvil and a lower V-shaped anvil to roll and draw, and then withdraw the long punch from the billet; Step 11: Rotate the billet 90° axially for the sixth time, use an upper wide anvil and a lower platform to level the end face and finish machining each part, that is, complete the punching forming of the deep blind hole of the cylinder block.

2. A multi-pass open-die forging punching forming method for deep blind holes of an engine cylinder block according to claim 1, characterized in that: In Step 1, the unilateral reduction amount of pre-drawing is not less than 60 mm.

3. A multi-pass open-die forging punching forming method for deep blind holes of an engine cylinder block according to claim 1, characterized in that: In Step 3, the reduction amount is controlled at 18% - 20%.

4. A multi-pass open-die forging punching forming method for deep blind holes of an engine cylinder block according to claim 1, characterized in that: The first-pass pre-punching of the blind hole and the second-pass mechanical reaming of the blind hole are carried out continuously, so that the variable-diameter punch moves to the punching depth of the second-pass mechanical reaming of the blind hole in one stamping.

5. A multi-pass open-die forging punching forming method for deep blind holes of an engine cylinder block according to claim 1, characterized in that: In Step 10, the rolling deformation amount ≥ 10%.

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