A multi-pass free forging and punching method for deep blind holes in an engine cylinder

Abstract

A multi-pass free forging punching method for deep blind holes in an engine cylinder block includes the following steps: jaw pressing, chamfering, pre-drawing, upsetting, wide anvil strong pressure drawing, rolling and drawing blanking, upsetting, step forming, pre-punching the blind hole in the first pass with a variable diameter punch, mechanically expanding the blind hole in the second pass, rolling forging and drawing, deep-drawing the blind hole in the third pass with a long punch, rolling forging and drawing, flattening the end face, and finishing the finished product. The blind hole forming process is controlled in multiple passes and stages, with the use of a variable diameter punch for pre-punching and mechanically expanding the blind hole, and a long punch for deep-drawing the blind hole. Furthermore, the forming effect is ensured by combining rolling forging and drawing and end face flattening processes. The multi-pass blind hole forming process can achieve staged shape control in each process, facilitate precise parameter control, suppress inner wall shrinkage, overcome the large inner wall shrinkage phenomenon of traditional punching methods, ensure fiber streamline integrity and dimensional reliability, and avoid the bottom folding phenomenon that is easily generated during traditional blind hole drawing. This method improves forging efficiency and provides more stable quality.

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:

[0007] 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;

[0008] Step 2: upsetting the blank using the upper cover plate and the lower drain plate;

[0009] Step 3: Use the WHF wide anvil strong pressing method to square the blank, and then round and lengthen it;

[0010] Step 4: Flip the blank 90° along the axial direction for the first time and use the upper cover plate and lower platform for upsetting;

[0011] Step 5: Flip the blank 90° along the axis for the second time, and use the upper flat anvil and the lower V anvil to stretch and clamp the blank;

[0012] Step 6: Flip the blank 90° along the axis for the third time, and use a variable diameter punch to pre-punch the blind hole for the first time;

[0013] The outer wall of the reducing punch is composed of a cylindrical surface, a large-diameter conical surface, and a small-diameter conical surface in the axial direction. The cylinder diameter corresponding to the blind hole port is defined as D, the small end diameter of the small-diameter conical surface is d0, the large end diameter of the small-diameter conical surface and the small end diameter of the large-diameter conical surface are d1, the large end diameter of the large-diameter conical surface and the diameter of the cylindrical surface are d2, the axial length of the small-diameter conical surface is H1, and the axial length of the large-diameter conical surface is H2. The size of the reducing punch satisfies:

[0014] D=(2.5~3)d0,

[0015] d1=(1.7~2)H1,

[0016] d2=(1.5~1.6)H2;

[0017] When pre-punching the blind hole in the first pass, the end face of the small-diameter conical surface of the reducing punch is pressed toward the cylinder body, and the punching depth is the axial length H1 of the small-diameter conical surface;

[0018] Step 7: After the blind hole is pre-punched to the punching depth in the first pass, the second pass of mechanical blind hole expansion is continued, so that the reducing punch continues to punch toward the cylinder body until the large diameter conical surface and part of the cylindrical surface of the reducing punch enter the inner side of the cylinder body;

[0019] Step 8: Flip the blank 90° along the axis for the fourth time, use the upper and lower flat anvils to perform roll forging and stretching, and then withdraw the reducing punch from the blank;

[0020] Step 9: According to the pre-expansion path of the variable diameter punch, use the long punch to perform the third deep punching of the blind hole;

[0021] Step 10: Flip the blank 90° along the axis for the fifth time, use the upper flat anvil and the lower V anvil to perform roll forging and stretching, and then remove the long punch from the blank;

[0022] Step 11: Flip the blank 90° along the axis for the sixth time, use the upper wide anvil and the lower platform to flatten the end surface, and fine-tune each part to complete the punching of the deep blind hole of the cylinder body.

[0023] Preferably, in step one, the pre-drawing length and single-side pressing amount are not less than 60 mm.

[0024] Preferably, in step three, the reduction amount is controlled to be 18%-20%.

[0025] Preferably, the first pre-punching of the blind hole and the second mechanical expansion of the blind hole are performed continuously, so that the variable diameter punch moves to the punching depth of the second mechanical expansion of the blind hole in one punching.

[0026] Preferably, in step ten, the rolling forging deformation is ≥10%.

[0027] According to the above technical solution, the beneficial effects of the present invention are:

[0028] The present invention adopts multi-pass and staged control of blind hole forming, adopts a variable diameter punch to pre-punch the blind hole and mechanically expand the blind hole, adopts a long punch to deep-draw the blind hole, and cooperates with processes such as rolling forging, drawing and end surface smoothing to ensure the forming effect. Multi-pass blind hole forming can realize staged shape control of each process, which is conducive to precise parameter control.

[0029] Using a variable-diameter punch within a specific size range to pre-punch and mechanically expand blind holes, and then punching two conical sections sequentially, this method better meets punching conditions and suppresses inner wall shrinkage. This overcomes the significant inner wall shrinkage associated with traditional punching methods, avoids the high forming pressures and press clearance issues associated with direct deep-drawing solutions, and enables more refined control of inner wall allowances, ensuring fiber streamline integrity and dimensional reliability, resulting in high forging efficiency and more stable quality. The subsequent deep-drawing process ensures the final size of the blind hole and avoids the bottom folding phenomenon that is common with traditional blind hole drawing.

[0030] By adding the rolling 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 size; the outer circle deformation problem caused by blind hole forging can be suppressed to ensure the consistency of the outer circle size; as the forging temperature decreases, the rolling forging and drawing is carried out at this stage to increase the deformation amount and further refine the grains, providing the necessary conditions for subsequent heat treatment; and it is more conducive to exiting the punch and realizing continuous forging. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the process of the present invention;

[0032] Figure 2 Schematic diagram of the size structure of the variable diameter punch. DETAILED DESCRIPTION

[0033] With reference to the accompanying drawings, the specific implementation is as follows:

[0034] A multi-pass free forging punching method for deep blind holes in an engine cylinder block is proposed. The diameter of the cylinder block is not less than 2000mm, the diameter of the blind hole is not less than 1000mm, and the depth of the blind hole is not less than 1500mm. While meeting the punching conditions and ensuring the size, the traditional direct deep punching method of blind holes is prone to damage the integrity of the metal flow line due to the small inner wall diameter and large blank margin. Therefore, a new process method is proposed, which includes the following steps. The specific process is as follows: Figure 1 shown.

[0035] 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. The single-side pressing amount of the pre-drawing length is not less than 60mm.

[0036] Step 2: Use the upper cover plate and the lower drain plate to upset the blank.

[0037] Step 3: Use the WHF wide anvil strong pressing method to square the blank, then round and lengthen it, and control the reduction amount to 18%-20%.

[0038] Step 4: Flip the blank 90° along the axial direction for the first time and use the upper cover plate and the lower platform for upsetting.

[0039] Step 5: Flip the blank 90° along the axis for the second time, and use the upper flat anvil and the lower V anvil to stretch and clamp the steps to make the blank.

[0040] Step 6: Flip the blank 90° along the axis for the third time, and use a variable diameter punch to pre-punch the blind hole for the first time.

[0041] like Figure 2 As shown, the outer wall of the reducing punch is composed of a cylindrical surface, a large-diameter conical surface, and a small-diameter conical surface in the axial direction. The cylinder diameter corresponding to the blind hole port is defined as D, the small end diameter of the small-diameter conical surface is d0, the large end diameter of the small-diameter conical surface and the small end diameter of the large-diameter conical surface are d1, the large end diameter of the large-diameter conical surface and the diameter of the cylindrical surface are d2, the axial length of the small-diameter conical surface is H1, and the axial length of the large-diameter conical surface is H2. The size of the reducing punch satisfies:

[0042] D=(2.5~3)d0,

[0043] d1=(1.7~2)H1,

[0044] d2=(1.5~1.6)H2.

[0045] When pre-punching the blind hole for the first time, the end face of the small-diameter conical surface of the reducing punch is pressed toward the cylinder body, the punching depth is the axial length H1 of the small-diameter conical surface, and the reducing punch moves into the cylinder body to the boundary position between the large-diameter conical surface and the small-diameter conical surface.

[0046] Step 7: After the blind hole is pre-punched to the punching depth in the first pass, the second pass of mechanical blind hole expansion is continued, so that the reducing punch continues to punch toward the cylinder body until the large diameter conical surface and part of the cylindrical surface of the reducing punch enter the inner side of the cylinder body.

[0047] The first pass of pre-punching the blind hole and the second pass of mechanically expanding the blind hole can be performed continuously, allowing the reducing punch to move to the punching depth of the second pass of mechanically expanding the blind hole in one punching pass. In addition, the reducing punch can be briefly stopped between the first and second passes. This method of punching two conical surfaces sequentially can better meet punching conditions and suppress inner wall shrinkage, overcoming the significant inner wall shrinkage of traditional punching methods. It also avoids the high forming pressure and easy excess of the press clearance problems of direct deep drawing solutions, and can more finely control the inner wall allowance, ensuring the integrity of fiber streamlines and dimensional reliability.

[0048] Step 8: Flip the blank 90° along the axis for the fourth time, use the upper and lower flat anvils to perform roll forging and stretching, and then withdraw the reducing punch from the blank.

[0049] Step 9: According to the pre-expansion path of the variable diameter punch, use a long punch to perform the third deep punching of the blind hole to ensure the final size of the blind hole and avoid the bottom folding phenomenon that is very easy to occur during the traditional blind hole drawing.

[0050] Step 10: Flip the blank 90° along the axis for the fifth time, and use the upper flat anvil and the lower V anvil to roll forge and stretch it. The rolling deformation is ≥10%, and then withdraw the long punch from the blank.

[0051] The rolling forging and stretching 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 consistency of outer circle dimension. As the forging temperature decreases, the rolling forging and stretching are carried out at this stage to increase the deformation amount and further refine the grains, providing the necessary conditions for subsequent heat treatment.

[0052] Step 11: Flip the blank 90° along the axis for the sixth time, use the upper wide anvil and the lower platform to smooth the end surface, repair the end surface deformation problem caused by the blind hole forging, ensure the flatness of the end surface, and refine each part to complete the punching of the deep blind hole of the cylinder body.

[0053] The cylinder forgings forged by the method of this embodiment have a small gross-to-net ratio, good metal streamline distribution, and excellent various testing indicators.

Claims

1. 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, characterized in that: The following steps are involved: 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° along the axial direction for the first time and use the upper cover plate and lower platform for upsetting; Step 5: Flip the blank 90° along the axis for the second time, and use the upper flat anvil and the lower V anvil to stretch and clamp the blank; Step 6: Flip the blank 90° along the axis for the third time, and use a variable diameter punch to pre-punch the blind hole for the first time; The outer wall of the reducing punch is composed of a cylindrical surface, a large-diameter conical surface, and a small-diameter conical surface in the axial direction. The cylinder diameter corresponding to the blind hole port is defined as D, the small end diameter of the small-diameter conical surface is d0, the large end diameter of the small-diameter conical surface and the small end diameter of the large-diameter conical surface are d1, the large end diameter of the large-diameter conical surface and the diameter of the cylindrical surface are d2, the axial length of the small-diameter conical surface is H1, and the axial length of the large-diameter conical surface is H2. The size of the reducing punch satisfies: D=(2.5~3)d0, d1=(1.7~2)H1, d2=(1.5~1.6)H2; When pre-punching the blind hole in the first pass, the end face of the small-diameter conical surface of the reducing punch is pressed toward the cylinder body, and the punching depth is the axial length H1 of the small-diameter conical surface; Step 7: After the blind hole is pre-punched to the punching depth in the first pass, the second pass of mechanical blind hole expansion is continued, so that the reducing punch continues to punch toward the cylinder body until the large diameter conical surface and part of the cylindrical surface of the reducing punch enter the inner side of the cylinder body; Step 8: Flip the blank 90° along the axis for the fourth time, use the upper and lower flat anvils to perform roll forging and stretching, and then withdraw the reducing punch from the blank; Step 9: Follow the pre-expansion path of the variable diameter punch and use the long punch to deep-draw the blind hole for the third time; Step 10: Flip the blank 90° along the axis for the fifth time, use the upper flat anvil and the lower V anvil to perform roll forging and stretching, and then remove the long punch from the blank; Step 11: Flip the blank 90° along the axis for the sixth time, use the upper wide anvil and the lower platform to flatten the end surface, and fine-tune each part to complete the punching of the deep blind hole of the cylinder body.

2. The multi-pass free forging and punching method for deep blind holes in an engine cylinder block according to claim 1, characterized in that: In step 1, the pre-draw length single-side pressing amount is not less than 60mm.

3. The multi-pass free forging and punching method for deep blind holes in an engine cylinder block according to claim 1, characterized in that: In step three, the reduction is controlled at 18%-20%.

4. The multi-pass free forging and punching method for deep blind holes in an engine cylinder block according to claim 1, characterized in that: The first pass of pre-punching the blind hole and the second pass of mechanically expanding the blind hole are performed continuously, so that the reducing punch moves to the punching depth of the second pass of mechanically expanding the blind hole in one punching.

5. The multi-pass free forging and punching method for deep blind holes in an engine cylinder block according to claim 1, characterized in that: In step 10, the rolling deformation is ≥10%.

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