I-shaped stress reduction and crack self-healing process

Abstract

The invention relates to the technical field of mold maintenance, in particular to an I-shaped stress reduction and crack self-healing process which comprises the following steps: digging a hole in an easy-to-crack or cracked part of a mold, inlaying an I-shaped reinforcing member, forming a relationship between a parent body and a child body, heating the I-shaped reinforcing member after inlaying, and carrying out self-healing on the I-shaped stress reduction and crack self-healing on the I-shaped reinforcing member. The son body is in interference fit with the mother body after being heated and expanded through temperature difference assembly, pre-compressive stress is generated, the tensile stress in the machining process needs to offset the pre-compressive stress firstly for the fragile part of the mold, and therefore the stress reduction effect is achieved, and the tensile stress in the machining process needs to offset the pre-compressive stress for the fractured part of the mold. The embedded I-shaped reinforcing piece can forcibly change the propagation path of potential cracks while eliminating original cracks, the crack self-healing effect is achieved, and finally, through the generated stress reduction effect and the crack self-healing effect, the crack self-healing effect is achieved, and the crack self-healing effect is achieved. And the situations that long profiles of large molds crack and are directly scrapped after cracking can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of mold maintenance, in particular to an I-shaped stress relief and crack self-healing process. Background Art

[0002] Long profiles of large molds are prone to cracking. Long profiles of large molds usually refer to structural parts or functional components with large size, slender shape and extension in the mold, such as guide pillars, guide sleeves, support beams, long strip inserts or runner structures in the mold cavity, etc. These components need to bear high loads or complex thermal cycles, and their length is much larger than the cross-sectional size, resulting in obvious anisotropy in mechanical properties. This geometric feature makes it susceptible to stress concentration, uneven thermal deformation and other factors during processing or use, becoming a weak link in the mold structure, and thus prone to cracking.

[0003] Currently in the field of mold manufacturing, if cracks occur in the long profiles of large molds, they are often directly scrapped due to the limitations of existing repair methods and repair costs, resulting in great losses. Therefore, an I-shaped stress relief and crack self-healing process is urgently needed to reduce the occurrence of cracks in the long profiles of large molds and the situation where they are directly scrapped after cracking. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present application provides an I-shaped stress relief and crack self-healing process.

[0005] The I-shaped stress relief and crack self-healing process provided by the present invention adopts the following technical solutions:

[0006] The I-shaped stress relief and crack self-healing process comprises the following steps: digging holes at crack-prone or cracked parts of a mold, and inlaying an I-shaped reinforcement piece, wherein the mold and the I-shaped reinforcement piece form a parent-child relationship, and the I-shaped reinforcement piece is heated after inlaying, and the I-shaped reinforcement piece is assembled by temperature difference so that the I-shaped reinforcement piece expands due to heat and then has an interference fit with the parent body, thereby generating pre-compression stress.

[0007] Preferably, the I-shaped reinforcement piece is made of a material having better thermal conductivity than the matrix.

[0008] Preferably, the I-shaped reinforcement piece is pre-frozen before inlaying.

[0009] Preferably, before embedding the I-shaped reinforcement member into the matrix, the matrix is ​​preheated.

[0010] Preferably, the heating temperature of the central region of the I-shaped reinforcement member is set to be higher than the heating temperature of the edge region.

[0011] Preferably, the central region of the I-shaped reinforcement is rapidly cooled, and the edge region of the I-shaped reinforcement is slowly cooled.

[0012] Preferably, the central region of the I-shaped reinforcement is cooled by high-pressure water mist spraying, and the edge region of the I-shaped reinforcement is cooled by air convection.

[0013] Preferably, sawteeth are machined on two symmetric outer sides of the I-shaped reinforcement, and the sawteeth on the outer side of the I-shaped reinforcement are triangular sawteeth.

[0014] Preferably, after the differential temperature assembly of the I-shaped reinforcement and the matrix is completed, a copper bar is embedded in the groove between adjacent sawteeth of the I-shaped reinforcement as a copper lining.

[0015] Preferably, a hammer or a vibration device is used to vibrate and knock the I-shaped reinforcement and the matrix until there is no metallic reverberation sound at the joint.

[0016] The beneficial effects of the present invention are as follows:

[0017] 1. By embedding an I-shaped reinforcement in the mold and using the principles of physical mechanics and thermal expansion and contraction, for the easily cracked parts of the mold, during the subsequent production and processing using the mold, the tensile stress during processing needs to first offset this layer of pre-compressive stress, thereby achieving the effect of stress reduction and avoiding the situation of cracking caused by stress concentration. For the already cracked parts of the mold, the embedded I-shaped reinforcement can not only eliminate the original cracks but also forcibly change the propagation path of potential cracks, achieving the effect of crack self-healing. Therefore, the I-shaped stress reduction and crack self-healing process of the present invention can reduce the cracking of long profiles of large molds and the situation of direct scrapping after cracking by producing the effects of stress reduction and crack self-healing.

[0018] 2. Based on the heating temperature of the central region of the I-shaped reinforcement being set higher than that of the edge region, and performing sub-region quenching on the basis of the above gradient heating, the hardness of the central region of the I-shaped reinforcement can be increased and the toughness of the edge region of the I-shaped reinforcement can be improved. The central hardness of the I-shaped reinforcement can ensure that it maintains sufficient strength under high-pressure environments and avoids the overall structure of the I-shaped reinforcement being easily damaged. The toughness of the edge region can better absorb the impact energy during the opening and closing of the mold and inhibit the generation of cracks, ultimately achieving better stress reduction and crack self-healing effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flowchart of the I-shaped stress reduction and crack self-healing process in an embodiment of the present application. DETAILED DESCRIPTION

[0020] The following will be combined Figure 1 The present invention is further illustrated by the following embodiments.

[0021] This embodiment discloses an I-shaped stress relief and crack self-healing process.

[0022] The I-shaped stress relief and crack self-healing process includes the following steps: digging holes in the crack-prone or cracked parts of the mold, and embedding I-shaped reinforcement pieces, so that the mold and the I-shaped reinforcement pieces form a parent-child relationship, and then heating the I-shaped reinforcement pieces after embedding, so that the I-shaped reinforcement pieces are expanded by heat through temperature difference assembly, and interference fit with the parent body, and pre-stress is generated. For the crack-prone parts of the mold, in the subsequent production and processing of the mold, the tensile stress during processing must first offset this layer of pre-stress, so as to achieve the effect of stress relief and avoid the situation where stress concentration causes cracking. For the cracked parts of the mold, the embedded I-shaped reinforcement pieces can eliminate the original cracks while forcibly changing the expansion path of the potential cracks, and achieve the effect of crack self-healing. In summary, the I-shaped stress relief and crack self-healing process of the present invention can reduce the cracking of long profiles of large molds and the direct scrapping after cracking by generating the effects of stress relief and crack self-healing.

[0023] The I-shaped reinforcement is made of a material with better thermal conductivity than the matrix. In this embodiment, the matrix is ​​made of 45# steel, and the thermal conductivity of 45# steel is about 38-54W / (m·K) at room temperature. Correspondingly, the I-shaped reinforcement is made of aluminum alloy, and the thermal conductivity of aluminum alloy is more than twice that of 45# steel, and the thermal expansion coefficient (23.6×10 -6 / ℃) is greater than 45 steel (11.5×10 -6 / ℃) and the difference is not big, so that the interference during temperature difference assembly is more controllable. In addition, the cost of aluminum alloy is low, which can further reduce the cost of preventing or remedying cracking of the mold. In other embodiments, the I-shaped reinforcement piece can also be made of materials with good thermal conductivity such as beryllium copper alloy and tungsten copper alloy. By using a material with better thermal conductivity than the parent body for the I-shaped reinforcement piece, the assembly speed between the daughter body and the parent body can be accelerated and the effect of interference assembly between the daughter body and the parent body can be improved.

[0024] The I-shaped reinforcement is pre-frozen before being embedded. In this embodiment, the I-shaped reinforcement needs to be placed in a -18°C freezer for 2 hours to shrink the I-shaped reinforcement before embedding it into the mold. After that, the temperature difference assembly is achieved by heating. The greater temperature difference improves the interference fit effect, generates greater pre-compression stress, and ultimately improves the stress reduction effect. In addition, before the pre-frozen I-shaped reinforcement is embedded in the matrix, the matrix is ​​preheated so that the I-shaped reinforcement embedded in the matrix can absorb the heat of the matrix, thereby speeding up the temperature difference assembly.

[0025] After the I-shaped reinforcement is embedded in the matrix, the edge area of the I-shaped reinforcement will absorb the heat of the preheated matrix. Therefore, when heating the I-shaped reinforcement, the heating temperature of the central area of the I-shaped reinforcement is set higher than that of the edge area to avoid overheating of the edge area of the I-shaped reinforcement. In addition, on the basis of the above gradient heating, regional cooling is carried out. Specifically, high-pressure water mist spraying cooling is carried out on the central area of the I-shaped reinforcement to achieve rapid cooling and improve hardness. Air convection cooling is used for the edge area of the I-shaped reinforcement to achieve slow cooling treatment and improve toughness. The central hardness of the I-shaped reinforcement can ensure that it maintains sufficient strength under high-pressure environment, avoiding easy damage to the overall structure of the I-shaped reinforcement. The toughness of the edge area can better absorb the impact energy during the opening and closing of the mold, inhibit the generation of cracks, and finally achieve better stress reduction and crack self-healing effects.

[0026] Sawteeth are machined on the two outer sides of the I-shaped reinforcement symmetrically, that is, sawteeth are machined on the two "one"-shaped outer sides of the I-shaped reinforcement. In this embodiment, the sawteeth on the outer side of the I-shaped reinforcement are triangular sawteeth. At the same time, an assembly gap is reserved on the hole wall when the matrix is dug. Through the above steps, when the I-shaped reinforcement is heated and in interference fit with the matrix, the sawtooth structure on the outer side of the I-shaped reinforcement, combined with its good toughness, can bite tightly on the straight hole wall of the matrix, forming a tenon-mortise-like structure to achieve the effect of preventing displacement and realizing close contact. After realizing the temperature difference assembly between the I-shaped reinforcement and the matrix, then a copper strip is embedded in the groove between adjacent sawteeth of the I-shaped reinforcement as a copper liner. Since the copper liner is relatively soft, it will be extruded and deformed when embedded, automatically filling the assembly gap between the I-shaped reinforcement and the matrix. After that, during the use of the mold, the copper liner can also use its high thermal conductivity to accelerate the temperature balance between the matrix and the sub-body, and can also absorb vibration energy to achieve stress buffering. Finally, a hammer or a vibrating device is used to vibrate and tamp the I-shaped reinforcement and the matrix to make the structure more compact. During this process, it is possible to judge whether the tamping is completed through the metal reverberation sound between the mold, the copper liner and the I-shaped reinforcement, and the tamping is carried out until there is no metal reverberation sound at the joint.

[0027] The above are all preferred embodiments of the present invention, and do not limit the protection scope of this application accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of this application should be covered within the protection scope of this application.

Claims

1. I-shaped stress relief and crack self-healing process, characterized in that: The following steps are involved: Holes are dug at crack-prone or cracked locations of the mold, and I-shaped reinforcement pieces are embedded. The mold and the I-shaped reinforcement pieces form a parent-child relationship. After embedding, the I-shaped reinforcement pieces are heated. Through temperature difference assembly, the I-shaped reinforcement pieces are expanded by heat and then have an interference fit with the parent body, thereby generating pre-compression stress.

2. The I-shaped stress relief and crack self-healing process according to claim 1, characterized in that: The I-shaped reinforcement piece is made of a material having a thermal conductivity better than that of the matrix.

3. The I-shaped stress relief and crack self-healing process according to claim 1, characterized in that: The I-shaped reinforcement piece is pre-frozen before being inlaid.

4. The I-shaped stress relief and crack self-healing process according to claim 1, characterized in that: Before embedding the I-shaped reinforcement member into the matrix, the matrix is ​​preheated.

5. The I-shaped stress relief and crack self-healing process according to claim 4, characterized in that: The heating temperature of the central area of ​​the I-shaped reinforcement member is set to be higher than the heating temperature of the edge area.

6. The I-shaped stress relief and crack self-healing process according to claim 5, characterized in that: The central area of ​​the I-shaped reinforcement member is cooled quickly, and the edge area of ​​the I-shaped reinforcement member is cooled slowly.

7. The I-shaped stress relief and crack self-healing process according to claim 6, characterized in that: The central area of ​​the I-shaped reinforcement piece is cooled by high-pressure water mist spraying, and the edge area of ​​the I-shaped reinforcement piece is cooled by air convection.

8. The I-shaped stress relief and crack self-healing process according to claim 7, characterized in that: Saw teeth are processed on two symmetrical outer sides of the I-shaped reinforcement member, and the saw teeth on the outer sides of the I-shaped reinforcement member are triangular saw teeth.

9. The I-shaped stress relief and crack self-healing process according to claim 8, characterized in that: After the temperature difference assembly of the I-shaped reinforcement member and the mother body is completed, a copper strip is then embedded in the groove between the adjacent saw teeth of the I-shaped reinforcement member to serve as a copper lining.

10. The I-shaped stress relief and crack self-healing process according to claim 9, characterized in that: The I-shaped reinforcement piece and the matrix are vibrated and hammered together by a hand hammer or a vibration device until there is no metal echo sound at the joint.

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