CN-121267550-B - Method for repairing cracks of large mold

CN121267550BCN 121267550 BCN121267550 BCN 121267550BCN-121267550-B

Abstract

The invention discloses a crack repairing method of a large die, which belongs to the technical field of die repairing and comprises the following steps of S1, stress field evaluation and repairing, S2, cooperative energy field stress regulation pretreatment, S3, low-stress damage cutting, namely, removing tortoise cracks in a mechanical processing mode in a region treated in the step S2 and processing the tortoise cracks to form a geometric groove with a mechanical interlocking effect, S4, gradient welding repairing, S5, zonal intelligent aging post-treatment, S6, self-adaptive processing and performance recovery, and a full-flow stress management system of stress field evaluation-composite energy field pretreatment-zonal intelligent aging, wherein the full-flow stress management system is specially used for solving the problems of complex structure and uneven stress distribution of the large die and realizing effective release of deep residual stress and solving the problem of secondary cracks caused by superposition thermal stress in the traditional repairing method.

Inventors

HE CHILING
CHEN YUEJUN
LIN HUANRAN
ZENG JIANAN
HUANG JIANFENG
TAN ZHAOMING
HE YUEHUA
Zhang Shangxing

Assignees

广州市型腔模具制造有限公司

Dates

Publication Date: 20260512
Application Date: 20251009

Claims (7)

1. S1, evaluating and repairing stress fields, namely acquiring a three-dimensional pattern of a tortoise crack of a mold and a residual stress distribution cloud picture in a repairing area by adopting three-dimensional scanning and nondestructive stress detection; S2, performing cooperative energy field stress regulation pretreatment, namely applying local deep cooling and pulse current composite energy field treatment to a repair area based on the residual stress distribution cloud image, wherein the specific process of the local deep cooling and pulse current composite energy field treatment is that the whole mold is preheated to 80-120 ℃, the preheated repair area and a high-stress area are subjected to local deep cooling by using liquid nitrogen, and then high-frequency pulse current is applied, so that the deep cooling area is quickly and uniformly heated to 300-400 ℃ under the Joule heating effect, and the temperature is kept; S3, cutting off the low-stress damage, namely removing the tortoise cracks in the area treated in the step S2 in a machining mode, and machining to form a geometric groove with a mechanical interlocking effect; S4, gradient welding repair, namely sequentially cladding at least three layers of functional materials which are in gradient transition with a matrix material in the groove by adopting a low heat input welding process, wherein each cladding layer is assisted by high-energy sound beam impact treatment; S5, carrying out regional intelligent aging post-treatment, namely carrying out regional temperature control aging heat treatment on the repair area based on the stress distribution cloud picture obtained in the step S1, wherein the regional temperature control aging heat treatment is combined with the local part and the whole part of the repair area so as to synchronously optimize the comprehensive performance of the repair body and the matrix; and S6, carrying out self-adaptive machining and performance recovery, namely carrying out finish machining on the repair area to a preset size according to the three-dimensional data obtained in the step S1 on a numerical control machine tool, and carrying out surface strengthening treatment on the profile.
2. The method for repairing cracks of a large mold according to claim 1, wherein the geometric groove in the step S3 has a circular arc transition at the bottom and a periodically varying wave-shaped side wall.
3. The method for repairing cracks of a large mold according to claim 2, wherein the at least three layers of functional materials which are in gradient transition with the matrix material in the step S4 comprise a transition layer, wherein the chemical components of the transition layer are similar to those of the matrix material of the mold so as to ensure good metallurgical bonding with the matrix, an intermediate layer, the strength of which is higher than that of the transition layer and the toughness of which is superior to that of a working surface layer, is used for buffering stress and inhibiting crack propagation, and the working surface layer, the high-temperature strength, the red hardness and the thermal fatigue resistance of which are superior to those of the matrix material so as to recover and improve the service performance of the surface of the mold.
4. The method for repairing cracks of a large mold according to claim 1, wherein the low heat input welding process in the step S4 is a cold metal transition technology or an ultra-high frequency pulse arc welding, and the high energy sound beam impact treatment is ultrasonic impact or laser impact.
5. The method for repairing cracks of a large mold according to claim 1, wherein the nondestructive stress testing method in step S1 is an X-ray diffraction method or an ultrasonic method.
6. The method for repairing cracks of a large mold according to claim 1, wherein the surface strengthening treatment in the step S6 is an ultrasonic nanocrystalline surface modification treatment or physical vapor deposition to prepare a wear-resistant coating.
7. The method for repairing cracks of a large mold according to claim 1, wherein in the step S4, when each layer of functional material is clad, a thermal infrared imager is synchronously used to monitor the temperature field distribution of the molten pool and the heat affected zone, and real-time temperature data is fed back to a welding power supply control system, so as to realize dynamic closed-loop control of welding heat input.

Description

Method for repairing cracks of large mold Technical Field The invention belongs to the technical field of mold repair, and particularly relates to a crack repair method for a large mold. Background The crazing lines of large die casting molds exhibit significant macroscopic, structural and high stress backgrounds, essentially different from shallow surface thermal fatigue cracks of small or conventional molds. The method is characterized in that cracks are in a deep and widely expanded network shape, are not only surface damage, but also are the result of releasing huge residual stress in a die, and are often accompanied by imperceptible structural deformation, so that the problem of surface quality is evolved into a 'body' which threatens the integrity of the whole structure. In addition, the large die casting is complex in structure, the insert molded surface is fully covered with deep bones, thin ribs and complex curved surfaces, so that cracks are distributed in the area with extremely poor processing accessibility, and the repair difficulty is further increased. In the face of such drawbacks, there are significant limitations to the primary repair strategies currently in the industry. Firstly, a large-scale cutting replacement method is adopted, namely the whole cracking area is cut off, and a small insert is manufactured again to be matched with the small insert. The method introduces a new stress concentration point due to secondary processing, and is difficult to ensure the matching precision of the large insert and the small insert on the complex molded surface, and flash or erosion is easy to generate in use. Secondly, the laser cladding technology is adopted, although local repair can be realized, the chemical components of the repair powder by the extremely high-grade matrix material are weak in performance of a bonding interface, the bonding interface is easy to cause cracking again in subsequent use, secondly, new thermal stress is superimposed on the original high-stress background by high heat input in the laser cladding process, secondary cracking is easy to induce or workpiece deformation is easy to occur, in addition, the process steps are complex, the parameter system is complex, the operator experience is seriously depended, and quality consistency is difficult to ensure on complex molded surfaces. Accordingly, there is a need for a crack repair method that can efficiently and reliably handle deep stress cracks. Disclosure of Invention In order to solve the problems in the prior art, the invention provides a method for repairing cracks of a large die, which solves the problems of internal stress and surface cracks of the large die casting die. The aim of the invention can be achieved by the following technical scheme: S1, evaluating and repairing stress fields, namely adopting three-dimensional scanning and nondestructive stress detection to obtain a three-dimensional pattern of the tortoise cracks and a residual stress distribution cloud picture in a repairing area of the mold; S2, preprocessing the stress regulation of the cooperative energy field, namely applying local deep cooling and pulse current composite energy field processing to a repair area based on the residual stress distribution cloud picture; S3, cutting off the low-stress damage, namely removing the tortoise cracks in the area treated in the step S2 in a machining mode, and machining to form a geometric groove with a mechanical interlocking effect; S4, gradient welding repair, namely sequentially cladding at least three layers of functional materials which are in gradient transition with a matrix material in the groove by adopting a low heat input welding process, wherein each cladding layer is assisted by high-energy sound beam impact treatment; S5, carrying out regional intelligent aging post-treatment, namely carrying out regional temperature control aging heat treatment on the local and whole combination of the repair area based on the stress distribution cloud image obtained in the step S1 so as to synchronously optimize the comprehensive performance of the repair body and the matrix; and S6, carrying out self-adaptive machining and performance recovery, namely carrying out finish machining on the repair area to a preset size according to the three-dimensional data obtained in the step S1 on a numerical control machine tool, and carrying out surface strengthening treatment on the profile. Preferably, the specific process of the local cryogenic and pulse current combined energy field treatment in the step S2 is to preheat the whole mould to 80-120 ℃, locally cryogenic the preheated repair area and the high stress area by using liquid nitrogen, and then applying high-frequency pulse current to quickly and uniformly heat the cryogenic area to 300-400 ℃ under the Joule heating effect and preserving heat. Preferably, in step S3, the bottom of the composite geometric groove is in a circular arc transition, and the side w