Umur cetakan
- 2024-10-29
Umur cetakan mengacu pada jumlah bagian yang dapat dibentuk dengan tetap memastikan kualitas bagian tersebut. Ini mencakup penajaman berulang-ulang dan penggantian bagian-bagian yang rentan hingga bagian utama cetakan diganti, sehingga terbentuk total bagian-bagian yang memenuhi syarat.
5 Pemeliharaan dan pemeliharaan
Kegagalan cetakan dibagi menjadi kegagalan abnormal dan kegagalan normal. Kegagalan abnormal (kegagalan awal) mengacu pada ketidakmampuan suatu cetakan untuk digunakan sebelum mencapai umur yang ditentukan pada tingkat industri tertentu. Bentuk awal kegagalan meliputi deformasi plastis, patah, dan keausan lokal yang parah. Kegagalan normal mengacu pada ketidakmampuan cetakan untuk melanjutkan layanan karena deformasi plastis yang lambat, keausan yang seragam, atau patah lelah setelah produksi dan penggunaan skala besar.
Jumlah produk berkualitas yang dihasilkan sebelum kegagalan normal cetakan disebut umur normal cetakan, disingkat umur cetakan. Jumlah produk berkualitas yang dihasilkan sebelum perbaikan cetakan pertama disebut umur pertama; Jumlah produk berkualitas yang dihasilkan dari satu perbaikan cetakan ke perbaikan berikutnya disebut umur perbaikan cetakan. Umur cetakan adalah jumlah umur awal dan umur setiap perbaikan berikutnya.
Umur suatu cetakan berkaitan dengan bentuk dan strukturnya, dan mengacu pada sifat material, desain, dan tingkat pembuatan cetakan selama jangka waktu tertentu. Refleksi komprehensif dari tingkat perlakuan panas, penggunaan, dan pemeliharaan cetakan. Umur cetakan sampai batas tertentu mencerminkan tingkat industri manufaktur metalurgi dan mekanik di suatu wilayah atau negara.
Ada banyak jenis cetakan dengan perbedaan yang signifikan dalam kondisi kerja dan bagian yang rusak, namun mode kegagalan secara kasar dapat diringkas menjadi tiga jenis: keausan, patah, dan deformasi plastis.
(1) Kegagalan keausan
Saat cetakan digunakan, cetakan bersentuhan dengan billet yang terbentuk dan menghasilkan gerakan relatif. Fenomena hilangnya material secara bertahap dari permukaan kontak akibat gerakan relatif permukaan disebut keausan.
(2) Kegagalan fraktur
Ketika cetakan mengalami retakan besar atau terpisah menjadi dua atau beberapa bagian dan kehilangan kemampuan servisnya, maka cetakan tersebut mengalami kegagalan patah. Patahan dapat dibedakan menjadi patahan plastis dan patah getas. Bahan cetakan sebagian besar adalah baja berkekuatan sedang hingga tinggi, dan bentuk patahannya sebagian besar adalah patah getas. Patah getas dapat dibagi menjadi patah satu kali dan patah lelah.
(3) Kegagalan deformasi plastis
Cetakan plastik mengalami tekanan yang signifikan dan tidak merata selama servis. Ketika tegangan pada bagian tertentu cetakan melebihi batas luluh bahan cetakan pada suhu tersebut, maka akan terjadi deformasi plastis melalui slip kisi, kembaran, slip batas butir, dll., Mengubah bentuk atau ukuran geometris, dan tidak dapat diperbaiki. sebelum servis, yang disebut kegagalan deformasi plastis. Mode kegagalan deformasi plastis meliputi gangguan, pembengkokan, perluasan rongga, keruntuhan, dan lain-lain.
Deformasi plastis suatu cetakan merupakan proses luluhnya bahan logam yang digunakan dalam cetakan. Terjadinya deformasi plastis terutama ditentukan oleh beban mekanis dan kekuatan suhu ruangan cetakan. Terjadinya deformasi plastis pada cetakan yang disajikan pada suhu tinggi terutama bergantung pada suhu kerja cetakan dan kekuatan suhu tinggi dari bahan cetakan.
(1) Pengaruh struktur cetakan
Struktur cetakan mempunyai pengaruh yang signifikan terhadap keadaan tegangan cetakan. Struktur cetakan yang masuk akal dapat memastikan bahwa cetakan mendapat tekanan yang seragam selama pengoperasian, tidak terlalu rentan terhadap pembebanan eksentrik, dan lebih sedikit konsentrasi tegangan. Ada banyak jenis cetakan, dengan perbedaan yang signifikan dalam bentuk dan lingkungan kerja,
(2) Pengaruh kondisi kerja cetakan
1) Material and temperature of formed parts
① The materials used for forming parts include metal and non-metal. Generally speaking, non-metallic materials have low strength, require less forming force, have less stress on the mold, and have a longer mold life. Therefore, the lifespan of metal forming molds is lower than that of non-metal forming molds.
② When forming high-temperature workpieces, the mold heats up due to the heat it receives. As the temperature increases, the strength of the mold decreases, making it prone to plastic deformation. At the same time, there is a significant temperature difference between the surface of the mold in contact with the workpiece and the non-contact surface, which causes temperature stress in the mold.
2) Equipment characteristics
① The precision and stiffness of the equipment are provided by the force of the mold forming the workpiece. During the forming process, the equipment will undergo elastic deformation due to the force applied.
② The force exerted by the speed equipment on the mold and workpiece gradually increases over a period of time, and the equipment speed affects the force application process. The higher the equipment speed, the greater the impact force on the mold per unit time (high impact); The shorter the time, the less time it takes for the impact energy to be transmitted and released, making it easier to concentrate locally, resulting in local stresses exceeding the yield stress or fracture strength of the mold material. Therefore, the higher the equipment speed, the more prone the mold is to fracture or plastic deformation failure.
3) Lubrication
Lubricating the relative motion surface between the mold and the billet can reduce direct contact between the mold and billet, decrease wear, and reduce forming force. At the same time, lubricants can also hinder heat transfer from the billet to the mold to a certain extent, reduce mold temperature, and be beneficial for improving mold life.
(3) The influence of mold material properties
The performance of mold materials has a significant impact on the lifespan of molds, including strength, impact toughness, wear resistance, corrosion resistance, hardness, thermal stability, and heat fatigue resistance.
(4) The impact of mold manufacturing process
1) During module forging, the temperature difference between the inside and outside caused by module heating and cooling will generate thermal stress; Improper selection of technical parameters during processes such as upsetting, punching, and expanding holes can easily lead to cracking of the forging blank. In addition, when the forging ratio exceeds a certain value, the transverse mechanical properties sharply decrease due to the formation of fibrous tissue, leading to anisotropy.
2) In the electrical machining of molds, varying degrees of deterioration layers may occur. In addition, due to local sudden heating and cooling, residual stress and cracking are easily formed.
3) Heat treatment of molds
Mold heat treatment is arranged after module forging and rough machining, and is almost the final process of mold processing. The selection of mold materials and the determination of heat treatment processes have a significant impact on the performance of molds.
(1) Purpose: To maintain optimal performance and prolong the service life of the equipment, ensuring normal production.
(2) Scope of application: Suitable for the repair and maintenance of molds.
(3) Regular inspection and maintenance: Regular maintenance and inspection should be carried out by mold repair and upper and lower mold personnel.
(4) The electrolytic ultrasonic cleaning method has better cleaning effect on the processed molds. While cleaning, it also plays a role in rust prevention
1. Daily routine inspection and maintenance:
Is the mold in operation in normal condition
a. Is there low-voltage locking protection; b. Whether the active parts such as guide posts, top rods, and rows are worn and lubricated properly. It is required to refuel at least once every 12 hours, and for special structures, the refueling frequency should be increased. c. Are the screws and locking clips of the fixed template of the mold loose;
1.2 Normal production conditions: Check whether the defects of the product are related to the mold;
1.3 When dismounting, a comprehensive inspection of the mold should be conducted and rust prevention treatment should be carried out: wipe dry the moisture in the mold cavity, core, ejection mechanism, and row position, and spray mold rust inhibitor or apply butter.
1.4 The mold after being removed from the machine should be placed in the designated location and recorded:
a. Mold condition: intact or in need of repair. b. The anti rust treatment method during mold making.
2. Quarterly routine inspections:
Mainly for cleaning and maintaining molds that have not been used for more than two months.
2.1 Open the mold and check the internal rust prevention effect. If there are any abnormal situations, rust prevention treatment must be carried out again. Molds that are not used for a long time should be coated with butter.
2.2 Return to its original position and make records.
Mold is the basic process equipment for mechanical industry production and an indispensable tool in the production of industrial products. The performance of molds made of mold steel requires strict production process supervision, and the raw materials for mold production must also be strictly controlled to prevent early failure, heat treatment cracking, and other defects caused by material problems.
The control of raw materials for molds is carried out from the following aspects:
1. Macro inspection
The chemical composition is decisive in ensuring the performance of steel, but qualified composition cannot fully explain the performance of steel. Due to the unevenness of the internal structure and composition of steel, macroscopic inspection largely supplements this deficiency. Macroscopic testing can observe the crystallization of steel, the failure of steel continuity, and the non-uniformity of certain components. Eight common macroscopic defects: segregation, porosity, inclusions, shrinkage, bubbles, white spots, cracks, and folds.
2. Evaluation of annealed tissue
The purpose of annealing is to reduce the hardness of steel, facilitate machining, and also prepare the structure for subsequent heat treatment.
3. Non-uniformity of carbides
Cr12 type martensitic steel contains a large amount of eutectic carbides in its microstructure, and the unevenness of carbides has a very important impact on its performance. Therefore, strict control must be exercised over the distribution of carbides.
In summary, due to the complexity of the production objects in mold factories and workshops, and the fact that they are mostly single pieces or small batches, it brings certain difficulties to the formulation and management of mold production quotas. In addition, the production methods, equipment, and technical qualities of each factory and workshop are not the same. Therefore, when formulating quotas, it is necessary to find appropriate methods to develop advanced and reasonable working hour quotas based on the actual situation of the factory and workshop, in order to improve labor productivity.
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