塑料模具加工主要分四個(gè)環(huán)節(jié)，分別是鍛造工藝，預(yù)備熱處理，淬火與回火，消應(yīng)力退火。下面就我們便來介紹下每個(gè)環(huán)節(jié)的注意點(diǎn)。
Plastic mold processing is mainly divided into four links: forging process, preliminary heat treatment, quenching and tempering, stress relief annealing. Now let's introduce the points needing attention in each link.
1、鍛造工藝。這是塑料模具工作零件制造過程中的重要環(huán)節(jié)。對(duì)于高合金工具鋼的塑料模具，通常對(duì)材料碳化物分布等金相組織提出技術(shù)要求。此外，還應(yīng)嚴(yán)格控制鍛造溫度范圍，制定正確的加熱規(guī)范，采用正確的鍛造力法，以及鍛后緩冷或及時(shí)退火等。
1. Forging process. This is an important link in the manufacturing process of plastic mold working parts. For the plastic mould of high alloy tool steel, technical requirements are usually put forward for the metallographic structure such as carbide distribution. In addition, the forging temperature range shall be strictly controlled, the correct heating specification shall be formulated, the correct forging force method shall be adopted, and the slow cooling or timely annealing after forging shall be carried out.
2、預(yù)備熱處理。應(yīng)視塑料模具工作零件的材料和要求的不同分別采用退火、正火或調(diào)質(zhì)等預(yù)備熱處理工藝，以改善組織，鍛造毛坯的組織缺陷，改善加工工藝性。高碳合金模具鋼經(jīng)過適當(dāng)?shù)念A(yù)備熱處理可網(wǎng)狀二次滲碳體或鏈狀碳化物，使碳化物球化、細(xì)化，推進(jìn)碳化物分布均勻性。這樣有利于保證淬火、回火質(zhì)量，提高模具壽命。
2. Prepare for heat treatment. Depending on the materials and requirements of plastic mold working parts, preliminary heat treatment processes such as annealing, normalizing or quenching and tempering shall be adopted respectively to improve the structure, eliminate the structural defects of forging blank and improve the processability. After proper preliminary heat treatment, high carbon alloy die steel can eliminate network secondary cementite or chain carbide, spheroidize and refine carbide and promote the uniformity of carbide distribution. This will help to ensure the quality of quenching and tempering and improve the service life of the die.
3、淬火與回火。這是模具熱處理中的關(guān)鍵環(huán)節(jié)。若淬火加熱時(shí)產(chǎn)生過熱，不僅會(huì)使工件造成較大的脆性，而且在冷卻時(shí)容易引起變形和開裂，嚴(yán)重影響模具壽命。沖模淬火加熱時(shí)特別應(yīng)注意防止氧化和脫碳，應(yīng)嚴(yán)格控制熱處理工藝規(guī)范，在條件允許的情況下，可采用真空熱處理。淬火后應(yīng)及時(shí)回火，并根據(jù)技術(shù)要求采用不同的回火工藝。
3. Quenching and tempering. This is the key link in die heat treatment. If overheating occurs during quenching and heating, it will not only cause great brittleness of the workpiece, but also easily cause deformation and cracking during cooling, which will seriously affect the service life of the die. Special attention shall be paid to prevent oxidation and decarburization during quenching and heating of die. The heat treatment process specification shall be strictly controlled. If conditions permit, vacuum heat treatment can be adopted. Tempering shall be carried out in time after quenching, and different tempering processes shall be adopted according to technical requirements.
4、消應(yīng)力退火。塑料模具加工零件后應(yīng)進(jìn)行消應(yīng)力退火處理，具目的是粗加工所造成的內(nèi)應(yīng)力，以免淬火叫產(chǎn)生過大的變形和裂紋。對(duì)于精度要求高的模具，在磨削或電加工后還需經(jīng)過消應(yīng)力回火處理，有利于穩(wěn)定模具精度，提高使用壽命。
4. Stress relief annealing. Stress relief annealing treatment shall be carried out after plastic mold parts are processed, with the purpose of eliminating the internal stress caused by rough machining, so as to avoid excessive deformation and crack caused by quenching. For molds with high precision requirements, stress relief tempering treatment is also required after grinding or electrical machining, which is conducive to stabilizing the accuracy of molds and improving the service life.
