热处理都要加热至Ac3、Acm线以上thermal treatment should heat the iron higher than Ac3、Acm全变为奥氏体all turn into austenite 过热度越大，晶粒越小 higher the superheat， the smaller grain is
冷却cooling
等温转变isothermal transformation curve
550度孕育期最短Transition time
P、S、TT 晶体小，力学性能好P晶体大，硬
马氏体：0.25为低碳马氏体，板条状马氏体 lath martensite 高强度、高硬度、塑性好 1.0为高碳马氏体，针状马氏体， acicular martensite 塑性不好
亚共析：M线上移
连续转变continuous cooling transformation(CCT) curve
又下偏移
通常用等温转变代替
钢的热处理工艺Heat treatment process
退火annealing
完全退火full annealing
亚共析钢hypoeutectoid steel热加工后降低硬度，加热至Ac3上30～50，缓慢冷却after hot working reducing hardness，slowly cooling
等温退火constant temperature annealing
快速冷却至A1下珠光体温度，等温至转换完全，快速降温，提高速度quickly cooling to temperature of pearlite，until transformation finished，then cooling to room temperature
球化退火spheroidizing annealing
过共析钢hypereutectoid steel得到球状渗碳体，降低硬度，提高塑性，改善切削性能，Acm上20～30get spherical cementite，reduce hardness，improve machinability
再结晶退火recrystallization annealing
去除加工硬化，加热至0.4Tmeliminate work hardness
去应力退火stress relief annealing
去除内应力，加热至0.3Tmeliminate inner force
正火normalizing
空冷 cooling in the air获得索氏体，中碳钢作为最终热处理，提高力学性能get Sorbite ，finial thermal process for medium carbon steel，improve mechanical property打碎网状渗碳体break secondary network cementite
淬火quenching／hardening
加热到Ac3、Ac1以上，以一定速度冷却，获得B或M，以提高硬度、耐磨性cooling with certain speed to require B、martensite，improve hardness、abrasion performance
单液淬火single stage quenching
碳钢用水，合金用油carbon steel use wateralloy use oil内应力大 inner stress is big
双液淬火double stage quenching
为了减少内应力to reduce inner stress
分级淬火 interrupted quenching
在贝氏体温度停留，待温度均匀后继续降温，减少内应力when temperature is uniform then continue cooling to reduce inner stress
等温淬火constant temperature quenching
产生贝氏体
回火tempering
淬火后，马氏体存在较大应力、不稳定，脆性大，回火提高塑性，降低内应力，获得回火马氏体、回火屈氏体、回火索氏体after quenching，martensite have large inner stress and it's unstable，fragility is bigtempering improve plasticity、reduce inner stress，get tempered martensite、troostite、sorbite
车刀、量具 淬火+低温回火turing tool、measure tool／quenching +low temperature tempering弹簧 淬火+中温回火spring／quenching + middle temperature tempering轴、齿轮 淬火+高温回火shaft gear／quenching and high temperature tempering
表面淬火+低温回火surface quenching
为了提高表面硬度、强度、耐磨性to improve surface‘s strength and hardness、abrasion performance
感应加热eddy-current heating
频率越低，深度越大，高频为200KHz，0.5～2mm
火焰加热flame heating
表面化学热处理Surface chemical heat treatment
渗氮nitridation
热处理影响因素thermal treatment‘s factor
脆硬性hardenability
淬透性quenching degree
