工艺设计

佳木斯大学热处理工艺设计说明书热处理工艺设计说明书设计题目拉刀的热处理工艺学院材料科学与工程年级2006级专业金属材料工程学生姓名惠亚军学号0607024216指导教师刘延国佳木斯大学热处理工艺设计说明书-1-目录1设计任务·······················································································11.1设计任务·················································································11.2设计的技术要求········································································12热处理件零件图·············································································23设计方案·······················································································33.1引言·······················································································33.2失效分析与变形的校直·······························································33.2.1拉刀的失效形式······································································33.2.2断裂的原因与预防································································33.2.3变形的原因与预防································································43.2.4拉刀变形的较直···································································54设计说明·······················································································74.1高速钢材料的选择·····································································74.1.1高速钢分类·········································································74.1.2具体材料的选择····································································74.2热处理工艺方法········································································74.2.1拉刀的热处理工艺路线··························································74.2.2准备工作············································································74.2.3退火··················································································84.2.4淬火与热较直······································································94.2.5回火··················································································94.2.6尾部淬火与清洗检查··························································104.2.7热处理工艺曲线图·····························································114.3热处理工艺过程中可能出现的问题和解决方法································114.3.1退火的缺陷和解决方法·························································114.3.2回火缺陷及解决办法····························································125质量检验······················································································135.1外观检查：·············································································135.2硬度检查：·············································································135.3变形检验：·············································································135.4显微组织检查：·······································································136热处理工艺卡片············································································15佳木斯大学热处理工艺设计说明书-2-参考文献····················································································16佳木斯大学热处理工艺设计说明书11设计任务1.1设计任务设计一个拉刀的热处理工艺。。拉刀在切削过程中要受到弯曲、剪切、冲击、扭转、振动、摩擦等力的作用，产生热量，所以要求拉刀具有较高的硬度、高耐磨性、一定的韧性和塑性，有的还要求热硬性。因此必须从拉刀的使用情况和失效形式合理的选择材料，制定热处理工艺，改善钢的组织，提高钢的性能要求，延长拉刀使用寿命。拉刀选材时要对材料的工艺性能加以注意。一般来说，碳钢的锻造、切削加工等工艺性能较好，其机械性能可以满足一般工作条件的要求。但强度不够高，淬透性较差。而合金钢淬透性好、强度高，但锻造、切削加工性能较差。我们可以通过改变工艺规程、热处理方法等途经来改善材料的工艺性能。1.2设计的技术要求拉刀在高速高温下工作，要承受较大的压力，摩擦和冲击。因此应具备以下性能：1较高的硬度。拉刀材料的硬度必须高于工件材料的硬度，常温硬度一般在62HRC以上。2足够的强度和韧度以承受切削力，摩擦和冲击，它反映了刀具材料抗脆性断裂和崩刃的能力。3较好的耐磨性和耐热性，以抵抗切削过程中的摩损，维持一定的切削时间，在高温下仍能保持较高的硬度。4导热性好，以便切削时产生的热能容易传导出去，从而降低切削部分的温度，减轻刀具磨损。5工艺性好，以便于制造，要求刀具有较好的可加工性，包括锻压，切削加工，热处理，可磨性等。6经济性好是评价刀具材料的重要指标之一，也是正确选用刀具材料，降低产品成本的主要依据。佳木斯大学热处理工艺设计说明书22热处理件零件图佳木斯大学热处理工艺设计说明书33设计方案3.1引言拉刀是一种比较精密而复杂的刀具，广泛应用与汽车、机械等行业，在高速高温下工作，要承受较大的压力，摩擦和冲击。拉刀应满足的性能要求有：一定的强度和塑性；较好的韧性、高的硬度和耐磨性；较好的尺寸稳定性，以保证零件较高的尺寸精度；较好的热稳定性，对高速钢来说应具有好的红硬性；有良好的热疲劳性能；较高的淬透性和磨削性，同时拉刀应具有较低的变形开裂倾向，较低的脱碳敏感性和较好的切削加工性。3.2失效分析与变形的校直3.2.1拉刀的失效形式拉刀的失效形式主要有崩刃、断裂、变形。3.2.2断裂的原因与预防断裂原因(1)材料硬度过高或过低工件的硬度在180～210HB时，拉削性能极佳，拉削后表面质量也十分好。当工件硬度低于170HB或高于240HB时，应对工件进行调质处理，以改善其切削性能。硬度过低，拉削时常出现堆屑而导致拉刀断裂。硬度过高，拉削时切削力将增大，拉刀长期超负荷工作会导致疲劳断裂。(2)材质不均匀如果工件的材质不均匀，热处理后的硬度也不一致，拉削时横向负荷不平衡，拉刀会偏向软的一侧而造成断裂。(3)刃磨质量差刃磨拉刀时，应严格保持刀齿固有的特点，否则会影响拉刀的使用。特别要保证拉刀原来容屑槽的深度和形状，否则，刀齿易崩断，甚至断裂。(4)工件的尺寸和形位精度不够拉削前，工件的孔应有一定的几何精度。如果孔和端面不垂直，拉刀会因受力不均而断裂。如工件预制孔过小，拉刀前导佳木斯大学热处理工艺设计说明书4部分被强行送入拉削时，易使拉刀被挤住而断裂。工件厚度大于拉刀允许的拉削长度，造成切屑堵塞，引起拉削刀急增，导致刀齿损坏或断裂。(5)清洁程度拉削后，拉刀上的切屑应清除干净。(6)机床保证机床足够的刚性和功率，工件定位应准确。(7)修磨因素修磨后的拉刀，个别刀齿的齿升量过大，不仅产生很大的切削力，并且易使切屑堵塞在容屑槽内，造成崩刃。(8)其它原因冷却润滑剂不足；托刀架与工件孔不同心；拉刀刀齿刃部宽度小于齿后部宽度，形成楔形等。断裂的预防措施热处理裂纹的产生是导致拉刀断裂的本质原因。因此预防断裂就是在热处理过程中防止产生裂纹。可采取如下措施：(1)对存在碳化物特别严重和其他冶金缺陷的原材料，不能投入生产。(2)采用合理安全的淬火工艺。(3)拉刀淬火加热前要先测炉温，保证炉温的准确性。并要做认真脱氧捞渣，以防引起脱碳和防止由于炉底炉渣温度较高而引起拉刀后顶尖孔处的局部过热。(4)分级槽和等温槽在拉刀冷却前，要先进行搅拌，使槽内温度上下均匀。3.2.3变形的原因与预防变形原因(1)原材料的显微组织严重的碳化物偏析；轧材纵向与横向组织与性能存在较大的差异；轧材纤维方向分布的碳化物不均匀等会导致拉刀的变形。(2)机械加工的影响机械加工前必须校直弯曲的轧材，如校直不当会产生应力集中，则会造成很大的弯曲变形；毛坯热处理前的切削加工也会形成切削应力和加工硬化，可将拉刀顶弯。(3)拉刀的几何形状形状不对称的拉刀，在淬火加热与冷却中各部位产生的热应力与组织应力不同，再者，因形状不同，在机械加工中产生的机械加工残余应力也不对称。以及拉刀本身细长形状都影响热处理时的弯曲变形。(4)热处理工艺的影响淬火温度过高、加热时间过长、预热不充分、冷却佳木斯大学热处理工艺设计说明书5速度过快、加热与冷却不均、冷却介质选择不当等，都能增加拉刀的弯曲变形。变形的预防措施采用如下措施，可减少拉刀热处理时产生的变形。1.选材由于拉刀毛坯一般不能进行锻造，目前可按下表(表2)所示碳化物不均匀度与拉刀的外径相应规定选材。表2.碳化物