【作者】 梁翠；

【导师】 徐金富； 徐胜华；

【作者基本信息】 华东理工大学 ， 材料工程， 2012， 硕士

【摘要】 铁基阀板的主要作用是将制冷压缩机上的气缸和输送管道相互隔离,保证活塞在气缸中做往复运动时不发生气体泄漏。为了保证气缸的密封性,铁基阀板必须具有较高的表面精度。采用粉末冶金法制备的铁基阀板在烧结过程中变形较大,经过整形工序后的平面度≤0.08mm,达不到平面度≤0.05mm的技术要求,还需要经过后续的磨削加工,这就延长了生产周期,增加了生产成本。为了优化铁基阀板的生产工艺,取消磨削工序,缩短生产周期,降低生产成本,本文主要分析了铁基阀板几何尺寸和平面度在各个生产工序中的变形情况,研究了混粉时间、装炉方式以及烧结方式对铁基阀板烧结变形的影响。结果表明：1.在实际生产过程中制备的铁基阀板生产工艺为：粉末原料混粉60min,经1120℃×15min烧结后,组织为白色的铁素体基体上弥散分布着黑色的珠光体,晶界上分布着少量的渗碳体,晶粒均匀细小,孔隙率较低；硬度为51.92HRB,密度为6.81g/cm3；经过预成型、烧结、整形工序后铁基阀板的长度和宽度逐渐增大,厚度不断减小；经过整形后铁基阀板的长度、宽度、厚度并分别达到50.06mm、42.03mm、3.55mm,符合铁基阀板几何尺寸要求；从预成型到烧结过程中,铁基阀板的平面度从0.10mm增大到0.16mm,通过整形可以使平面度降低到0.08mm。2.随着混粉时间的延长,铁基阀板平面度呈先减小后增加的趋势,当原料粉末混粉时间为90min时,烧结后的铁基阀板平面度达到最小值0.14mm,通过整形可以使平面度降低到0.06mm,硬度为53.3HRB,密度为6.82g/cm3、致密度为84.03%。3.采用单排装炉,按阀板凹槽相对并彼此错开顺序摆放,放在炉子中间装炉的装炉方式,烧结后铁基阀板平面度最小,其值为0.14mm,整形可以使平面度降低到0.06mm。4.随着烧结压力的增加,铁基阀板平面度呈先减小后增加的趋势,当烧结压力为0.36MPa,即定力矩扳手的力矩为30Nm时,烧结后铁基阀板平面度去最小值0.24mm,经过整形可以使平面度降低到0.06mm,硬度为54.8HRB,密度为6.82g/cm3,致密度为87.55%。5.采用真空管式高温炉在实验室中制备的铁基阀板生产工艺为：粉末原料混粉90min,采用单排装炉,按阀板凹槽相对并彼此错开顺序摆放,放在炉子中间装炉的装炉方式,经1150℃×15min烧结后,铁基阀板平面度为0.17mm,经过整形可以使平面度降低到0.06mm,硬度为57.6HRB,密度为6.83g/cm3,致密度84.17%。更多还原

【Abstract】 The main function of a iron-based valve plate is to separate cylinder and transmission pipeline of the refrigeration compressor, making sure that the gas doesn’t leak out when the piston moving reciprocatingly in the cylinder. To ensure the sealing of cylinder, a high level of surface accuracy is required for the plate. Considering that they deforming so much that their flatness being only lower than 0.08 mm, the plates prepared by powder metallurgy need a subsequent grinding process to satisfy the technical requirement that the flatness must be lower than 0.05mm. This thesis focuses on investigating the deformation of size and flatness of the plates during different production process, in order to optimize production process, to cancel grinding, to shorten production cycle and to lower production cost. Thus, The influence of many factors, such as mixing time, charging mode and sintering processing, on the deformation of plates were investigated.1. The production process of the iron-based valve plates prepared in the practical production is as follows:the powder mixture undergoing mixing time of 60 min and sitering process of 1120℃×15 min. With black perlite dispersively distributing into the white ferrite matrix and a little cementite existing at the grain boundary, the as-prepared plates had fine grains, low porosity, hardness of 59.5 HRB and density of 6.81 g/cm3. After preforming, sintering and reshaping, the length and the width gradualy increased, while the thickness decreased, reaching to 50.06 mm,42.03 mm and 3.55 mm, respectively. This size satisfies the requirement. From preforming to sintering, the flatness of the plates increased from 0.10 mm to 0.16 mm, then it could be lowered to 0.08 mm by reshaping.2. As the mixing time increased, the flatness of the plate firstly decreased and then increased. It reached to a minimum of 0.14 mm after sintering at the mixing time of 90 min and could be reduced to 0.06 mm by reshaping. The hardness was 53.30 HRB, along with density of 6.82 g/cm3 and compactness of 84.03%.3. The flatness reached to a minimun of 0.14 mm after sintering when using the following charging mode. The plates were single-row charged with their grooves opposing and staggering to each other and located in the cetre of the furnace. By reshaping, the flatness reduced to 0.06 mm.4. As the sintering pressure increased, the flatness of the plate firstly decreased and then increased. The minimun value appeared at the pressure of 0.36MPa, namely 30 Nm of the moment of the fixed moment spanner, and could be could be reduced to 0.06 mm by reshaping. The hardness was 66.67 HRB, along with density of 6.82 g/cm3 and compactness of 84.09%.5. The production process of the iron-based valve plates prepared using vaccum tube furnace in the lab was that the plates were single-row charged with their grooves opposing and staggering to each other and located in the cetre of the furnace, with powder mixture mixing time of 90 min, then sintered at 1150℃×15min. The flatness of the as-prepared plate was 0.17 mm and could be reduced to 0.06 mm. The hardness was 57.60 HRB, along with density of 6.83 g/cm3 and compactness of 84.17%.更多还原