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The Deformation Law and Its Influnecing Factors of Iron-based Valve Plate in Sintering Process

Author: LiangCui
Tutor: XuJinFu；XuShengHua
School: East China University of Science and Technology
Course: Materials Engineering
Keywords: Iron-based valve plate powder metallurgy deformation law sintering process
CLC: TF124.5
Type: Master's thesis
Year: 2012
Downloads: 4
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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%.

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CLC: > Industrial Technology > Metallurgical Industry > Metallurgical Technology > Powder metallurgy (metal ceramic technology ) > Powder molding, sintering and post-processing > Sintering process
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