A Study on Steel Quenching Applications of PVP Type Polymer Quenchant

Autor: Yung-Tsun Shih, 施永村
Rok vydání: 2012
Druh dokumentu: 學位論文 ; thesis
Popis: 100
The article is to investigate the effect of quenchant parameters of concentration, fluid velocity (agitation intensity), temperature for PVP type SQ1501 aqueous polymer quenchant on quenching characteristics of steel by a series of experiments. Quenching experiments of some kinds selected steel alloy materials (JIS-SKT4, B30PH, 4M, AISI-4140M and JIS-SCM440) specimens were conducted at laboratory; a series of pilot tests of steel products at the heat treatment factory also were carried out to demonstrate the experimental results. The experimental results show that the full hardness of the above mentioned quenched steel alloy materials JIS-SKT4, B30PH, 4M and AISI-4140M were decreased as concentration of polymer quenchant is increased from14.3% to 20% with fluid velocity 0.05~0.1m/s at room temperature, the hardness of the low hardenability alloy steel was affected significantly by concentration increasing. It will induce quenching crack of high hardenability alloy steel JIS-SKT4 and AISI-4140M as concentration of polymer quenchant was decreased to 9.1%；the surface hardness of low hardenability alloy steel JIS-SCM440 will be increased to HRC52~55 as concentration of polymer quenchant was decreased to 5.9%.The influence of fluid velocity (agitation intensity) on hardening depth of high hardenability alloy steels(JIS-SKT4、B30PH and AISI-4140M) is insignificant compared to the low hardenability alloy steel JIS-SCM440. While temperature of polymer quenchant was increased from 26℃ to 50℃with polymer concentration of 14.3% at 0.05~0.1m/s fluid velocity, the hardness of three kinds alloy steels(JIS-SKT4, B30PH and AISI-4140M) were decreased about HRC2~3; but 4M was decreased significantly about HRC9~10. According to the experiment results from laboratory, the optimum parameter of PVP type SQ1501 aqueous polymer quenchant is 14.3% concentration, middle agitation intensity (fluid velocity is about 0.05 ~0.1m/s); and quenchant temperature is at room temperature. The above selected steel alloy materials JIS-SKT4, B30PH, 4M and AISI-4140M will obtain good harden uniformity as they were quenched in PVP type SQ1501 aqueous polymer quenchant under this optimum parameter. But the hardness of low hardenability alloy bar steel JIS-SCM440 can not fit the hardness demand；it is founded that the trapped air will affect cooling rate of polymer quenchant at boiling stage during experiment process, it will cause seriously the hardness drop；thus it is necessary to avoid air entrapping during cycling agitation. Using the experiment results, we carried out a series of pilot tests of steel products at heat treatment factory. The results show the surface hardness of different thickness bulk steel materials for B30PH which were quenched and tempered is lower than the hardness specification demand; however, the hardness difference of cross-section can fit the demand (hardness difference < HRC4). Therefore the surface hardness and hardness difference of cross-section will fit the demand provided that the full hardness of quenched material is increased about HRC2 and then through tempering treatment, or to decrease the tempering temperature. The hardness of the other bulk steel materials JIS-SKT4, B30PH and AISI-4140M can not completely fit the hardness demand of specification. The product pilot tests show that the hardness of JIS-SCM440 steel plate materials with 45, 50mm thickness and JIS-SCM440、SNCM439 circular bar steel materials with different diameters can fit the hardness demand of specification (HRC 28~32); but the hardness of JIS-S50C bar steel in product pilot test is too low (HRC18~21) to fit the hardness demand of specification(HRC22~25), therefore it is necessary to decrease the tempering temperature to 450 ℃for this carbon steel. The result hardness difference for JIS-SCM440 circular bar steel material between experiment at laboratory (1st generation quenching equipment) and pilot test at the heat treatment factory can be improved by the modification on agitation system of quenching equipment (2nd generation quenching equipment); after increasing fluid velocity (agitation intensity) in the 2nd generation quenching equipment, it is to demonstrate again the hardness result fit expectable demand.
Databáze: Networked Digital Library of Theses & Dissertations
Externí odkaz: