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Effect of water atomization quenching on thin steel sheet 35CrMnSiA

Fan Zhiyang, Li Xianjun, Liu Junjie, Hu Bo, Zhou Tong, Hao Yuan

Heat Treatment of Metals 2021, 46 (5): 267-271. doi:10.13251/j.issn.0254-6051.2021.05.047

Abstract （51）

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A set of experimental equipment for atomized water spray quenching was designed to study change of the temperature drop curves of thin steel sheet 35CrMnSiA under the vertical state during spray quenching, and by using Inverse Heat Transfer module in the DEFORM software to complete the solution of the comprehensive heat transfer coefficient on the tested steel sheet. The results show that, when the tested steel sheet meets as-follow conditions, with the nozzle size of 5 mm, distance from nozzle to the sheet surface is 300 mm, and the nozzle pressure is 0.1, 0.2 and 0.3 MPa respectively, the surface heat transfer coefficient of that is correspondingly lower in the high temperature zone above 450 ℃ and the low temperature zone below 200 ℃. But the tested steel sheet can obtain a higher surface heat transfer coefficient in the middle temperature zone. Compared with the nozzle pressure of 0.1 MPa, the tested steel sheet of that has a significant improvement under the nozzle pressure of 0.2 MPa. While increasing the nozzle pressure to 0.3 MPa, the cooling capacity has little improvement.

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Influence of oil pollution on cooling characteristics of PAG water-based quenchant

Liu Chengmiao, Dong Lihua, Li Qinghong, Zhu Hongling, Ren Lin

Heat Treatment of Metals 2021, 46 (5): 272-275. doi:10.13251/j.issn.0254-6051.2021.05.048

Abstract （48）

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In order to explore the influence of oil pollution on cooling performance of water-based quenchant, the cooling rate curve and hardening capacity of quenchant with different oil contents were tested. The mechanism of oil pollution influencing the quenchant cooling performance was discussed by analyzing the specific quenching process and characteristic value function. The results show that when the oil content in the quenchant exceeds 0.3%, the cooling performance of the quenchant is significantly worse, specifically, the boiling stage is delayed, the cooling rate decreases obviously at high temperature stage and the hardening capacity of the quenchant is also reduced. But the content of oil has little effect on the quenching distortion of workpiece.

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Numerical simulation and experimental verification of influence of quenching media on residual stress of 7075 aluminum alloy

Tang Peng, Lu Shengcheng, Xiao Peixin, Li Jiadong, He Wanyao

Heat Treatment of Metals 2024, 49 (1): 284-290. doi:10.13251/j.issn.0254-6051.2024.01.046

Abstract （10）

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Experimental verification method and numerical simulation of ABAQUS in different medias were used to explore the mechanism of three quenching medias (water, 10%NaCl solution and engine oil) on the mechanical properties and residual stress of 7075 aluminum alloy. The numerical simulation results show that the residual stress after quenching in three medias shows the typical stress distribution characteristics of "internal tension and external compression". Moreover, the residual stress of the specimen after quenching with 10%NaCl solution is the highest, and that with engine oil is the lowest, which is related to the heat exchange state of the aluminum alloy surface in different medias. The tested results show that the salt crystals precipitated in the brine quenching process can make the vapor film on the surface of the specimen broken and have a better heat exchange rate, while layer of oil film formed in the engine oil quenching process reduces the heat exchange rate between the specimen and oil, leading to differences in mechanical properties of the alloys quenched in different medias. According to the hardness values of the quenched specimen from large to small, the three quenching medias are 10%NaCl solution, water and engine oil, which is consistent with the order of residual stress in the simulation results.

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Effect of quenching medium on microstructure and properties of 7050 aluminum alloy hot forgings

Shi Peifei, Zhang Hui

Heat Treatment of Metals 2024, 49 (1): 290-295. doi:10.13251/j.issn.0254-6051.2024.01.047

Abstract （13）

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A 7050 aluminum alloy hot forging for automobile was selected, and the specimens were rapidly heated to 746 K with a rate of 20 K/min and held for 1 h. Then the specimens were rapidly transferred to the PAG polymer solution with concentrations of 0% (water), 5%, 10%, 20%, 30% and air to quench respectively, and finally the aging treatment was carried out using the T74 process (393 K for 6 h and 436 K for 12 h). The effects of different PAG quenchant concentrations on the residual stress, second-phase particles, tensile strength and yield strength of the 7050 aluminum alloy specimens were analyzed. The results show that with the increase of PAG quenchant concentration, the residual stress of the aluminum alloy specimens gradually weakens, the volume fraction of the second phase gradually increases, and the tensile strength and yield strength gradually decrease. Considering comprehensively, the PAG quenchant concentration of 10%-20% can meet the technical requirements, with which the quenched specimens of the 7050 aluminum alloy have relatively low residual stress, the tensile strength is 512-519 MPa and the yield strength is 472-478 MPa, and meeting the mechanical properties requirements of tensile strength greater than 510 MPa and yield strength greater than 455 MPa.

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