Simultaneous Improvement of Toughness and Fatigue Life in a Typical Ultrahigh Strength Steel by a New Deep Cryogenic Treatment Process

Guo, Peng; Deng, Lei; Wang, Xinyun; Jin, Junsong

doi:10.2355/isijinternational.isijint-2020-397

Cited by 5 publications

(4 citation statements)

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“…It is better to include tempering after cryogenic operation which results in fine and homogenous distribution of carbides. [48][49][50][51][52][53][54][55][56][57][58][59][60][61][62][63][64] A Typical Cryo-treatment cycle has ramp down, soaking period, ramp up and tempering as shown in Figure 5. and explained below:…”

Section: Mechanismmentioning

confidence: 99%

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Effect of cryogenic treatment on properties of materials: A review

Singh

Pandey

2022

Proceedings of the Institution of Mechanical Engineers, Part E:

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The objective of this review paper is to introduce Cryogenic temperature effect on different properties of materials. Results showed that cryogenic operation improves properties like hardness, fatigue strength, tensile strength, toughness and resistance to wear in comparison to conventional operations. The improvement is a result of microstructural changes at cryogenic temperature which helps in conversion of austenite to martensite and carbide nucleation. The results also showed that doing tempering before or after cryogenic operation has significant influence on material properties which helps to achieve better carbide distribution. Different heat treatment sequences which involve tempering before or after Deep Cryogenic Treatment (DCT), provides varied results. Soaking time at cryogenic temperature also has an important role in refinement of microstructure and affect material properties.

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Section: Mechanismmentioning

confidence: 99%

“…It is better to include tempering after cryogenic operation which results in fine and homogenous distribution of carbides. 48–64…”

Section: Introductionmentioning

confidence: 99%

Effect of cryogenic treatment on properties of materials: A review

Singh

Pandey

2022

Proceedings of the Institution of Mechanical Engineers, Part E:

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“…Cryogenic treatment has been found to reduce the residual austenite content after heat treatment [ 5 , 6 ]. It also helps regulate residual stresses [ 7 ], refine the microstructure of the material, improve its properties, and extend the service life of the workpiece [ 8 ]. By enhancing existing processes and adopting cryogenic treatment, it is possible to overcome the limitations of conventional heat treatment methods and optimize the performance of 51CrV4 steel.…”

Section: Introductionmentioning

confidence: 99%

Impact of Cryogenic Treatment Process on the Performance of 51CrV4 Steel

et al. 2023

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The working load on automotive components is continuously rising, and the mechanical performance requirements for component materials are rising along with the growth trend toward light weight and high dependability in automobiles. In this study, the response characteristics of 51CrV4 spring steel were taken to be its hardness, wear resistance, tensile strength, and impact toughness. Prior to tempering, cryogenic treatment was introduced. Through the Taguchi method and gray relational analysis, the ideal process parameters were discovered. The ideal process variables were the following: a cooling rate of 1 °C/min, a cryogenic temperature of −196 °C, a holding time of 24 h, and a cycle number of three. An analysis of variance revealed that the holding time had the greatest effect on the material properties, with an effect of 49.01%. The yield limit of 51CrV4 was increased by 14.95% and the tensile strength was increased by 15.39% with this group of processes, and the wear mass loss was reduced by 43.32%. The mechanical qualities had a thorough upgrade. Microscopic analysis revealed that cryogenic treatment resulted in refinement of the martensite structure and significant differences in orientation. Additionally, bainite precipitation occurred, exhibiting a fine needle-like distribution, which positively influenced impact toughness. Analysis of the impact fracture surface showed that cryogenic treatment led to an increase in dimple diameter and depth. Further analysis of the elements revealed that calcium (Ca) weakened the negative effect of sulfur (S) on 51CrV4 spring steel. The overall improvement in material properties provides guidance for practical production applications.

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“…2 Deformation mechanism and modeling of 300M high-strength steel. (a) Dynamic and static softening mechanism during multi-pass hot deformation [24] ; (b) Modeling procedure for the constitutive model of multi-pass deformation [25] ; (c) Validation of the established constitutive model under single-pass and multi-pass deformation [26] 大型构件在一个变形道次结束时，往往会进入道次间的保温阶段。在变形道 A c c e p t e d https://engine.scichina.com/doi/10.1360/TB-2021-1122 次间的保温过程中发生的静态软化机制对材料的宏微观变化也会产生重要的影响。静态软化机制主要包括静态回复、静态再结晶及亚动态再结晶机制 [44,45] 。对于低层错能材料，静态回复机制的影响很小，主要考虑静态及亚动态再结晶机制对材料静态软化行为的影响 [46] 。当变形过程中材料的应变小于临界应变时，在随后的保温过程中材料主要发生静态再结晶机制；反之，则在后续的保温过程中会同时发生静态以及亚动态再结晶机制 [47] 。通常而言，静态再结晶过程需要较长的孕育期，而亚动态再结晶过程则没有孕育期。对于 300M 高强钢，Zhao 等人 [48,49] 通过原位实验方法分别研究了其亚动态再结晶和静态再结晶机制，发现亚动态再结晶晶粒尺寸随着保温温度、应变速率以及保温时间的增加而增加，亚动态再结晶过程主要包括晶粒的吞并、三叉晶处的晶界迁移现象等；而静态再结晶过程中，应变速率对再结晶晶粒尺寸的影响远小于变形温度，静态再结晶机制为应变诱导晶界迁移机制。因此静态软化过程对材料的晶粒尺寸具有显著的影响。此外，静态软化过程对材料的力学性能也会产生重要影响。Zeng 等人 [50] 通过纳米压痕实验研究了静态软化过程对 300M 高强钢微观尺度力学性能的影响，发现随着静态软化分数的增加，变形晶粒和再结晶晶粒的微观硬度都会减小。 Chen 等人 [51] 研究了不同的第一道次变形量、变形温度、应变速率、保温时间以及变形道次下， 300M 高强钢静态软化机制对其宏观力学性能的影响。他们发现，通过优化变形参数，合理利用静态软化机制，可以有效降低材料多道次变形过程中的变形抗力。除了上述的再结晶机制，晶粒长大现象会出现在大型构件锻造过程的各阶段，包括变形前的加热保温阶段、热变形阶段以及变形后的保温阶段。Chen 等人 [52] 通过原位观察的方法研究了初始晶粒尺寸、初始微观组织、保温温度及保温时间对 300M 高强钢保温过程晶粒演化的影响，结果表明初始晶粒尺寸及初始微观组织对最终的晶粒尺寸无明显影响，而保温温度对晶粒尺寸演化起到关键作用。晶粒长大主要是依靠晶界迁移实现，位于晶界两侧的原子跃迁是一个热激活过程，当原子所具有的能量超过能量壁垒时，即可发生跃迁，降低材料系统内能，晶界开始移动。保温温度越高，材料内部的原子更容易被激活，晶界迁移速度更快，宏观上看就是晶粒开始长大。洪橙等人 [53] 增加。为了实现晶粒尺寸及形貌的可预测性，夏祖瑜等人 [54] 基于热激活机制、曲率驱动机制以及能量耗散理论，采用元胞自动机模型对 300M 高强钢保温过程中的晶粒长大进行了模拟，模拟结果与实验结果能够很好的吻合。在大型构件最终变形完成后，锻件会经历冷却阶段并进入后续的热处理工序。对于 300M 高强钢，在冷却过程中会发生相变现象。Chen 等人 [55] 通过原位实验构建了材料连续冷却过程的相图，并揭示了冷却过程中不同微观组织的形成机理，这对实际变形后锻件的冷却速度控制具有重要的指导意义。Guo 等人 [56] [52] 基于晶界迁移理论建立了 300M 高强钢保温过程的晶粒长大模型。 Guo 等人 [33] 建立了变形参数与动态再结晶晶粒尺寸之间的关系。 Zhao 等人 [36]…”

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