Sensitivity of the Impact Toughness and Microstructure of 15CrNi3MoV Steel Under Different Quenching Rates

The sensitivities of the mechanical properties and microstructure of 15CrNi3MoV alloy steel under different quenching rates were investigated in the present study.After subjection to quenching with four different cooling rates(water cooling,forced air cooling,static air cooling and furnace cooling)followed by tempering,the microstructure was characterized by scanning electron microscopy(SEM),electron back-scattered diffraction(EBSD),and transmission electron microscopy(TEM);and the low-temperature(−20°C)impact toughness was evaluated.The results showed that the tempered microstructure and mechanical properties had high sensitivity to the quenching rate.With a decrease in the quenching rate,the low-temperature impact energy of tempered specimens decreased with increasing fluctuation.Correspondingly,the fracture morphology changed from completely ductile to brittle.In addition,as the quenching cooling rate decreased,the as-quenched matrix changed from a lathy to a polygonal structure with the presence of carbides and martensite-austenite(M-A)constituents,and the effective grain size increased.Tempered martensite with dispersed fine carbides was found in the tempered water cooling specimen,and tempered bainite with a polygonal structure containing large carbides and rare incomplete undecomposed M-A constituents was found in the tempered forced air cooling,static air cooling and furnace cooling specimens.The small effective grain size and fine carbides contributed to the good temperature impact toughness of the tempered water cooling specimens.

回火冷却速率对30CrMnSiA组织与性能的影响

对退火态30CrMnSiA钢进行了回火冷却速率实验,探究回火后冷却速率对30CrMnSiA钢性能的影响及其组织演变规律。结果表明,回火冷却速率对30CrMnSiA钢硬度影响较小、对冲击韧性有一定影响,30CrMnSiA钢经510℃回火后表面主要受到压应力、心部受到拉应力,且回火冷速越快,试样表面残余应力越大。回火过程中C元素主要与Fe元素结合形成铁碳化合物,少量C元素与Cr、Si元素形成铬碳化合物、硅碳化合物。快冷范围内冷却速率对碳化物含量及尺寸影响较小。

核电站压力容器用SA508-3钢厚截面锻件热处理冷却速度

研究了不同截面厚度的ＳＡ５０８－３钢热处理冷却速度与力学性能的关系。实验结果表明，当平均冷速≤１８℃／ｍｉｎ时，钢的强度和韧性较低，达不到标准要求。当冷却速度为５８～１６８℃／ｍｉｎ时，其淬火组织为下贝氏体，经６５０℃回火后组织变成回火贝氏体和均匀分布的合金碳化物，使ＳＡ５０８－３钢具有良好的强度和低温韧性。

核电站压力容器用锰铬钼镍低碳合金钢大截面锻件断裂韧性研究

研究了含锰、铬、钼、镍压力容器用钢的化学成分和热处理条件对断裂韧性（ＫＩＣ）的影响。实验结果表明：对大截面锻件来说，适当增高合金中镍含量的同时，必须改变冷却速度，获得细小板条下贝氏体组织，回火后贝氏体铁素体板条中均匀分布着细小弥散的碳化物，可使ＦＡＴＴ明显移向低温，增加上平台能量，提高断裂韧性。

高速钢中共晶碳化物的研究进展

综述了在常规凝固条件下高速钢中共晶碳化物的研究现状,阐述了铸态组织中常见的三种类型共晶碳化物的形貌,重点探讨了Si、W、Mo、V、Nb、Ti及其他微量元素等对高速钢共晶碳化物析出的影响机制,并分析了改变冷却速度对共晶碳化物M2C形态、尺寸和分布的影响,概述了退火、淬火和回火工艺对高速钢碳化物组织转变的影响研究,对高速钢中共晶碳化物的进一步研究提出了建议。

冷却剂环境下应变速率对国产RPV低合金钢疲劳寿命影响的试验研究

为研究分析压水堆核电站冷却剂环境下国产反应堆压力容器低合金钢材料的服役疲劳寿命,在实际反应堆压力容器产品锻件上取样并加工成测试试样,采用高温高压循环水试验回路开展模拟反应堆一回路冷却剂环境的材料疲劳试验,获得了疲劳试验数据和应变速率对低合金钢环境疲劳寿命的影响规律,分析了试验数据与ASME规范平均/设计疲劳曲线的关系,评价了ASME规范设计疲劳曲线和环境疲劳修正系数的适用性。

淬火冷却速度和回火参数对核压力容器SA508-3钢强韧性的影响

利用自行研制的模拟热处理炉研究了淬火冷却速度和回火参数对核压力容器用SA508-3钢强韧性的影响。结果表明SA508-3钢对淬火冷速敏感,随着冷速增加强,韧性显著提高。回火参数对SA508-3钢的强韧性也有明显影响,随着回火参数的增加,强度下降,冲击性能呈峰值曲线变化。综合分析认为,采取加速冷却,回火参数控制在19.08~19.50范围内,SA508-3钢可获得高的强韧性。