热处理工艺对16MnR钢脆性转变温度的影响

对16MnR钢热轧板进行了不同的热处理。用系列冲击试验(能量)法,结合冲击断口形貌变化确定了脆性转变温度。光镜(OM)和扫描电镜(SEM)显微组织观察表明,脆性转变温度与热处理及其引起的组织变化密切相关;并且脆性转变温度按下列热处理态顺序降低:热轧态、正火、淬火后高温回火。     

热处理工艺对16MnR钢脆性转变温度的影响

对16MnR钢热轧板进行了不同的热处理。用系列冲击试验（能量）法，结合冲击断口形貌变化确定了脆性转变温度。光镜（0M）和扫描电镜（SEM）显微组织观察表明，脆性转变温度与热处理及其引起的组织变化密切相关；并且脆性转变温度按下列热处理态顺序降低：热轧态、正火、淬火后高温回火．     

V添加量对建筑结构用型钢低温冲击性能的影响

以建筑用型钢Q390为对象,研究了微合金化元素V对合金低温冲击性能、韧脆性转变温度的影响。结果表明,添加V后,试验钢的晶粒细化,断口韧窝细小且深,有效提高低温冲击吸收能量,并降低韧脆性转变温度。但V元素的添加量应在0.05wt%左右,否则其作用将减弱。     

韧脆转变温度曲线特点

正1韧脆转变韧脆转变温度:对体心立方晶体金属及合金或者某些密排六方晶体金属及合金当温度低于某一温度Tk时,材料由韧性状态转变为脆性状态,冲击吸收功明显下降,断裂机理由微孔聚集型变为穿晶解理,断口特征由纤维状变为结晶状,这就是低温脆性。此时的转变温度Tk称为韧脆转变温度,也称冷脆转变温度。     

U165超高强度钻杆钢韧脆转变临界点的表征方法

采用冲击吸收能量法、剪切断面率法以及非剪切区颈缩比法对U165超高强度钻杆钢的韧脆转变温度进行了表征。结果表明：U165钻杆钢的韧脆转变温度约为1.8℃,高于1.8℃时,断裂模式逐渐变为韧性断裂,低于1.8℃时,断裂模式逐渐变为脆性断裂。非剪切区颈缩比法得到的试验钢的韧脆转变温度与冲击吸收能量法、剪切断面率法得到的基本一致,这说明非剪切区颈缩比法可用于表征试验钢的韧脆转变温度。3种方法相互结合,能够更有效地表征材料的韧脆转变温度。     

焊接接头的抗动载断裂特性

阐述了焊接材料的脆性和延性断裂的裂纹产生与扩展过程,以及脆性和延性断裂的断口形貌特征。在承受动载的试验方法中,示波冲击试验能够同时测出材料的启裂功和止裂功,文中介绍了以下三种材料的示波冲击试验结果:低碳贝氏体钢模拟热影响区不同部位的冲击吸收能量,10Ni5CrMoV钢焊接区不同部位的冲击吸收能量以及HQ100钢在不同热输入时过热区的冲击吸收能量。     

冲击试验计算机数据采集和处理系统

1 前言 缺口试样的摆锤冲击弯曲断裂试验,已有几十年的历史。它可灵敏地检测材料的回火脆性、白点、粗晶,特别是脆性转变温度等,成为材料质量和加工工艺控制的重要指标,是大多数金属材料必测的力学性能。 随着断裂力学的发展研究,材料在动载下的形变断裂过程,成为发展新材料的重要课题。     

球墨铸铁的低温力学性能

正铁素体球铁在低温下的抗拉强度随温度下降而升高,珠光体球铁则反之。这两种铸铁的断后伸长率在低温下都有所下降,但铁素体球铁的下降幅度较大。球铁在低温下的冲击值与温度有很大关系。一般将冲击值开始急剧下降的温度作为韧性—脆性转变温度。铁素体球铁的冲击值远高于珠光体球铁,韧性—脆性转变温度远低于室温(在-50℃)。珠光体球铁的韧性一脆性转变温度在室温以下。铁素体球铁的低温冲击值随含磷量的升高而急剧降低;提高含硅量使低温冲击值迅速下降,并使韧性—     

38CrMoAl钢镗杆断裂原因分析

38CrMoAl镗杆在使用过程中突然断裂,从化学成分、显微组织、力学性能和冲击性能对其进行了分析。结果表明,钢的化学成分符合标准,镗杆为脆性断口,组织异常,冲击吸收能量很低,冲击断口也为脆性。断裂主要原因是镗杆有明显的上贝氏体组织,而且晶粒粗大。经分析是因加热温度高,冷却速度慢所致。提出了相应的改进措施。     

38CrMoAl镗杆断裂原因分析

38CrMoAl镗杆在使用过程中出现突然断裂,从化学成分、显微组织、力学性能和冲击性能对其进行了分析。结果表明,钢的化学成分符合标准,镗杆为脆性断口,组织异常,冲击吸收能量很低,冲击断口也为脆性。断裂主要原因是镗杆有明显的上贝氏体组织,而且晶粒粗大。经分析是因加热温度高,冷却速度慢所致。提出了相应的改进措施。     

Correlation study of microstructure,hardness, and Charpy impact properties in heat affected zones of three API X80 linepipe steels containing complex oxides

This study investigated the correlation between the microstructure, hardness, and Charpy impact properties in heat affected zones (HAZs) of API X80 linepipe steels containing complex oxides. Three types of steels were fabricated by adding Ti, Al, and Mg to form complex oxides; their microstructures, hardness, and Charpy impact properties were investigated. The number of complex oxides increased as the excess amount of Ti, Al, and Mg was included in the steels. The simulated HAZs containing a number of oxides showed a high volume fraction of intra-granular transformation microstructure (IGT) region because the oxides acted as nucleation sites for the ferrites. According to the correlation study between the heat input, volume fraction of the IGT region, and Charpy impact properties, it was found that ductile fractures predominantly occurred when the volume fraction of the IGT region was 65 % or higher, and the Charpy absorbed energy was excellent over 200 J. When the volume fraction of the IGT region was 45 % or lower, the Charpy absorbed energy was poor below 50 J as brittle cleavage fractures prevailed. These findings suggest that the active nucleation of the ferrites in the oxide-containing steel HAZs is related to the improvement of the Charpy impact properties of the HAZs.     

Room-Temperature Charpy Impact Property of 3D-Printed 15-5 Stainless Steel

In this study, the room-temperature Charpy impact property of 3D-printed 15-5 stainless steel was investigated by a combined experimental and finite element modeling approach. The experimentally measured impact energy is 10.85 ± 1.20 J/cm², which is comparable to the conventionally wrought and non-heat treated 15-5 stainless steel. In parallel to the impact test experiment, a finite element model using the Johnson–Cook material model with damage parameters was developed to simulate the impact test. The simulated impact energy is 10.46 J/cm², which is in good agreement with the experimental data. The fracture surface from the experimentally tested specimen suggests that the 3D-printed specimens undergo predominately brittle fracture.     

Impact toughness of tungsten films deposited on martensite stainless steel

Tungsten films were deposited on stainless steel Charpy specimens by magnetron sputtering followed by electron beam heat treatment. Charpy impact tests and scanning electron microscopy were used to investigate the ductile-brittle transition behavior of the specimens. With decreasing test temperature the fracture mode was transformed from ductile to brittle for both kinds of specimens with and without W films. The data of the crack initiation energy, crack propagation energy, impact absorbing energy, fracture time and deflection as well as the fracture morphologies at test temperature of-70 ℃ show that W films can improve the impact toughness of stainless steel.     

回火温度对37CrMnMo钢冲击性能的影响

通过冲击、拉伸试验、光学显微镜和扫描电镜,研究了钻杆接头用37CrMnMo钢在不同回火温度下的显微组织形貌及强度和冲击性能的影响的变化规律。结果表明,37CrMnMo钢经水淬后于500～640 ℃回火后得到回火索氏体,随回火温度的上升其抗拉强度与屈服强度由平缓降低变为陡降趋势。500 ℃的回火组织中碳化物呈现层片状分布,冲击吸收能量为30.94 J;600 ℃回火后碳化物呈均匀弥散分布,冲击吸收能量为117.49 J;经过640 ℃回火后,显微组织中碳化物粗化,直接导致冲击吸收能量下降。故37CrMnMo钢试样在870 ℃淬火后于不同温度回火,碳化物的形貌对其强韧性起着关键作用。     

Impact property analysis of weld metal and heat-affected zone for low-alloy carbon steel multi-pass welded joint

Welded joint impact performances of low-alloy carbon steel plates welded by full-automatic gas metal arc welding (GMAW) were evaluated. To clarity the effect of impact temperature on impact properties of weld metal (WM) and heat-affected zone (HAZ), Charpy V impact tests at different temperatures and fracture surface analysis were carried out. The Charpy V impact energy decreases with the decreasing test temperature both for the WM and HAZ, while the proportion of crystal zone on WM and HAZ impact fracture surface increases with the decreasing test temperature. Research results indicate that the welding defects (void and slag) make the impact energy of WM more scattered and lower than that of HAZ.     

Numerical and experimental evaluation of the impact performance of advanced high-strength steel sheets based on a damage model

The impact performance in a Charpy impact test was experimentally and numerically studied for the advanced high-strength steel sheets (AHSS) TWIP940 and TRIP590 as well as the high-strength grade known as 340R. To characterize the mechanical properties, uni-axial simple tension tests were conducted to determine the anisotropic properties and strain rate sensitivities of these materials. In particular, the high-speed strain-rate sensitivity of TRIP590 and 340R (rate sensitive) was also characterized to account for the high strain rates involved in the Charpy impact test. To evaluate fracture behavior in the Charpy impact test, a new damage model including a triaxiality-dependent fracture criterion and hardening behavior with stiffness deterioration was introduced. The model was calibrated via numerical simulations and experiments involving simple tension and V-notch tests. The new damage model along with the anisotropic yield function Hill 1948 was incorporated into the ABAQUS/Explicit FEM code, which performed reasonably well to predict the impact energy absorbed during the Charpy impact test.     

�й����ձ��������ֲ�Ʒ�ı�V�ͳ�������׼�Ա�

 夏比（Charpy）冲击试验是评价冲击载荷下材料塑性变形和断裂过程中吸收能量的能力的试验方法。虽然试验中测定的冲击吸收功Ak值不能作为表征金属制件实际抵抗冲击载荷能力的韧性判据,但是因为其试样加工简便,试验时间短,实验数据对材料组织结构、冶金缺陷等敏感,因而成为评价金属材料冲击韧性的一种传统力学性能试验方法,被世界各国广泛采用。不同国家的冲击试验标准对试验机、试样、试验程序和试验结果的处理与修约的规定不尽相同,对日本的JIS 标准、美国的ASTM标准和中国的GB标准中关于钢产品的冲击试验规定进行比较,列举了它们之间的差异并对这些差异对试验结果的影响进行讨论。由于均源自ISO148,中国和日本的冲击试验标准对冲击试验机及其附件、冲击试样、冲击试验程序和冲击试验结果处理与修约的规定基本一致,只是日本标准对试样部分尺寸的允许偏差要求较中国严格。与日本和中国的标准相比,ASTM标准在试验机及其附件、试验程序、试样和试验结果处理与修约方面的规定存在较大差异。ASTM使用刀刃曲率半径8 mm的摆锤,同一组试样得到的冲击吸收功可能与中国标准存在差异。对试验温度的控制要求更严格,分别为规定温度的±2 ℃和±1 ℃。冲击试样取样位置和对冲击试样方向的定义也不完全相同。ASTM标准对试样尺寸的允许偏差更严格,缺口角度分别为45±2°和45±1°、缺口深度分别为2±0.15 mm和2±0.025 mm以及相邻面角度分别为90±2°和90±0167°;由此引起的冲击吸收功变化也较小。ASTM标准的试验结果处理与修约方面与中国标准也有较大区别。     

Influence of Martensite Volume Fraction on Impact Properties of Triple Phase (TP) Steels

Ferrite-bainite-martensite triple phase (TP) microstructures with different volume fractions of martensite were obtained by changing heat treatment time during austempering at 300 °C. Room temperature impact properties of TP steels with different martensite volume fractions (V _M) were determined by means of Charpy impact testing. The effects of test temperature on impact properties were also investigated for two selected microstructures containing 0 (the DP steel) and 8.5 vol.% martensite. Test results showed reduction in toughness with increasing V _M in TP steels. Fracture toughness values for the DP and TP steels with 8.5 vol.% martensite were obtained from correlation between fracture toughness and the Charpy impact energy. Fractography of Charpy specimens confirmed decrease in TP steels’ toughness with increasing V _M by considering and comparing radial marks and crack initiation regions at the fracture surfaces of the studied steels.     

焊接热输入对Q890高强钢热影响区裂纹扩展的影响

采用Gleeble1500热模拟试验机,研究不同热输入对Q890高强钢焊接热影响区粗晶区的微观组织和韧性影响规律. 结果表明,随着热输入的增加,粗晶区的微观组织表现出从马氏体组织向马氏体、贝氏体的混合组织,再向贝氏体、粒状贝氏体的混合组织的转变. 当热输入为19.7 kJ/cm时,冲击吸收功最高为83 J,主要原因是由于先相贝氏体分割后相马氏体,大角度晶界密度最大,改善了冲击韧性. 当热输入较高时,粗晶区脆化的原因是由于M-A组元呈链状分布,造成局部应力集中,成为裂纹起裂和扩展的主要通道.     

关于超高强度套管夏比冲击吸收能规定值的讨论

通过对套管、钻杆管体的载荷、失效模式及夏比冲击吸收能的要求的对比分析,对超高强度套管、钻杆及钻柱构件夏比冲击吸收能要求的区别,尤其对夏比冲击吸收能平均值为屈服强度下限值的1/10的经验式的适用性进行了讨论,指出将该经验式推广至载荷状态和失效模式不同的深井超高强度套管及套管柱在理论上和实践上都是缺乏依据并且是有害的。对深井超高强度套管提出不适当的过高的韧性要求,只能造成性能过剩和制造成本的上升。