Cu、As和Sn对低合金钢连铸坯第Ⅲ脆性区的影响

为了研究残余元素Cu、As和Sn对钢高温延塑性的影响,采用Gleeble-1500热模拟试验机测试了含有一定量Cu、As和Sn低合金钢连铸坯的高温延塑性,得到了低合金钢第Ⅲ脆性温度区在920~730℃之间.结果表明:第Ⅲ脆性温度区脆化的主要原因是奥氏体单相区低温域钢中Cu、As和Sn等残余元素在奥氏体晶界的偏聚削弱晶界结合能,导致试样沿晶脆性断裂;奥氏体和铁素体两相区在原奥氏体晶界析出的网状铁素体导致试样沿晶开裂.钢中的Cu、As和Sn元素增加第Ⅲ脆性温度区的宽度和脆性凹槽的深度,同时提高第Ⅲ脆性温度区的上限临界温度.     

铌钛微合金钢异型坯高温塑性研究

在GLLEEBLE3800热模拟试验机上进行了铌钛复合微合金化钢异型坯的高温拉伸试验,并对断口形貌进行了分析,确定了钢材的脆性温度区,第I脆性区的温度范围为1 300℃至熔点,高温塑性区的温度范围为950～1 300℃,第Ⅲ脆性区的温度范围为700～900℃,高温塑性区为微孔聚集韧性断裂,呈现典型的韧窝结构,在第Ⅲ脆性区为准解理断裂,呈现典型的河流花样结构。     

中碳微合金化钢高温延塑性的研究

借助Gleeble1500热模拟试验机测试了含Nb和含Nb、Ti两种中碳微合金化钢的高温力学行为,分析了析出物、相变、动态再结晶对微合金化钢高温延塑性的影响。结果表明:试验钢种无第Ⅱ脆性区出现;含Nb钢第Ⅲ脆性区的温度范围为950~700℃,含Nb、Ti钢第Ⅲ脆性区的温度范围为900~725℃;微合金化元素Ti的加入可以细化奥氏体晶粒使含Nb微合金化钢高温塑性槽变窄、变浅;析出物沿晶界多而细小的析出和γ→α相变是第Ⅲ脆性区微合金化钢高温延塑性变差的主要原因。实际生产中通过优化二冷区水量,采用弱冷,可以有效降低微合金化钢表面微裂纹的发生率。     

高洁净低合金钢16MnR连铸坯高温延塑性研究

采用Gleeble-1500热模拟试验机测试了高洁净度16MnR钢连铸坏的高温延塑性。16MnR钢的第I脆性温度区在凝固温度-1360℃之间,第Ⅲ脆性温度区在750-700℃之间。由于钢中氮、氧、硫等杂质含量很低,因此第Ⅲ脆性温度度范围很窄,主要发生在γ α两相区,在该脆性区内钢的脆化程度很低。     

含钒低合金钢铸坯高温延塑性研究

采用Gleeble-1500热模拟试验机测试了含钒低合金钢铸坯的高温延塑性,利用扫描电镜、金相显微镜对断口形貌及金相组织进行分析。低合金钢的第Ⅰ脆性温度区在Ts~1 370℃之间,第Ⅲ脆性温度区在915~710℃之间。第Ⅲ脆性区间由奥氏体低温域晶界滑移楔形裂纹造成的沿晶脆性断裂和奥氏体晶界先共析铁素体薄膜造成的沿晶韧性断裂两部分组成。钢中的V对钢的第Ⅲ脆性凹槽的影响比较大,脆化向低温区域延伸。     

高碳钢连铸板坯高温力学性能

采用Gleeble-1500热模拟试验机测量了高碳钢连铸板坯的高温力学性能,得到了第Ⅰ、第Ⅲ脆性温度区的温度范围.结果表明:第Ⅰ脆性温度区脆化的主要原因是晶界部位的低熔点物质在高温下首先熔化,从而导致试样沿晶界开裂;第Ⅲ脆性温度区脆化的主要原因是在奥氏体部位析出的网状铁素体导致试样沿晶界开裂;在奥氏体单相区,由于氮化铝的析出导致钢种的塑性恶化.     

集装箱板钢高温延塑性研究

本实验采用Gleeble-1500热－力学模拟实验机,测试了集装箱板钢－IV5934E1钢连铸坯试样从熔点到600℃温度区间的高温力学行为,以断面收缩率（R．A．）为标准对钢的高温延塑性进行了评价。采用金相、扫描电镜等手段对拉伸试样急冷后断口的组织、形貌进行了分析,得到IV5934E1钢各脆性区的脆化原因及机理。结果表明：在熔点－600℃的温度区间内,IV5934E1钢存在第I和第Ⅲ两个脆性区。第I脆性区内,高温下晶界处富含硫、氧等杂质是导致沿晶断裂主要原因;第Ⅲ脆性区内,钢的脆性主要发生在（r＋a）两相区高温域（800℃－775℃）,由于先共析铁素体沿晶界析出使钢的塑性降低。IV5934E1钢中高含量的磷和铜未对钢的高温延塑性产生不良影响。     

含铌微合金高强度钢Q345C连铸坯的热塑性

 通过Gleeble-2000 试验机研究了Q345C钢连铸坯的高温热塑性。利用扫描电镜、金相显微镜、透射电镜观察了第Ⅰ、Ⅲ脆性温度区内拉伸试样断口部位的显微组织及形貌,分析了动态再结晶、相变、析出物等对微合金化钢高温延塑性的影响。结果表明：在1×10-3/s应变速率下, Q345C钢存在两个脆性温度区,即第Ⅰ脆性区（1200～1300℃）和第Ⅲ脆性区（600～875℃）,无第Ⅱ脆性区出现;最高塑性出现在1050℃左右,断面收缩率（Z）达到85.8%;在第Ⅲ脆性区,沿奥氏体晶界析出膜状铁素体抗拉能力较低,晶界处存在夹杂物以及微合金元素的析出物,是钢的热塑性降低的主要原因。     

碳、铬和钼对冷微钢铸坯高温力学性能的影响

通过GLEEBLE-3500热模拟机,研究了六种不同碳、铬和钼含量对冷镦钢(/%:0.19C,0.36C,0.19C-0.96Cr,0.39C-0.98Cr,0.19C-0.91Cr-0.21Mo和0.37C-0.98Cr-0.22Mo)在650～1200℃温度内的高温力学性能的影响。结果表明,六种钢在650～850℃温度都存在明显的第Ⅲ脆性区。第Ⅲ脆性区的起始温度随着碳含量减少和铬含量的添加移向更高温度。铬的添加使得材料的高温塑性恶化,促进第Ⅲ脆性区扩大。而钼的添加可改善含铬冷镦钢的第Ⅲ脆性区塑性。     

Q345C连铸坯高温热塑性的研究

在Gleeble-2000热模拟机上,针对Q345C钢连铸坯,进行了高温热塑性测试.分析了Q345C钢试样的断口性质及显微组织与塑性的关系.研究了第Ⅲ脆性区的脆化原因.实验结果表明:在1 300～600℃区间存在两个脆性温度区,其中第Ⅲ脆性温度域为600～850℃,其断面收缩率RA范围是60.23%～29.61%;指出了该钢种在实际生产条件下适宜的铸坯矫直温度.     

低熔点元素铋对钢脆化行为的影响

 为了探明钢中低熔点元素铋在切削加工和高温变形生产过程中的“两面性”作用,借助切削加工试验、高温热塑性试验及微观组织结构分析,研究了不同温度范围内铋对钢脆化行为的影响。结果表明,在切削加工过程中,低熔点元素铋对钢的脆化作用,使铋易切削钢易于形成对切削加工有利的“C形”脆性屑,从而获得优良的可切削加工性能,该脆化行为主要与钢中铋的液态金属脆化作用有关,显著降低钢在铋熔点温度附近的塑性。在高温变形温度区间,低熔点元素铋对钢脆化行为的影响,主要与奥氏体晶界上铋膜的偏聚有关,脆化晶界,显著降低钢在1 000 ℃及以下试验温度时的热塑性。     

Gleeble模拟热轧工艺对磷非平衡晶界偏聚的影响

 采用Gleeble 3500热模拟试验机研究了轧制和卷取温度下磷元素晶界偏聚与热轧板高温热塑性的关联机制。研究结果表明,含磷钢中磷元素晶界偏聚符合空位-磷原子复合体非平衡共偏聚理论,800 ℃以上轧制温度对磷元素晶界偏聚引起的钢板脆性影响较小,而在500～650 ℃温度范围存在磷元素偏聚导致的热塑性低谷区,且在该温度区施加1%拉伸预应变将加剧磷元素晶界偏聚和钢板脆性。因此,本试验成分含磷钢热轧生产中卷取温度设定应避免550 ℃塑性低谷。     

2205双相不锈钢的高温变形行为研究

在Gleeble-1500热模拟试验机上进行热-力模拟试验,得到实验数据并分析试样的热塑性、变形抗力,并利用金相显微镜对其进行金相组织的分析。在950~1 200℃温度区间进行高温拉伸试验,绘制出样品的热塑性曲线与热强度曲线,通过热塑性曲线说明在950~1 200℃范围内具有良好的塑性,通过热强度曲线可以观察到屈服强度随温度的升高而降低;在变形温度为950~1 200℃,应变速率为0.1,1,5和10 s-1时进行高温压缩试验,绘制出真应力-应变曲线和变形抗力曲线,结果显示,变形抗力随应变量的增大而迅速达到最大值,而后趋于平缓,随着温度的升高,变形抗力呈下降的趋势。     

油气田用SUP13Cr5Ni2Mo超级马氏体不锈钢热变形加工图研究

在Gleeble-3800热模拟试验机上,研究了SUP13Cr5Ni2Mo合金的热塑性及热变形行为,并建立了合金的热加工图。结果表明,在900～1 300℃,合金均具有较好的热塑性;通过热加工图分析得出,合金适宜初始加工温度范围在1 100～1 200℃,采用此参数变形获得的组织细小均匀。     

Non-isothermal reduction as a method of determining the softening – melting temperature of iron-ore pellets and sinters

An attempt was made to develop a simplified procedure of determining the softening-melting temperature ranges for iron-ore pellets and sinters. For this purpose, the non-isothermal reduction of a sinter (pellet) sample in a graphite crucible was used in the temperature range of 1000-1550°C, where the sample was heated at a rate of 5K/min. The investigations have shown that the variation of the reduction rate as a function of time and temperature is clearly related to the occurring phenomena of softening and melting of these materials. The existing areas of the maximum and minimum reduction rates correspond to the temperature ranges of softening-melting of the materials. It is also possible to determine the temperature of separation of the metallic phase from the slag phase. The examination of industrial pellets by the non-isothermal reduction method has confirmed the usefulness of this method for the comparative analysis of the thermoplastic properties of iron-ore pellets and sinters, and for predicting their usefulness for the blast furnace process.     

13Cr超级马氏体不锈钢热变形特性

为了探讨生产13Cr超级马氏体不锈钢合适的热变形温度,在Gleeble1500热模拟试验机上对13Cr超级马氏体不锈钢进行了应变速率为2.5 s-1、不同变形温度下的高温热塑性试验及热压缩试验,对变形后的试样进行了金相组织观察,并对回火后组织中逆变奥氏体含量进行了测定。结果表明,13Cr超级马氏体不锈钢回火前的马氏体板条粗大,回火后的马氏体发生显著的细化;根据高温热塑性曲线、热变形过程再结晶组织及回火后逆变奥氏体含量,确定13Cr超级马氏体不锈钢适宜的变形温度为1 050~1 150 ℃。     

Evaluation of mechanical and thermal properties of Poly (butylene terephthalate) (PBT) composites reinforced with wollastonite

Particulate filled polymer composites are becoming attractive because of their wide applications and low cost. Present study deals with the preparation and characterization of PBT/wollastomte composites and analyzing the effect of incorporation of varying concentration of wollastonite on the mechanical, thermal, and morphological properties of PBT thermoplastic composite for future industrial applications. In the composites wollastonite content was varied by 0–30 % by weight. Tensile strength exhibited a marginal increase whereas a dramatic increase was observed in modulus with an increase in filler content. The experimental results were also compared with theoretical predictions which revealed good level of interfacial interaction in the composites. Thermal analysis revealed an increase in percent crystallinity and also the onset crystallization temperature thereby indicating the nucleating efficiency of wollastonite. Study of the fracture surface by SEM revealed a change in the micromechanical deformation process with an increase in filler content.     

超级双相不锈钢S32760凝固过程Thermo-Calc热力学软件的应用

利用Thermo-Calc热力学计算软件得到S32760(022Cr25Ni7Mo3WCuN)超级双相不锈钢凝固过程中的相图,确定了S32760双相钢是FA (铁素体-奥氏体)凝固模式,通过改变奥氏体和铁素体的形成元素的含量,确定在不同的化学成分下的热加工性能、Cr₂N和σ相析出温度,得到S32760双相钢热加工温度区间随着奥氏体形成元素C、N、Ni、Mn含量的增加而变大,随着铁素体形成元素Si、Cr、Mo含量的增加而减小,而W对热加工性能没有影响。根据热力学计算,确定了最优的化学成分(/%:0.022C,0.30Si,0.80Mn,25.60Cr,6.20Ni,0.54Cu,3.50Mo,0.54W,0.27N),S32760双相钢最佳热塑性温度为1 195℃,Cr₂N相的析出温度为1 050℃,σ相析出温度为1 020℃,热加工区间为145℃,并且通过了后续的现场实践验证。     

Temperature Dependent Deformation Mechanisms of Alloy 718 in Low Cycle Fatigue

Recent developments in the area of water cooled gas turbine design have created a need for low cycle fatigue test data for alloy 718 in the temperature range of 204 to 649 °C. To support this need, data were generated in the room temperature to 649 °C range. As noted by previous investigators, there was a crossover in fatigue lives at low strain depending on temperature. At high strain ranges the lowest fatigue life was exhibited at the higher temperatures. However, in the low strain, long life regime this trend reversed with the fatigue life at a given strain range exhibiting a peak at some intermediate temperature. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) studies were conducted on the fatigue specimens to determine the nature of the cyclic deformation process as a function of strain range and temperature, the principal mode of deformation was by mechanical twinning. However, at the two highest temperatures, the primary process for deformation was slip. The principal difference between the strain-life behavior of the specimens cycled at 538 and 649 °C, and those cycled at the three lower temperatures (204, 316, 427 °C) is interpreted in light of this change in deformation process with temperature.     

Removal of binder from silicon nitride specimens

Conclusions A study was made of the effects of temperature and holding time upon the process of binder removal from silicon nitride specimens prepared by the thermoplastic slip-casting technique. It was established that, to obtain high-quality blanks, treatment should be performed under isothermal conditions at a temperature of 80–100°C, which ensures that a large proportion of the binder used is removed through the liquid phase. In the manufacture of parts calling for close size limits, it is necessary to allow for the appreciable shrinkage exhibited by castings during the binder removal operation.Translated from Poroshkovaya Metallurgiya, No. 7 (151), pp. 99–101, July, 1975.