HRB500E高强度抗震钢筋冷弯脆断原因分析

某公司生产的HRB500E高强度抗震钢筋在冷弯试验中发生脆断现象。利用直读光谱仪、光学显微镜、扫描电镜、能谱仪等分别对脆断钢筋的化学成分、显微组织、断口形貌及夹杂物成分等进行了检验和分析。结果表明:钢液氧化所产生的大量超长、超宽硅酸盐类夹杂物是导致该HRB500E高强度抗震钢筋冷弯脆断的主要原因。     

核电承压设备用钢SA738Gr．B焊接性能试验研究

本文通过对SA738Gr．B钢焊接冷裂纹敏感性试验、手工焊和埋弧焊焊接试验,分析了钢板焊接冷裂纹敏感性和焊接接头的综合力学性能及显微组织,结果表明武钢SA738Gr．B钢具有优异的焊接性能,能够满足我国极寒地区核电站用钢要求。     

示波冲击试验评价正火12Cr1MoV钢回火脆化敏感性

采用示波冲击试验及断口形貌分析技术，研究了正火１２Ｃｒ１ＭｏＶ钢回火试样的夏比冲击断裂过程及能量消耗，提出了采用裂纹扩展功与萌生功之比做为衡量回火脆化敏感性及一般材料韧脆断裂状态的性能指标，该指标与冲击断口形貌特征有较好的对应关系。文中还对正火１２Ｃｒ１ＭｏＶ钢的回火脆化敏感性进行了评价。     

921A钢的韧脆转变温度研究

采用V型缺口试样，以冲击吸收功、脆性断面率结合断口形貌的变化对921A钢的韧脆转变温度进行了测定与分析。试验表明，921A钢韧脆转变温度为FATT50=-100℃。     

20钢板冷弯成型开裂分析

8mm厚的20钢板在冷弯成型时开裂,呈木纹状断口.经冷弯试验,电镜分析和金相分析发现钢板纵向冷弯完好,横向冷弯开裂,开裂原因为板材中存在带状偏析和硫化锰夹杂所致.     

35CrNi3MoV钢韧脆转变温度测定

通过系列温度冲击试验，采用Ｖ，Ｕ型缺口的试样，以冲击吸收功，纤维断面率结合断口微观形貌的变化对３５ＣｒＮｉ３ＭｏＶ钢的韧脆转变温度进行测定分析，试验表明：３５ＣｒＮｉ３ＭｏＶ钢韧脆转为温度为－６０℃。     

摆动凸轮失效分析

采用化学成分分析、硬度测试和断口分析等方法分析了某载重车辆钢摆动凸轮断裂的原因。结果表明：摆动凸轮断裂是由于回火脆而导致的脆性断裂。     

硫化氢介质条件下换热器管束钢的腐蚀行为

采用腐蚀失重及慢应变速率拉伸试验(SSRT)方法,对20钢和08Cr2AlMo钢在饱和H2S水溶液中的腐蚀行为进行了研究.结果表明,08Cr2AlMo钢在饱和H2S水溶液中的耐腐蚀能力优于20钢,但存在比较明显的点蚀倾向;在饱和H2S水溶液中两种钢都具有硫化氢应力腐蚀开裂(SSCC)敏感性,应力腐蚀开裂大多发生在塑性变形区,应力水平要求比较高,20钢的断口属于韧脆混合型断口,08Cr2AlMo钢断口则属于典型的准解理脆性断口.     

低合金高强钢氢致裂纹敏感性的研究

本文采用三点弯曲试验对低合金高强钢氢致裂纹及氢致脆化的敏感性进行了研究,用脆化度I_COD=(δ_cr-δ_crH)/δ_cr作为氢致脆化的判据。高强钢三点弯曲试样的断口形态受应力强度因子K和氢量H的影响,随着K值增加和氢量减少,断口形态由I G→QC_(HE)→DR过渡。根据本研究工作的试验条件,用声发射(AE)捕捉启裂点和监视裂纹的扩展是可行的。     

核用SA508-4N钢粗晶区再热裂纹敏感性评价

采用等温恒速拉伸方法评价了核用SA508-4N钢焊接粗晶区(CGHAZ)的再热裂纹敏感性。使用激光共聚焦、扫描电镜和透射电镜观测和分析粗晶区和断口处的组织、裂纹以及断口形貌,结果表明：SA508-4N钢的母材为回火马氏体,较高含量的碳和铬影响碳化物的大小和分布状态,粗晶区马氏体的形成不利于抑制再热裂纹的产生。碳化物的析出使晶内和晶界的强度不同,当晶内强度大于晶界强度时形成沿晶脆性断裂;当晶内和晶界强度的差距较小时断裂形式包括穿晶和沿晶断裂。SA508-4N钢粗晶区对再热裂纹不敏感,成分A粗晶区的抗再热裂纹能力比成分B的高。在实际生产中,优选的工艺参数为：成分A、焊接t_8/5为25 s、焊后热处理温度580℃。     

An alternate method for determination of brittleness of ceramics and polymers

As opposed to a pendulum scratching test for the determination of brittleness parameter for ceramics and polymers, this paper proposes an alternate brittleness parameter based on indentation analysis. The important advantages are that (i) no elaborate experiments are needed, and (ii) the proposed brittleness parameter has physical implications. The proposed parameter is as effective as the pendulum test for categorizing the brittleness of ceramics and polymers.     

Brittleness of materials: implications for composites and a relation to impact strength

Brittleness of materials—whether it occurs naturally or with aging—affects significantly performance and manifests itself in various properties. In the past, brittleness was defined qualitatively, but now a definition of brittleness for viscoelastic materials exists, enabling analysis of all types of polymer-based materials. The quantity brittleness, B, has been evaluated for neat thermoplastics, but here composites and metal alloys are also assessed. The physical significance of brittleness is connected to the dimensional stability of materials. The connections of brittleness to tensile elongation and to fatigue are explored while its relationship to surface properties—specifically wear by repetitive scratching—is examined more closely. The economic impact of wear results in monetary loss associated with failure and reduced service life of plastic parts—thus its connection to brittleness finds use across a broad spectrum of industrial applications which utilize plastics for manufacturing, processing, etc. We also demonstrate a correspondence between impact strength (Charpy or Izod) and brittleness of polymers. It is shown that the assumption hardness is equivalent to brittleness is inaccurate; this fact has important implications for interpreting the results of mechanical testing of viscoelastic materials.     

激光重熔处理对渗硼层脆性的影响

利用两种工艺方案对渗硼层进行了激光重熔处理，并通过声发射技术对表层脆性进行了定量测试。结果表明，激光重熔处理在不同程度上降低了渗硼层的脆性，相对脆性最大降低了71．3％。通过改变渗硼层的形貌和组织结构，消除FeB和渗层内的缺陷，改善界面结合强度和适当降低表层硬度从而使硼原子得到重新分布等方式均能降低表层脆性。     

Cr及RE元素对硼化物层脆性的影响

对渗硼工艺形成的硼化物层脆性进行了分析,认识其剥落脆性是影响硼化物层脆性的主要因素,探讨了Ｃｒ及ＲＥ元素对降低硼化物脆性的机理,同时用ＥＥＴ理论对含Ｃｒ硼化物的价电子结构进行了研究。     

Intermediate-temperature brittleness of a ferritic 17Cr stainless steel

A ferritic 17Cr stainless steel was tensilely tested at high temperatures and an intermediatetemperature brittleness, which showed a low reduction of area, was observed. The brittleness occurred near 810 to 970 K. The intermediate-temperature brittleness shifted to higher temperatures at higher tensile strain rates.     

影响氟醚橡胶脆性温度的试验因素

按GB/T 1682-1994规定的方法测定了硫化压力、试样裁切方向对氟醚橡胶脆性温度的影响。结果表明:氟醚橡胶的脆性温度不仅与硫化压力有关,而且与试样的裁切方向有关。一般情况下,氟醚橡胶的脆性温度随着硫化压力的增大而略有上升,其垂直压延方向的脆性温度比平行压延方向的脆性温度要低1～2℃,这说明氟醚橡胶具有压延效应。     

10CrNi4MoV钢回火脆性机制研究

对于采用两种回火冷却速度的试样，进行系列温度夏氏冲击试验，研究了耐压壳体用新型高强度、高韧性、可焊接结构钢１０ＣｒＮｉ４ＭｏＶ的回火脆性倾向。结果表明：该钢在缓慢冷却条件下有一定程度的回火脆性。本文还采用扫描电镜、透射电镜对其机制进行了探讨。     

Size-scale transition from ductile to brittle failure: structural response vs. crack growth resistance curve

The concept of brittleness number is revised emphasizing the distinction between a stress-intensification treatment and an energy treatment. In the case of power-law hardening materials the relation between plastic stress-intensity factor and J-integral is translated into a relation between stress brittleness number and energy brittleness number. The structural response generally depends on both such numbers and, therefore, is not physically similar when varying the size-scale of the body. A connection is then established between structural response and crack growth resistance curve, the relevant parameters of a scale-invariant J-resistance curve being related to the energy brittleness number.     

Ein Zerkleinerungskennwert für Betone

Based on quasi-brittle fracture models, a brittleness parameter is derived which characterises the resistance of concrete materials against mechanical fragmentation. Fragmentation tests in a laboratory jaw crusher are performed to verify this parameter. The brittleness parameter includes compressive strength and maximum aggregate size which can both be evaluated easily in practice. Resistance against mechanical fragmentation decreases if values for the brittleness parameter increase.     

Stress Corrosion Cracking and Blue Brittleness of Rotor Steels in High Temperature Aqueous Solutions

The tensile behaviors of two bolt steels 20Cr12NiMoWV and 25Cr2MoV, and rotor steel 30Cr2Ni4MoV used in a nuclear power plant were studied at different temperatures up to 280 degreesC in air and aqueous solution. The results showed that blue brittleness occurred near 230 degreesC and 180 degreesC for steels 30Cr2Ni4MoV and 25Cr2MoV, respectively. No blue brittleness was found for the steel containing higher Cr content. Susceptibility to stress corrosion cracking.(SCC) for the steels in aqueous solution at the test temperatures was very low except at the blue brittleness temperature. At the blue brittleness temperatures, however, the susceptibility to SCC was very high.