蒸汽过热器管断裂失效分析

某奥氏体不锈钢制蒸汽过热器管在加碱煮炉过程中发生断裂。采用力学性能测定、宏微观检验及能谱分析,对该断裂管进行了分析研究。结果表明,蒸汽过热管断裂失效是由碱脆造成的。     

铈和磷对中碳锰钢低温回火脆性的影响

本文采用冲击试验和断口扫描电镜，俄歇谱分析等方法，研究了铈对不同磷含量的中碳锰钢低温回火脆性的影响。结果表明，磷在奥氏体晶界偏聚是导致含磷锰钢产生低温回火脆性的原因，而铈的加入，可减少磷的偏聚程度，增加回火马氏体的冲击值，从而降低中碳锰钢的回火脆性。     

Basic studies leading to the development of an ultrahigh strength,high fracture toughness low-alloy steel

Ultrahigh strength steels have been used increasingly in recent years for critical aircraft and aerospace structural applications. In such applications, though materials performance is of prime consideration, cost and availability makes the low-alloy steels an attractive option. This paper describes the development of an ultrahigh strength NiSiCrCoMo low-alloy steel, supported by significant findings obtained from the basic studies that were aimed at understanding how solute additions influence fracture resistance of iron, with and without the presence of carbon. The results of the basic studies, in combination with the work of Garrison (1986) on a NiSiCr steel, have profitably been employed in the development of a NiSiCrCoMo low-alloy steel possessing a strength-toughness combination quite comparable to the highly alloyed 250-grade maraging steel. Reproducibility of attractive strength and toughness properties has been established in tonnage scale melts. This steel, in the softened condition, has good formability and machinability. Weld parameters have also been established. The NiSiCrCoMo low-alloy steel thus meets the requirements of performance and cost rendering it an attractive option for advanced structural applications.     

食品机械的防腐蚀措施

介绍了食品机械的腐蚀机理及其防止措施。     

800MPa级低碳贝氏体高强钢板拉伸断口分层机理

针对800 MPa级低碳贝氏体高强钢板拉伸测试时出现断口分层问题,使用扫描电镜对断口分层面进行了观察,并结合力学性能测试结果分析。研究表明,钢板中Ti和Nb偏析,大面积聚合析出,严重破坏了钢基体沿厚度方向的整体性,造成厚度方向塑性较差,成为拉伸断口出现分层的先天性因素,通过修改成分设计、降低钢水浇铸过热度和拉速以及提高铸坯出钢温度,改善中心偏析,再配合560～580℃回火,可有效改善钢板拉伸断口形貌,保证足够的强度和断后伸长率。     

Effect of residual hydrogen content on the tensile properties and crack propagation behavior of a type 316 stainless steel

The tensile properties and crack propagation rate in a type 316 austenitic stainless steel prepared by vacuum induction melting method with different residual hydrogen contents (1.1–11.5 × 10⁻⁶) were systematically investigated in this research work. The room temperature tensile properties were measured under both regular tensile (12 mm/min) and slow tensile (0.01 mm/min) conditions, and the fracture properties of the tensile fractures with both rates were analyzed. It shows that the hydrogen induced plasticity loss of stainless steel strongly depends on the tensile rate. Under regular tensile condition, there is no plastic loss even when the hydrogen content is up to 11.5 × 10⁻⁶ while in the slow tensile condition, the plastic loss can be clearly identified rising with the increasing H contents. The fatigue crack propagation rate was tested at room temperature, and the crack growth rate formula (Paris) of the 316 stainless steels with varied H contents were obtained. The fatigue crack propagation rate test shows that the crack growth rate of the 316 stainless steel with 8.0–11.5 × 10⁻⁶ hydrogen is significantly higher than that of benchmark steel.     

Effect of pre-strain on hydrogen embrittlement of metastable austenitic stainless steel under different hydrogen conditions

The effects of internal hydrogen and environmental hydrogen on the hydrogen embrittlement of 304 austenitic stainless steels (ASSs) with varying degrees of pre-strain were investigated by a tensile test under cathodic hydrogen-charged, gaseous hydrogen and hydrogen-charged and gaseous hydrogen combined conditions. The internal hydrogen embrittlement of the 304 ASSs increased with increasing pre-strain, while the hydrogen embrittlement caused by the environment hydrogen increased and then decreased with increasing pre-strain. The hydrogen embrittlement mechanisms caused by the internal hydrogen or environmental hydrogen were different. The cracks caused by internal hydrogen or environmental hydrogen are mainly initiated in grain interior or at grain boundary, respectively. Under the coupling condition of internal hydrogen and environmental hydrogen, the hydrogen embrittlement of 304 ASSs was the strongest and increased with increasing pre-strain. Environmental hydrogen was dominant for low levels of pre-deformed specimens. Internal hydrogen was dominant for high levels of pre-deformed specimen.     

7A09CT73铝合金挤压型材热处理工艺研究

系统地讨论了7A09CT73铝合金挤压型材的热处理工艺,特别是二阶段时效工艺对7A09CT73型材组织性能的影响,初步确定了7A09CT73型材热处理工艺、组织、性能三者的关系。     

SA675Gr70锅筒吊杆制造工艺方法

SA193-B16材质锅筒吊杆的弯曲加工方法是正火兼热弯,再进行淬火加回火处理.     

Hydrogen entry into Fe and high strength steels under simulated atmospheric corrosion

Electrochemical hydrogen permeation tests of Fe sheets under two cyclic corrosion test (CCT) conditions were performed to understand hydrogen entry behavior under atmospheric corrosions. Hydrogen entry into 1300 MPa-class high strength steels under two CCT conditions was also investigated using thermal desorption analysis. One CCT consisted of salt spray, dry and wet stages (Salt Spray CCT; SSCCT), and the other consisted of dry and wet stages after NaCl deposition (Dry–Wet CCT; DWCCT). The corrosion rates of Fe and the steels were almost constant under SSCCT and they decreased under DWCCT with time. Nevertheless, both CCTs resulted in increases in hydrogen permeation current and diffusible hydrogen content with time indicating enhancement of hydrogen entry. Corrosion current monitored by means of an atmospheric corrosion monitoring sensor consisting of Fe anode and Ag cathode decreased obviously under dry stage of the CCTs, whereas hydrogen permeation was high at the beginning of the dry stage. The discrepancy between hydrogen entry and corrosion rate indicates that the hydrogen entry is not directly controlled by corrosion rate. Increase in acidity of underlying rust layer with growth of rust layer monitored using a W/WO₃ electrode is considered to be one of the factors affecting the hydrogen entry efficiency.