焊接速度对18-8不锈钢接头组织形态的影响

以18-8不锈钢为研究材料，采用TIG焊方法，仅改变焊接速度来观察接头组织形态的变化。研究发现：在固态相变区中，焊接速度越大，该区残留的δ-铁素体愈多且在晶内按一定方向平行分布。在1150℃以下接近1150℃的热影响区中，仅在晶界出现δ-铁素体，焊接速度越大，该区晶粒越小，晶界δ-铁素体数量愈多。焊接速度对焊缝中δ-铁素体形态有影响，但不太明显。     

M50NiL轴承钢淬回火组织特征及拉压疲劳裂纹的萌生

摘要：通过拉压疲劳试验及微观组织观察研究了M50NiL轴承钢淬回火组织特征及对疲劳裂纹萌生的影响作用。结果表明,试验钢的组织主要为板条马氏体,少量δ-铁素体及M2C、MC碳化物;扫描电镜观察发现1070℃淬回火试样δ-铁素体及临近的聚集球状M2C碳化物,δ-铁素体位于晶界处,尺寸主要为4~8μm,钢中碳化物尺寸最大为2.66μm;1100℃淬回火试样δ-铁素体相界存在大量片状的M2C碳化物,尺寸在8μm以上的δ-铁素体数量增加,最大为17.51μm;1070℃淬回火试样的疲劳极限为713MPa,主要起裂源为Al2O3、Al2O3-CaO夹杂物,循环次数随夹杂物尺寸的增大而降低,且Al2O3-CaO夹杂更易引起试样的疲劳断裂;1100℃淬回火试样的疲劳极限为707MPa,主要起裂源为δ 铁素体组织缺陷,起裂源于8μm以上δ-铁素体的相界处,疲劳寿命受应力及δ-铁素体尺寸影响。     

固溶处理对超低碳奥氏体不锈钢00Cr24Ni13铸坯δ-铁素体转变的影响

研究了1000～1200℃ 1～3 h固溶、淬火或空冷对超低碳奥氏体不锈钢00Cr24Ni13(/%:≤0.02C、23～25Cr、13～14 Ni)200 mm×1 250 mm铸坯8铁素体转变的影响。结果表明,随固溶温度升高和保温时间延长铸坯中δ铁素体量减少;随固溶温度的升高,铸坯中的连续网状δ铁素体断开并且长大,空冷则会促使高温下长大的δ铁素体向小尺寸颗粒状组织转变;当铸坯试样在1 200℃保温3 h空冷后,网状δ铁素体完全转变成弥散分布的小于10μm的颗粒状铁素体组织,δ铁素体相比例也由14.3%降至7.3%。相对于颗粒状铁素体,网状δ铁素体的奥氏体-铁素体两相界面在轧制中更容易产生裂纹。     

化学成分和热处理温度对T122耐热钢中δ-铁素体含量的影响

采用Thermocalc热力学计算研究了化学成分和温度对T122钢中δ-铁素体含量的影响,计算和相应试验结果表明,化学成分和热处理温度变化对δ-铁素体含量影响显著,铬含量降低,氮含量和碳含量增加,能明显降低δ-铁素体含量。在1 030~1 070℃的温区热处理,δ-铁素体含量最低;超过1 200℃热处理会产生γ-Fe→γ-Fe+δ-Fe转变,即在低于1 200℃处理不含δ-铁素体的钢中会生成δ-铁素体。     

2Cr12NiWMoVNb钢的δ-铁素体含量的控制

对于汽轮机叶片用钢来说,δ-铁素体含量的控制是非常重要的.本文针对2Cr12NiWMoVNb钢δ-铁素体含量时常发生超标(＞5%)的情况,分析了δ-铁素体形成的原因,提出了控制该钢δ-铁素体含量具体方法.     

ZG06C13Ni4Mo马氏何不锈铸钢组织对性能的影响

ＺＧ０６Ｃｒ１３Ｎｉ４Ｍｏ马氏何不锈钢水轮机铸件的组织和性能试验分析的结果表明，若出现类似魏氏体组织的δ铁素体时，铸钢件的冲击韧性急剧下降。经正火处理可消除该铸件钢中的δ－铁素体相。     

P92钢中δ-铁素体内Laves相的长大规律

 用透射电镜、扫描电镜对两炉δ-铁素体含量不同的P92钢中的Laves相形貌与尺寸进行了分析与测量。结果表明：在时效状态下,δ-铁素体内也有Laves相析出,其尺寸显著大于马氏体基体中的Laves相;δ-铁素体含量越高,δ-铁素体内的Laves相尺寸与增长速度越大;δ-铁素体含量对马氏体基体中的Laves相尺寸影响不大。     

1Cr12Mo钢δ-铁素体含量的控制

本文介绍了如何控制1Cr12Mo钢的铁素体含量，着重分析了δ-铁素体形成的原因，指出了控制该钢艿一铁素体含量的具体方法。     

2Cr12NiMoVNb钢的δ铁素体含量的控制

对于汽轮机叶片用钢来说，δ铁素体含量的控制是非常重要的。本文针对2Cr12NiMoVNb钢δ铁素体含量在已往的生产中时常发生超标（＞5％）的情况，分析了δ铁素体形成的原因，提出了控制该钢δ铁素体含量具体方法。     

2Cr12NiMWoVNb钢的δ—铁素体含量的控制

对于汽轮机叶片用钢来说，δ－铁素体含量的控制是非常重要的。本文针对2Cr12NiMWoVNb钢δ－铁素体素体含量时常发生超标（＞5％）的情况，分析了δ－铁素体形成的原因，提出了控制该钢δ－铁素体含量具体方法。     

Structure of Widmanstatten crystals of ferrite and cementite

Structural analysis of Widmanstatten crystals in У8, 10, and 5Л carbon steel shows that Widmanstatten ferrite is first deposited at the austenite grain boundaries in cast 50Л steel. The intervals are filled with polyhedral ferrite. The plates of Widmanstatten ferrite and cementite are laminar in structure. The layer thickness is ～10 3 nm or less. Analysis of the fine structure of the Widmanstatten plates confirms that the layers of plate crystals grow by diffusional migration of steps along their broad boundaries. The laminar structure of the crystals of Widmanstatten ferrite and cementite explains their behavior in plastic deformation of the steel.     

镍对Cr-Ni-Si系铸造不锈钢性能的影响

研究了Ｃｒ－Ｎｉ－Ｓｉ系耐浓硝酸铸造不锈钢的化学成分,耐蚀性、冲击韧性。试验结果表明,含７％Ｎｉ的铁素体－奥氏体双相钢,具有良好的冲击韧性和耐腐蚀性能。     

Influence of dendritic crystallization on the structure and properties of continuous-cast pipe blanks

The influence of dendritic crystallization on the structure and properties of continuous-cast pipe blanks (diameter 150 mm) made from steel with 0.2% C is studied, in the cast and heat-treated states. Dendritic crystallization results in different chemical composition of the austenite and the boundary between the crystals, with different properties. That affects the structure of the steel. Besides the familiar factors, the improvement in the mechanical properties of cast subeutectoid steel after heat treatment is associated with the formation of impurity-rich ferrite in segregated sections of the dendritic structure.     

稀土对低合金耐磨铸钢组织和性能的影响

采用扫描电镜分析,硬度测试和摩擦性能测试等手段,研究了稀土对低合金耐磨铸钢组织和性能的影响。结果表明,在低合金耐磨铸钢中添加0.15%稀土,可细化合金铸态组织,增加铸态组织中的铁素体数量,减少珠光体数量,同时可细化热处理后合金的贝氏体组织,使铁素体形态和大小分布均匀,马氏体数量减少。添加稀土后可使铸态合金硬度提高9.4%,摩擦系数由0.136 9减小为0.081 9。     

Thermomechanical processing of microalloyed powder forged steels and a cast vanadium steel

The effects of controlled rolling on transformation behavior of two powder forged (P/F) microalloyed vanadium steels and a cast microalloyed vanadium steel were investigated. Rolling was carried out in the austenitic range below the recrystallization temperature. Equiaxed grain structures were produced in specimens subjected to different reductions and different cooling rates. The ferrite grain size decreased with increasing deformation and cooling rate. Ferrite nucleated on second phase particles, deformation bands, and on elongated prior austenite grain boundaries; consequently a high fractional ferrite refinement was achieved. Deformation raised the ferrite transformation start temperature while the time to transformation from the roll finish temperature decreased. Cooling rates in the cast steel were higher than in P/F steels for all four cooling media used, and the transformation start temperatures of cast steels were lower than that of P/F steel. Intragranular ferrite nucleation, which played a vital role in grain refinement, increased with cooling rate. Fully bainitic microstructures were formed at higher cooling rates in the cast steel. In the P/F steels inclusions and incompletely closed pores served as sites for ferrite nucleation, often forming a ‘secondary’ ferrite. The rolling schedule reduced the size of large pores and particle surface inclusions and removed interconnected porosity in the P/F steels. Formerly Postgraduate Researcher in the Department of Metallurgy and Materials Science, UMIST/University of Manchester, United Kingdom     

Effectiveness of barium-bearing ferroalloys in steel smelting

The influence of barium-bearing ferroalloys on the mechanical properties of cast and deformed steel is studied. Such ferroalloys greatly reduce the metal’s content of gases and nonmetallic inclusions, increase the impact strength of steel for railroad castings, and improve the plasticity of high-strength shipbuilding steel.     

电渣重熔Mn18Cr18N钢铸态热塑性与组织的关系

研究了电渣重熔Ｍｎ１８Ｃｒ１８Ｎ钢的高温热塑性及其与组织的关系。结果表明，Ｍｎ１８Ｃｒ１８Ｎ钢热塑性曲线具有高温脆性区、高温塑性区和二次脆性区。Ｍｎ１８Ｃｒ１８Ｎ钢在高温脆性区塑性变差的原因是由于奥氏体晶界成为位错晶界；在高温塑性区塑性良好是由于奥氏体晶粒发生大量的孪生变形；在二次脆性区塑性变差是由于铸态组织的成分偏析导致晶界局部析出薄膜状铁素体。     

Production and quality investigation of 20GML steel castings for pipeline fittings

The technology of OAO Izhorskie Zavody and OOO OMZ Liteinoe Proizvodstvo of OMZ Corporation for the production of 20GML steel castings is described. Quality analysis of cast pipeline parts is performed.     

72A帘线钢线材冷拔笔尖状断裂分析和改进工艺措施

72A帘线钢线材拉丝笔尖状断裂的推动力,为拉拔时的不均匀变形。心部粗大的先共析铁素体和粗片状渗碳体易形成粗拉时的裂纹源;中心偏析产生的裂纹多出现在中拉工序。控制连铸坯中心碳偏析指数≤1.1,采用相变前≥15℃/s快冷,相变区600～620℃近似等温的控冷策略,获得先共析铁素体含量≤0.8%,索氏体率达90%的均匀组织,基本杜绝了72A线材直拉时笔尖断裂的产生。     

Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification

Unmodified, Na-modified, and Sr-modified castings of Al-7?pct Si and Al-12.5?pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer and the effectiveness of the feeders were greater in the castings made with the steel chills due to the increased thermal gradients and consequent increase in the directionality of solidification.