Effect of Heat Treatment on Prior Grain Size and Mechanical Property of a Maraging Stainless Steel

Effect of the heat treatment, including solution treatment (ST) and aging treatment (AT), on the prior austenite grain (PAG) size, microstructure and mechanical properties of a precipitation hardening maraging stainless steel was investigated. The results indicate that the relations between PAG size and yield strength (σy) under both ST and AT conditions obey the Hall-Petch relationship. Furthermore, after ST at 1050℃for 1 h cryogenic treated (CT) at -70℃ for 8 h AT at 535℃ for 4 h, the tested steel showed its ultimate tensile strength (σb) and σy over 1900 MPa and 1750 MPa, respectively.     

Effect of Aging Time and Temperature on Mechanical Properties and Microstructural Evolution of 2205 Ferritic-Austenitic Stainless Steel

Duplex stainless steels(DSS)with ferritic–austenitic microstructures offer good combination of resistance to pitting corrosion and high strength that are not concomitantly attainable using conventional single phase austenitic or ferritic stainless steels.The DSS used in this investigation was 2205 alloy having a stable mi-crostructure consisting of about 45%ferrite and 55%austenite at ambient temperature.In order to investigate aging behavior of this steel and the influences on mechanical properties,differe...     

热处理对SLM 18Ni300马氏体时效钢力学性能的影响

为探究热处理对激光选区熔化（Selective Laser Melting,SLM）成形18Ni300马氏体时效钢力学性能的影响,利用激光选区熔化技术制备18Ni300马氏体时效钢试样,分别对成形试样进行时效处理、固溶处理和固溶+时效处理。通过金相显微镜、扫描电镜、硬度计和拉伸试验机,分别测试分析了不同热处理SLM 18Ni300马氏体时效钢的微观组织、显微硬度和拉伸性能。固溶+时效处理后,SLM 18Ni300马氏体时效钢激光熔池消失;组织为均匀致密的板条马氏体,且均有细小析出物弥散分布于晶界和板条间;抗拉强度和硬度显著提高,但延伸率明显下降。此外,固溶+时效处理后材料的强塑积可以得到改善。     

Relief of Residual Stresses in 800 MPa Grade High Strength Steel Weldments by Explosion Treatment and its Effect on Mechanical Properties

The explosion treatment technique has been used in the relief of residual stresses in 800 MPa grade high strength steel manual welded joints. The residual stresses on surface and through thickness of the weldment were measured for both as-welded and explosion-treated sample, the mechanical properties of welded joints under different conditions were also tested. The effect of explosion treatment on the fracture toughness of materials with a residual defect was investigated by crack opening displacement （COD） test. The results show that explosion treatment can reduce not only the surface residual stress but also the residual stress through thickness in the welded joints. The effect of explosion treatment on the mechanical properties and a residual defect in welded joint were inconspicuous.     

中温热处理对铁素体不锈钢显微组织和抗拉强度的影响

研究了中温热处理对2种高碳铁素体不锈钢430和Cr21显微组织和抗拉强度的影响,热处理温度分别为700℃、800℃、900℃.对于430来说,通过中温热处理可以使马氏体脆性降低,其中700℃处理后其抗拉强度最高.而Cr21可以通过中温热处理控制其碳化物的析出来改变其力学性能.在800℃处理后其抗拉强度达到最大值.通过对冲击断口的扫描电镜分析发现,中温热处理不仅提高了430不锈钢的抗拉强度,而且其韧性也有一定提高.对于Cr21来说,虽然热处理提高了其抗拉强度,但是断口仍具有一定的脆性特征.     

高强度奥氏体不锈钢的发展

工程应用对奥氏体不锈钢的强度、韧性、低磁性和耐蚀性的要求不断提高。本文综述了高强度奥氏体不锈钢(RP0.2≥400MPa)的发展趋势,以及几种高强度奥氏体钢的化学成分和力学性能。     

T250马氏体时效钢的显微结构变化对性能的影响

多种手段的显微结构研究显示,T250马氏体时效钢在时效过程受到晶粒尺寸的影响。时效析出细小的弥散相起到沉淀强化作用,同时产生的逆转奥氏体以膜片状分布在晶界和亚晶界起到明显的软化作用,这些组织结构特征是材料的强韧性和晶粒尺寸关系不明显的原因。     

敏化处理对2205双相不锈钢组织与力学性能的影响

采用金相显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)方法及力学性能测试等研究手段,研究了敏化处理对2205双相不锈钢显微组织及力学性能的影响.结果表明:850℃敏化处理.在α/γ和α/α相界析出σ,X相,并且随着敏化时间的延长,析出相含量增加;敏化处理后材料的强度有所提高,塑性明显降低,拉伸微观断口以解理平面...     

合金元素对马氏体时效强化不锈钢耐腐蚀性能的影响

对4种不同成分的马氏体时效不锈钢进行96h中性盐雾试验,观测其锈蚀形貌。结果表明,Mo能有效地抑制氯离子的点腐蚀倾向,提高钢的抗晶间腐蚀能力;过高的Ti含量严重恶化合金钢的耐腐蚀性能;Cu的加入显著提高了合金钢的耐盐雾腐蚀能力。因此,从耐腐蚀性的角度考虑合金钢的成分进一步优化应适当降低Ti的含量,增加Mo和Cu的含量。     

时效温度对00Cr12Ni10MoTi马氏体时效不锈钢组织与性能的影响

使用X射线衍射(XRD)、扫描电镜(SEM)、电子背散射衍射(EBSD)、透射电镜(TEM)和拉伸和冲击实验等手段,研究了时效温度对00Cr12Ni10MoTi马氏体时效不锈钢的组织和力学性能的影响。结果表明：随着时效温度的升高,实验钢的强度逐渐提高,析出强化效应明显增强。在500℃时效后基体中析出大量棒状Ni₃Ti,实验钢的强度达到峰值。随着时效温度的升高,实验钢的室温和低温冲击韧性衰减,在400℃时效后低温(-196℃)冲击功出现最低值51 J。时效温度升高到500℃后,实验钢的冲击韧性回升,因为马氏体基体中生成的逆转变奥氏体抑制了裂纹萌生并缓解其扩展。在500℃时效产生了Ni₃Ti析出强化效应和逆变奥氏体韧化效应,使实验钢具有良好的强韧性匹配。     

390MPa级Ti+Nb超低碳高强度BH钢组织性能研究

对Ti+Nb+B复合处理超低碳高强度BH钢的热轧、冷轧和连续退火进行实验。结果表明:试制的超低碳高强度BH钢退火板的屈强比为0.536,烘烤硬化值为44MPa,具有较为优良的成形性能和烘烤硬化性能,抗拉强度为394MPa,达到了390MPa级超低碳高强度BH钢板的强度要求。物理化学相分析表明:添加在超低碳高强度BH钢中的B除了析出了2mg/kg的BN,大部分的B在钢中以间隙固溶的形式存在,对超低碳高强度BH钢基体起到了固溶强化的作用。     

固溶温度对OOCr26Ni8Mo3Ti不锈钢组织和力学性能的影响

对ＯＯＣｒ２６Ｎｉ８Ｍｏ３Ｔｉ不锈钢在不同固溶处理状态下的组织结构和力学性能进行了研究，试验结果表明，当固溶温度９５０～１０００℃时，由于组织有害σ相（ＴＣＰ）的存在，使其力学性能呈现出典型的σ相脆性特征，而固溶温度为１０５０℃时，合金的组织为Ｆ相（ｂｃｃ）＋Ａ相（ｆｃｃ），σ相消失，所以合金具有强度高，塑性，韧性好等优良的综合力学性能，当因溶温度分别为１１００℃和１１５０℃时，合金几乎为单相Ｆ组     

马氏体时效钢带状组织产生的原因及消除方法

马氏体时效钢具有超高强度和良好的综合性能。但是,该合金在锻造成形过程中存在大量带状组织,这种组织严重影响了材料的使用性能,如使材料各向异性,塑性降低,冲击韧性及断面收缩率下降等。本文重点探讨了带状组织产生的内因,并通过热处理工艺试验探索了消除带状组织的方法,试验研究表明,合金经过1050℃×2h＋820℃×1h热处理后,材料的带状组织基本碎化或消除,组织和成分细小均匀,有效地改善了材料的力学性能。     

Effects of Nitrogen Concentration on Microstructure and Antibacterial Property of Copper-Bearing Austenite Stainless Steels

Austenite antibacterial stainless steels have been found to have wide applications in hospitals and food industries. In recent years epsilon copper precipitation in antibacterial stainless steels has obtained much research interest due to its antibacterial action. The objective of this study was to determine the effects of nitrogen concentration on the precipitation of epsilon copper and antibacterial property. Two kinds of austenite antibacterial stainless steels containing copper and different nitrogen concentration （0.02 and 0.08 wt pct, respectively） were prepared and the microstructures were characterized by a combination of electron microscopy and thermodynamic analysis. A mathematical expression was deduced to predict the effect of nitrogen concentration on the activity coefficient of copper, In（fCu/f^0cu）=0.53524＋4.11xN-0.48x^2N. Higher nitrogen was found to increase the free energy difference of copper concentration distribution between precipitation phase and austenite matrix, stimulate the aggregation of copper atoms from austenite, increase the precipitation amount and consequently enhance the antibacterial property of steel.     

热轧钒微合金TRIP钢的微观组织和力学性能

对一种钒微合金TRIP钢进行了热轧试验,并研究其微观组织特征及力学性能.结果表明,将终轧温度控制在Ae3附近,热轧后的钒微合金TRIP钢具有由铁素体,粒状贝氏体和一定量残余奥氏体组成的复相组织.EBSD分析结果表明,其中75%以上的铁素体晶粒尺寸在l-6 μm;绝大多数晶界取向差角度位于29°-60°.当终轧温度为83...     

不锈钢与渗碳钢惯性摩擦焊接头的组织与性能

目的 研究0Cr18Ni12Mo2Ti不锈钢与20CrMnMo渗碳钢的惯性摩擦焊焊接接头的组织与力学性能。方法 通过金相、能谱分析、显微硬度、拉伸试验对焊接接头进行组织与力学性能分析。结果 焊接试样上0Cr18Ni12Mo2Ti不锈钢一侧飞边尺寸比20CrMnMo渗碳钢一侧飞边小;焊接接头熔合区仅为50 μm,熔合线附近元素扩散层很窄,其中0Cr18Ni12Mo2Ti不锈钢仍为奥氏体组织,20CrMnMo钢组织由铁素体与珠光体转变为马氏体与索氏体,20CrMnMo一侧热力影响区组织为细小的片状珠光体与铁素体;焊缝区的显微硬度为358HV,高于2种母材;焊接接头抗拉强度大于590 MPa,断后伸长率大于32%,断裂位置均在0Cr18Ni12Mo2Ti不锈钢母材一侧。结论 采用惯性摩擦焊工艺可实现不锈钢与渗碳钢的高强连接。     

不锈钢激光点焊接头组织和力学性能研究

目的 改善SUS301L–HT不锈钢激光点焊焊接性能。方法 以2 mm SUS301L–HT不锈钢为母材进行激光点焊试验,并分析焊接接头的金相组织、硬度、拉伸性能以及断口形貌等。结果 焊点表面无损坏、压痕均匀、无较大焊接变形,表面无飞溅、母材颜色无明显变化。焊核区的微观组织主要是柱状晶,柱状晶依附于未熔化母材晶粒向焊核中心生长。母材硬度最高,约为309HV;焊核中心附近区域硬度适中,约为255HV,热影响区硬度最小,不到220HV。点焊接头断裂形式多为纽扣式断裂且发生在热影响区。结论 不锈钢激光点焊整体质量较好,可用于轨道列车车体加工。     

铜在高强度合金钢及焊缝金属中的作用

评述了铜对高强度低合金钢及焊缝性能的影响 ,详细阐述了铜在钢中的溶解特性和沉淀强化机理。并对今后的研究工作提出了建议     

高强马氏体不锈钢板材厚度方向组织与性能

采用金相显微镜、扫描电镜及能谱仪显微分析和力学性能测试等方法研究了高强马氏体不锈钢板的析出相－铁素体的形貌、成分及其板厚方向性能与横向性能的差别。结果表明，０Ｃｒ１６Ｎｉ５Ｍｏ钢在轧板之后形成的沿轧制方向的铁素体层严重影响板厚方向的塑性，但通过适当的热处理可以改变这种层状铁素体结构，进而大幅度改善板厚方向的塑性。     

Effect of Strain Rate,Adiabatic Heating and Phase Transformation Phenomena on the Mechanical Behaviour of Stainless Steel

Abstract: The influence of strain rate on the stress–strain behaviour of an AISI 304 austenitic stainless steel sample was investigated. For this purpose, uniaxial tensile tests were performed at room temperature for different strain rates. Microstructural measurements of transformed martensitic phase as a function of plastic strain, and thermal analyses of the specimens were carried out as well. It was found that increasing the strain rate from 10^?4 to 10^?1 s^?1 leads to a 25% improvement in uniform elongation. Moreover, a ‘curve‐crossing’ phenomenon was observed for the hardening behaviour measured at different strain rates. These results were rationalized in terms of martensitic phase transformation suppressed by a temperature increase in the specimens deformed with high strain rates.