σ相对S32205双相不锈钢力学性能和耐蚀性的影响

通过JMatPro软件模拟计算和试验结合的方式研究了S32205双相不锈钢中σ相的析出行为及对其力学性能和耐蚀性的影响。结果表明：通过JMatPro软件模拟计算得到的S32205双相不锈钢σ相析出鼻尖温度为875℃。当S32205双相不锈钢在875℃保温0～90 min,σ相含量快速增加,当保温时间增加至90～120 min时,σ相含量缓慢上升,而当保温时间为120～240 min时σ相含量达到饱和,最大为6.1%,与模拟计算结果基本符合。随着保温时间逐渐增加,S32205双相不锈钢的屈服强度、抗拉强度及显微硬度先快速增加后逐渐保持稳定,而伸长率呈下降趋势,强度和硬度与σ相体积含量成正比关系,σ相强化机理由Orowan强化机制转变为σ相的高弹性应变能强化机制。不同σ含量的S32205双相不锈钢的电化学试验结果表明随着σ相的含量逐渐增多,基体越容易贫Cr, S32205双相不锈钢越容易产生腐蚀,耐蚀性逐渐降低。     

固溶处理对桥梁用S32205钢显微组织和耐腐蚀性能的影响

对S32205双相不锈钢进行(950~1150)℃×2 h的不同固溶处理,通过显微组织观察、XRD、酸性条件电化学腐蚀、中性盐雾腐蚀等手段和方法,研究了不同温度固溶处理对S32205钢显微组织和耐腐蚀性能的影响。结果表明,经(950~1150)℃×2 h固溶处理的S32205双相不锈钢,随着温度的升高组织中铁素体逐渐增多,奥氏体逐渐减少。1050℃×2 h固溶处理后,S32205双相不锈钢组织晶粒最为细小。经(1000、1050、1100)℃×2 h固溶处理的S32205双相不锈钢中,1050℃×2 h固溶处理的S32205钢试样酸性腐蚀倾向性最小,酸性环境下抗腐蚀性能也明显好于40Cr钢。     

S32205双相不锈钢薄壁焊管生产工艺初探

介绍了等离子弧焊接双相不锈钢S32205薄壁管的试制过程。通过研究显微金相、常温拉伸、点腐蚀和爆破等试验结果,分析了热处理对焊缝组织和性能的影响。提出要严格控制双相不锈钢S32205热处理的温度和时间,否则容易保留过量的铁素体,甚至析出σ或X等脆性相,影响焊接接头性能。     

成分差异对低成本热轧双相钢组织性能的影响

实验室真空感应炉冶炼C-Mn钢、Nb-Ti钢和含Cr钢,轧后采用三段式冷却工艺试制低成本热轧双相钢,分析了成分差异对热轧双相钢组织性能的影响。结果表明,三种成分均可得到铁素体和马氏体双相组织;三者比较而言,C-Mn钢的铁素体含量较高,塑性好,但强度级别低;由于Nb-Ti钢中微合金元素Nb的固溶拖曳作用抑制相变,铁素体含量低,但细晶强化作用提高了钢板的屈服强度,屈强比增加;含Cr钢显微组织中马氏体含量最高,抗拉强度随之增高,屈强比较Nb-Ti钢降低。     

细匀化处理对双相不锈钢组织及性能的影响

以2205双相不锈钢为研究对象,通过微拉伸力学性能测试、金相显微观察、断口扫描分析及浸泡腐蚀与电化学腐蚀等分析,研究其通过过饱和单相处理并经重度冷变形及固溶处理实现双相不锈钢细匀化后的组织特征及其性能变化。结果表明,过饱和单相区工艺可明显细化奥氏体相且使其分布均匀,显著提高两相组织的均质化程度,有助于消除各向异性,并使得抗拉强度增大;不同工艺下材料的抗拉强度值与显微硬度值之间满足一定关系。经6%的FeCl_3溶液浸泡加速腐蚀试验及电化学试验获得的极化曲线结果综合评价,细匀双相组织的耐蚀性较好。     

屈服强度700 MPa级冷轧耐候双相钢的组织与性能

介绍了鞍钢连续退火机组试制屈服强度700 MPa级冷轧耐候双相钢的工艺流程,并对所研究钢板进行了力学性能测试和显微组织分析。结果表明,通过常规喷气冷却连退工艺处理,试验钢的屈服强度达到742 MPa,抗拉强度为952 MPa,断后伸长率为11.5%,屈强比为0.78。试验钢组织由铁素体和马氏体的双相细晶组织构成,铁素体位错密度较高,马氏体呈板条状,其体积分数约为65%,马氏体发生部分分解,回火过程中有一定量的合金渗碳体析出。通过微合金元素Nb和Ti的细晶强化和沉淀强化,提高了试验钢的强度。     

变形温度对超级双相不锈钢S32750性能的影响

超级双相不锈钢高温塑性变形过程中由于铁素体和奥氏体两相变形机制的不同,使得在成型过程中极易产生裂纹从而导致产品报废。本试验根据相关国家标准,通过无损检测、拉伸试验、显微硬度试验并结合显微组织分析对超级双相不锈钢S32750成形工艺中的温度参数进行研究。结果显示:在选定的变形量下,随着温度的升高,铁素体数量显著增加,铁素体相的强化作用将会大于晶粒长大的负面影响,从而使得试样抗拉强度随着温度的升高而逐渐增加,伸长率达到峰值32%后开始降低。因此最佳的高温塑性变形温度为1200℃,并对此钢种的锻造工艺优化提出了相关建议。     

S32760超级双相不锈钢棒材的生产实践

通过合理调整材料内控化学成分,控制合适相比,优化生产工艺,成功生产出S32760超级双相不锈钢棒材,成品以固溶处理状态交货,其各项性能指标满足标准要求。同时按照ASTM G48 A法进行腐蚀对比试验,对比钢种包括S32205、S31803、316L、904L。结果显示,试验温度25℃时,S32760与一般双相不锈钢S32205/S31803腐蚀率相当,但试验温度达50℃时,S32760表现出明显优异的耐腐蚀性能。     

UNS S32205双相不锈钢焊接接头力学性能研究

采用钨极氩弧焊(GTAW)、药芯焊丝电弧焊(FCAW)和电子束焊(EBW)方法制备了UNS S32205双相不锈钢焊接接头,综合运用拉伸试验、热力学计算、SEM、TEM等测试技术与理论分析方法对比研究了焊接微区的组织特征并探索了其对力学性能的影响规律。结果表明,双相不锈钢GTAW、FCAW、EBW以及焊后热处理EBW焊缝和热影响区的强度均高于母材。在Ar保护气中添加2%N2增强了N原子在奥氏体内的固溶强化效果,进而提高了GTAW焊缝强度。FCAW焊缝中引入了大量的夹杂,致使其强度和塑性均低于GTAW焊缝。EBW焊缝中形成了过量的铁素体并析出了大量细小的硬质Cr2N,因此其强度高于母材。     

离子渗氮工艺对S32205双相不锈钢综合性能的影响

在不同温度下对S32205双相不锈钢进行离子渗氮,利用光学显微镜、显微硬度计、电化学测试仪、XRD等对渗氮层组织性能进行分析。结果表明,400℃离子渗氮4 h工艺条件下,渗氮层由γN相构成,自腐蚀电位由基材的-0.294 V升高至-0.271 V,表面硬度可达到966 HV0.01,为基材表面硬度的2.5倍,渗氮层深为8μm,该温度下离子渗氮可同时提高S32205双相不锈钢耐蚀性和表面硬度。随着渗氮温度升高,在450℃和500℃渗氮时虽然渗氮层深和硬度明显提高,然而由于Cr N的析出,耐蚀性均低于基材。     

Friction stir welding of duplex stainless steels

Duplex stainless steels are successful in a variety of applications such as the food industry, petrochemicals and plants for desalination of seawater, where high corrosion resistance and high mechanical strength are required. However, the beneficial microstructure may change during fusion welding steps, and it can compromise the performance of these materials. Friction stir welding is a solid-state process avoiding typical problems concerning solidification such as solidification cracks, liquation and segregation of alloying elements. Superduplex stainless steels can avoid unbalanced proportions of ferrite and austenite, formation of secondary deleterious phases and grain growth of ferrite in the heat-affected zone. Consolidated friction stir welded joints with full penetration 6 mm thick were obtained for UNS S32101 and S32205 duplex and S32750 and S32760 superduplex stainless steels. The friction stir welds were submitted to tensile tests indicating an improvement of strength in welded joints, showing increased yield and tensile strength for all studied cases. Regarding the microstructural characterization, an outstanding grain refinement was observed in the welded joint, achieving grain sizes as small as 1 μm. This refinement was associated with the combination of microstructural restoration mechanisms in the dual-phase microstructure promoted by severe deformation associated with a high temperature during the welding process.     

Experimental Investigation on Friction Welding of UNS S32205 Duplex Stainless Steel

UNS S 32205 duplex stainless steel specimens were joined by continuous drive friction welding process. The experiments were conducted as per the Taguchi（L16 orthogonal array） method. The friction welding process parameters such as heating pressure, heating time, upsetting pressure, upsetting time, and speed of rotation were fixed with low,medium, and high levels of range based on the machine capacity, and the required knowledge was acquired from the preliminary experiments. The joint characterization studies included micro structural examination and evaluation of mechanical properties of the joints. Microhardness variation, impact toughness, and tensile strength of the joints were evaluated. Neither a crack nor an incomplete bonding zone was observed. The tensile strength of the joints was higher than the strength of the base material, and the friction and upsetting pressures were found to influence the joint strength. The tensile strength of all the welds was observed to be increasing with an increase in the rotational speed. The toughness of the friction welds was evaluated at room temperature and also at subzero（cryo） temperature conditions. The toughness for friction welds was found to be superior to the fusion welds of duplex stainless steel at room temperature and cryo conditions. Weldments exhibited better corrosion resistance than the parent material.     

特种金属及合金中厚板在线酸洗技术探讨

酸洗过程是钛和钛合金中厚板高质量制造瓶颈工序;双相不锈钢中厚板难以在线酸洗,为国内外难题。在卧式连续喷淋酸洗机组上,以TA2钛、304不锈钢、S32205双相不锈钢中厚板为代表,提出、论述4元素(H、N、O、F)组成的硝酸和氢氟酸,两段式混酸(HNO₃+HF)液酸洗技术,它包括:两段式混酸(HNO₃+HF)液酸洗技术构思;两段式混酸(HNO₃+HF)液质量浓度数值范围;两段式混酸(HNO₃+HF)液物质的量表。应用该技术,实现了TA2钛、304不锈钢、S32205双相不锈钢等宽产品范围特种金属及合金中厚板在线酸洗。酸洗后表面呈银白色、色泽均匀,满足了标准和用户关于表面质量的要求。     

Cu对S32205双相不锈钢管生产的影响

通过对S32205双相不锈钢穿孔开裂样品分析,确定了在相同的穿孔工艺条件下,铁素体含量越少,穿孔开裂比例越大,应用归纳的方法,确认了S32205的热加工性能与残余元素Cu元素有关。随着Cu含量的增加,σ相的析出温度保持不变,Cr2N析出温度增加,另外其最佳热塑性点40%A温度也在增加,最佳热塑性区间(40%A-Cr2N相析出)的范围在Cu含量超过0.2%后明显减小。因此,控制S32205双相不锈钢中残余元素Cu的含量,确保其含量在0.2%的范围内,可以得到最优的热加工性能。     

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 奥氏体-铁素体双相不锈钢S32205在国内外企业中基本上采用酸耗高、效率低的槽式酸洗方法进行酸洗。通过对S32205氧化层中所含的合金元素以及氧化物结构进行分析研究，结合现场对比试验，改进了各工序操作要点并调整酸洗参数，开发了一种在线连续酸洗S32205的工艺。该工艺酸洗的钢板不但酸耗低、效率高，而且表面色泽均匀，符合用户要求。     

固溶处理对节镍型2101双相不锈钢组织及力学性能的影响

采用光学显微镜、透射电镜和X射线衍射等研究了固溶处理对2101节镍型双相不锈钢连铸坯边部试样的组织、相比例和力学性能的影响。结果表明:在1050~1150℃固溶处理时,双相不锈钢具有很好的高温塑性;在1000~1150℃温度范围,随着温度的升高,实验钢的断面收缩率和铁素体相比例先减小后增加;随着固溶温度增加,实验钢的抗拉强度逐渐降低,但在1050℃时有所增加,这是由于在此温度固溶过程中,铸态试样相界处Cr2N析出相完全溶解,使得大量的N原子集中在相界处,促进了相界附近的铁素体相发生相变,转变成奥氏体相,导致在此1050℃时实验钢铁素体相的比例减小,断面收缩率减小,抗拉强度增加。     

低碳锰钢强韧化机制的研究

在实验室对低碳锰钢进行了控轧控冷试验.利用光学显微镜和透射电子显微镜等测试手段,对试验结果进行了研究.结果表明,具有铁素体和贝氏体复相组织的低碳锰钢具有较高的强度和良好的韧性.贝氏体相变强化对低碳锰钢屈服强度的贡献可达30%,贝氏体铁素体板条的细化和铁素体亚晶的存在可以降低碳锰钢的脆性转变温度.具有铁素体和贝氏体复相组织的低碳锰钢除了固溶强化之外,主要强化机制为细晶强化和贝氏体相变强化.     

固溶温度对2507双相不锈钢力学性能及耐蚀性的影响

利用光学显微镜、扫描电镜、XRD、拉伸试验机和电化学综合测试仪等研究了不同固溶温度对2507超级双相不锈钢组织、力学性能和耐蚀性的影响。采用Thermo-Calc热力学软件计算了2507双相不锈钢的热力学平衡相图,并与测试结果进行了对比。研究结果表明,经1050 ℃及以上温度固溶后,σ相溶解;随着固溶温度的升高,铁素体相含量增加,奥氏体相含量降低,α/γ相体积分数比增加;1050~1100 ℃固溶30 min并水冷时,双相不锈钢具有较好的综合力学性能,屈服强度、抗拉强度和伸长率分别大于600 MPa、840 MPa和35%。1050 ℃固溶30 min时,双相钢可获得较好的耐蚀性能。     

Localized corrosion of lean duplex stainless steels in H2S-containing wet atmosphere from urban wastewater treatment units

With lower alloying costs and higher mechanical properties, lean duplex stainless steels can be a good alternative to the more commonly used austenitic stainless steels. A study was initiated to define the limits of the use of lean duplex stainless steels for urban wastewater treatment (WWT) units. This paper gives and discusses the corrosion results in an aerated wet atmosphere containing H₂S at different levels. Exposures were performed both at laboratory scale and in the field WWT plant for 1 year. A specific probe was also designed to study the corrosion process below water condensate film contaminated with H₂S. Under such conditions, the properties of stainless steel were strongly modified with an enhanced risk of localized corrosion. The results obtained on lean duplex materials (UNS S32101, S32202, and S32304) are compared with austenitic UNS S30403 and UNS S31603 and with the more standard duplexes UNS S82441 and UNS S32205. The results show that lean duplexes can be used in aerated wet atmospheres in case of moderate contamination of H₂S (<10 ppm) and chloride (<200 ppm). For higher contaminations (e.g., H₂S around 100 ppm/chloride around 1000 ppm) the duplex S32205 should be preferred.     

冷却速度对C-Si-Mn系热轧双相钢组织性能的影响

通过实际的热轧实验,研究了轧后冷却速度对C-Si-Mn系热轧双相钢组织形貌和力学性能的影响。研究发现,轧后冷却速度对热轧双相钢的显微组织和力学性能有很大的影响。热轧双相钢具有三种典型的组织形貌,而不同的组织形貌通过不同的强化机制赋予热轧双相钢不同的力学性能。通过不同冷却速度下的双相钢热轧实验,可以使热轧双相钢获得良好的力学性能。