高锰氮奥氏体不锈钢塑性变形机制及组织-性能的研究

研究了Fe-22Cr-25Mn-2Si-0.7N型奥氏体不锈钢在不同工艺条件下的组织结构及其力学性能.此种奥氏体不锈钢,不仅可节约贵重金属镍,且具有较高的强度和塑性,具有在弱腐蚀环境中代替304等含镍不锈钢的可能性.探讨了两种不同的成型条件下这种奥氏体不锈钢的性能.首先,奥氏体不锈钢经过模铸热轧成4 mm的板材,分别在1323,1373和1473 K下固溶处理30 min后淬火至室温.对其力学性能的检测发现,最佳固溶处理温度为1373 K.在此条件下可以得到较好的强度、塑性及成型性综合性能(屈服强度为580 Mpa,抗拉强度930 Mpa,延伸率为45%,屈强比为0.62).另外,利用双辊铸轧的方法探讨了这种不锈钢的薄带近终型成形工艺,得到了屈服强度为500 Mpa,延伸率为15%的铸态薄带.采用XRD,OM,SEM和TEM对不锈钢的显微组织进行了分析和检测.结果发现,变形孪晶是影响高锰氮不锈钢塑性变形的重要机制.     

固溶处理对冷等静压成形双相不锈钢显微组织和耐腐蚀性能的影响北大核心

将316L和430水雾化不锈钢粉末按照65:35的质量比混合,采用冷等静压-真空烧结工艺制备了双相不锈钢,在1150~1300℃进行固溶处理,每次保温1 h。研究了不同固溶处理温度双相不锈钢显微组织的演变,利用动电位极化和电化学阻抗谱研究了固溶处理温度对双相不锈钢耐腐蚀性能的影响。结果表明:随着固溶处理温度增加,铁素体含量逐渐增加,奥氏体含量逐渐减少,晶粒逐渐长大;1300℃时,铁素体与奥氏体两相比例为39.1:60.9,此时双相不锈钢具有较好的耐腐蚀性能。     

固溶处理对冷等静压成形双相不锈钢显微组织和耐腐蚀性能的影响

将316L和430水雾化不锈钢粉末按照65:35的质量比混合,采用冷等静压-真空烧结工艺制备了双相不锈钢,在1 150～1 300℃进行固溶处理,每次保温1 h。研究了不同固溶处理温度双相不锈钢显微组织的演变,利用动电位极化和电化学阻抗谱研究了固溶处理温度对双相不锈钢耐腐蚀性能的影响。结果表明:随着固溶处理温度增加,铁素体含量逐渐增加,奥氏体含量逐渐减少,晶粒逐渐长大;1 300℃时,铁素体与奥氏体两相比例为39.1:60.9,此时双相不锈钢具有较好的耐腐蚀性能。     

节镍无磁不锈钢Cr18Ni6Mn3N的组织及性能

研究了节镍无磁不锈钢Cr18Ni6Mn3N的热轧及固溶后的力学性能和耐蚀性能,分析了其固溶和时效析出后的组织演变规律、冷变形过程中形变诱发马氏体相变及其磁性能.结果表明:该不锈钢的固溶组织为单相奥氏体,其力学性能和耐蚀性能均高于SUS304不锈钢;800℃保温4 h后,在晶界析出粒状氮化物,随着保温时间延长,逐渐沿晶界凸起片层状析出物并向晶内生长,保温20 h后,凸出的片层状析出物直径达20μm.冷轧压下率18.3%时尚未发现形变诱发马氏体组织,随着变形量增大,马氏体含量增多,磁导率上升,但与相同条件下的SUS304不锈钢相比,冷轧板固溶后相对磁导率可降至1.002,因此可用于低成本无磁不锈钢领域.      

热处理对316L不锈钢组织和性能的影响

通过试验研究了不同热处理工艺对316L不锈钢组织和性能的影响.试验结果表明,1 000℃固溶处理30min的硬度最大(77.8 HRB)、晶粒最细.若提高固溶处理温度,可以改善钢的抗腐蚀性,但温度过高,会降低钢的硬度.与固溶处理相比,由于发生时效硬化,固溶处理后进行时效处理的硬度更高、显微组织更好.     

超(超)临界锅炉用Super304H钢管研究试制

对Super304H的冶炼、冷加工、固溶热处理工艺进行了研究;观察了钢坯和钢管的显微组织.通过在EF和LF炉中深度脱硫,钢中硫的质量分数可达0.005%以下;钢坯中具有极少量的δ铁素体,钢管具有单相奥氏体组织;钢的冷加工硬化与其他18Cr-8Ni型不锈钢相当,冷加工性能优异,可采用类似的冷加工工艺;固溶热处理对钢管晶粒度有明显影响.试制钢管的化学成分及各项室温性能完全符合技术条件要求.     

高强高韧高氮奥氏体不锈钢的热加工工艺

通过调整热变形和热处理工艺参数,对含氮0.52%的Cr-Mn-Mo-N高氮奥氏体不锈钢的组织与力学性能的关系进行了系统研究.研究结果表明,高氮奥氏体不锈钢中析出氮化物对塑性的损害高于残留铁素体的作用,热变形组织对材料的强化作用高于残留铁素体.在1 000～1 050℃温度范围内终轧并水冷至室温的高氮不锈钢的组织为单一奥氏体,且强韧性能优异.通过采用合理的热变形工艺,可以不经后续热处理直接轧制出与固溶态相比,屈服强度、抗拉强度和加工硬化速率更高,屈强比更低且延伸率基本不变的高氮奥氏体不锈钢.     

热处理对26-5型双相不锈钢组织和机械性能的影响

从组织稳定性角度研究了热处理对26-5型铁素体-奥氏体双相不锈钢组织和机械性能的影响。结果指出,不同固溶处理温度对钢中两相比例及作为第二相的奥氏体的形态有显著影响,选择合适的固溶处理制度,对双相不锈钢的性能有决定性意义。固溶处理后,再在较低温度下加热时,由于铁素体相不够稳定而将发生变化,从而在两个温度范围内导致脆化。为了使双相不锈钢具有满意的工程性能,在生产和加工制造过程中,应避免在易产生脆化的温度范围内长时间停留。     

固溶温度对17Cr-1Ni-3Mn-0.12N经济型不锈钢组织及力学性能影响

针对一种新成分体系17Cr经济型不锈钢，通过室温拉伸试验、显微组织观察、X射线衍射等手段，研究了不同固溶温度对17Cr不锈钢显微组织和力学性能的影响，遴选出最佳的热处理温度区间，同时明确了固溶温度对该类型不锈钢奥氏体稳定性的影响。结果表明，17Cr不锈钢在900～1 000℃固溶处理会发生上下屈服，1 200℃固溶处理不发生相变诱导塑性(TRIP)效应，其最佳的固溶处理温度区间为1 050～1 150℃。不同固溶温度处理后试验钢均呈现铁素体、奥氏体和马氏体三相并存的组织；随着固溶温度升高，淬火马氏体相变发生率先降后增，奥氏体的热力学稳定性先升高后下降，同时TRIP效应减弱、抗拉强度降低、断后伸长率提高，奥氏体力学稳定性升高。分析拉伸试样断口可知，试样由马氏体处起裂呈解理断裂，而铁素体在断裂过程中阻碍了裂纹扩展。本研究为经济型双相不锈钢成分及显微组织设计提供了新的思路和理论基础。     

高强度不锈钢板的控轧控冷工艺

同溶退火能有效地使奥氏体不锈钢组织均匀化和提高耐蚀性。然而,固溶处理产品不适宜于结构应用,因为屈服强度低。日本钢管公司福山工厂为使奥氏体不锈钢的显微组织、力学性能和耐蚀性有最佳的结合,研究了控轧控冷工艺     

冷轧变形量对304不锈钢力学性能的影响

 研究304奥氏体不锈钢薄板的硬度随冷轧变形量的变化规律,为奥氏体不锈钢薄板工业生产提供指导。同时,采用金相显微镜、维氏硬度测量、X-射线衍射仪和透射电镜研究了不同变形量冷轧对304不锈钢显微组织和机械性能的影响。在室温对0.5mm厚退火板材进行冷轧,使冷轧变形量从10%增加到52%。结果表明,形变诱发马氏体相变是导致304不锈钢冷轧时产生加工硬化的主要原因,冷轧可以显著提高钢的强度和硬度。当冷轧变形至40%时,304不锈钢的维氏硬度是未变形时的2.2倍,屈服强度、抗拉强度分别增大到未变形时的4.2倍（880MPa）和1.8倍（1312MPa）。     

Effect of Cu on Surface Microcrack of Austenitic Stainless Cold Rolled Coil

In order to find out the cause of surface microcrack on 304 austenitic stainless cold rolled coils which is produced in a steel plant of China, lots of studies have been carried out. The results indicated that the copper guide of steekle mill used in hot rolling process contacts directly with the hot rolled coil, so parts of copper melt and glued to the surface of the stainless steel plates due to a higher temperature of stainless steel plates than the copper melting temperature, which leads to deterioration of austenitic grain boundaries. Shear stress produced in the process of repeat-rolling on finishing mill induces the surface microcracks and promotes it. After changing the copper guide to the cast steel one, such kinds of surface microcracks have never appeared.     

304奥氏体不锈钢带氧化铁皮直接冷轧技术的研究

结合现场生产实际,通过在试验室对奥氏体不锈钢304黑皮卷直接进行压下率分别为10%,20%,30%的冷轧然后退火酸洗的试验,证明在退火酸洗工艺相同的情况下,通过在热轧后进行一定压下率的直接轧制,可以获得与传统No.1产品相比晶粒尺寸等级相同、表面粗糙度更低、力学性能和耐蚀性相近的2E产品,并且获得更大的热轧产品厚度范围,降低冷轧一个轧程后的产品厚度.因此根据不同客户的要求,可以用2E产品替代No.1产品.     

Hot Mechanical Properties of 24Cr‐14Ni High Alloy Billets

24Cr‐14Ni alloys have gained importance in high temperature applications. Because of δ‐ferrite and α phase formation, 24Cr‐14Ni austenitic stainless steel billets are difficult to hot work. The mechanical properties at high temperature of such stainless steels are investigated on a hot tensile test machine according to hot‐rolling conditions, under different time and temperature regimes. These 24Cr‐14Ni stainless steels were also hot rolled under various reduction ratios. The influences of the reduction ratio on the hot mechanical properties and phase transformation from δ‐ferrite into σ phase in 24Cr‐14Ni stainless steels are discussed in detail. The results obtained can be a contribution to improve the hot rolling of this high alloy stainless steel.     

Development and Application of On-Line Solution Annealing Process for 304 Austenitic Stainless Steel

After hot rolling, 304 austenitic stainless steel requires a solution annealing treatment to prevent intergranular corrosion and eliminate work hardening effects. Compared to traditional offline processes, on-line solution annealing offers advantages in terms of cost and time savings. However, both recrystallization behavior and M₂₃C₆ carbide precipitation behavior are significantly influenced by the cooling process after rolling, which poses conflicting requirements. This study investigates the precipitation behavior of M₂₃C₆ carbides and the recrystallization softening behavior during the continuous cooling process of hot-rolled samples. The kinetics equations are derived using the Scheil's additivity rule. The temperature profiles in different regions of the plate are studied using finite element analysis. A practical approach for online solution annealing is proposed and applied in industrial testing.     

TTS443高铬铁素体不锈钢的开发

针对304(Crl8-Ni8型)奥氏体不锈钢和430(Cr17型)铁素体不锈钢的特性,通过试验和分析Cr、Cu、Nb、Ti等合金元素对铁基合金材料性能的影响,开发出一种高铬铁素体不锈钢-TTS443(/%:O.010C、21Cr、0.40Cu、0.25Nb、0.20Ti、O.012N) 。该钢种的耐蚀性能与304奥氏体不锈钢相当,具有良好的成形性与焊接性能,TTS443铁素体不锈钢是304奥氏体不锈钢理想代替材料。     

新型节镍奥氏体不锈钢的成分设计及生产试制

 综合传统AISI300系奥氏体不锈钢和高氮奥氏体不锈钢的优缺点,开发一种新型节镍奥氏体不锈钢。为了研究其最优成分和工业试制工艺,通过Thermo-Calc热力学计算软件设计成分、热轧试生产试验钢和微观测试方法分析试验钢。结果表明,新型节镍奥氏体不锈钢最优的成分范围(质量分数)为N0.2%~0.3%、C小于0.1%、Cr 18%~20%、Mn 8%~10%、Ni 1%~2%,Fe余量。在1 240 ℃等温会析出大量的铁素体,以至于在1 150 ℃开轧时不能消除,出现裂纹,在改进热轧温度后,控制铁素体含量,得到无裂纹热轧卷。     

Advances in the Optimization of Thin Strip Cast Austenitic 304 Stainless Steel

This study is about the latest advances in the optimization of the microstructure and properties of thin strip cast austenitic stainless steel (AISI 304, 1.4301). Concerning the processing steps the relevance of different thin strip casting parameters, in‐line forming operations, and heat treatments for optimizing microstructure and properties have been studied. The microstructures obtained from the different processing strategies were analysed with respect to phase and grain structures including the grain boundary character distributions via EBSD microtexture measurements, the evolution of deformation‐induced martensite, the relationship between delta ferrite and martensite formation in austenite, and the texture evolution during in‐line deformation. It is observed that different process parameters lead to markedly different microstructures and profound differences in strip homogeneity. It is demonstrated that the properties of strip cast and in‐line hot rolled austenitic stainless steels are competitive to those obtained by conventional continuous casting and hot rolling. This means that the thin strip casting technique is not only competitive to conventional routes with respect to the properties of the material but also represents the most environmentally friendly, flexible, energy‐saving, and modern industrial technique to produce stainless steel strips.     

Influence of strain-induced phase transformation on the surface crystallographic texture in cold-rolled-and-aged austenitic stainless steel

Stainless steels (SSs) having a stable and metastable austenitic phase were studied to see the influence of strain-induced phase transformation in the metastable austenitic stainless steel on the evolution of texture during cold rolling and aging. AISI 304L and 316L SS plates were unidirectionally cold rolled up to a 90 pct reduction and aged at different aging temperatures. The strain-induced transformation of austenite to α′-martensite phase and the evolution of texture in both the phases were studied as a function of rolling reduction as well as aging temperature in the metastable 304L austenitic stainless steel. The X-ray diffraction (XRD) technique was employed to quantify the volume fractions and characterize the texture of austenite and martensite phases in the rolled and aged conditions. Results are compared with the texture evolution in the stable austenitic 316L SS.