304不锈钢冷板表面纵向色差产生机理分析

对304不锈钢冷板表面纵向色差产生机理进行试验研究,得出304不锈钢冷轧板表面纵向色差是因为不锈钢冷板表面微观粗糙度有差异,使其反光性产生差异,在视觉效果上形成"色差".     

运用6σ方法提高304不锈钢冷板板型质量

运用六西格玛方法,分析造成304不锈钢冷板板型不稳定的原因,并进行试验设计,针对性地实施改进,改进效果比较理想,达到了提高304不锈钢冷板板型质量的目的。     

烧结温度对粉末冶金304不锈钢组织和性能的影响北大核心

采用真空烧结制备了304奥氏体粉末冶金不锈钢,研究了不同烧结温度对粉末冶金304不锈钢材料显微组织、密度、抗拉强度和耐腐蚀性能的影响。结果表明:随着烧结温度由1210℃升高到1300℃,304不锈钢烧结体组织孔隙数量减少、孔隙尺寸明显减小,当烧结温度提高到1360℃时,烧结体组织中晶粒逐渐长大并粗化,孔隙尺寸增大。随着烧结温度升高,烧结体的密度、硬度、抗拉强度和耐腐蚀性能先增大后减小。最佳烧结温度为1300℃,此时烧结试样具有最大的密度、硬度和抗拉强度,分别为7.23 g/cm^(3)、HRB68.88、344.19 MPa,试样的自腐蚀电流最小,具有最佳的耐腐性能。     

304不锈钢冷轧板表面产生“斑点”缺陷原因试验分析

通过实验室及现场模拟对比试验，采用扫描电镜和金相观察方法分析讨论了304不锈钢冷板表面产生“斑点”缺陷的原因。试验结果表明，表面“斑点”缺陷是由于滴落在钢板上的煤焦油高温氧化的结果。     

底材和退火对纳米/微米晶复合304不锈钢组织和力学性能的影响

通过铝热反应熔化法在铜底材和玻璃底材上制备块体纳米晶/微米晶复合的304不锈钢,研究了不同底材和退火工艺对钢的组织和力学性能的影响。研究发现2种底材上制备的不锈钢均包含纳米晶和微米晶,铜底材和玻璃底材上制备的材料的晶粒尺寸分别为28.8nm和30.0 nm,退火后变为21.4 nm和22.7nm。铜底材上制备的304不锈钢抗拉强度,屈服强度和伸长率分别为521 MPa,279 MPa和8.1%,退火后分别为1 001 MPa,475 MPa和9.3%。玻璃底材上制备的304不锈钢抗拉强度、屈服强度和伸长率分别为358 MPa,221 MPa和7.5%,退火后分别为1 023 MPa,461 MPa和8.6%。表明等温退火能够提高纳米晶/微米晶复合304不锈钢的性能。     

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）。     

304不锈钢冷轧板线鳞缺陷改进实践

针对304不锈钢冷轧板表面发生的线鳞缺陷,采用扫描电子显微镜对缺陷表面及横截面形貌和成分进行分析,并对影响线鳞缺陷的因素进行了探讨。结果表明,304不锈钢线鳞缺陷主要由CaO-SiO_2-Al_2O_3-MgO系夹杂物引起的。通过在AOD还原阶段使用低铝硅铁或适量降低AOD出钢渣碱度,降低了304不锈钢铸坯中夹杂物熔点,对于改善夹杂物的塑性变形能力有利。此外,加快连铸交接炉换包节奏,提高最小中包液位达85%以上,稳定中间包流场;同时增加大包余钢量至5～6 t,避免大包下渣,从源头限制夹杂物,提高钢液洁净度。以上改进措施实施后, 304不锈钢冷轧板线鳞缺陷降级率能稳定控制在0.2%以内。     

304不锈钢线鳞缺陷成因分析及改进措施

针对304不锈钢表面产生的线鳞缺陷,从线鳞夹杂物的形态、开口度的变化等方面分析了不锈钢表面线鳞缺陷的成因。在生产304不锈钢实践中,通过提高塞棒材质耐侵蚀性能、确保LF炉软搅拌和镇静时间、控制中间包吨位等相关措施,稳定304不锈钢浇铸期间塞棒开口度的变化,从而达到有效降低304不锈钢线鳞缺陷的目的。     

晶界工程处理对304不锈钢耐蚀性能和力学性能的影响

通过扫描电子显微镜、电化学工作站、晶间腐蚀试验及万能材料拉伸试验机研究了晶界工程处理对304不锈钢耐腐蚀性能和力学性能的影响。结果显示,经8%冷轧变形及1 100℃退火6 min处理后的304不锈钢,与1 050℃固溶处理30 min的304不锈钢相比,低重合位置点阵(coincidence site lattice,ΣCSL)晶界比例从45.1%增加到77.8%,Σ3晶界比例从42.0%增加到65.5%。并且在迁移的随机晶界上引入了具有低晶界能的特殊晶界片段退火孪晶,降低了大角度晶界网络的连通性,优化了晶界分布,提升了304不锈钢抗晶间腐蚀性能。晶界工程处理对304不锈钢的力学性能影响较小,晶界工程处理后,其抗拉强度和屈服强度小幅度降低,分别降低了20 MPa和13 MPa,伸长率提高了8%。     

C、N元素对304不锈钢冷冲压成形性能的影响

304不锈钢具有良好的冷加工成形性,但其成分中各元素含量的不同将导致该材料冷加工成形性能差异很大。通过拉伸试验、杯突试验及拉深成形试验,研究分析了C、N元素对304不锈钢冷轧薄板拉深、胀形等冷冲压成形性能的影响。研究结果显示,C、N元素的增加有利于提高304不锈钢材料的延伸率、屈服强度、抗拉强度及硬度,并在适当的范围内可提高冷冲压胀形成形性能,但对冷冲压拉深成形性能不利;同时C元素对材料延伸率及冷冲压成形性能的影响比N元素显著。     

Fracture Behavior of Cold Sprayed 304 Stainless Steel Coating During Cold Rolling

 The fracture behavior of cold sprayed 304 stainless steel coating in cold rolling process was studied. The 304 stainless steel coatings were deposited on low carbon steel substrate by cold gas dynamic spray (CGDS) and then cold rolled, respectively. The fracture morphology of the coatings was observed and analyzed, and the crack distributions along the longitudinal rolling direction of the coatings were also investigated and discussed. The results showed that the cohesive strength of the cold sprayed 304 stainless steel coating was too low to be cold rolled. Microcracks were formed in the as-sprayed coatings and ran perpendicularly to the rolling direction. The spacing distance between these cracks decreased with the increase of the cold rolling reduction. In addition, it was also found that the initial crack generated at the surface of the coating and propagated from the surface to the interface along the weakly bonded particles. A theoretical analysis was developed for the coating fracture. It gave a critical minimum cohesive bonding strength of the coating for non-breaking in cold rolling process. The crack propagation manner of the cold rolled coatings was also discussed.     

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.     

Effect of Grain Size on Mechanical Properties of Nickel-Free High Nitrogen Austenitic Stainless Steel

The fine grained structures of nickel-free high nitrogen austenitic stainless steels had been obtained by means of cold rolling and subsequent annealing.The relationship between microstructure and mechanical properties and gain size of nickel-free high nitrogen austenitic stainless steels was examined.High strength and good ductility of the steel were found.In the grain size range,the Hall-Petch dependency for yield stress,tensile strength,and hardness was valid for grain size ranges for the nickel-free high nitrogen austenitic stainless steel.In the present study,the ductility of cold rolled nickel-free high nitrogen austenitic stainless steel decreased with annealing time when the grain size was refined.The fracture surfaces of the tensile specimens in the grain size range were covered with dimples as usually seen in a ductile fracture mode.     

冷轧硅脱氧304不锈钢中氧化物夹杂的演变行为

 为实现固态钢基体内夹杂物在冷轧过程中的控制，将硅脱氧304不锈钢热轧板经多道次冷轧至不同的厚度，利用扫描电子显微镜对试样内夹杂物在冷轧过程中的演变行为进行了研究。结果表明，硅脱氧304不锈钢内夹杂物的类型主要为低熔点SiO2-CaO-MnO-Al2O3，其在热轧板内的形貌为大尺寸长条状。冷轧时，这些长度为2.0～23.0 μm的长条状氧化物夹杂发生断裂，形成多个1.0～3.0 μm小尺寸夹杂物。随着冷轧压下量的增加，断裂后形成的夹杂物尺寸逐渐减小。但当夹杂物尺寸降低至约0.5 μm时，夹杂物不再发生断裂。同时，断裂后形成的小尺寸夹杂物之间的距离与夹杂物的初始尺寸无关，由冷轧板的伸长率决定。     

304不锈钢带材电致塑性轧制

 在自行研制的电致塑性轧机上,对304不锈钢带材进行多道次的冷轧和电致塑性轧制,对比研究不同轧制方式下材料的变形抗力、硬度、抗拉强度及伸长率等性能变化,并对微观组织进行系统分析。结果表明,轧制过程中引入适当的高能脉冲电流,能显著降低材料的变形抗力。各道次电轧后的试样强度低于冷轧试样,伸长率则显著提高,变形能力大大改善。同时,电轧可减少或取消材料加工中的退火工序,提升生产效率。这对寻找一条清洁环保、节能高效的生产工艺道路有十分重要的工程意义。     

Effect of Cyclic Thermal Process on Ultrafine Grain Formation in AISI 304L Austenitic Stainless Steel

As-received hot-rolled commercial grade AISI 304L austenitic stainless steel plates were solution treated at 1060 °C to achieve chemical homogeneity. Microstructural characterization of the solution-treated material revealed polygonal grains of about 85-μm size along with annealing twins. The solution-treated plates were heavily cold rolled to about 90 pct of reduction in thickness. Cold-rolled specimens were then subjected to thermal cycles at various temperatures between 750 °C and 925 °C. X-ray diffraction showed about 24.2 pct of strain-induced martensite formation due to cold rolling of austenitic stainless steel. Strain-induced martensite formed during cold rolling reverted to austenite by the cyclic thermal process. The microstructural study by transmission electron microscope of the material after the cyclic thermal process showed formation of nanostructure or ultrafine grain austenite. The tensile testing of the ultrafine-grained austenitic stainless steel showed a yield strength 4 to 6 times higher in comparison to its coarse-grained counterpart. However, it demonstrated very poor ductility due to inadequate strain hardenability. The poor strain hardenability was correlated with the formation of strain-induced martensite in this steel grade.     

热处理工艺对2%硼304B7不锈钢组织性能的影响

为改善2%硼304B7不锈钢的力学性能,研究分析了含硼304B7不锈钢经不同热处理工艺固溶处理后硼化物的组成、形态、分布及304B7不锈钢力学性能的变化规律。试验结果表明:硼化物由Cr2B和（FeCr）2B两相组成;铸态时硼化物呈网状分布,轧态时硼化物呈块状沿轧制方向带状分布;硼化物的热稳定性较好,经高温固溶处理后硼化物的量变化不大,其中1 150℃保温1 h水冷为304B7不锈钢较合适的热处理制度,处理后析出的硼化物尺寸较小,分布弥散,其整体力学性能相对较好,冲击功达到了 10.4 J,屈服强度达到348 MPa,抗拉强度到达659 MPa。     

冷轧退火板DP钢成材率低原因分析

摘要：以冷轧退火板DP980为研究对象,结合生产过程中的工艺过程参数,利用金相显微镜、电子显微镜、显微硬度计、室温拉伸试验机对热轧卷、冷硬卷、退火卷试样的显微组织、硬度、强度、伸长率等进行了分析。结果表明,热轧卷生产过程中,为了控制带尾抛钢稳定性而降低卷取速度,导致带尾卷取温度较低,力学性能不均,遗传到冷轧工序转变为厚度波动。目前,冷轧各工序通过切头尾的方法,对于此问题进行控制,也就导致了DP钢成材率较低。