Effect of stabilizing elements Nb and Ti on the microstructure and properties of low carbon ferritic stainless steel

The effect of stabilizing elements, such as Nb and Ti, on the microstructure and properties of low carbon ferritic stainless steel （FSS） has been investigated. The results of the Thermo-calc simulation have shown that the interstitial elements, such as C and N, may be completely stabilized by the addition of Nb and Ti. With the increase of Nb and Ti contents ,the α ＋ γ two phases gradually transfer to a single α-phase under a high temperature condition ,and the content of the carbide M23 C6 gradually decreases. The microstructure has indicated that the combined addition of Nb and Ti can promote the recrystallization of the band structure and form more uniform equiaxed grains. Also, with the increase of Nb and Ti contents,the elongation, the r-value and the corrosion resistance of cold-rolled and annealed sheets are improved prominently. In comparison with the effect of Ti ,the addition of Nb is more beneficial to the increase of r-value and the corrosion resistance.

Advanced manufacturing technologies of large martensitic stainless steel castings with ultra low carbon and high cleanliness

The key manufacturing technologies associated with composition, microstructure, mechanical properties, casting quality and key process control for large martensitic stainless steel castings are involved in this paper. The achievements fully satisfeid the technical requirements of the large 700 MW stainless steel hydraulic turbine runner for the Three Gorges Hydropower Station, and become the major technical support for the design and manufacture of the largest 700 MW hydraulic turbine generator unit in the world developed through our own efforts. The characteristics of a new high yield to tensile strength (R p0.2/R m ) ratio and high obdurability martensitic stainless steel with ultra low carbon and high cleanliness are also described. Over the next ten years, the large martensitic stainless steel castings and advanced manufacturing technologies will see a huge demand in clean energy industry such as nuclear power, hydraulic power at home and abroad. Therefore, the new high yield o tensile strength (R p0.2/R m ) ratio and high obdurability martensitic stainless steel materials, the fast and flexible manufacturing technologies of large size castings, and new environment friendly sustainable process will face new challenges and opportunities.

Effect of Mn on the microstructure and property of 13Cr stainless steel

Mn is a weak element for austenite formation and its effect on martensitic stainless steel is seldom researched. The microstructure and property of 13Cr martensitic stainless steel with varied Mn content and low carbon content were studied. The research demonstrates that Mn enlarges the austenitic zone at a high temperature and increases the strength and hardness of martensitic stainless steel. Following the addition of Mn,the corrosion resistance property of low carbon 13Cr stainless steel only decreases slightly. The strength and hardness of low carbon 13Cr stainless steel containing Mn is similar to that of high carbon 13Cr stainless steel.

400系列不锈钢的应用及生产浅述

从节约战略资源镍的观点出发介绍了400系列不锈钢目前在国内外的广泛应用及其发展前景,将400系列不锈钢与其他类型的不锈钢进行了比较,并对该钢的生产工艺作一浅述。

400系不锈钢酸洗污泥资源化利用试验研究

针对400系不锈钢酸洗过程生成的污泥悬浊物数量较大的问题,通过压滤机方式将酸洗污泥进行收集,对收集的酸洗污泥进行成分分析,发现混酸污泥的Cr、Fe元素含量接近高碳铬铁的金属含量。将混酸污泥替代高碳铬铁进行了Cr17型不锈钢冶炼试验,冶炼装置使用坩埚容量为2 kg的中频感应熔装置。通过试验发现,混酸污泥可替代高碳铬铁应用于不锈钢的冶炼生产,但工业化生产前应采取措施保证Cr元素的收得率。

降低400系不锈钢中夹杂物级别的优化改进措施

针对400系不锈钢的脱氧特点及夹杂物来源,明确了钙处理和精炼渣系优化两个降低钢中夹杂物的优化改进措施,维持300 m纯钙线喂入量,配以25%左右的萤石,渣系二元碱度由2.3降低至2.1,可以降低400系不锈钢中的B类夹杂物缺陷,B类夹杂物≤0.5级合格率达到95%。

Microstructure and Mechanical Properties of a Dissimilar Friction Stir Weld between Austenitic Stainless Steel and Low Carbon Steel

Dissimilar fusion welding of austenitic stainless steels to carbon steels has some metallurgical and technical problems. It was suggested that the solid-state nature of friction stir welding （FSW） can overcome these problems and produce a sound weld with reliable mechanical properties. In this study, plates of 304 stainless steel and st37 steel were welded together by FSW at tool rotational speed of 600 r/rain and welding speed of 50 ram/rain. In the stir zone （SZ） of 304 stainless steel, the results showed a refined grain structure with some features of metadynamic recrystallization. In the SZ of st37 steel, the hot deformation of material in the austenite region produced small austenite grains. These grains transformed to fine ferrite and pearlite by cooling the material after FSW. The production of fine grains increased the hardness and tensile strength in the SZ of both sides with respect to their base metals （BMs）.

熔模铸造400系列不锈钢铸件表面麻点缺陷探索

400系列不锈钢材质在熔模铸造生产中易发生氧化,导致铸件产生麻点及麻坑缺陷。在制壳过程中加一层石墨砂,使浇注后钢液与型壳接触面形成还原性气氛,可防止麻点麻坑的产生,保证成品率,提高生产效率。

泰钢400系不锈钢冶炼工艺路线优化

泰钢冶炼400系不锈钢原工艺为电炉+TSR二步法冶炼工艺。通过开发铁水罐铁水脱磷、TSR炉全铁水一步法冶炼工艺,以及优化LF和连铸工艺,生产的400系不锈钢板坯的各项质量指标均满足工艺要求,吨钢冶炼成本降低200元以上。

400系列不锈钢渣磁选金属回收试验研究

酒钢主要生产300系列奥氏体不锈钢和400系列铁素体不锈钢,冶炼过程所产生的各种钢渣混合热泼经过一次处理后集中堆存。本文通过对400系列不锈钢渣磁选金属回收试验研究,提高产品回收率,实现有益元素的资源化利用。

不锈钢400系列除尘灰用于小高炉冶炼的经济性评价

将400系列除尘灰用小高炉冶炼含铬铁水供不锈钢使用会显著提高其中Cr的回收价值。本文对不同途径实现单座小高炉配加400系列除尘灰的可行性进行了初步的对比分析,并对400系列除尘灰利用的经济性进行了评估。

邢钢低碳400系铁素体不锈钢AOD控氮工艺实践

在低碳400系不锈钢中,氮能恶化晶间腐蚀、低温冲击韧性、缺口敏感性和焊接等性能。因此,在低耗、高效前提下降低其氮含量成为AOD冶炼中的重要课题。结合生产试验,通过探讨回归分析法在其吹氩脱氮工艺控制中的应用,结合脱氮的热力学计算对AOD生产实践数据的分析,由拟合方程确定的AOD冶炼410S不锈钢和低碳430不锈钢时氮氩切换点为吹氮450 m^3时切换氩气,410S不锈钢正常冶炼时一般吹氩量控制在1550 m^3,低碳430不锈钢AOD吹氩量一般控制在2050 m^3时可以将AOD终点氮含量控制在0.0090%以下,并降低氩气消耗。

邢钢400系低碳易切削不锈钢控碳工艺实践

430F、430FR等低碳易切削不锈钢成品碳含量≤0.035%,由于邢钢采用60 t AOD-LF-CC的低成本生产工艺,其中经常采用造价昂贵的低碳合金和增加末期脱碳时间来保证产品碳合格率,相比同系列的低碳430铁素体不锈钢,吨钢成本升高达100元。通过提高AOD脱碳温度和调整过程碱度,实现出钢[C]≤0.015%。在出钢和精炼工序采用镁钙材质渣线代替镁碳材质渣线的钢包,并调整精炼炉渣氧化性,实现精炼过程平均增碳量≤0.007%。低碳易切削不锈钢整体成品碳含量合格率由76%提高到了≥92%,实现AOD-LF-CC工艺连续生产低碳430系列易切削不锈钢。

温度和应变幅对亚稳奥氏体不锈钢S321低周疲劳行为的影响

在室温和650℃的环境下对S321、S321H不锈钢进行了0.5%、0.7%、0.9%应变幅下的低周疲劳试验,并在室温下对S321和S321H开展了多个寿命点的疲劳加载历史试验,结合X射线衍射定量分析测算形变诱发马氏体的含量。结果表明:形变诱发马氏体的生成会导致奥氏体钢持续循环硬化,室温下合金在初次硬化后继续二次硬化,而在650℃下没有形变诱发马氏体生成,合金在初次硬化后进入循环稳定阶段。循环过程中,碳含量越低,形变诱发马氏体含量越多,合金的循环硬化程度更高。两种温度下,两种材料的疲劳寿命在低应变幅下都相差不大,应变幅越大,两种材料的疲劳寿命相差越大,因此,可以考虑服役条件为低应变幅时使用S321不锈钢代替S321H不锈钢。

大同绕城高速路面改造工程低碳耐久型不锈钢护栏的应用分析

低碳耐久型不锈钢护栏具有节能环保效果优、耐腐蚀性能好、回收利用价值高等优点,可用作战略物资,并且可以有效防止车辆发生交通安全事故。依托大同绕城高速公路路面改造工程,通过对项目工可资料、门架交通量等数据进行分析,并依据相关规范对项目不锈钢护栏进行了布设,后对低碳耐久性不锈钢护栏的应用现状进行了分析,最后对其发展方向进行了总结。

马氏体板条细化机制及其对马氏体钢力学性能的影响

以00Cr11Ni4Mo低碳马氏体不锈钢为研究对象,研究一次正火、循环正火、正火+回火处理对其组织和性能的影响,分析马氏体板条细化对低碳马氏体钢力学性能的影响,并阐明马氏体板条的细化机制。结果表明,采用一次正火温度为900℃的热处理工艺得到的屈服强度、极限抗拉强度、延伸率分别为961 MPa、1093 MPa、20.7%,综合力学性能最佳;随着正火温度的升高,马氏体板条粗化,其极限抗拉强度和屈服强度下降,塑性呈先上升后下降的趋势。循环正火热处理并没有达到提高材料强度的效果,对塑性的改善也有限。正火+回火热处理工艺细化了马氏体板条,但并未提高材料的强度。通过马氏体板条细化来提高材料强度具有一定的局限性,需要综合考虑更多影响材料强塑性的因素。

不同冶炼工艺对J409L低碳氮不锈钢纯净度的影响

通过气体分析仪、X荧光法、金相显微镜、扫描电镜及能谱仪对比分析了一步法(AOD+LF)和二步法(AOD+VOD+LF)工艺冶炼J409L低碳氮不锈钢各工序全氧含量、炉渣组分、夹杂物的控制情况。结果表明:一步法工艺冶炼的J409L在LF精炼过程、连铸中包试样的T[O]均较高;Al脱氧能力明显较强,二步法VOD工序具有更良好的脱氧效果;一步法冶炼炉渣组分的SiO_(2)含量偏高,Ti收得率偏低;不同冶炼工艺生产J409L,连铸中包钢液的夹杂物类型一致,均为Ti氧化物包裹Al-Si氧化物的复合夹杂物。

华龙一号主管道电渣锭成分偏析控制

华龙一号核电主管道采用X2CrNiMo 18.12(控氮)超低碳奥氏体不锈钢制造,该钢种碳含量低,铬、镍含量高且范围窄,尤其是N含量控制难度大,对质量要求苛刻;同时主管道锭型达到百吨级,易产生成分偏析,通过对大型主管道电渣锭成分偏析的分析与研究,阐述了大型单相电渣锭成分均匀性的控制方法,并取得了良好的效果。

低加热速率下ZG06Cr13Ni4Mo低碳马氏体不锈钢回火过程的相变研究

利用热膨胀仪、透射电子显微镜(TEM),X射线能谱仪(EDX),X射线衍射仪(XRD)等对ZG06Cr13Ni4Mo在0.05℃/s低加热速率下回火过程中逆变奥氏体的产生机理进行了研究.结果表明:低加热速率下ZG06Cr13Ni4Mo在A_s—A_f区间回火产生的逆变奥氏体中富集了奥氏体化元素Ni,且不含高密度位错,马氏体向逆变奥氏体的转变是扩散型相变,高于600℃回火得到的逆变奥氏体不稳定,在随后冷却过程中部分发生马氏体转变,一次回火在620℃时能得到最大量的逆变奥氏体;620—660℃一次回火生成的逆变奥氏体在冷却过程中产生大量弥散分布的马氏体,增加了600℃二次回火时逆变奥氏体的形核位置,使二次回火后逆变奥氏体含量显著增加。

氯离子对电站常用金属材料腐蚀行为的影响

介绍了氯离子对电站常用碳钢、低合金钢和不锈钢在电站停用期间腐蚀行为(简称停用腐蚀)影响的研究进展,讨论了氯离子对碳钢、低合金钢和不锈钢的停用腐蚀作用机理和影响因素。结果表明:碳钢、低合金钢和不锈钢的停用腐蚀作用机理不同,碳钢和低合金钢停用腐蚀的主要诱因是凝结水和水中溶解氧存在,不锈钢停用腐蚀的发生主要归因于表面溶液介质中氯离子的浓缩。降低空气湿度、金属表面成膜和隔绝空气是抑制氯离子对金属材料造成停用腐蚀的较好方法。