抗晶间腐蚀奥氏体不锈钢的晶界工程

Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels can not be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment, etc. Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such a~ coincidence-site-lattice (CSL) boundaries have strong resistance to intergranular corrosion. The concept of grain boundary design and control has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of CSL boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion. A thermomechanical treatment was tried to improve the resistance to the sensitization by GBE. A type 304 austenitic stainless steel was cold-rolled and solution-heat-treated, and then sensitization-heat-treated. The grain boundary character distribution was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction The frequency of CSL boundaries indicated a maximum at the small reduction. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material. A high density of annealing twins were observed in the thermomechanical-treated specimen. The results suggdst that the therrmomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface. The effects of carbon content and other minor elements on optimization in grain boundary character distribution (GBCD) and thermomechanical parameters were also examined during GBE.     

高铬铁素体不锈钢2Cr25N挤压管脆性问题探讨

针对2Cr25N挤压管脆性问题,在实验室进行了不同热处理制度的力学性能和金相实验,并从理论上分析了此批挤压管出现脆性现象的原因,得出了因管材高温水淬后析出马氏体使挤压管产生脆性的结论。     

Cold deformation and heat treatment influence on the microstructures and corrosion behavior of AISI 304 stainless steel

Abstract

In the present study AISI 304 stainless steel with different degrees of cold deformation and annealing parameters were investigated. Microstructural evolutions by optical micrography and scanning electron microscopy showed relatively fully austenitic ultrafine-grained structure obtained after annealing at 700°C for 80 min. The volume fraction of α′-martensite increased with increasing compressive deformation rate and maximum volume fraction of α′-martensite was attained in the samples subjected 0?65% strain. The potentiodynamic polarization results in 3% NaCl indicated that the corrosion current density increased with cold deformation, while after annealing, it reduced from 2?86 to 2?29 μA cm^?2, showing an enhancement of corrosion resistance. The immersion test showed that the austenitic ultrafine-grained structure exhibits moderate and more uniform pitting corrosion attack compared to the coarser grain in NaCl solution.

Dans cette étude, on a examiné un acier inoxydable AISI 304 ayant différents taux de déformation à froid et différents paramètres de recuit. L’analyse de l’évolution de la microstructure par micrographie optique et par microscopie électronique à balayage a montré une structure à grains ultrafins et presque complètement austénitique obtenue après un recuit à 700°C pendant 80 minutes. La fraction volumique de martensite α′ augmentait avec l’augmentation du taux de déformation en compression et la fraction volumique maximale de martensite α′ était atteinte par les échantillons soumis à une déformation de 0·65%. Les résultats de polarisation potentiocinétique dans 3% de NaCl indiquaient que la densité du courant de corrosion augmentait avec la déformation à froid, alors qu’après le recuit, elle était réduite de 2·86 μA/cm² à 2·29 μA/cm², montrant ainsi une augmentation de la résistance à la corrosion. L’épreuve d’immersion dans la solution de NaCl a montré que la structure austénitique à grains ultrafins exhibait une attaque par corrosion localisée modérée et plus uniforme comparée au grain plus grossier.     

超低碳不锈钢HR-1挤压管试制工艺研讨

超低碳奥氏体不锈钢00Cr17Ni14M02（HR-1）具有较高的附加值,钢管公司挤压车间首次试制HR-1小规格厚壁管,通过挤压＋冷拔两次试制的研究,最终生产出了符合标准的HR-1挤压无缝管,并为今后生产同类小规格厚壁管积累了宝贵的生产经验。     

TP347H大规格厚壁管工艺优化探讨

TP347HФ63mm×13mm大规格厚壁管市场需求量较大,在保证成品管材质量的前提下提高成材率是我公司提高边际利润的有效办法。本文探讨在LG90轧机新增Ф110/Ф 63mm孔型,一道次轧制大规格厚壁管材可行性。在实际生产中一道次出成品不仅提高了生产效率、降低了生产步骤费用、同时也大大的提高TP347H的成材率。     

不同机械加工设备对奥氏体不锈钢变形层厚度的影响

应用剪板机、立式铣床、卧式铣床、双端面铣床、金相砂轮切割机5种机械加工设备对7种不同厚度规格的奥氏体不锈钢进行铣削,并对加工后的试样分别做了金相、硬度试验研究、分析。结果表明金相砂轮切割机对不锈钢组织性能影响最小,剪板机切割的试样组织发生了转变,切削时加工硬化最为严重。     

不锈钢Ⅲ型试样的氢致开裂和应力腐蚀

研究了奥氏体不锈钢Ⅲ型试样的氢致开裂和应力腐蚀。结果表明,动态充氢时Ⅲ型试样也能发生氢致滞后断裂,且裂纹沿原缺口平面形核和扩展。从而可获得宏观平滑的扭转断口,但断口上存在少量沿45°面的二次裂纹,一系列实验表明动态充氢能促进奥氏体不锈钢室温蠕变,故在恒扭矩下充氢能使扭转角不断增大,直至试样被扭断。奥氏体不锈钢Ⅲ型试样在42%沸腾MgCl₂溶液中也能发生应力腐蚀开裂,且裂纹在与缺口平面成45°的平面上形核和扩展。实验表明,无论是Ⅰ型还是Ⅲ型,应力腐蚀的门槛值均比氢致滞后断裂门槛值要低,例如K_ⅠSCC/K_ⅠX=0.18,K₍ⅠH/K_ⅠX=0.58,K_ⅢSCC/K_ⅢX=0.13 K_ⅢH/K_ⅢX=0.62。     

06Cr17Mn6Ni4Cu2N低镍奥氏体不锈钢热变性行为研究

通过对06Cr17Mn6Ni4Cu2N低镍奥氏体不锈钢热变性行为研究：在一定的变形温度和变形程度下,流变应力随着应变速率的增加而增加;在一定的应变速率下,随着变形温度的升高,流变应力逐渐下降;热加工图呈现出两个峰值区域和三个失稳区域。     

Effects of ternary elements on the ductility of TiAl

TiAl alloys have great potential for applications at high temperature due to their excellent material properties. However, the low ductility at the room-temperature restricted its application greatly. It is very important to find approaches of improving the ductility of the material. In this study, effects of ternary elements (Zr, Hf, V, Nb, Ta, Cr, Mo, W, Cu and Zn) on the ductility of TiAl were investigated by first-principle calculations. Results revealed that the addition of the atoms of Zr, Hf, Cu and Zn could improve the ductility of TiAl by changing the lattice parameter, the electronic structure, and the elastic constants of TiAl. The calculation results can be used as a reference for selecting alloying elements for ductility improvement of TiAl alloys.     

439铁素体不锈钢的研制

439是在430不锈钢基础上降低C＋N含量,添加Nb、Ti等稳定化元素发展起来的新型不锈钢材料,已逐步代替304不锈钢应用于电梯面板等行业。为开发满足用户使用要求的439不锈钢,试验室研究了成分、热处理制度对439不锈钢性能的影响,结果表明：Ti、Nb稳定化元素的添加对改善439不锈钢综合性能比较有利、热轧439退火再冷轧可明显改进深冲性能。生产试制结果表明,宝钢生产的439冷轧产品完全能满足用户对材料的性能要求。     

铜对奥氏体抗菌不锈钢性能的影响

 研究了不同铜含量的奥氏体抗菌不锈钢的抗菌性能、腐蚀性能和力学性能。样品经过热轧、抗菌热处理、冷轧、退火处理后,进行了抗菌试验、腐蚀试验等。试验结果表明,随着铜含量的增加,抗菌性逐渐提高;其耐点蚀性随着铜含量的增加呈提高的趋势;强度随着铜含量的增加先减后增,塑性先增后减。     

不锈钢控氮理论计算与实践

采用不同的氮在钢中的溶解度公式,计算了两种含氮不锈钢冶炼时所需要的氮气压力,并在50kg真空感应炉上,通过改变氮气压力,对两种不锈钢进行了氮含量控制实践。结果表明,采用Fujio测定值的理论计算值与试验实测值吻合度较高,同时给出了钢中氮含量的理论计算公式。     

铁素体不锈钢的开发研究

本文介绍了铁素体不锈钢的主要缺陷以及为克服这些不足所进行的研究,根据这些研究和冶炼工艺的进步,确定了超纯铁素体不锈钢发展的必然性.     

粉末冶金马氏体不锈钢材料的研制

在对含碳1%的Cr14MoMnSi马氏体不锈钢材料的粉末冶金工艺研究中,分析烧结温度对密度和硬度的影响。结果表明:该材料有比粉末冶金440C马氏体不锈钢更为宽范的烧结温度;有很高的烧结密度和淬火硬度。该材料合适的粉末冶金工艺为:成形密度5.8～6.0g/cm3;真空烧结温度1235～1255℃,保温时间2h;淬火温度1050℃,冷却介质氮气。烧结态相对密度可达98.6%;淬火硬度54～58HRC。     

Textural changes during recovery annealing of a heavily cold-rolled Fe–Mn–Al–Si–C alloy

A heavily cold-rolled (80%) high manganese austenitic steel was subjected to isochronal and isothermal heat treatments, in order to study the texture development during the recovery stage. Progress of recovery was negligible after annealing at 500°C for 60?min, but annealing for 60?min at 800°C led to complete recrystallisation, and appearance of the final texture was very similar to that of a copper type deformation texture. Isothermal heat treatments at 600°C revealed that at the very early stage of recovery, there was a weakening of brass type deformation texture, but it was followed by a sharpening of Bs component. At the same time, there was a shift of peak intensity towards Bs/Goss location. After this stage of intermediate sharpening, the texture sharpness experienced a continuous weakening with further progress of recovery.     

The Nitrogen Solubility in Molten Stainless Steel

Nitrogen solubility in the austenitic stainless steel melts was measured in the laboratory by bubbling nitrogen gas under different partial pressures of nitrogen and temperatures. A new thermodynamic model for the calculation of nitrogen solubility in molten stainless steel in a wide range of alloy concentrations, temperatures, and pressures has been successfully established by introducing a new term for the effect of pressure on the nitrogen activity coefficient. The calculation results were in good agreement with the measured values. The influences of temperature, nitrogen partial pressure and chemical composition on the nitrogen solubility in molten stainless steel are discussed based on the calculated results. It is possible to produce high nitrogen steels at normal pressure by optimizing the design of the alloy composition and controlling the lowest melting temperature from a thermodynamic point of view.     

原材料对不锈钢市场的影响

介绍了我国镍金属的生产和消费情况,世界镍金属的价格变化,我国不锈钢材的市场价格以及太钢不锈钢的赢利水平。