高氮无镍奥氏体不锈钢的研究与发展

高氮无镍奥氏体不锈钢比传统镍奥氏体不锈钢具有更优良的力学性能及明显的成本优势,并且避免了镍过敏问题,是金属生物材料的研究热点之一.本文阐述了高氮无镍奥氏体不锈钢的成分设计思路,分析了合金元素和生产工艺对氯溶解度的影响,介绍了氮气加压熔炼法和粉末冶金法两类高氮不锈钢制备技术的原理及特点,讨论了高氯无镍不锈钢的力学性能、耐蚀性能和生物相容性,对国内外高氮无镍奥氏体不锈钢的开发应用现状及存在的问题进行了深入分析,并指明了高氮无镍奥氏体不锈钢的发展趋势.     

高氮低镍奥氏体不锈钢的力学性能及析出相

通过对高氮低镍奥氏体不锈钢(0Cr25Ni2Mn17Mo1NbN)进行1100℃固溶处理,水冷,利用万能拉伸试验机测试其力学性能并和316L奥氏体不锈钢进行对比。将高氮低镍奥氏体不锈钢在不同温度(700、750、800℃)时效2 h,利用光学显微镜和洛氏硬度计,观察不同温度下时效2 h试验钢的析出状况和试验钢的硬度,利用扫描电镜、透射电镜来观察和分析试验钢800℃析出物的形貌及种类。试验结果表明,高氮低镍奥氏体不锈钢在1100℃固溶处理后有良好的力学性能,高氮低镍奥氏体不锈钢在800℃大量析出相为σ相,其次是Cr2N,伴有少量Cr23C6析出,还有微量Nb(C,N)析出。析出相形态有胞状、短棒状和片状布满整个基体。试验钢时效后的硬度值要比时效前(固溶态)的硬度值高,且试样随时效温度升高其硬度值呈现上升趋势。     

专利信息

正·CN108465791A[中文]发明名称——一种低镍高氮奥氏体不锈钢连铸结晶器保护渣摘要本发明涉及一种低镍高氮奥氏体不锈钢连铸结晶器保护渣,属于金属冶炼辅料技术领域。按重量份数计,低镍高氮奥氏体不锈钢连铸结晶器保护渣中化学成分包括33.538.25重量份的CaO、25.429.6重量份的SiO2、36重量份     

生物友好不锈钢的生产及在手表产品上的应用

探讨了加入氮替代不锈钢中的镍生产生物友好的无镍高氮奥氏体不锈钢。研究了无镍高氮奥氏体不锈钢手表外观件的坯件成型工艺,通过优化工艺,缩小了无镍高氮奥氏体不锈钢与传统手表用奥氏体不锈钢的成型工艺差异,生产出了生物友好不锈钢(bio-steel)手表。     

低镍和无镍奥氏体不锈钢的研究现状及进展

低镍和无镍奥氏体不锈钢以锰、氮等元素取代Cr-Ni不锈钢中的镍元素而具有较低的成本、优异的综合性能.综述了以锰代镍的Cr-Mn不锈钢,低镍Cr-Mn-Ni-N不锈钢,高氮无镍的Cr-Mn-N不锈钢及其在生物医用领域的研究和应用进展,并对低镍和无镍奥氏体不锈钢的发展进行了展望.     

氮含量对无镍含钼奥氏体不锈钢相变的影响

以Cr18 Mn14 Mo3无镍含钼不锈钢为基本成分,设计并冶炼了电渣重熔锭实测氮含量为0.008％～0.770％的4炉高氮CrMnMo奥氏体不锈钢(氮含量设计范围为0.004％～0.850％),对各试验钢的平衡相转变进行了热力学计算,对试验钢的显微组织形貌进行了观察.结果表明:试验钢的氮含量在0.40％到0.85％区...     

无镍高氮不锈钢表壳的车削工艺及磨损机理探讨

探讨了无镍高氮奥氏体不锈钢的加工特点及其应用于手表表壳的车削加工工艺。通过YG8硬质合金材料刀具对无镍高氮奥氏体不锈钢表壳的干车削试验,以扫描电镜(SEM)观察刀具的磨损形貌,并通过能谱(EDS)分析磨损表面的成分构成,初步推断刀具的磨损机理主要为黏结磨损。最终通过改进刀具几何参数和调整切削参数,提高了YG8材料刀具加工无镍高氮奥氏体不锈钢的效率。     

高温渗氮工艺对高氮无镍不锈钢组织及力学性能的影响

采用高温渗氮在奥氏体/铁素体双相不锈钢表面形成了奥氏体高氮层。试验结果表明,渗氮层氮含量可达1.0%,与原材料相比氮含量增加了2倍。原始双相组织已经转变为奥氏体,渗氮层深度达到2 mm以上。采用合理优化的高温渗氮工艺,可在提高不锈钢强度、硬度的同时,其伸长率、断面收缩率仍然保持较高的水平。高温渗氮工艺制备高氮无镍不锈钢的最佳工艺参数为:加热温度1200℃、氮气压力0.3 MPa、保温时间24 h。     

高能球磨和冷压烧结制备Cr-Mn-Mo-N无镍不锈钢

采用高能球磨结合高温渗氮方法制备了Cr18Mn12Mo3N无镍高氮不锈钢粉末,随后利用冷压烧结工艺获得了无镍高氮奥氏体不锈钢材料。结果表明：制备的高氮复合粉末近球形,具有良好的成形性;Cr18Mn12Mo3N不锈钢的最佳烧结温度为1250℃,相对密度达到97．1％,氮含量为0．79％（质量分数）;经过1150℃固溶处理水冷后能获得完全奥氏体组织,其钝化电位范围宽,点蚀电位高,抗点蚀性能显著优于316L不锈钢。     

日本试验生产高氮不锈钢

提高不锈钢含氮量 ,能够改善钢的耐蚀性和强度 ,使奥氏体相稳定、减少镍用量 ,这样无论在质量和成本方面都可以取得一定的效果。在常压下冶炼高氮不锈钢 ,其氮含量最多增加到与气相平衡的值 (约为0 2 2 %) ,但是在浇注时由于氮在固相中溶解度降低 ,在钢锭中会出现气孔缺陷。为了进一步提高不锈钢含氮量 ,并且消除在铸锭时产生的气孔缺陷 ,日本大同特殊钢公司把现有 5 0ｋｇ常压感应炉改造成加压感应炉(最高压力 0 4ＭＰａ) ,通入氮气进行高氮不锈钢冶炼试验 ,浇注时也采用加压浇注防止气孔缺陷产生。所冶炼的不锈钢牌号为ＳＵＳ30 4、Ｘ30…     

Effects of Post-weld Heat Treatment on Microstructure,Mechanical Properties and the Role of Weld Reinforcement in 2219 Aluminum Alloy TIG-Welded Joints

In as-welded state, each region of 2219 aluminum alloy TIG-welded joint shows diff erent microstructure and microhardness due to the diff erent welding heat cycles and the resulting evolution of second phases. After the post-weld heat treatment, both the amount and the size of the eutectic structure or θ phases decreased. Correspondingly, both the Cu content in α-Al matrix and the microhardness increased to a similar level in each region of the joint, and the tensile strength of the entire joint was greatly improved. Post-weld heat treatment played the role of solid solution strengthening and aging strengthening. After the post-weld heat treatment, the weld performance became similar to other regions, but weld reinforcements lost their reinforcing eff ect on the weld and their existence was more of an adverse eff ect. The joint without weld reinforcements after the post-weld heat treatment had the optimal tensile properties, and the specimens randomly crack in the weld zone.     

The First Phase of the SRIF Industrialized Base in ＂West Area＂ Has Been Put into Operation

After nearly two years＇ tense construction, the first phase of industrialized base of Shenyang Research Institute of Foundry （SRIF）, located at the Tiexi Casting and Forging Industrial Park in the west of Tiexi District, has now been completed and formally put into operation.     

Thermodynamics Study on the Decomposition of Chromite with KOH

Institute of Process Engineering, Chinese Academy of Sciences, China, has proposed a method for oxidative leaching of chromite with potassium hydroxide. Understanding the mechanism of chromite decomposition, especially in the potassium hydroxide fusion, is important for the optimization of the operating parameters of the oxidative leaching process. A traditional thermodynamic method is proposed and the thermal decomposition and the reaction decomposition during the oxidative leaching of chromite with KOH and oxygen is discussed, which suggests that chromite is mainly destroyed by reactions with KOH and oxygen. Meanwhile, equilibrium of the main reactions of the above process was calculated at different temperatures and oxygen partial pressures. The stable zones of productions, namely, K2CrO4 and Fe2O3, increase with the decrease of temperature, which indicates that higher temperature is not beneficial to thermodynamic reactions. In addition, a comparison of the general alkali methods is carried out, and it is concluded that the KOH leaching process is thermodynamically superior to the conventional chromate production process.     

Influence of Heat Treatment on Damping Behaviour of the Magnesium Wrought Alloy AZ61

The effect of isochronal heat treatments for 1h on variation of damping, hardness and microstructural change of the magnesium wrought alloy AZ61 was investigated. Damping and hardness behaviour could be attributed to the evolution of precipitation process. The influence of precipitation on damping behaviour was explained in the framework of the dislocation string model of Granato and Lücke.     

Effect of Rare Earth Doping on Impedance,Modulus and Conductivity Properties of Multiferroic Composites:0.5(BiLa_xFe_(1-x)O_3)–0.5(PbTiO_3)

The Lanthanum-doped bismuth ferrite–lead titanate compositions of 0.5(Bi LaxFe1-xO3)–0.5(Pb Ti O3)(x = 0.05,0.10,0.15,0.20)(BLxF1-x-PT) were prepared by mixed oxide method.Structural characterization was performed by X-ray diffraction and shows a tetragonal structure at room temperature.The lattice parameter c/a ratio decreases with increasing of La(x = 0.05–0.20) concentration of the composites.The effect of charge carrier/ion hopping mechanism,conductivity,relaxation process and impedance parameters was studied using an impedance analyzer in a wide frequency range(102–106Hz) at different temperatures.The nature of Nyquist plot confirms the presence of bulk effects only,and non-Debye type of relaxation processes occurs in the composites.The electrical modulus exhibits an important role of the hopping mechanism in the electrical transport process of the materials.The ac conductivity and dc conductivity of the materials were studied,and the activation energy found to be 0.81,0.77,0.76 and 0.74 e V for all compositions of x = 0.05–0.20 at different temperatures(200–300 °C).     

Using Finite Element and Contour Method to Evaluate Residual Stress in Thick Ti-6Al-4V Alloy Welded by Electron Beam Welding

This work was to reveal the residual stress profile in electron beam welded Ti-6Al-4V alloy plates(50 mm thick) by using finite element and contour measurement methods.A three-dimensional finite element model of 50-mmthick titanium component was proposed,in which a column–cone combined heat source model was used to simulate the temperature field and a thermo-elastic–plastic model to analyze residual stress in a weld joint based on ABAQUS software.Considering the uncertainty of welding simulation,the computation was calibrated by experimental data of contour measurement method.Both test and simulated results show that residual stresses on the surface and inside the weld zone are significantly different and present a narrow and large gradient feature in the weld joint.The peak tensile stress exceeds the yield strength of base materials inside weld,which are distinctly different from residual stress of the thin Ti-6Al-4V alloy plates presented in references before.     

Microstructures and Tensile Properties of Ultrafine-Grained Ni–(1–3.5) wt% SiC_(NP) Composites Prepared by a Powder Metallurgy Route

Silicon carbide nanoparticle-reinforced nickel-based composites(Ni–Si CNP),with a Si CNPcontent ranged from1 to 3.5 wt%,were prepared using mechanical alloying and spark plasma sintering.In addition,unreinforced pure nickel samples were also prepared for comparative purposes.To characterize the microstructural properties of both the unreinforced pure nickel and the Ni–Si CNPcomposites transmission electron microscopy(TEM) was used,while their mechanical behavior was investigated using the Vickers pyramid method for hardness measurements and a universal tensile testing machine for tensile tests.TEM results showed an array of dislocation lines decorated in the sintered pure nickel sample,whereas,for the Ni–Si CNPcomposites,the presence of nano-dispersed Si CNPand twinning crystals was observed.These homogeneously distributed Si CNPwere found located either within the matrix,between twins or on grain boundaries.For the Ni–Si CNPcomposites,coerced coarsening of the Si CNPassembly occurred with increasing Si CNPcontent.Furthermore,the grain sizes of the Ni–Si CNPcomposites were much finer than that of the unreinforced pure nickel,which was considered to be due to the composite ball milling process.In all cases,the Ni–Si CNPcomposites showed higher strengths and hardness values than the unreinforced pure nickel,likely due to a combination of dispersion strengthening(Orowan effects) and particle strengthening(Hall–Petch effects).For the Ni–Si CNPcomposites,the strength increased initially and then decreased as a function of Si CNPcontent,whereas their elongation percentages decreased linearly.Compared to all materials tested,the Ni–Si CNPcomposite containing 1.5% Si C was found more superior considering both their strength and plastic properties.     

Directional Growth of Tin Crystals Controlled by Combined Solute Concentration Gradient Field and Static Magnetic Field

A new method was introduced to achieve directional growth of Sn crystals. Microstructures in liquid(Pb)/liquid(Sn) diffusion couples were investigated under various static magnetic fields. Results show that the β-Sn crystals mainly reveal an irregular dendritic morphology without or with a relatively low static magnetic field(B0.3 T). When the magnetic field is increased to 0.5 T, the β-Sn dendrites close to the final stage of growth begin to show some directional character. With a further increase in the magnetic field to a higher level(0.8–5 T), the β-Sn dendrites have an enhanced directional growth character, but the dendrites show a certain deflection. As the magnetic field is increased to 12 T, the directional growth of the β-Sn dendrites in the center of the couple is severely destroyed. The mechanism of the directional growth of the β-Sn crystals and the deflection of the β-Sn crystals with the application of static magnetic field was tentatively discussed.     

Growth Kinetics of Single Inclusion Particle in Molten Melts

On the basis of the single-particle framework, a new theory on inclusion growth in metallurgical melts is developed to study the kinetics of inclusion growth on account of reaction and collision. The studies show that the early growth of inclusion depends on reaction growth and Brawnian motion collision, and where the former is decisive, the late growth depends on turbulence collision and Stokes＇ collision, and where the former is dominant; collision growth is very quick during the smelting process, lessened in the refining process, but nearly negligible in the continuous casting process.     

Theoretical Analysis for the Motion and Temperature of Melt Droplets in Spray Degassing Process

The motion of melt droplets in spray degassing process was analyzed theoretically. The height of the treatment tank in spray degassing process could be determined by the results of theoretical calculation of motion of melt droplets. To know whether the melt droplets would solidify during spraying process, the balance temperature of melt droplets was also theoretically analyzed. Then proof experiments for theoretical results about temperature of melt droplets were carried. In comparison, the experimental results were nearly similar to the calculation results.