Influences of Alloying Elements on Oxidation Behavior of Steels and Microstructure of Oxide Scales

In order to figure out the oxidation behavior of steels during heating,five micro-alloyed steels were subjected to continuous and isothermal oxidation using the thermo gravimetric analyzer and the Gleeble-3500thermo-mechanical simulator.The microstructure of oxide scales,especially the thickness fractions of Fe2O3,Fe3O4 and FeO layers,was analyzed using the scanning electron microscope(SEM),electron probe microanalyzer(EPMA)and electron backscattered diffraction(EBSD)techniques.The micro-alloyed steels containing alloying elements(Si,Cr,Ni and Cu)show a higher oxidation resistance compared with the low carbon steel.It is found that alloying elements accumulated at scale/substrate interface during high temperature oxidation.Alloying elements function in two ways in the oxidation of steels:one is enhancing the scale/substrate interface and consequently suppressing the blister of scales;and the other is impeding the outward diffusion of iron cations from substrate to scales,resulting in the decrease of oxidation rate.As the diffusion of iron cations is impeded,the thickness fractions of Fe2O3 and Fe3O4of micro-alloyed steels are more than those of low carbon steels.     

Effect of Alloying Elements on Thermal Wear of Cast Hot-Forging Die Steels

The effect of main alloying elements on thermal wear of cast hot-forging die steels was studied. The wear mechanism was discussed. The results show that alloying elements have significant influences on the thermal wear of cast hot-forging die steels. The wear rates decrease with an increase in chromium content from 3% to 4% and molybdenum content from 2% to 3%, respectively. With further increase of chromium and molybdenum contents, chromium slightly reduces the wear resistance and molybdenum severely deteriorates the wear resistance with high wear rate. Lower vanadium/carbon ratio （1.5-2.5） leads to a lower wear resistance with higher wear rate. With an increase in vanadium/carbon ratio, the wear resistance of the cast steel substantially increases. When vanadium/carbon ratio is 3, the wear rate reaches the lowest value. The predominant mechanism of thermal wear of cast hot-forging die steels are oxidation wear and fatigue delamination. The Fe2O3 and Fe3O4 or lumps of brittle wear debris are formed on the wear surface.     

TRIP钢中合金元素的作用和处理工艺的研究进展

 为了给TRIP钢的试制提供参考,对各种合金元素在TRIP钢中的作用进行了描述,并介绍了热轧和冷轧TRIP钢的处理工艺。认为TRIP钢的研究、生产、应用与双相钢相似,能生产双相钢的生产线即可生产TRIP钢。为生产符合我国国情的TRIP钢,应加强微合金元素钒、钛在TRIP钢中作用的基础研究。     

高Co—Ni二次硬化马氏体钢中合金元素对相变的影响

利用“固体与分子经验电子理论”（ＥＥＴ）分析了高Ｃｏ－Ｎｉ二次硬化马氏体钢中几种主要合金元素在不同状态下的价电子结构，认为Ｃｏ、Ｎｉ在奥氏体中与Ｃ相互作用较强，它们能降低Ｃ的扩散能力，推迟马氏体相变。在马氏体回火过程中，Ｃｏ 和Ｎｉ溶入渗碳体形成的合金渗碳体，在较高的温度下分解，使固溶于基体中的Ｍｏ 与位错充分结合。在渗碳体分解后，Ｍｏ 与Ｃ形成富Ｃ、Ｍｏ的溶质簇，或以Ｍ２Ｃ的形式析出，在基体内弥散分布，形成二次硬化。     

Effect of Alloying Elements（Sb,B） on Recrystallization and Oxidation of Mn-Containing IF Steel

 The effects of minor alloying elements (antimony, boron) on the recrystallization and oxidation of Mn-containing interstitial free (IF) steels were investigated using confocal scanning laser microscope (CSLM) under controlled atmosphere of 95% Ar and 5% H2 (volume percent) at different temperatures. The results indicated that oxidation and recrystallization were primarily controlled by the grain boundaries, which moved due to release of the stored energy or acted as the fast path diffusion of alloying elements. It was found that the addition of antimony suppressed both surface oxidation and internal oxidation, whereas boron addition accelerated surface oxidation but decreased internal oxidation. The reasons caused were that the alloying elements of antimony or boron were known to segregate on the surfaces or grain boundaries to occupy the surface adsorption sites, which were expected to be less catalytic than bare iron on the transportation of alloying elements. The recrystallization was also retarded through adding minor antimony and boron elements. The oxidation kinetics of formation of grain boundary oxides were studied through calculating the areas along grain boundaries, and it was found that the areas parabolically increased with increasing time.     

合金元素对中碳硅锰钼钒钢连续冷却转变及淬透性的影响

本文用顶端淬火法测定了40、40Si₂、40Mn₂、40Mo和40Si₂Mn₂钢的连续冷却转变曲线和淬透性曲线,同时研究了硅锰钼钒钢中不同硅或锰含量对钢的淬透性的影响,通过对试样中心为半马氏体时钢的淬透性乘子的计算,相对定量地说明了硅、锰对钢的淬透性的作用规律。
通过试验表明,硅使铁素体一珠光体的转变温度上升,使连续冷却转变曲线稍向右移,当钢中加入钼或锰后,使钢的转变温度和时间有较大地降低和延缓,尤其是锰钢。当钢中同时存在有硅和锰,则硅、锰的复合作用远比单一的锰或硅要大得多,使连续冷却转变曲线更往右下方移动。单一的合金元素对钢的淬透性影响最大的是锰,其次是钼,而硅的效果最小。但硅加到40Mn钢中,大大地提高了钢的淬透性,其复合作用不是简单地单个元素作用的叠加,而是乘子关系。为了保证40硅锰钼钒钢有足够的淬透性,必须加入大于1.5％的锰,硅保持在1.3％左右,当然还应加入适量的钼。     

合金元素影响高速钢中MC碳化物析出温度的热力学计算

高速钢中初生ＭＣ碳化物从液相中的析出温度是决定初生ＭＣ碳化物尺寸的主要因素。本文采用冶金热力学估算了合金元素Ｓｉ、Ａｌ、Ｗ、Ｍｏ等对初生ＭＣ碳化物析出温度的影响，提出了相应的计算机程序。结果表明，Ｓｉ和Ａｌ提高通用高速钢中ＭＣ碳化物的析出温度，而Ｗ、Ｍｏ等对ＭＣ碳化物析出温度影响不大。理论估算和实验结果相吻合。     

合金元素对ICP-AES分析磷的准确度的影响

研究了高铬镍铜钼合金元素对ICP-AES法分析磷的准确度的影响,优选了适宜的仪器测定参数和分析谱线,研究了基体效应、共存元素间干扰及干扰校正方法。结果表明,方法检出限可达到0.010μg/mL,回收率在97.0%～104.0%之间,相对标准偏差小于10%,方法准确可靠。     

合金元素Cr,Al对Sn-Ag-Cu基无铅钎料高温抗氧化和润湿性的影响

研究了少量合金元素Cr，Al对Sn-3．0Ag-0．5Cu（305）无铅钎料高温抗氧化性的影响。钎料在液态下的表面颜色变化以及热重分析表明，Cr，Al能明显改善305合金钎料的抗氧化性能。通过合金元素Cr，AI的抗氧化机制和X射线衍射分析得出：Al和Cr在钎料表面形成致密氧化膜，形成“阻挡层”，抑制了钎料的氧化。同时也比较了合金元素Cr，Al对305钎料润湿性能的影响，结果表明：单独加Al不利于钎料的铺展，少量的Cr和Al同时加入对钎料的铺展没有太大的影响。实验证实：Cr和Al的共同作用明显提高了Sn-3．0Ag-0．5Cu钎料的高温抗氧化性，同时对钎料的润湿性也没有恶化作用。     

铝对310S耐热钢高温抗氧化性能的影响研究

采用增重法研究了通过WS-4非自耗真空电弧炉制备的w(Al)为2%～10%的310S耐热钢在1 200℃×30h空气中的抗氧化性能.用扫描电镜(SEM)观察了氧化层的表面形貌,X射线衍射仪(XRD)分析了氧化膜层的相组成.研究表明:加人铝后显著提高了310S钢的高温抗氧化性能,且310S钢的高温抗氧化性能随着铝含量的增...     

合金元素对马氏体时效不锈钢Ms温度影响的定量分析

在现有各钢种马氏体转变开始温度 (Ms)经验计算公式的基础上 ,分析了合金元素对钢的Ms的影响 ,经验算提出马氏体时效不锈钢的Ms(℃ ) =5 5 0 - 330C - 35Mn - 1 7Ni - 1 2Cr - 2 1Mo - 1 0Cu - 5W - 1 0Si-0Ti+1 0Co +30Al。用该经验公式得出马氏体时效不锈钢Ms计算值与试验值符合较好 ,误差范围± 2 0℃ ,平均误差 1 1 .2 2℃。     

Effects of Alloying Elements on High-Temperature Oxidation and Sticking Occurring During Hot Rolling of Modified Ferritic STS430J1L Stainless Steels

In the present study, mechanisms of sticking that occurs during hot rolling of modified STS430J1L ferritic stainless steels were investigated by using a pilot-plant-scale rolling machine, and the effects of alloying elements on sticking were analyzed by the high-temperature oxidation behavior. The hot-rolling test results indicated that the Cr oxide layer formed in a heating furnace was broken off and infiltrated the steel, thereby forming Cr oxides on the rolled steel surface. Because the surface region without oxides underwent a reduction in hardness rather than the surface region with oxides, the thickness of the surface oxide layer favorably affected the resistance to sticking. The addition of Zr, Cu, and Ni to the ferritic stainless steels worked in favor of the decreased sticking, but the Si addition negatively affected the resistance to sticking. In the Si-rich steel, Si oxides were continuously formed along the interfacial area between the Cr oxide layer and the base steel, and interrupted the formation and growth of the Cr oxide layer. Because the Si addition played a role in increasing sticking, the reduction in Si content was desirable for preventing sticking.     

Effect of Si Content and Temperature on Oxidation Resistance of Fe-Si Alloys

Hot-rolled Fe-(0.75-2.20)Si(mass%)alloys were oxidized in dry air at 600-1200 ℃.The oxidation process was carried out by thermal gravimetric analysis(TGA).At 600-1150 ℃,oxidation gain curves were approximately parabolic.Electron probe microanalysis(EPMA)was applied to investigate cross-section morphology of oxide layer and element distribution across the layer.At lower temperature of 700℃,the oxide layer consisted of internal oxidation zone(IOZ),inner Si-rich layer(conglomerate of fayalite and magnetite)and outer hematite layer,while at higher temperature of 1200℃,fayalite and wustite were observed in external oxide scale.Liquidus temperature of fayalite was detected by differential scanning calorimetry(DSC).Through comparing the oxidation mass gain and parabolic rate constant of the alloys,it was found that oxidation resistance of Fe-Si alloy was enhanced by increasing Si content below 1150 ℃ while increasing Si content of the alloy resulted in higher oxidation rate above 1150 ℃ owing to the liquid fayalite formation.     

Effect of Water Vapor on O2- Content in Ironmaking Slag

In principle,slag basicity can be expressed as the concentration of free oxygen(O2-) in the slag system.This free oxygen content is equilibrated with different silicate anions in addition to other components in the silicate-based slags.X-ray photon spectroscopy(XPS) and scanning electron microscope equipped with energy dispersive spectrometer(SEM-EDS) were used to investigate the effect of water vapor on the free oxygen content in ironmaking slags.It was found that water in the gas atmosphere plays a significant role in the silicate anion equilibria.Water decreases the amount of free oxygen in the studied slags,with the free oxygen expressed as percentage of the total oxygen decreasing in the order of the following gas mixtures:CO+CO2(44%,pH2 O = 0 k Pa) CO+CO2+H2+H2O(41%,pH2 O = 10.13 k Pa) H2+H2O(37%,pH2 O = 14.19 k Pa).The content of free oxygen ion affects the distribution of elements such as sulfur,phosphorus,and manganese.In addition,it affects the iron oxide content in the slag as well as the interaction between slag and furnace lining.     

Influence of Alloying Elements Corrosion Resistance of Cold on Mechanical Properties and Rolled C-Mn-Si TRIP Steels

 The rust layer plays an important role in the corrosion of steel in chlorinated environments. Salt spray, potentiodynamic polarization curve and tensile test were conducted in laboratory for the specimens after two-stage heat treatment. The influence of the alloying elements on mechanical properties and corrosion resistance of three kinds of steels was investigated by observing the microstructure and the morphologies of rust layer. The results show that the highest value (29%) of total elongation for steel A is obtained. The mechanical property of the specimen for steel C exhibits best strength ductility balance (21384 MPa·%) because of the presence of the multiphase microstructures after a two-stage heat treatment and the addition of the alloying elements. The corrosion products are known to be a complex mixture of Fe3O4, Fe2O3 and α-FeOOH for steel C. The presence of the alloying elements results in the formation of compact and dense rust layers in steel B and C. Passive film protects the substrate of TRIP (transformation induced plasticity) steel containing a complex mix of multiphase. Superior corrosion performance is exhibited for steel C with low alloying contents due to the enrichment of alloying elements within the rust layers.