月桂酸微波反应制备焊条抗吸潮膜研究

利用月桂酸微波反应的方法在焊条药皮表面制备了抗吸潮保护膜.将烘于的焊条放入溶有一定量月桂酸和Fe3O4粉末的石油醚溶液中,取出烘干后进行微波反应,使焊务表面具有抗吸潮性能.用FT-IR、SEM、EDS对所得焊条保护膜的成分和形貌进行了分析,并进行了熔敷金属扩散氢测试.研究结果表明,Fe3O4在吸收微波后能融化月桂酸并使...     

铝-镓合金的生产工艺

氢气是干净的新能源,铝和水反应制取氢的成本低廉.但是,铝和水反应制取氢的过程中,反应生成物Al2O3在铝表面形成致密的保护膜,使反应不能持续进行.镓可以破坏铝表面的保护膜,使铝和水制取氢反应得以持续进行.镓分两次和铝熔体混合,制成铝-镓合金.     

低氢型焊条药皮抗吸潮性研究

从低氢型焊条药皮易吸潮原因出发,提出了提高低氢型焊条药皮抗吸潮能力的解决途径,并用相关试验论证了其使用的可行性.     

屈服强度460MPa级药芯焊丝扩散氢含量研究

扩散氢是导致钢结构产生冷裂纹或脆化的原因之一。本文以屈服强度460 MPa级药芯焊丝为例,研究了造渣剂中易吸潮粉料在高温熔炼后的再吸潮率,以及对应药芯焊丝的扩散氢含量。结果表明,当采用Li F作为助熔剂时,Li F与粉料反应生成Li的硅酸盐,因Li的硅酸盐溶液干燥后形成一种不溶于水的膜,覆盖在易吸潮物质的表面使其不易吸潮;Li2CO3效果不明显,冰晶石虽然可有效降低粉料中的结晶水,但粉料再吸潮率高,对控制药芯焊丝扩散氢含量作用不大。     

熔渣的溶氢能力与熔敷金属的扩散氢

分别改变碱性焊条熔渣中CaO和Mgo与气保护药芯焊丝熔渣中Al2O3和MgO组元的相对含量,研究其对熔敷金属扩散氢的影响.结果表明,碱性焊条熔渣中,用同等质量MgO取代CaO导致熔敷金属扩散氢大幅度提高;药芯焊丝焊接熔渣中,脱氧产物若不是以Al2O3为主而是以MgO为主,熔敷金属扩散氢则大幅度提高.分析认为,熔渣成分的变化导致其溶氢能力的变化是这一结果的主要因素,即Ca2 离子导致熔渣含氧量的提高及氢在Al2O3中具有较高的溶解度等提高了熔渣的溶氢能力.     

表面氧化层对低碳钢氢渗透行为的影响

利用气相氢渗透技术,测定了#10碳钢表面镀Pd和预氧化两种状态(在80-330℃温度范围内)的有效氢渗透率和扩散系数,结果表明:低于150℃,表面氧化层(主要为Fe3O4)对氢在钢中的渗透有明显的阻碍作用,有效氢渗透率降低约1个数量极,扩散系数降低3-4倍,但在180℃,10kPa氢压力的条件F,表面氧化层开始被还原、氢渗透逐步回复到由钢中的体扩散所控制.氢在氧化钢中的渗透速率满足Sievert定律.     

PCrNi3MoVA钢表面溅射NiCrAlY涂层的高温氧化行为

用磁控溅射方法在PCrNi3 MoVA钢表面制备NiCrAlY涂层,涂层在空气中850 ℃恒温氧化100 h,借助XRD、SEM和EDAX对涂层表面氧化膜进行分析,检测其恒温抗氧化能力.结果表明,涂层大大提高了基体的抗氧化性,涂层表面主要生成了与基体粘附性好的Al2O3氧化膜,在柱状晶间隙较大处生成了NiCr2O4氧化膜与Fe2O3氧化膜;同时涂层的Ni元素与基体的Fe元素发生了明显的互扩散,而Cr元素在界面富集,Al元素主要集中在表面和界面,与氧发生反应生成Al2O3.     

不同方法制备Fe-Si合金的高温氧化行为

采用电弧熔炼(CA)和机械合金化(MA)技术制备了晶粒尺寸差别较大的二元单相Fe-Si合金,并研究了其在900～1000 ℃纯O2中的高温氧化行为.结果表明2种方法制备的Fe-1Si和Fe-3Si合金氧化后均形成了Fe2O3→Fe3O4 FeO→FeO→FeO SiO2结构的氧化膜,均未形成连续的SiO2保护膜.机械合金化Fe-Si合金的氧化速度均大于相同温度下同成分的熔炼Fe-Si合金,这是因为细晶材料及其氧化生成的氧化膜中包含了更多的晶界,为合金各元素及氧提供了更多的短路扩散通道,使它们的扩散速度均有明显提高,SiO2富集区(FeO SiO2)的快速形成对Fe的进一步向外扩散起到了一定的阻挡作用,但这对提高合金抗高温氧化性能所起的正影响不及Fe的快速扩散对其造成的负影响.     

Mg_2Cu基储氢合金的表面复相改性

采用机械球磨法制备Mg2Cu合金,并以该合金为基础,添加质量分数为5%的单质(C、Co、Ni、Cu)或氧化物(Cr2O3、Fe3O4、TiO2、V2O5),通过机械球磨对合金进行表面复相改性。采用p—c—T测试仪测定合金的储氢性能,研究添加不同单质和氧化物对Mg2Cu合金储氢性能的影响。结果表明:在200℃和300℃下,添加C或Fe3O4能够有效提高Mg2Cu合金的活性,使其易与氢气反应,并缩短吸氢时间,增大吸氢量,改善放氢效果;在400℃下,添加Co、Ni、TiO2或Fe3O4能够有效缩短吸氢时间,改善合金的综合储氢性能。     

宁波材料所等在新型苛刻海洋环境服役涂层材料研究中获进展

MCrAlY(M=Fe,Co,Ni等)合金具有优异的抗氧化和抗腐蚀性能,作为热障涂层的粘结层材料或单层涂层材料在航空发动机热端部件中得到广泛应用.该类合金优异的抗氧化和抗腐蚀性能主要归因于在宽温域范围内,其表面能够形成一层稳定、致密且连续的氧化物保护膜(以Al2O3和Cr2O3为主).然而,在苛刻海洋环境中,除了潮湿空气的氧化,发动机部件还会遭到高腐蚀性氯盐的侵蚀.前期研究表明,Cr2O3在高温下与NaCl和H2O发生反应,导致连续氧化物保护膜被破坏,从而缩减发动机寿命.因此,亟需为发动机部件开发一种新型高温腐蚀防护涂层,以满足高盐高湿热海洋环境服役需求.     

Effect of oxygen-containing additives on weld penetration in self-shielded flux cored arc welding

The effect of Fe₂O₃ and Li₂CO₃ additives in flux core on the weld metal oxygen content and weld penetration in self-shielded flux cored arc welding were studied schematically. The result shows that the oxygen content in the weld metal and weld penetration both increased with the Fe₂O₃ addition increased in the range of 5wt.% to 20wt.% . The oxygen content in the weld metal was increased with the Li₂CO₃ addition increased in the range of 1wt.% to 8 wt.%. However, the weld penetration decreased when Li₂CO₃ addition exceeding 4 wt.%. High-speed photographic images show that when Fe₂O₃ addition in flux core exceeding 15wt.%, droplet became excessively large, so that spatters were frequently generated in large numbers. In this study, Fe₂O₃ and Li₂CO₃ in the amount of 11wt.% and 4wt.%, respectively, jointly added in the flux core can achieve a deeper weld penetration with sound usability characteristics.     

Leaching of blended copper slag in microwave oven

Leaching of blended slag (BS) was investigated in a microwave oven using hydrogen peroxide and acetic acid. The BS was a mixture of converter and flash furnace slag containing 51% Fe₂O₃, 3.8% CuO, and 3.2% ZnO. The important variables that influence the metal extraction yield were leaching time, liquid-solid ratio, H₂O₂ and CH₃COOH concentrations. The preferred leaching conditions were as follows: CH₃COOH concentration 4 mol/L; H₂O₂ concentration 4 mol/L; microwave power 900 W; leaching time 30 min; liquid-solid ratio 25 mL/g BS; leaching temperature 100 °C. Under these conditions, the metal extractions of 95% Cu, 1.6% Fe, and 30% Zn were obtained. The results were compared with the traditional leaching results. It is evident that microwave heating causes a reduction in the leaching time. Also, the extraction yield results indicate that selective leaching of BS can be achieved under the preferred conditions. The dissolution kinetic of BS in hydrogen peroxide with acetic acid is controlled by a shrinking unreacted core model equation. The apparent activation energy and reaction order were found to be 16.64 kJ/mol and 1.09, respectively.     

煤矿液压支架专用LZ55焊条的研究及应用

本文研究了碱性焊条工艺性的影响因素,探讨了焊缝金属的含氢量、焊条药皮的吸湿性、焊缝金属的强韧化特性等。在此基础上,研制了高韧性、高抗裂性、超低氢及操作工艺性优良的,适用于屈服极限为400～450牛顿级的低合金钢液压支架专用LZ55焊条。该焊条已应用于FDT4×550型液压支架的焊接生产,各项性能完全符合部颁技术条件要求。     

Effect of slag variations on ANSI/AWS A5.1–91 E6013 electrode properties: replacement of TiO2 in electrode coating with MnO,FeO, CaO,MgO, K2O,or Na2O

Abstract

The present work is part of a research programme to study the effect of variation of the coating composition of covered rutile manual electrodes on both operational and deposited weld metal properties. According to previous results obtained for rutile electrodes, an increase of slag basicity, achieved through modifications in the coating, produces an improvement of the impact properties of the deposited weld metal, as well as a decrease in the diffusible hydrogen, along with beneficial changes in the operational properties of the electrode. The aim of the present work is to study the influence of the replacement of titanium oxide with oxides of alkali metals (sodium and potassium), alkaline earth metals (calcium and magnesium), and iron and manganese oxides in the coating of an ANSI/AWS A5.1–91 E6013 type electrode on the operational characteristics of the electrode and the microstructure, mechanical properties, and diffusible hydrogen content of the electrode weld metal. Tensile strength and Charpy V notch impact properties were measured in the all weld metal samples produced using each of the seven electrodes designed for the present study. A cross-section from each coupon was used to determine the chemical composition of the deposit and to carry out a metallographic study using a light microscope. As a result of the addition of different oxides, changes in the operational properties were observed using both direct and alternating current, as well as a decrease in the diffusible hydrogen content in the weld metal. Also, electrodes in which rutile was substituted by sodium oxide in the coating showed an improvement in the impact properties of the deposit.     

Preparation and microwave absorption properties of Ni–B alloy-coated Fe3O4 particles

The Fe₃O₄ particles that were activated with Pd-Sn catalytic nuclei by single-step activation were used as cores for obtaining nickel- and boron-decorated particles with shell/core structure via electroless plating. The materials were characterized by TEM, SEM, EDX, X-ray diffraction, VSM and microwave network analyzer. The results showed that Fe₃O₄ particles coated with Ni–B alloy films had reduced metal deposition in the reaction solution. There was no peak of amorphous alloy Ni–B by XRD but the inverse spinal Fe₃O₄. The calculated results indicate that the Fe₃O₄ densely coated with Ni–B exhibits better absorption performance than the pure Fe₃O₄ in the range of 2–18 GHz, such as more powerful absorbing capability and a wider electromagnetic wave absorbing frequency band.     

CLAM钢焊缝在550℃流动的铅铋合金中的腐蚀行为

为了研究中国低活化马氏体(CLAM)钢TIG焊缝在流动的铅铋共晶合金(LBE)中的腐蚀行为,对CLAM钢TIG焊缝及母材在550 ℃,不同相对流速(1.70,2.31,2.98 m/s)的LBE中进行1 500 h的腐蚀试验. 结果表明,腐蚀试样表面均存在双层结构的氧化层,外氧化层由疏松的Fe₃O₄组成,内氧化层由致密的(Fe, Cr)₃O₄组成;随着LBE相对流速的增加,提高了CLAM基体材料中的Fe,Cr元素向LBE中的溶解速率和LBE中的O元素向CLAM基体材料中的扩散迁移速率,加剧了试样表面的腐蚀程度,最终导致试样表面氧化层的厚度不断增厚;经过相同条件的腐蚀试验后,CLAM钢焊缝试样的抗腐蚀性能比母材试样低.     

稀土氧化钇对高强度钢焊条熔敷金属组织和性能影响

基于Ni-Cr-Mo-V合金体系,研究了稀土氧化钇对800 MPa高强度钢焊条焊缝微观组织和性能的影响.结果表明,Y₂O₃含量在0~0.02%范围内变化时,随着Y₂O₃含量的增加,焊缝熔敷金属组织中先共析铁素体逐渐降低,针状铁素体含量逐渐增加,强度和低温冲击韧性均逐渐增加,且当Y₂O₃含量为0.02%时,焊缝熔敷金属低温冲击韧性达到最大值;当Y₂O₃含量超过0.02%时,焊缝熔敷金属组织中针状铁素体含量下降,低温冲击韧性降低.综合考虑上述因素,该高强度钢焊条中Y₂O₃最佳添加量为0.02%左右.     

A Comparative Study on the Reduction Mechanism of Fe2O3 Under Different Heating Methods

The mechanisms for magnetizing roasting of Fe₂O₃ into Fe₃O₄ under microwave heating and electrical heating have been studied through thermogravimetric analyses, x-ray diffraction (XRD) measurements, and reaction kinetic calculations. In the reduction process, activated carbon was used as a reducing agent and argon as the protective gas. The results of heating tests indicated that the temperature heating speed during microwave heating is 50 times faster than that of electrical heating. The maximum conversion ratio of Fe₂O₃ by microwave heating is 24.5% higher than that by electrical heating. XRD results showed that the required temperature for Fe₂O₃ to completely convert into Fe₃O₄ by microwave heating is 200°C lower than that by electrical heating. Reaction kinetics parameters calculation results showed that the controlling step of microwave magnetizing is a phase boundary reaction of the contracted ball at 250–450°C with an apparent activation energy of 45 kJ/mol, whereas the controlling step of electrical magnetizing is a chemical reaction of stochastic coring at 450–650°C with an apparent activation energy of 225 kJ/mol.     

High Temperature Corrosion and Characterization Studies in Flux Cored Arc Welded 2.25Cr-1Mo Power Plant Steel

Higher productivity is registered with Flux cored arc welding (FCAW) process in many applications. Further, it combines the characteristics of shielded metal arc welding (SMAW), gas metal arc welding (GMAW), and submerged arc welding (SAW) processes. This article describes the experimental work carried out to evaluate and compare corrosion and its inhibition in SA 387 Gr.22 (2.25Cr-1Mo) steel weldments prepared by FCAW process with four different heat inputs exposed to hydrochloric acid medium at 0.1, 0.5, and 1.0 M concentrations. The parent metal, weld metal, and heat-affected zone are chosen as regions of exposure for the study carried out at 100 °C. Electrochemical polarization techniques such as Tafel line extrapolation (Tafel) and linear polarization resistance (LPR) have been used to measure the corrosion current. The role of hexamine and mixed inhibitor (thiourea + hexamine in 0.5 M HCl), each at 100 ppm concentration is studied in these experiments. Microstructural observation, hardness survey, surface characterization, and morphology using scanning electron microscope (SEM) and x-ray diffraction (XRD) have been made on samples to highlight the nature and extent of film formation. The film is found to contain Fe₂Si, FeSi₂, FeMn₃, Fe₇Mo₃, Fe₃O₄, FeO, FeCr, AlO₇Fe₃SiO₃, and KFe₄Mn₇₇Si₁₉.