Influence of Rare Earth on Property of Low Chromium Semi-Steel

The influence of rare earth( RE) content on mechanical properties and abrasion resistance of low chromium semi-steel was studied by means of metallographic examination,scanning electron microscopic examination and mechanical property test. The experiment results show that RE can improve the comprehensive properties,especially in combination with proper heat treatment. The optimum properties of low chromium semi-steel modified by RE of 0. 25 % could be obtained by normalization at 950 ℃ for 3 h. The main reason is the change in morphology and distribution of eutectic carbide and the precipitation of granular carbides.

Mechanical Property of Low Chromium Semi-Steel Grinding Ball Prepared by Cross Rolling

The preparing method,rolling technology and mechanical properties of low chromium semi-steel grinding ball by cross rolling were studied.The results show that when the low chromium semi-steel bar is forged from55mm to50mm,cross-rolled into grinding ball at 1 000-1 050℃,air cooled and tempered at 550℃for 2h,the best mechanical properties,especially the abrasive resistance under the action of hard abrasive,can be obtained.

Effect of Rare Earth Elements on Thermal Fatigue Property of Low Chromium Semi-Steel

The effect of rare earth elements on eutectic carbide′s morphology of low chromium semi steel in as cast state and after heat treatment was investigated, and accordingly, the thermal fatigue property of this material was studied. The results show that RE can improve the eutectic carbide′s morphology, inhibit the formation and propagation of thermal fatigue cracks, therefore, promote the thermal fatigue property, which is more noticeable in case of the RE modification in combination with heat treatment. The optimal thermal fatigue property can be obtained when treated with 0.2% RE modification as well as normalization at 950 ℃ for 3 h.

Low-Energy Multi-Impact Fracture Resistance of Cross Rolled Low Chromium Cast Semi-Steel Containing Rare Earth Grinding Ball

The low-energy multi-impact fracture resistance of the cross rolled low chromium cast semi-steel containing RE grinding balls was studied. Moreover, its damage mode was analyzed by means of metallographic examination, scanning electron microscopic examination and drop ball test. The results show that it can obtain extractive impact fracture resistance after proper heat treatment. More advantages were obtained for the ball worked in the condition of low-imp ductility act. The main reasons are the function of RE and the change in morphology of eutectic carbide network.

Effect of Rare Earth Element on Formation and Propagation of Thermal Fatigue Crack in Low-Chromium Semi-Steel

The formation and growth of thermal fatigue crack in low-chromium semi-steel were investigated by means of optical microscope and scanning electron microscope, and the function of RE in low-chromium semi-steel was analyzed. The results show that the thermal fatigue cracks are mainly generated at eutectic carbides, and the cracks not only grow and spread but also join each other. RE can improve the eutectic carbide′s morphology, inhibit the generation and propagation of thermal fatigue cracks, and therefore promote the activation energy for the crack′s propagation, which is especially more noticeable in case of the RE modification in combination with heat treatment. The mathematical model of the crack propagation is put forward.

Influence of chromium on the initial corrosion behavior of low alloy steels in the CO_2–O_2–H_2S–SO_2 wet–dry corrosion environment of cargo oil tankers

The influence of Cr on the initial corrosion behavior of low-alloy steels exposed to a CO2–O2–H2S–SO2 wet–dry corrosion environment was investigated using weight-loss measurements, scanning electron microscopy, N2 adsorption tests, X-ray diffraction analysis, and electrochemical impedance spectroscopy. The results show that the corrosion rate increases with increasing Cr content in samples subjected to corrosion for 21 d. However, the rust grain size decreases, its specific surface area increases, and it becomes more compact and denser with increasing Cr content, which indicates the enhanced protectivity of the rust. The results of charge transfer resistance(Rct) calculations indicate that higher Cr contents can accelerate the corrosion during the first 7 d and promote the formation of the enhanced protective inner rust after 14 d; the formed protective inner rust is responsible for the greater corrosion resistance during long-term exposure.

Synthesis of Mesoporous Chromium Aluminophosphate (CrAlPO) via Solid State Reaction at Low Temperature

Mesoporous chromium aluminophosphate （CrAIPO） was successfully synthesized via solid state reaction （SSR） route at low temperature in the presence of a cationic surfactant cetyltrimethyl ammonium bromide （CTAB） and inorganic sources such as A1C13 · 6H20, CrCI3 · 6H20 and NaH2PO4 · 2H20. Characterizations by means of powder X-ray diffraction （XRD）, N2 adsorption- desorption, high resolution transmission electron microscopy （HR-TEM）, scanning electron micrography （SEM）, energy dispersion spectroscopy （EDS）, thermo-gravimetry （TG）, Fourier transform infrared spectroscopy （FT-IR）, and ultraviolet visible light spectroscopy （UV-Vis） were carried out to understand both the pore characteristics and electron transition route of these obtained materials. The experimental results show that the meso-CrA1PO materials with various Cr/A1 molar ratios possess a mesostructure and a specific surface area of 193 to 310 m2/g corresponding to an average pore size of 5.5 to 2.2 rim, respectively. The maxium content of Cr in meso-CrA1PO materials synthesized via SSR route can achieve 16.7wt%, being significantly higher than that of the meso-CrA1PO prepared via a conventional sol-gel route. Meanwhile, the formation mechanism of the meso-CrA1PO was also proposed.

Effect of Cooling Rate on Structure and Properties of Wear-Resistant Low Chromium Cast Iron after Hot Deformation

The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the cooling rate is closely related to the structure and properties, and for the cast iron, the best comprehensive mechanical properties were obtained by forced air cooling with a cooling rate as about 7 ℃/s. The reason and regularity for the change of mechanical properties were analyzed.

Influence of Heating Temperature on Property of Low Chromium Wear Resistant Cast Iron Containing Rare Earth

The influence of heating temperature on mechanical properties of low chromium wear resistant cast iron containing rare earth elements was studied by means of metallographic examination, scanning electron microscopic examination and mechanical property test. The experimental results show that heating temperature has great effect on impact toughness (α_k), bending fatigue (σ_(bb)) and relative toughness (σ_(bb)×f), but little effect on hardness (HRC). When the specimen was held at 960 ℃ for 3 h, it has better comprehensive mechanical properties, and the reason and regularity of the change for mechanical properties of the cast iron were reviewed.

低初黏凝胶体系中多元酸铬交联剂的合成

为改善聚合物驱油后低效无效循环严重的问题,通过正交实验,以乳酸、醋酸、顺丁烯二酸为三氯化铬的多元络合剂,乙二醇及抗坏血酸钠为原料,合成并筛选出初始黏度低、成胶时间可控的多元酸铬交联剂。实验结果表明:多元酸铬交联剂最优合成条件为反应时间6 h,合成温度70℃,三元酸与三氯化铬投料质量比2∶1,pH=4~5。在清水中成胶后凝胶体系初始黏度为19.96 mPa·s,延缓时间0~30 d可控,最终成胶黏度在2 800 mPa·s以上。

Microstructure and Properties of Low Temperature Composite Chromized Layer on H13 Tool Steel

Low temperature composite chromizing is a process composed of a plain ion-carbonitriding or ion-nitriding at 550-580℃, followed by a low-temperature chromizing in a salt-bath of 590℃. The microstructure and properties of the low temperature composite chromized layer on H13 tool steel were investigated using metallography, X-ray diffraction, microanalysis, hardness and wear tests. It was found that this low temperature process was thermo-dynamically and kinetically possible, and the composite chromized layer on H13 steel, with a thickness of 3-6 μm, consisted of three sub-layers (bands), viz. the outer Cr-rich one, the intermediate (black) one, and the inner, original white layer. After chromizing, the former diffusion layer was thickened. The results of X-ray diffraction showed that the composite chromized layer contained such nitrides and carbides of chromium as CrN, Cr2N, (Cr, Fe)23C6, and (Cr, Fe)7C3, as well as plain α-(Fe, Cr). A high surface microhardness of 1450-1550 HV0.025, which is much higher than that obtained by the conventional ion carbonitriding and ion nitriding, was obtained. In addition, an excellent wear resistance was gained on the composite chromized layer.

Removal of Hexavalent Chromium from Aqueous Solution by Adsorption on Palm Oil Fuel Ash (POFA)

This study investigated the removal of hexavalent chromium, Cr(VI) from aqueous solution by adsorption using palm oil fuel ash (POFA), an agricultural waste from the palm oil industry. POFA adsorbent was characterized by X-ray diffraction (XRD) analysis. Batch adsorption study revealed that the optimum conditions for the removal were as follows: pH 2, adsorbent dosage 80 g/L and contact time of 6 min, which resulted in 92% removal and 0.464 mg/g maximum adsorption capacity. Adsorption isotherm and kinetic studies showed that Freundlich isotherm and pseudo-second-order kinetic models fitted best to the experimental data. Column adsorption study at 5 mL/min of flow rate showed that 90% removal was obtained at 2 min of contact time which represented its breakthrough point. The column reached saturation at 30 min and the maximum column adsorption capacity recorded was 0.412 mg/g. The column adsorption behavior showed good fit with both Thomas and Yoon-Nelson kinetic models. These findings suggested that the utilization of POFA as a low-cost adsorbent to remove Cr(VI) from wastewater, either in batch or fixed bed adsorption system is not only effective, but concurrently will help to reduce wastes from the palm oil industry.

Prevention of burn-on defect on surface of hydroturbine blade casting of ultra-low-carbon refining stainless steel

The burn-on sand is common surface defect encountered in CO2 -cured silicate-bonded sand casting of hydroturbine blade of ultra-low-carbon martensitic stainless steel,its feature,causes and prevention measures are presented in this paper.Experiments showed that the burn-on defect is caused by oxidization of chromium in the molten steel at high temperature and can be effectively eliminated by using chromium-corundum coating.

浅析改善高透离线可钢Low-E玻璃耐加工性的方法

通过对真空磁控溅射方法生产的高透可钢Low-E镀膜采用氧化镍铬作为银层保护层和使用氧化锆作为最外层保护层的方法对膜层进行改善。对制备试样分别进行不同浓度的盐酸及氢氧化钠溶液浸泡,对膜面作不同莫氏硬度及不同程度的研磨测试,而后对可见光透过率和膜面形貌进行测量对比。实验表明:通过使用氧化镍铬作为银层保护层及氧化锆作为最外层保护层可以明显改善高透可钢Low-E抗划伤性,同时氧化锆可提高膜层的耐腐蚀性能而氧化镍铬的使用会降低耐腐蚀性。本实验为加工异地可钢产品尤其是高透双银产品膜层设计提供了一定的理论及实践指导。

提高钒钛铁水中钒回收率的工艺优化实践

随着高炉原燃料结构的变化,为提高炼钢工序钒回收率,分别研究了脱硫烧损、铁水成分、底吹工艺及翻渣频次等对钒渣中钒回收率的影响,调整了提钒和脱硫顺序,采取了先提钒后脱硫模式,减少了脱硫钒烧损,同时根据低硅高铬型铁水特性调整了冷料结构,严格控制钒渣渣态,保证钒渣中金属铁的沉降,并改造了提钒炉底吹元件,由之前的毛细管式透气砖改造为现在的环缝式透气砖,提高了复吹效果,翻钒渣频次由之前的2炉一翻改为现在的3炉一翻,通过以上措施的实施使得炼钢工序钒回收率由之前的78.5%提高至82%左右,进一步提高了钒效益,降低了生产成本。

稀土元素对低铬半钢热疲劳性能的影响

研究了稀土元素对低铬半钢铸态及经热处理后组织中的共晶碳化物形状的影响 ,在此基础上着重研究了该材料的热疲劳性能。结果表明 :稀土元素能改善共晶碳化物的形状 ,抑制热疲劳裂纹的萌生与扩展 ,提高其热疲劳性能 ,尤其稀土变质后再经热处理后效果更明显。当试样经 0 2 0 % (质量分数 )稀土变质后经 95 0℃ ,3h正火处理时 ,热疲劳性能最佳。

稀土变质及热处理对低铬半钢力学性能的影响

从改变碳化物形貌的角度研究了稀土变质处理与热处理之间的协同作用。结果表明 ,综合运用稀土变质处理和热处理工艺是改善低铬半钢共晶碳化物的形貌 ,提高综合力学性能的有效途径。

低铬半钢热变形后的冷却方式对其组织与力学性能的影响

对低铬半钢经 35 %热变形后用 4种不同冷却方式冷却后的组织与力学性能进行了研究 ,结果表明 ,热变形后冷却方式显著影响低铬半钢的力学性能。其中 ,低铬半钢经SST10 1淬火液冷却和风冷后的综合力学性能较好。

稀土变质与热处理复合作用对低铬半钢冲击疲劳行为的影响

利用冲击疲劳试验 ,研究了稀土变质及热处理对低铬半钢抗冲击疲劳性能的影响。结果表明 :稀土与热处理复合作用 ,可加速网状共晶碳化物向孤立块状的转变 ,促进粒状碳化物的析出 ,有效地推迟裂纹产生的时间 ,降低裂纹扩展速率 ,提高其冲击疲劳抗力。