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 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.

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.

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.

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.

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 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.

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。

水苏糖铬在家蚕糖尿病模型上的降糖活性研究

目的:研究水苏糖铬在家蚕糖尿病模型上的降糖活性。方法:在低温条件下(15~20℃),通过高糖喂养,建立家蚕糖尿病(高血糖)模型进行实验研究。模型分为空白组、高糖组、氯化铬对照组、水苏糖组、水苏糖铬低、中、高剂量组。分别将药液喷洒桑叶上,对各模型组进行给药,测量并分析家蚕血糖变化。结果:空白组家蚕血糖处于较低水平,且比较稳定。高糖组家蚕血糖快速上升并且保持高血糖水平。水苏糖铬组、水苏糖组和氯化铬对照组家蚕的血糖在快速上升后均有所降低,其中水苏糖铬组降血糖效果比水苏糖组、氯化铬组稳定。结论:说明水苏糖铬对糖尿病家蚕具有一定的降血糖作用,为研究有机铬作为辅助药提供了参考。

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.

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。

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.

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。

低铬X65管线钢CO2腐蚀产物膜的特征及形成机制

利用高温高压CO_2腐蚀模拟实验以及ESEM,EDS,XPS和SEM等分析技术,研究了4种不同含Cr量的X65管线钢的腐蚀速率、腐蚀形态和腐蚀产物膜结构特征.结果表明:含Cr量高的钢平均腐蚀速率小,无Cr和含1%Cr的钢的腐蚀形态为局部腐蚀,含3%和5%Cr的钢的腐蚀形态为全面腐蚀.在高温高压CO_2腐蚀环境中,含Cr钢的腐蚀产物膜为FeCO_3和Cr(OH)_3竞争沉积形成的多层结构,其中1Cr-X65和3Cr-X65的腐蚀膜具有3层结构,5Cr-X65的腐蚀膜是双层结构.Cr在腐蚀产物膜层中出现局部富集,远高于基体中的Cr含量.高含Cr量使腐蚀产物膜中的Cr(OH)_3含量高,并提高了腐蚀膜的保护性能,从而引起腐蚀形态发生转变,腐蚀速率降低.FeCO_3和Cr(OH)_3共沉积层膜对低铬钢的抗CO_2腐蚀性能具有关键的影响.

CO_2腐蚀产物膜的微观形貌和结构特征

研究了碳钢、低Cr钢在不同条件下形成CO2腐蚀产物膜的微观形貌、成分和结构特征.结果表明,N80(碳钢)、1Cr-L80形成的腐蚀产物膜主要由FeCO3晶体堆垛而成,而3Cr-L80、5Cr-L80的表层则形成大面积的含Cr化合物,主要为Cr(OH)3和Cr2O3.这些Cr的化合物脱水后比较疏松,容易形成龟裂,在静态条件下,碳钢和含Cr钢的腐蚀产物膜均具有分层结构,碳钢外层与内层腐蚀产物膜的成分变化不大,主要为Fe、Ca碳酸复盐.含Cr钢的内层腐蚀产物膜中出现Cr元素的富集,外层主要为Fe、Ca碳酸复盐.随着Cr含量的增加,材料的腐蚀产物膜向非晶态转变.在静态条件下,低Cr钢比碳钢的腐蚀速率稍大;在动态(1.5m/s)条件下,含Cr钢的腐蚀速率明显低于碳钢,而且腐蚀速率随着Cr含量的增加而下降.

B_(117)催化剂上一氧化碳中温变换的本征动力学

在常压、５３３～６７３Ｋ的温度范围内，测定了市售Ｂ１１７型低铬一氧化碳中温变换催化剂的催化活性。通过对实验数据的处理，得到了不同数学模型所表示的速率方程及其动力学参数，并得知双曲函数速率方程中所含的常数Ａ实际上是温度和转化率的函数。