Microstructure and properties of cutting magnesium-brass containing no lead

A new environmental friend cutting brass containing magnesium instead of lead was produced by casting, extruding and drawing. Its microstructure was observed and its mechanical, chemical and cutting properties were stutied. The results show that the global secondary particles which are brittle and soft intermetallics, distribute in grains and on grain boundries, which is helpful for improvement of cutting ability of the brass. The tensile strength, yield strength, elongation and area reduction of halfhard magnesium-brass are (550MPa,) (280MPa,) (16.30%,) (32.4%,) respectively. The cutting ability of magnesium-brass corresponds to that of lead-brass C3604 judged by the size and appearance of chips of alloy and by the cutting force. The magnesium-brass has excellent corrosion resistance.

Identification of Rare Earth Phase in the Deformed High Lead-Brasses

Deformed high lead-brasses have excellent machining characteristics and good mechanical and physicalproperties.They are widely used in mechanical,clock-watch and pen-making field.Especially,they are suit-able for deep-hole machining.Because of their worse hot-working characteristics,there exists trouble inproduction process.It is reported that the rare earth metals could improve the hot-rolling property,but themechanism is still unclear.

Effect of the Rare Earths on the High Temperature Properties of Deformed Leaded-Brasses

The effect of the rare earths on the high temperature properties of deformed leaded-brasses has been stu- died with the high temperature tensile test.The results show that the rare earth additives can increase elongation of alloys at high temperature,but they had little effect on the maximum flow stress.With the help of SEM. X-ray diffraction instrument,quantitative metallography analysis instrument,etc.,the effect of the rare earth elements on the mierostrueture of alloys has also been examined.

Study on the Effect of Production Parameters and Raw Materials Used on the Mechanical Properties of Leaded Brass (CuZn40Pb2) Alloy

Leaded brass alloys used progressively in many applications such as gas valves production owing to their excellent machinability, corrosion resistance and some other specifications. However, the production processes of these alloys involve some problems appearing in the last activities of production as a result of cumulative defects of previous production processes. Therefore, the current investigation studies the effect of process parameters during casting, hot extrusion and cold drawing production stages of CuZn40Pb2 leaded brass alloy on the mechanical properties. Starting with casting process, two types of charges were used. The first charge consists of 100% recycles while the second contains 30% of pure materials such as Cu, Zn and Pb in addition to the recycles. For each production stage, alloy hardness, micro-hardness, ultimate tensile strength and elongation were examined. The results illustrated that high hardness values are obtained during casting process due to some impurities such as iron and the effect of cooling rate through solidification. The hardness values decrease during extrusion process and then rise again by cold drawing for the charge of 30% pure materials. Micro-hardness values for the fractured tensile test samples appeared higher than others due to work hardening effect. The best mechanical properties as ultimate tensile strength of CuZn40Pb2 alloy products are appeared into cold forming samples with the 30% pure material added.

飞机生保系统氧气导管接头腐蚀原因分析

[目的]飞机生保系统氧气导管接头装机后多次发生腐蚀问题,为保证飞机质量安全,亟需明确其腐蚀原因。[方法]针对小平管嘴与外套螺母配合面及附近区域均出现腐蚀的现象进行了形貌、组织及成分分析,并通过模拟实验来验证腐蚀成因。[结果]确定了表面腐蚀产物为不规则及泥纹花样的Cu、Zn氧化物,且存在较高含量的K、Ca、Na异常元素。氧气导管小平管嘴沟槽处容易残留中性钾皂液,在表面浸润的情况下形成了大片不规则的钾皂残留物;其余开放表面接触过中性钾皂后,在未洗净的情况下易产生不规则及泥纹花样的Cu、Zn氧化物颗粒。另外,由于焊接后小平管嘴表层脱锌形成了疏松多孔组织,因此其表面更容易吸附钾皂成分,从而加速腐蚀。[结论]氧气导管在气密试验后表面残留中性钾皂成分是导致其腐蚀的根本原因。建议气密试验后将导管彻底洗净或更换气密试验检测剂。

氯化物与硫酸盐浓度比对黄铜-铅电偶腐蚀的影响

以供水管道中黄铜与铅焊接的电偶连接为研究对象,探究不同氯化物与硫酸盐浓度比(CSMR)对黄铜-铅电偶腐蚀的影响。分析了黄铜-铅电偶腐蚀的金属释放量、电化学行为及腐蚀产物。结果表明,CSMR使得多电偶对中阳极极性改变。在CSMR=0~0.5时,铅锌同作为阳极;CSMR=1时锌单独作为阳极;而CSMR=∞时,铅单独作为阳极。铅的腐蚀产物为棒状的PbCO_(3)及片状的Pb_(3)(CO_(3))2(OH)2,锌的产物为板状的ZnO_(2),而铜和锡的产物分别为颗粒状Cu2O和块状SnO_(2)。当供水管道中黄铜与含铅材料电偶连接时,为减少铅的释放,建议将CSMR控制在1左右。

The Kinetics of Pb Removal from Brass Scrap Using Compound Separation

2 wt% Ca was added to molten brass containing 3.2 wt% Pb. The composition and grain size of the formed Ca-Pb compound were examined in detail using SEM-EDS and XRD. This revealed that the composition of the Ca-Pb compound depends on the grain size of the liquid phase Pb and the diffusion phenomenon of the Ca in the Ca-Pb compound formed on the surface of the Pb. When the Pb has a fine grain, a compound composed only of Ca-Pb compounds is formed. When the grain size of the Pb is several μm, Ca-Pb compounds containing unreacted Pb in the center are formed. These compounds aggregate into a larger compound grain. From the evaluation of the floating force (the resultant force of the weight and buoyancy of the Ca-Pb compounds formed) and the rising terminal velocity of the Ca-Pb compound within the molten brass, it was found that the floating force and rising terminal velocity depend on the composition and grain size of the Ca-Pb compound. It was found that since Ca-Pb compounds with a floating force greater than 10-6 g ·cm/s2 have a very large rising terminal velocity, they reach the surface of the molten brass in a short time after compound formation and then continue to float on the surface of the molten brass. Thus they can be removed by skimming. The effects of the grain size of the Ca-Pb compound on the floating force and the rising terminal velocity were greater than those of the composition of the Ca-Pb compound.

Mechanism of Pb Removal from Brass Scrap by Compound Separation Using Ca and NaF

The Mechanism of Pb removal from brass scrap by compound separation using Ca and NaF addition was investigated. Because large Ca-Pb compound particles formed by Ca addition rise to the surface of the molten brass, they can be skimmed off from the molten brass. However, fine Ca-Pb compound particles remain in the molten brass because of low buoyancy. By subsequent NaF addition, the reaction between Ca-Pb compound and NaF takes place at their contact regions, resulting in the formation of solid CaF2, liquid Pb and Na gas. Pb is mainly present at the Ca-Pb compound-CaF2 interface. CaF2 acts as a binder for aggregation of fine Ca-Pb compound particles, resulting in the formation of light and large composite compounds, which rise to the surface of the molten brass. A high Pb removal rate is achieved by skimming off.

电动阀电驱动器铜套断裂原因分析

某乙烯装置甲烷再生单元电动阀门电驱动器更换磨损铜套后连续发生铜套断裂现象,采用宏观检查、硬度与冲击试验、金相检验、断口微观观察与能谱分析等方法对铜套失效原因进行分析,结果表明断裂原因是电动阀在超过关限位位置存在卡滞,电驱动器输出较大的驱动力矩,以较大应力作用在材料性能较弱的铅黄铜铜套凸缘和下部梯形螺纹上,发生了凸缘及梯形螺纹的断裂。提出了电驱动器阀门检修的要求。

β相控制法改进黄铜合金的热加工性能

通过立式半连铸方法制备了Cu-40Zn-1Pb-0.15Fe-0.03Ni双相黄铜合金,针对热轧开裂问题,采用Gleeble-3500热模拟机对合金进行圆柱体压缩试验和扁平压缩试验,研究了双相黄铜合金在变形温度为600~780℃及应变速率为0.01~10 s^(-1)的条件下的热变形行为和热轧工艺性能。通过应力-应变曲线分析得到了合金的本构方程,计算绘制了热加工图,分析了热机械加工(TMP)诱导的α-β相变对α和β相的形成和铅颗粒分布的影响,利用热加工图结合显微组织确定了合金的热变形的流变失稳区和最佳变形参数。结果表明:双相黄铜合金加工过程主要存在两个失稳区:1)变形温度为670~710℃,应变速率为2.5~10 s^(-1)的区域;2)变形温度为750~780℃,应变速率为5~10 s^(-1)的区域。在较低温区(690℃以下),合金为α+β双相组织,且随着温度升高合金中β相占比逐渐增大、α相逐渐球化;在中温区(700~750℃),合金基本为β单相组织,利于热轧加工;在高温区(750℃以上),从β相组织的晶界处生长出针状α相,容易造成合金热轧开裂。

精密结构件用铅黄铜的性能研究

精密结构件的材料常为铅黄铜,但国产铅黄铜存在加工易变形、表面粗糙、刀具损耗大等问题,造成国内市场缺口。通过金相、拉伸、氨熏和加工验证试验,对比了不同产地材料在金相组织、残余内应力和力学性能方面存在的差异,分析总结了性能良好的铅黄铜材料特点,优化了铅黄铜残余内应力检测方法,修正了早期铅黄铜加工性能的评估经验数据,为材料的改进和选用提供了方向。结果表明:精密结构件用铅黄铜的加工性能与其金相组织、残余内应力和力学性能有关,为保证加工性能优良,其铅相应该均匀弥散且平均尺寸不超过15μm,抗拉强度与伸长率之比应介于15~35 MPa/%之间;铅黄铜的残余内应力,采用氨熏实验法加裂纹显示剂的方法可清晰检测,在270℃保温4 h可有效消除残余内应力。

饮用水系统黄铜零部件无铅害化处理技术研究

研制了一种用于饮用水系统黄铜零件表面除铅的除铅溶液,并开发了与之相关的黄铜零件表面除铅工艺。X射线能谱分析证明,经表面除铅处理后的黄铜零件表面的含铅量低于标准规定值。

无铅易切削镁黄铜的组织与性能

采用熔铸、挤压、拉拔的方法生产出了以镁代铅的环保型易切削黄铜材。对易切削黄铜的微观组织进行了观察,并对其力学、化学和切削性能分别进行了研究。结果表明:镁黄铜晶内和晶间有白色和黑色的球状第二相粒子分布,该粒子为金属间化合物,具有脆而不硬的特点,对提高合金切削性能有利。半硬态镁黄铜的抗拉强度为550 MPa,屈服强度为280 MPa,延伸率为16.30%,断面收缩率为32.4%。从切削过程中切削力的大小以及切屑的形貌、大小可以判断,镁黄铜的切削性能接近于C3604铅黄铜。镁黄铜在酸中和盐中的耐蚀性均较好,比较而言耐盐性要好一些。

稀土和硼细化处理对铸造铅黄铜组织和脱锌腐蚀性能的影响

研究了加入稀土和硼细化处理对铸造铅黄铜组织和脱锌腐蚀性能的影响。结果表明,加入稀土和硼后明显地细化了铸造铅黄铜的组织,使粗大的α、β板条状组织变成短小的片状或等轴状组织。用硼处理的组织细化效果要好于用稀土处理的效果,同时可以减轻铸造黄铜的脱锌腐蚀倾向。细化处理后壳杯试样的表面由未细化的粗糙表面变为光滑表面,结晶面组织由柱状晶变为等轴晶。加入细化剂可以明显改善黄铜抗脱锌腐蚀性能。

电磁场对铅黄铜水平连铸坯组织及偏析的影响

研究了铅黄铜在无磁场、低频交变电磁场下水平连铸得到的铸坯横截面宏观组织、微观组织形貌及合金元素Pb的分布,并对其机理进行了分析。试验结果表明,在铅黄铜水平连铸的过程中施加低频交变电磁场能有效地细化晶粒及影响合金元素在横截面上的分布,并且电磁场有效地抑制了在常规水平连铸过程中出现的铸坯横截面上中下部位组织分布不均匀的现象。表现在铸坯横截面的凝固组织由上方主要为细小柱状晶、下方为粗大柱状晶变为均为细小的等轴晶,铸锭上部凝固滞后的现象消除;合金元素Pb的宏观偏析得到抑制,并且电流为30Hz、100A的组织优于30Hz、80A的组织。

铋含量对黄铜脱锌腐蚀性能的影响

采用显微组织分析和脱锌腐蚀实验方法,研究了不同铋含量对黄铜的微观组织以及黄铜脱锌腐蚀性能的影响。结果表明,铋在铸态黄铜中为单质相,不固溶于基体中,主要以薄膜状存在于晶界上。在黄铜中加入铋可以明显改善黄铜的脱锌腐蚀性能,并且随着Bi含量的增加,黄铜的耐脱锌腐蚀性能增加。

热处理对锻造铅黄铜组织和性能的影响

研究了退火温度对锻造铅黄铜组织和力学性能的影响.对铸造成型的商用铅黄铜进行720℃、60%变形量的锻造镦粗加工后,采用500~700℃不同温度的热处理工艺处理.结果表明：铅黄铜的铸态组织为粗大的树枝晶,锻造后的晶粒被拉长,与铸态的硬度值相比,锻造后的硬度明显增加,产生明显的加工硬化现象;锻造铅黄铜经过热处理后,细长的晶粒明显变短,随着退火温度的升高,晶粒逐渐细小、均匀化,并且发生再结晶,拉长的晶粒逐渐变为等轴晶.620℃、640℃退火后,铅黄铜的组织基本转变为细小、均匀的等轴晶,退火温度超过640℃时,随着温度的升高,晶粒长大.不同温度退火处理后,随着退火温度的升高,硬度逐渐降低,620℃退火后硬度趋于稳定,加工硬化消除.铅黄铜经720℃、60%变形锻造后,合适的退火温度为620~640℃.

铅黄铜阀芯部件开裂分析

针对一批铅黄铜阀芯部件加工过程中出现开裂的异常现象,采用化学成分分析、硬度测试、宏观和微观检验以及X射线衍射等方法分析了产生开裂的原因。结果表明:该部件失效属于局部应力作用下的脆性开裂,原材料中铅和杂质元素含量过高,以及退火不完全是主要原因,并提出了改进建议。

新型铜合金细化添加剂对铸造铅黄铜变质处理效果的影响

新型细化添加剂对铸造铅黄铜变质处理的效果表明,细化效果良好,铸造铅黄铜组织由粗大的板条状变为细小的针状或等轴状,组织均匀性提高,同时可显著提高铅黄铜的力学性能。细化效果衰退较慢,静置保温180min后,材料仍具有较好细化效果和力学性能。新型铜合金细化添加剂对铸件壁厚不敏感,壁厚3mm～12mm,均可获得较好的细化效果和性能;采用新型铜合金细化添加剂变质处理可大幅度提高铅黄铜的流动性,变质处理后,铅黄铜的流动性比未变质处理的平均提高了29.78%。

无铅易切削硒铋黄铜的研究

介绍了无铅易切削硒铋黄铜的制备工艺,于中频感应炉中制备了无铅易切削硒铋黄铜铸锭,并对其组织和力学性能以及抗腐蚀性进行了测定。结果表明,铋以铜铋中间合金形式在1200℃加入时,铋均匀分布在铜合金中。该工艺制备的无铅易切削硒铋黄铜具有较HPb59-1好的力学性能、机加工性能和抗脱锌腐蚀性能。通过物相与组织形貌分析,解释了铋改善铜合金切削性能的机理。