Lead-antimony alloys properties

Table 1. Mechanical Properties of Lead—Antimony Alloys ...

Tia is also used as an ahoyiag element ia lead—antimony alloys to improve fluidity and to prevent drossiag, ia lead—calcium alloys to improve mechanical properties and enhance electrochemical performance, ia lead—arsenic alloys to maintain a stable composition, and as an additive to low melting alloys. 

Antimony is used to make alloys with a number of different metals. An alloy is made by melting and mixing two or more metals. The properties of the mixture are different than those of the individual metals. One of the most common of these alloys is one made with lead. Lead-antimony alloys are used for solder, ammunition, fishing tackle, covering for electrical cables, alloys that melt at low temperatures, and batteries. 

Depending on their properties the lead—antimony alloys adopted in the battery industry can be generally classified into four basic groups ... 

It seems that only alloys with particular properties are suitable for casting grids for lead—acid batteries. Lead—calcium alloys, similar to lead—antimony alloys, belong to the age-hardening or precipitation-hardening group of alloys. With decrease of temperature, the solubility of calcium in the a-Pb solid—solution decreases and it precipitates in the form of small Pb3Ca particles. A similar picture was described earlier for the Pb—Sb alloys. 

Important for the maintenance-free properties of these batteries was the possibility to use antimony-free grid alloys instead of the conventional lead-antimony alloys, which were used only at this time. Because antimony in the grid alloys provides a high cycle life for the battery, it was necessary to develop more sophisticated methods in battery manufacturing in order to achieve the required product properties. 

Excellent antifriction properties and good hardness (qv) make lead—antimony—tin alloys suitable for journal bearings. The alloys contain 9—15 wt % antimony and 1—20 wt % tin and may also contain copper and arsenic, which improve compression, fatigue, and creep strength important in bearings. Lead—antimony—tin bearing alloys are Hsted in ASTM B23-92 (7). 

Rea.ctivity ofLea.d—Ca.lcium Alloys. Precise control of the calcium content is required to control the grain stmcture, corrosion resistance, and mechanical properties of lead—calcium alloys. Calcium reacts readily with air and other elements such as antimony, arsenic, and sulfur to produce oxides or intermetaUic compounds (see Calciumand calciumalloys). In these reactions, calcium is lost and suspended soHds reduce fluidity and castibiUty. The very thin grids that are required for automotive batteries are difficult to cast from lead—calcium alloys. 

Wrought lead—calcium—tin alloys contain more tin, have higher mechanical strength, exhibit greater stabiUty, and are more creep resistant than the cast alloys. RoUed lead—calcium—tin alloy strip is used to produce automotive battery grids in a continuous process (13). Table 5 Hsts the mechanical properties of roUed lead—calcium—tin alloys, compared with lead—copper and roUed lead—antimony (6 wt %) alloys. 

Lead—copper alloys are specified because of superior mechanical properties, creep resistance, corrosion resistance, and high temperature stabiUty compared to pure lead. The mechanical properties of lead—copper alloys are compared to pure lead, and to lead—antimony and lead—calcium alloys in Tables 4 and 5. 

Solders are alloys that have melting temperatures below 300°C, formed from elements such as tin, lead, antimony, bismuth, and cadmium. Tin—lead solders are commonly used for electronic appHcations, showing traces of other elements that can tailor the solder properties for specific appHcations. 

Lead and Alloys Chemical leads of 99.9 percent purity are used primarily in the chemical industry in environments that form thin, insoluble, and self-repairable protective films, e.g., salts such as sulfates, carbonates, or phosphates. More soluble films such as nitrates, acetates, or chlorides offer little protection. Alloys of antimony, tin, and arsenic offer limited improvement in mechanical properties, but the usefulness of lead is limited primarily because of its poor structural qualities. It has a low melting point and tensile stress as low as 1 MPa (145 Ibf/in ). 

Antimony appeared in all notes at a low level and was rubbed off both front and back, indicating its presence in the inks. If it was not added deliberately, it might have been present as an impurity in lead. Antimony frequently is alloyed with lead to increase its strength and to improve the electrical properties of lead plates in storage batteries and often is present in reclaimed lead. 

Q Britannia metal is harder than pewter. This tin-antimony alloy s properties can be varied by the addition of zinc, copper, lead, or bismuth. o When heat from a fire melts the Wood s metal plug in a sprinkler head, water that was held back by the plug is freed. 

Bearing metals, used as the bearing surfaces of sliding-contact bearings, are usually alloys of tin, lead, antimony, and copper. They contain small, hard crystals of a compound such as SnSb embedded in a soft matrix of tin or lead. The good bearing properties result from orientation of the hard crystals to present flat faces at the bearing surface. 

The use of lead alloy (traditionally lead-antimony, with 5 per cent or less antimony) for the inert grids is based on the metal s excellent corrosion resistance, alloying capability and castability, and the benefits it imparts in paste to grid adhesion. Due to these properties, and its relatively low cost, lead remains a highly suitable material for the manufacture of efficient and competitive battery systems, despite its weight. 

---