Typical uses. Simple, highly stressed castings of uniform cross section. High in cost. Intricate castings subject to microporosity and cracking due to shrinkage. Not readily welded. Sometimes used in the artificially aged condition (T5 temper) but usually in the solution-heat treated and artificially aged condition (T6 temper) to develop properties fully Mechanical Properties Tensile properties. T6 temper: tensile strength, 310 MPa (45 ksi); yield strength, 195 MPa (28 ksi); elongation in 50 mm (2 in.), 10% Fatigue properties. At least equal to those of the Mg-Al-Zn alloys Mass Characteristics Density. 1.83 g/cm 3 (0.066 lb/in. 3 ) at 20 °C (68 °F) Thermal Properties Liquidus temperature. 635 °C (1175 °F) Solidus temperature. 530 °C (985 °F) Coefficient of linear thermal expansion. 27.0 μm/m · K (15.0 μin./in. · °F) at 20 to 200 °C (68 to 390 °F) Fabrication Characteristics Weldability. Not readily weldable. Addition of Th or rare earths decreases porosity and improves weldability. Casting temperature. Sand castings, 705 to 815 °C (1300 to 1500 °F) Tin and Tin Alloys Revised by William B. Hampshire, Tin Research Institute, Inc. Introduction TIN was one of the first metals known to man. Throughout ancient history, various cultures recognized the virtues of tin in coatings, alloys, and compounds, and the use of the metal increased with advancing technology. Today, tin is an important metal in industry even though the annual tonnage used is much smaller than those of many other metals. One reason for the small tonnage is that, in most applications, only very small amounts of tin are used at a time. Tin Production and Consumption Tin is produced from both primary and secondary sources. Secondary tin is produced from recycled materials (see the article "Recycling of Nonferrous Alloys" in this Volume). Figure 1 shows the consumption of primary and secondary tin in the United States during recent years. Figure 2 shows 1988 data for the relative consumption of tin in the United States by application. Fig. 1 U.S. consumption of primary and secondary tin in recent years Fig. 2 Relative consumption of tin in the United States by application. 1988 data. Source: U.S. Bureau of Mines Primary Production. Tin ore generally is centered in areas far distant from centers of consumption. The leading tin- producing countries (excluding the USSR and China) are, in descending order, Brazil, Indonesia, Malaysia, Thailand, Bolivia, and Australia (1988 totals). These countries supply over 85% of total world production. Cassiterite, a naturally occurring oxide of tin, is by far the most economically important tin mineral. The bulk of the world's tin ore is obtained from low-grade placer deposits of cassiterite derived from primary ore bodies or from veins associated with granites or rocks of granitic composition. Primary ore deposits can contain very low percentages of tin (0.01%, for example), and thus large amounts of soil or rock must be worked to provide recoverable amounts of tin minerals. Unlike ores of other metals, cassiterite is very resistant to chemical and mechanical weathering, but extended erosion of primary lodes by air and water has resulted in deposition of the ore as eluvial and alluvial deposits. Underground lode deposits of tin ores are worked by sinking shafts and driving adits, and the rock is broken from the working face by drilling and blasting. Cassiterite is recovered from eluvial and alluvial deposits by dredging, gravel pumping, and hydraulicking. In open-pit mining, a much less widely employed mining method, mechanical and manual methods are used to move tin-bearing materials. After ball mill concentration of the ore, a final culling is provided at dressing stations. The final concentrates, which contain 70 to 77% tin, are then sent to the smelter, where they are mixed with anthracite and limestone. This charge is heated in a reverberatory furnace to about 1400 °C (2550 °F) to reduce the tin oxide to impure tin metal, which is again heated in huge cast iron melting pots to refine the metal. Steam or compressed air is introduced into the molten metal, and this treatment, plus addition of controlled amounts of other elements that combine with the impurities, results in tin of high purity (99.75 to 99.85%). This high-purity tin often is treated again by liquating or electrolytic refining, which provides tin with a purity level approaching 99.99%. After the tin is refined, it is cast into ingots weighing 12 to 25 kg (26 to 56 lb) or bars in weights of 1 kg (2 lb) and upwards. Tin normally is sold by brand name, and the choice of brand is determined largely by the amounts of impurities that can be tolerated in each end product. High-purity brands of tin may contain small amounts of lead, antimony, copper, arsenic, iron, bismuth, nickel, cobalt, and silver. Total impurities in commercially pure tin rarely exceed 0.25%. Tin in Coatings Tinplate. The largest single application of tin worldwide is in the manufacture of tinplate (steel sheet coated with tin), which accounts for about 40% of total world tin consumption. Since 1940, the traditional hot dip method of making tinplate has been largely replaced by electrodeposition of tin on continuous strips of rolled steel. Electrolytic tinplate can be produced with either equal or unequal amounts of tin on the two surfaces of the steel base metal. Nominal coating thicknesses for equally coated tinplate range from 0.38 to 1.5 μm (15 to 60 μin.) on each surface. The thicker coating on tinplate with unequal coatings (differential tinplate) rarely exceeds 2.0 μm (80 μin.). Tinplate is produced in thicknesses from 0.15 to 0.60 mm (0.006 to 0.024 in.). Over 90% of world production of tinplate is used for containers (tin cans). Traditional tinplate cans are made of three pieces of tin-coated steel: two ends and a body with a soldered side seam. Innovations in can manufacture have produced two-piece cans made by drawing and ironing. Tinplate cans find their most important use in the packaging of food products, beer, and soft drinks, but they are also used for holding paint, motor oil, disinfectants, detergents, and polishes. Other applications of tinplate include signs, filters, batteries, toys, and gaskets, and containers for pharmaceuticals, cosmetics, fuels, tobacco, and numerous other commodities. Electroplating accounts for one of the major uses of tin and tin chemicals. Tin is used in anodes, and tin chemicals are used in formulating various electrolytes and for coating a variety of substrates. Tin electroplating can be performed in either acid or alkaline solutions. Sodium or potassium stannates form the bases of alkaline tinplating electrolytes that are very efficient and capable of producing high-quality deposits. Advantages of these alkaline stannate baths are that they are not corrosive to steel and that they do not require additional agents. Acid electrotinning solutions operate at higher current densities and higher plating rates and require additions of organic compounds. A number of alloy coatings can be electroplated from mixed stannate-cyanide baths, including coatings of tin-zinc and tin-cadmium alloys and a wide range of tin-copper alloys (bronzes). The bronzes range in tin content from 7 to 98%. Red bronze deposits contain up to 20% tin; high-tin bronzes, called speculum, usually contain about 40% tin. Tin-nickel and tin-lead electrodeposits are plated from acid electrolytes and are important coatings for printed circuits and electronic components. Tin-cobalt plate is used in applications requiring an attractive finish and good corrosion resistance. Two ternary alloy electrodeposits are used by industry. These are the copper-tin-lead for bearing surfaces and the copper- tin-zinc alloy for coatings in certain electronic applications. Hot Dip Coatings. Coating steel with lead-tin alloys produces a material called terneplate (see the article "Lead and Lead Alloys" in this Volume). Terneplate is easily formed and easily soldered. It is used as a roofing and weather-sealing material and in the construction of automotive gasoline tanks, signs, radiator header tanks, brackets, chassis and covers for electronic equipment, and sheathing for cable and pipe. Hot dip tin coatings are used both on wire for component leads and on food-handling and food-processing equipment. In addition, hot dip tin coatings are used to provide the bonding layer for the babbitting of bearing shells. Pure Tin Commercial tin is considered to be pure when it contains a minimum of 99.8% Sn. Of the various types of commercially pure tin, about 80 to 90% is a high-purity commercial tin known as Grade A tin as specified in ASTM B 339. According to this specification, Grade A tin must have a minimum tin purity of 99.85% Sn and maximum residual impurities of 0.04% Sb, 0.05% As, 0.030% Bi, 0.001% Cd, 0.04% Cu, 0.015% Fe, 0.05% Pb, 0.01% S, 0.005% Zn, and 0.01% (Ni + Co). Other specifications for commercially pure tin include: • U.S. government specification QQT-371, Grade A (99.75% Sn) • British specification BS 3252, Grade T (99.8% Sn) • German specification DIN 1704, Grade A2 (99.75% Sn) Table 1 summarizes selected physical, thermal, electrical, and optical properties of pure tin. Further information is contained in the article "Properties of Pure Metals" in this Volume. General applications of Grade A tin include tinplate foil, collapsible tubes, block tin products, and pewter. Table 1 Physical, thermal, electrical, and optical properties of commercially pure tin Property Value Physical properties Atomic number 50 Atomic weight 118.69 Crystal structure α phase or β phase Density, g/cm 3 (lb/in. 3 ) α phase at 1 °C (33.8 °F) 5.765 (0.2083) β phase at 20 °C (68 °F) 7.168 (0.2590) Liquid surface tension at 400-800 °C (750-1470 °F), mN/m 700-0.17 × T + (25 + 0.015 × T) (a) Hardness, HB At 20 °C (68 °F) 3.9 At 60 °C (140 °F) 3.0 At 100 °C (212 °F) 2.3 Modulus of elasticity, GPa (10 6 psi) Cast (coarse grain) 41.6 (6.03) Self-annealed (fine grain) 44.3 (6.43) Poisson's ratio 0.33 Volume change on freezing, % 2.8% Volume change on phase transformation, % ~27% Thermal properties Melting point, °C ( °F) 231.9 (449.4) Boiling point, °C ( °F) 2270 (4118) Phase transformation temperature on cooling (β phase to α phase), °C (°F) 13.2 (55.8) Latent heat of fusion, J/g (Btu/lb) 59.5 (25.6) Latent heat of phase transformation, J/g (Btu/lb) 17.6 (7.57) Latent heat of vaporization, kJ/g (Btu/lb) 2.4 (1.03 × 10 3 ) Specific heat, J/kg · K (Btu/lb · °F) α phase at 10 °C (50 °F) 205 (49 × 10 -3 ) β phase at 25 °C (77 °F) 222 (53 × 10 -3 ) Linear coefficient of thermal expansion, 10 -6 /K α phase at - 100 °C (-150 °F) 18.1 α phase at -50 °C (-60 °F) 19.2 β phase at 100 °C (212 °F) 23.8 β phase at 150 °C (300 °F) 26.7 Thermal conductivity, W/m · K βphase at 100 °C (212 °F) 60.7 β phase at 200 °C (390 °F) 56.5 Electrical properties Electrical conductivity (volumetric) at 20 °C (68 °F) 15.6% IACS Electrical resistivity, μΩ· m At 0 °C (32 °F) 0.110 At 100 °C (212 °F) 0.155 At 200 °C (390 °F) 0.200 Optical properties (546.1 nm wavelength) Reflectance index Film, 42-200 nm thick 0.70 Bulk solid 0.80 Refractive index Film, 42-200 nm thick 2.4 Bulk solid 1.0 Absorptive index Film, 42-200 nm thick 1.9 Bulk solid 4.2 (a) T, temperature in degrees Kelvin Mechanical Properties. Typical tensile properties of commercially pure tin are given in Table 2. Hardness and elasticity values are given in Table 1. Table 2 Tensile properties of commercially pure tin Temperature Yield strength °C °F MPa ksi Elongation in 25 mm (1 in.), % Reduction in area, % Strained at 0.2 mm/m · min (0.0002 in/in. · min) -200 -328 36.2 5.25 6 6 -160 -256 90.3 13.10 15 10 -120 -184 87.6 12.71 60 97 -80 -112 38.9 5.64 89 100 -40 -40 20.1 2.92 86 100 0 32 12.5 1.81 64 100 23 73 11.0 1.60 57 100 Strained at 0.4 mm/m · min (0.0004 in./in. · min) 15 59 14.5 2.10 75 . . . 50 122 12.4 1.80 85 . . . 100 212 11.0 1.60 55 . . . 150 302 7.6 1.10 55 . . . 200 392 4.5 0.65 45 . . . Note: It is uncertain if the inconsistencies among these data are due to differences in purity or the difference in straining rate. Creep Characteristics. Like lead, tin is subject to creep deformation and rupture even at room temperature. Consequently, tensile strength may not be an important design criterion because creep rupture can occur at stresses even below the yield strengths in Table 2. For example, one series of tests on a commercially pure tin resulted in the following creep characteristics at room temperature: Initial stress MPa psi Time, days Extension, % 1.083 157.0 551 3.5 1.351 196.0 551 7 2.256 327.1 173 * 101 2.772 402.1 79 * 132 3.227 468.1 21 * 119 4.214 611.2 4.6 105 7.069 1025.2 0.5 * 78 Fatigue Strength. Rotating-cantilever fatigue tests on a commercially pure tin resulted in fatigue strength levels of 2.9 MPa (430 psi) for 10 7 cycles at 15 °C (59 °F) and 2.6 MPa (380 psi) for 10 8 cycles at 100 °C (212 °F). Because creep deformation of tin occurs at room temperature, fatigue strengths may be influenced by creep-fatigue interaction and thus may depend on the frequency and/or waveform of stress cycling. Impact Strength. Charpy V-notch tests on commercially pure tin at various temperatures resulted in the following impact strengths: Temperature Charpy V-notch impact energy °C °F J ft · lbf -80 -112 3.7 2.75 -60 -76 11.5 8.5 -15 5 28.5 21.0 0 32 44.1 32.5 150 302 22.7 16.75 190 374 20.3 15.0 215 419 2.7 2.0 Specific Damping Capacity. Tests on bars vibrating at audio frequencies in the free-free mode produced these results: Temperature Logarithmic decrement °C °F Polycrystalline Single crystals 25 77 0.022 0.0010 50 122 0.045 0.0013 75 167 0.060 0.0015 100 212 0.054 0.0018 125 257 0.045 0.0024 150 302 0.060 0.0032 Chemical Properties and Corrosion Behavior. Tin reacts with both strong acids and strong alkalies, but it is relatively resistant to near-neutral solutions. Oxygen greatly accelerates corrosion in aqueous solutions. In general, with mineral acids the rate of attack increases with the temperature and concentration. Dilute solutions of weak alkalies have little effect on tin, but strong alkalies are corrosive even in cold dilute solutions. Salts with an acid reaction at tack tin in the presence of oxidizers or air. Tin resists demineralized waters but is slightly attacked near the water line by hard tap waters. The corrosion resistance of tin in specific environments is summarized in Table 3. Additional information on the corrosion of tin is given in Corrosion, Volume 13 of ASM Handbook, formerly 9th Edition Metals Handbook. Table 3 Resistance of tin to specific corroding agents Corrosive agent Resistance Remarks Acid, acetic Slight attack Increased by air Acid, butyric Resistant . . . Acid, citric Moderate attack At water line Acids, fatty Moderate attack . . . Acid, hydrochloric Severe attack In presence of air Acid, hydrofluoric Severe attack In presence of air Acid, lactic Moderate attack Increased by air Acid, nitric Severe attack . . . Acid, oxalic Moderate attack (a) Acid, phosphoric Resistant . . . Acid, salts Severe attack Air present Acid, sulfuric Severe attack (b) Acid, tartaric Slight attack . . . Air Resistant . . . Ammonia Resistant . . . Bromine Severe attack . . . Carbon tetrachloride Resistant . . . Chlorine Severe attack . . . Iodine Severe attack . . . Milk Resistant . . . Motor fuel Resistant . . . Petroleum products Resistant . . . Potassium hydroxide Severe attack Increased by air Sodium carbonate Slight attack . . . Sodium hydroxide Severe attack Increased by air Water, distilled Resistant . . . Water, sea Slight attack . . . (a) Most corrosive of common organic acids. [...]... Elongation, % (a) Elongation in 50 mm (2 in .) (b) Izod impact energy of 0.9 J (0.7 ft · lbf) at 200 °C (390 °F) (c) Fatigue strength for 2 × 107 cycles, R.R Moore-type test 5 in .) deep The Brinell hardness values listed are the 8 (d) Tensile strength of 45 MPa (6.5 ksi) at 100 °C (212 °F) and 20 MPa (2.9 ksi) at 175 °C (345 °F) (e) Gage length equals 4 Area (f) Cast from 315 °C (600 °F) into mold at. .. ( 320- 430 psi) for a strain rate of 10-4 m/m per day at room temperature Rupture life: 1000 h under stress of 4.5 MPa (650 psi) at 26 °C (79 °F); 1000 h under stress of 1.4 MPa (200 psi) at 80 °C (176 °F) Dynamic liquid viscosity Estimated, 2.0 mPa · s (0. 020 poise) at the liquidus temperature Liquid surface tension Estimated: 468 mN/m at 330 °C (626 °F), 461 mN/m at 430 °C (806 °F) Electrical conductivity... thickness of the babbitt is shown in Fig 3, which also shows the marked influence of operating temperature Table 12 Physical properties and compressive strengths of selected tin-base bearing alloys Designation Specific gravity Compressive yield strength(a)(b) At 20 °C (68 °F) At 100 °C (212 °F) At 20 (68 °F) Hardness, HB(d) Compressive ultimate strength(a)(c) °C Solidus temperature Liquidus temperature... elastic modulus of 53 GPa (7.7 × 106 psi) A density of 7.28 g/cm3 (0.263 lb/in.3 ) A liquidus temperature of 295 °C (563 °F) A solidus temperature of 244 °C (471 °F) Table 9 Typical mechanical properties of pewter Form and condition Section thickness Tensile strength Elongation in 50 mm (2 in .), % Hardness, HB mm in MPa ksi Chill cast(a) 19.05 0.750 23.8 Sheet, annealed 1 h at 205 °C (400 °F), air cooled... s (e) Chill cast hardness of 27 HB Table 13 Mechanical properties of selected tin-base babbitt alloys See Table 12 for compressive strengths ASTM alloy B 23 Condition Typical strength tensile Izod strength impact Fatigue strength 106 psi J ft · lbf MPa ksi 2(a) 50 7.3 3.4(b) 2.5(b) 26(c) 3.8(c) 9 2(a) 77(d) 11.2(d) 18(e) 33(c) 4.8(c) 87(f) 12.6(f) 52(g) 7.6(g) ksi Chill cast 64... 110(a) 125 257 19.3 2.80 180(a) 150 302 12.4 1.80 180(a) Cast in 200 °C (390 °F) molds 0 32 59 8.6 50(b) -40 -40 76 11.0 50(b) -80 -112 97 14.1 55(b) - 120 -184 119 17.3 30(b) -160 -256 112 16.2 10(b) -200 -328 109 15.8 5(b) (a) In 22.5 mm (0.89 in .) (b) In 25.4 mm (1.00 in .) When measuring the tensile properties of bulk solder, the results depend greatly on the casting and testing conditions For example,... Temperature of superconductivity 7.05 K Critical field, 83.2 mT at 1.3 K Table 7 Effect of temperature on properties of 60-40 solder cast at 300 °C (570 °F) in steel molds (specimens not machined) Temperature °C °F Tensile strength MPa Elongation, % ksi Cast in 150 °C (300 °F) molds 19 66 56.4 8.18 60(a) 50 122 45.4 6.58 80(a) 75 167 41.7 6.05 90(a) 100 212 30.9 4.48 110(a) 125 257 19.3 2.80 180(a) 150... deformation at all temperatures; zinc has a similar effect at 38 °C (100 °F), but causes little or no change at room temperature Zinc has a marked effect on the microstructures of some of these alloys Small quantities of aluminum (even less than 1 %) will modify their microstructures Bismuth is objectionable because, in combination with tin, it forms a eutectic that melts at 137 °C (279 °F) At temperatures... 70(d) Sheet, quenched from 220 °C (428 °F) 2.5 0.1 51 7.4 28(d) Sheet, aged 150 °C (302 °F) 2.5 0.1 61 8.8 28(d) Wire, extruded 3.5 0.14 59 8.5 63 Wire, extruded and annealed 24 h at 225 °C (437 °F) 3.5 0.14 54 7.8 10 (a) Brinell hardness, 20 (b) Brinell hardness, 17 (c) Izod impact value, 30 J (22 ft · lbf); shear strength, 46 MPa (6.7 ksi) (d) In 50 mm (2 in .) Table 15 Creep-rupture characteristics of. .. (3.3 ksi) for strip annealed for 3 h at 100 °C (212 °F) 21 MPa (3.1 ksi) for strip annealed for 3 h at 200 °C (390 °F) 28 MPa (4.0 ksi) for cold-rolled strip (80% reduction) Bursting of a tube 25 mm (1 in .) in diameter and 0.1 mm (0.004 in .) in wall thickness occurred with an internal pressure of 320 kPa (46 psi) In a bend test, a flattened impact-extruded collapsible tube 0.1 mm (0.004 in .) in wall . 1. 80 18 0 (a) Cast in 200 °C (390 °F) molds 0 32 59 8.6 50 (b) -40 -40 76 11 .0 50 (b) -80 -11 2 97 14 .1 55 (b) -12 0 -18 4 11 9 17 .3 30 (b) -16 0 -256 11 2 16 .2 10 (b) -200 . % 1. 083 15 7.0 5 51 3.5 1. 3 51 19 6.0 5 51 7 2.256 327 .1 173 * 10 1 2.772 402 .1 79 * 13 2 3.227 468 .1 21 * 11 9 4. 214 611 .2 4.6 10 5 7.069 10 25.2 0.5 * 78 Fatigue. Elongation, % Cast in 15 0 °C (300 °F) molds 19 66 56.4 8 .18 60 (a) 50 12 2 45.4 6.58 80 (a) 75 16 7 41. 7 6.05 90 (a) 10 0 212 30.9 4.48 11 0 (a) 12 5 257 19 .3 2.80 18 0 (a) 15 0 302 12 .4 1. 80