Foseco Non-Ferrous Foundryman’s Handbook Part 2 doc

8 Foseco Non-Ferrous Foundryman’s Handbook The physical properties of metals (Continued) Element Thermal conductivity (W/m · K) Resistivity (␮ohm · cm at 20°C) Vol · change on melting (%) Density (g/cm 3 ) Coeff · of expansion (ϫ 10 –6 /K) Brinell hardness no · Al 238 2.67 6.6 2.70 23.5 17 Sb 23.8 40.1 1.4 6.68 11 30 As – 33.3 – 5.73 5.6 – Ba – 60 – 3.5 18 – Be 194 3.3 – 1.85 12 – Bi 9 117 –3.3 9.80 13.4 9 Cd 103 7.3 4.7 8.64 31 20 Ca 125 3.7 – 1.54 22 13 C 16.3 ––2.30 7.9 – Ce 11.9 85.4 – 6.75 8 – Cr 91.3 13.2 – 7.10 6.5 350 Co 96 6.3 – 8.90 12.5 125 Cu 397 1.69 4.1 8.96 17 48 Ga 41 ––5.91 18.3 – Au 316 2.2 5.2 19.3 14.1 18.5 In 80 8.8 – 7.3 24.8 1 Ir 147 5.1 – 22.4 6.8 172 Fe 78 10.1 5.5 7.87 12.1 66 Pb 35 20.6 3.4 11.68 29 5.5 Li 76 9.3 1.5 0.53 56 – Mg 156 4.2 4.2 1.74 26 25 Mn 7.8 160 – 7.4 23 – Hg 8.7 96 3.75 13.55 61 – Mo 137 5.7 – 10.2 5.1 147 Ni 89 6.9 – 8.9 13.3 80 Nb 54 16 – 8.6 7.2 – Os 87 8.8 – 22.5 4.6 – Pd 75 10.8 – 12.0 11.0 50 P –––1.83 6.2 – Pt 73 10.6 – 21.45 9.0 52 K 104 6.8 2.8 0.86 83 0.04 Rh 148 4.7 – 12.4 8.5 156 Si 139 10 3 –10 6 – 2.34 7.6 – Ag 425 1.6 4.5 10.5 19.1 25 Na 128 4.7 2.5 0.97 71 0.1 Sr – 23 – 2.6 100 – S 272 ––2.07 70 – Ta 58 13.5 – 16.6 6.5 40 Te 3.8 1 · 6 ϫ 10 5 – 6.24 –– Tl 45.5 16.6 – 11.85 30 – Sn 73.2 12.6 2.8 7.3 23.5 – Ti 21.6 54 – 4.5 8.9 – W 174 5.4 – 19.3 4.5 – U2827– 19.0 –– V 31.6 19.6 – 6.1 8.3 – Zn 120 6.0 6.5 7.14 31 35 Zr 22.6 44 – 6.49 5.9 – Tables and general data 9 Densities of casting alloys Alloy BS1490 g/ml Alloy BS1400 g/ml Aluminium alloys Copper alloys Pure Al 2.70 HC copper HCC1 8.9 Al–Si5Cu3 LM4 2.75 Brass CuZn38Al DCB1 8.5 Al–Si7Mg LM25 2.68 CuZn33Pb2Si HTB1 8.5 Al–Si8Cu3Fe LM24 2.79 CuZn33Pb2 SCB3 8.5 AlSi12 LM6 2.65 Phosphor bronze CuSn11P PB1 8.8 Cast steels CuSn12 PB2 8.7 Low carbon <0.20 7.86 Lead bronze Med. carbon 0.40 7.86 CuSn5Pb20 LB5 9.3 High carbon >0.40 7.84 Al bronze CuAl10Fe2 AB1 7.5 Low alloy 7.86 Gunmetal Med. alloy 7.78 CuSnPb5Zn5 LG2 8.8 Med./high alloy 7.67 Copper nickel CuNi30Cr2FeMnSi CN1 8.8 Stainless 13Cr 7.61 Cast irons 18Cr8Ni 7.75 Grey iron 150 MPa 6.8–7.1 200 7.0–7.2 Other alloys 250 7.2–7.4 Zinc base 300 7.3–7.4 ZnAl4Cu1 6.70 Whiteheart malleable 7.45 Blackheart malleable 7.27 Lead base White iron 7.70 PbSb6 10.88 Ductile iron (s.g.) 7.2–7.3 Tin base (Babbit) 7.34 Ni-hard 7.6–7.7 Inconel Ni76Cr18 8.50 High silicon (15%) 6.8 10 Foseco Non-Ferrous Foundryman’s Handbook Approximate bulk densities of common materials Material kg/m 3 lb/ft 3 Material kg/m 3 lb/ft 3 Aluminium, cast 2560 160 Lead 11370 710 wrought 2675 167 Limestone 2530–2700 158–168 Aluminium bronze 7610 475 Ashes 590 37 Magnesite 2530 158 Mercury 13 560 847 Brass, rolled 8390 524 Monel 8870 554 swarf 2500 157 Babbit metal 7270 454 Nickel, cast 8270 516 Brick, common 1360–1890 85–118 Nickel silver 8270 516 fireclay 1840 115 Bronze 8550 534 Phosphor bronze 8580 536 Pig iron, mean 4800 300 Cast iron, solid 7210 450 Pig iron and scrap turnings 2240 140 (cupola charge) 5400 336 Cement, loose 1360 85 Chalk 2240 140 Sand, moulding 1200–1440 75–90 Charcoal, lump 290 18 silica 1360–1440 85–90 Clay 1900–2200 120–135 Silver, cast 10500 656 Coal 960–1280 60–80 Steel 7850 490 Coal dust 850 53 Coke 450 28 Tin 7260 453 Concrete 2240 140 Copper, cast 8780 548 Water, ice 940 58.7 Cupola slag 2400 150 liquid 0°C 1000 62.4 100°C 955 59.6 Dolomite 2680 167 Wood, balsa 100–130 7–8 oak 830 52 Fire clay 1440 90 pine 480 30 French chalk 2600 162 teak 640 40 Wrought iron 7700 480 Glass 2230 139 Gold, pure 19 200 1200 Zinc, cast 6860 428 22 carat 17 500 1090 rolled 7180 448 Graphite, powder 480 30 solid 2200 138 Tables and general data 11 Patternmakers’ contraction allowances Castings are always smaller in dimensions than the pattern from which they are made, because as the metal cools from its solidification temperature to room temperature, thermal contraction occurs. Patternmakers allow for this contraction by making patterns larger in dimensions than the required castings by an amount known as the “contraction allowance”. Originally this was done by making use of specially engraved rules, known as “contraction rules”, the dimensions of which incorporated a contraction allowance such as 1 in 75 for aluminium alloys, or 1 in 96 for iron castings. Nowadays, most patterns and coreboxes are made using computer- controlled machine tools and it is more convenient to express the contraction as a percentage allowance. Predicting casting contraction can never be precise, since many factors are involved in determining the exact amount of contraction that occurs. For example, when iron castings are made in greensand moulds, the mould walls may move under the pressure of the liquid metal, causing expansion of the mould cavity, thus compensating for some of the metal contraction. Cored castings may not contract as much as expected, because the presence of a strong core may restrict movement of the casting as it is cooling. Some core binders expand with the heat of the cast metal causing the casting to be larger than otherwise expected. For these reasons, and others, it is only possible to predict contractions approximately, but if a patternmaker works with a particular foundry for a long period, he will gain experience with the foundry’s design of castings and with the casting methods used in the foundry. Based on such experience, more precise contraction allowances can be built into the patterns. 12 Foseco Non-Ferrous Foundryman’s Handbook The usually accepted contraction allowances for different alloys are given in the following table. Alloy Contraction allowance (%) Aluminium alloys Al–Si5Cu3 LM4 Al–Si7Mg LM25 1.3 Al–Si8Cu3Fe LM24 Al–Si12 LM6 Beryllium copper 1.6 Bismuth 1.3 Brass 1.56 Bronze, aluminium 2.32 manganese 0.83–1.56 phosphor 1.0–1.6 silicon 1.3–1.6 Cast iron, grey 0.9–1.04 white 2.0 ductile (s.g.) 0.6–0.8 malleable 1.0–1.4 Copper 1.6 Gunmetal 1.0–1.6 Lead 2.6 Magnesium alloys 1.30–1.43 Monel 2.0 Nickel alloys 2.0 Steel, carbon 1.6–2.0 chromium 2.0 manganese 1.6–2.6 Tin 2.0 White metal 0.6 Zinc alloys 1.18 Tables and general data 13 Volume shrinkage of principal casting alloys Most alloys shrink in volume when they solidify, the shrinkage can cause voids in castings unless steps are taken to “feed” the shrinkage by the use of feeders. Casting alloy Volume shrinkage (%) Carbon steel 6.0 Alloyed steel 9.0 High alloy steel 10.0 Malleable iron 5.0 Al 8.0 Al–Cu4Ni2Mg 5.3 Al–Si12 3.5 Al–Si5Cu2Mg 4.2 Al–Si9Mg 3.4 Al–Si5Cu1 4.9 Al–Si5Cu2 5.2 Al–Cu4 8.8 Al–Sil0 5.0 Al–Si7NiMg 4.5 Al–Mg5Si 6.7 Al–Si7Cu2Mg 6.5 Al–Cu5 6.0 Al–MglSi 4.7 Al–Zn5Mg 4.7 Cu (pure) 4.0 Brass 6.5 Bronze 7.5 Al bronze 4.0 Sn bronze 4.5 14 Foseco Non-Ferrous Foundryman’s Handbook Comparison of sieve sizes Sieves used for sand grading are of 200 mm diameter and are now usually metric sizes, designated by their aperture size in micrometres (␮m). The table lists sieve sizes in the British Standard Metric series (BS410:1976) together with other sieve types. Sieve aperture, micrometres and sieve numbers ISO/R.565 series (BS410:1976) BSS ASTM (␮m) No. ␮m No. ␮m (1000) 16 1003 18 1000 710 22 699 22 710 500 30 500 30 500 355 44 353 45 350 250 60 251 60 250 (212) 72 211 70 210 180 (150) 100 152 100 149 125 120 125 90 150 104 150 105 63 200 76 200 74 (45) 300 53 325 44 Notes: The 1000 and 45 sieves are optional. The 212 and 150 sieves are also optional, but may be included to give better separation between the 250 and 125 sieves. Tables and general data 15 Calculation of average grain size The adoption of the ISO metric sieves means that the old AFS grain fineness number can no longer be calculated. Instead, the average grain size, expressed as micrometres (␮m) is now used. This is determined as follows: 1 Weigh a 100 g sample of dry sand. 2 Place the sample into the top sieve of a nest of ISO sieves on a vibrator. Vibrate for 15 minutes. 3 Remove the sieves and, beginning with the top sieve, weigh the quantity of sand remaining on each sieve. 4 Calculate the percentage of the sample weight retained on each sieve, and arrange in a column as shown in the example. 5 Multiply the percentage retained by the appropriate multiplier and add the products. 6 Divide by the total of the percentages retained to give the average grain size. Example ISO aperture (␮m) Percentage retained Multiplier Product ≥710 trace 1180 0 500 0.3 600 180 355 1.9 425 808 250 17.2 300 5160 212 25.3 212 5364 180 16.7 212 3540 150 19.2 150 2880 125 10.6 150 1590 90 6.5 106 689 63 1.4 75 105 ≤63 0.5 38 19 Total 99.6 – 20 335 Average grain size = 20 335/99.6 = 204 ␮m 16 Foseco Non-Ferrous Foundryman’s Handbook Calculation of AFS grain fineness number Using either the old BS sieves or AFS sieves, follow, steps 1–4 above. 5 Arrange the results as shown in the example below. 6 Multiply each percentage weight by the preceding sieve mesh number. 7 Divide by the total of the percentages to give the AFS grain fineness number. Example BS sieve number % sand retained on sieve Multiplied by previous sieve no · Product 10 nil –– 16 nil –– 22 0.2 16 3.2 30 0.8 22 17.6 44 6.7 30 201.0 60 22.6 44 1104.4 100 48.3 60 2898.0 150 15.6 100 1560.0 200 1.8 150 270.0 pan 4.0 200 800.0 Total 100.0 – 6854.2 AFS grain fineness number = 6854.2/100 = 68.5 or 68 AFS Foundry sands usually fall into the range 150–400 ␮m, with 220–250 ␮m being the most commonly used. Direct conversion between average grain size and AFS grain fineness number is not possible, but an approximate relation is shown below: AFS grain fineness no. 35 40 45 50 55 60 65 70 80 90 Average grain size (␮m) 390 340 300 280 240 220 210 195 170 150 While average grain size and AFS grain fineness number are useful parameters, choice of sand should be based on particle size distribution. Tables and general data 17 Recommended standard colours for patterns Part of pattern Colour As-cast surfaces which are to be left unmachined Red or orange Surfaces which are to be machined Yellow Core prints for unmachined openings and end prints Periphery Black Ends Black Core prints for machined openings Periphery Yellow stripes on black Ends Black Pattern joint (split patterns) Cored section Black Metal section Clear varnish Touch core Cored shape Black Legend ‘‘Touch’’ Seats of and for loose pieces and loose core prints Green Stop offs Diagonal black stripes with clear varnish Chilled surfaces Outlined in Black Legend ‘‘Chill’’ [...]... filled unfiltered 30 25 Tensile strength: MPs Frequency Frequency 30 25 20 15 10 5 0 160 20 0 24 0 Range 28 0 20 15 10 5 0 320 Tensile strength: MPs 160 20 0 24 0 Range 160 20 0 24 0 Range 28 0 320 Bottom filled unfiltered Frequency Frequency Bottom filled filtered 30 25 20 15 10 5 0 Tensile strength: MPs 28 0 320 30 25 20 15 10 5 0 Tensile strength: MPs 160 20 0 24 0 Range 28 0 320 Figure 2. 1 Histograms showing... Table 2. 1a BS EN 1706:1988 alloys commonly used for sand casting Alloy group Alloy designation Numerical Al Cu Al SiMgTi Al Si7Mg Al Si10M Al Si Al Si5Cu Al Si9Cu Al Si(Cu) Al Mg Al ZnMg Chemical symbols EN AC -21 000 EN AC -21 100 EN AC-41000 EN AC- 420 00 EN AC- 421 00 EN AC- 422 00 EN AC-43000 EN AC-43100 EN AC-4 320 0 EN AC-43300 EN AC-44000 EN AC-44100 EN AC-4 420 0 EN AC-45000 EN AC-4 520 0 EN AC-45300 EN AC-4 620 0... AlSi7Mg AlSi10Mg AlSi AlSi5Cu AlSi9Cu AlSi(Cu) AlSiCuNiMg AlMg AlZnMg 27 Chemical symbols EN AC -21 000 EN AC -21 100 EN AC-41000 EN AC- 420 00 EN AC- 421 00 EN AC- 422 00 EN AC-43000 EN AC-43100 EN AC-4 320 0 EN AC-43300 EN AC-44000 EN AC-44100 EN AC-4 420 0 EN AC-45000 EN AC-45100 EN AC-4 520 0 EN AC-45300 EN AC-45400 EN AC-4 620 0 EN AC-46300 EN AC-46400 EN AC-46600 EN AC-47000 EN AC-48000 EN AC-51000 EN AC-51100 EN AC-51300...18 Foseco Non-Ferrous Foundryman’s Handbook Dust control in foundries Air extraction is used in foundries to remove silica dust from areas occupied by operators The following table indicates the approximate air velocities needed to entrain sand particles Terminal velocities of spherical particles of density 2. 5 g/cm3 (approx.) BS sieve size 16 30 44 60 100 150 20 0 Particle dia (␮m) Terminal... – System of dimensional tolerances, which is applicable to the dimensions of cast metals and their alloys produced by sand moulding, gravity diecasting, low 22 Foseco Non-Ferrous Foundryman’s Handbook Figure 1 .2 The average tolerance (taken as 2. 5␴) exhibited by various casting processes (From Campbell, J (1991) Castings, Butterworth-Heinemann, reproduced by permission of the publishers.) pressure... AC-Al EN AC-Al Cu4MgTi Cu4Ti Si2MgTi Si7Mg Si7Mg0,3 Si7Mg0,6 Si10Mg(a) Si10Mg(b) Si10Mg(Cu) Si9Mg Si11 Si 12( b) Si 12( a) Si6Cu4 Si5Cu3Mg Si5Cu3Mn Si5Cu1Mg Si5Cu3 Si8Cu3 Si7Cu3Mg Si9Cu1Mg Si7Cu2 Si 12( Cu) Si12CuNiMg Mg3(b) Mg3(a) Mg5 Mg5(Si) Zn5Mg Table 2. 4 lists the BS 1490:1988 “LM alloys” and their approximate equivalents in European, National and International Standards Table 2. 5 shows the chemical composition... Cu4Ti Si2MgTi Si7Mg Si7Mg0,3 Si7Mg0,6 Si10Mg(a) Si10Mg(b) Si10Mg(Cu) Si9Mg Si11 Si 12( b) Si 12( a) Si6Cu4 Si5Cu3Mn Si5Cu1Mg Si8Cu3 Si9Cu1Mg Si7Cu2 Si 12( Cu) Mg3(b) Mg3(a) Mg5 Mg5(Si) Zn5Mg Aluminium casting alloys Table 2. 1b BS EN 1706:1988 alloys commonly used for chill casting Alloy group Alloy designation Numerical AlCu AlSiMgTi AlSi7Mg AlSi10Mg AlSi AlSi5Cu AlSi9Cu AlSi(Cu) AlSiCuNiMg AlMg AlZnMg 27 Chemical... a cast alloy is 20 0 MPa, the designer must use a lower figure, say 150 MPa, as the strength of the alloy to take into account the variability of properties If the spread of the distribution curve can be reduced, then a higher design strength, say 170 MPa can be used, even though the process mean for the alloy and the casting process stays the same 24 Foseco Non-Ferrous Foundryman’s Handbook Top filled... (From Foseco Foundry Practice, 22 6, July 1995.) The strength of castings does not follow the normal bell-shaped distribution curve Figure 2. 1 shows the range of tensile strengths found in 12. 5 mm diameter test bars cast in an Al–Si7 Mg alloy into resin bonded sand moulds using various pouring methods: top or bottom filled, filtered or unfiltered In all cases the process mean tensile strength is about 26 0... standards, it partially supersedes BS 1490:1988 which will be withdrawn when EN 1559–4 is published BS EN 1559–1:1997 Founding Technical conditions of delivery General BS EN 1676:1997 Aluminium and aluminium alloys Alloyed ingots for remelting Specifications PrEN 1559–4 Founding Technical conditions of delivery Additional requirements for aluminium castings 26 Foseco Non-Ferrous Foundryman’s Handbook BS . 1000 710 22 699 22 710 500 30 500 30 500 355 44 353 45 350 25 0 60 25 1 60 25 0 (21 2) 72 211 70 21 0 180 (150) 100 1 52 100 149 125 120 125 90 150 104 150 105 63 20 0 76 20 0 74 (45) 300 53 325 44 Notes:. 1.9 425 808 25 0 17 .2 300 5160 21 2 25 .3 21 2 5364 180 16.7 21 2 3540 150 19 .2 150 28 80 125 10.6 150 1590 90 6.5 106 689 63 1.4 75 105 ≤63 0.5 38 19 Total 99.6 – 20 335 Average grain size = 20 335/99.6 =. 19.1 25 Na 128 4.7 2. 5 0.97 71 0.1 Sr – 23 – 2. 6 100 – S 27 2 – 2. 07 70 – Ta 58 13.5 – 16.6 6.5 40 Te 3.8 1 · 6 ϫ 10 5 – 6 .24 –– Tl 45.5 16.6 – 11.85 30 – Sn 73 .2 12. 6 2. 8 7.3 23 .5 – Ti 21 .6 54