specifi cation on casting blueprints, they should defi ne the chem- istry of the ingot used to make the cast components, not the fi nal castings. The number XXX.0 for castings includes a chemistry dif- ferent from the ingot specifi cations. This leaves room for chemistry changes that can occur during remelting. The addition of casting returns, such as scrap castings, to the charge material also can alter the casting chemistry. The primary difference is that the XXX.0 specifi cations allow for some magnesium loss (due to burn out) and iron or zinc pickup that may be experienced during process- ing. The alloy chemistry of the fi nal 356 cast component should fall within the limits of the 356.0 specifi cations but may not meet the chemical specifi cation for the 356.1 ingot. Final cast components also should be properly designated.


If a blueprint designates 356.1 as the casting alloy, it would be improper to designate the fi nal castings as 356.1. Components should be shipped designated as 356.0 castings. Metal Matrix Composites—Aluminum metal matrix compos-


ites (Al-MMCs) consist of nonmetallic reinforcements incorpo- rated into an aluminum matrix. Reinforcements can be continu- ous or discontinuous, the most common being silicon carbide. Other reinforcements include boron, alumina and graphite fi bers, as well as various particles, short fi bers and whiskers. Al-MMCs have better stiffness, wear resistance and thermal conductivity than base aluminum alloys. The American National Standards Institute specifi es that Al-MMCs be identifi ed as follows: Matrix/ reinforcement/volume%/form. Using this formula, a 356 aluminum alloy reinforced with 20% SiC particulate would be designated as 356/SiC/20p.


Heat Treatment Many aluminum castings meet property requirements in the


as-cast condition and do not require further processing. How- ever, to improve properties and enhance strength and ductility, aluminum castings often are thermally processed by a series of heating and cooling cycles called heat treatment. This thermal processing involves three basic operations: solution, quench and age. Solution treatment involves heating the casting to near the eutectic temperature to dissolve the eutectic constituent and form a solid homogeneous solution. Following this solution treatment, castings can be quenched or


rapidly cooled, often in boiling water, which helps retain the homo- geneous solution at room temperature. A third step used in heat treatment of aluminum castings is natural or artifi cial aging, which increases strength and hardness. Age hardening principles also can be used to tailor heat treatments to each application. Combinations


This electric valve housing was cast in C355 aluminum via semi- permanent mold casting.


2010 Casting sourCe DireCtory Metal Casting Design & PurChasing 31


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44  |  Page 45  |  Page 46  |  Page 47  |  Page 48  |  Page 49  |  Page 50  |  Page 51  |  Page 52  |  Page 53  |  Page 54  |  Page 55  |  Page 56  |  Page 57  |  Page 58  |  Page 59  |  Page 60  |  Page 61  |  Page 62  |  Page 63  |  Page 64  |  Page 65  |  Page 66  |  Page 67  |  Page 68  |  Page 69  |  Page 70  |  Page 71  |  Page 72  |  Page 73  |  Page 74  |  Page 75  |  Page 76  |  Page 77  |  Page 78  |  Page 79  |  Page 80  |  Page 81  |  Page 82  |  Page 83  |  Page 84  |  Page 85  |  Page 86  |  Page 87  |  Page 88  |  Page 89  |  Page 90  |  Page 91  |  Page 92  |  Page 93  |  Page 94  |  Page 95  |  Page 96  |  Page 97  |  Page 98  |  Page 99  |  Page 100  |  Page 101  |  Page 102  |  Page 103  |  Page 104  |  Page 105  |  Page 106  |  Page 107  |  Page 108  |  Page 109  |  Page 110  |  Page 111  |  Page 112  |  Page 113  |  Page 114  |  Page 115  |  Page 116  |  Page 117  |  Page 118  |  Page 119  |  Page 120  |  Page 121  |  Page 122  |  Page 123  |  Page 124  |  Page 125  |  Page 126  |  Page 127  |  Page 128  |  Page 129  |  Page 130  |  Page 131  |  Page 132  |  Page 133  |  Page 134  |  Page 135  |  Page 136  |  Page 137  |  Page 138  |  Page 139  |  Page 140  |  Page 141  |  Page 142  |  Page 143  |  Page 144  |  Page 145  |  Page 146  |  Page 147  |  Page 148  |  Page 149  |  Page 150  |  Page 151  |  Page 152  |  Page 153  |  Page 154  |  Page 155  |  Page 156  |  Page 157  |  Page 158  |  Page 159  |  Page 160  |  Page 161  |  Page 162  |  Page 163  |  Page 164  |  Page 165  |  Page 166  |  Page 167  |  Page 168  |  Page 169  |  Page 170  |  Page 171  |  Page 172  |  Page 173  |  Page 174  |  Page 175  |  Page 176  |  Page 177  |  Page 178  |  Page 179  |  Page 180  |  Page 181  |  Page 182  |  Page 183  |  Page 184  |  Page 185  |  Page 186  |  Page 187  |  Page 188  |  Page 189  |  Page 190  |  Page 191  |  Page 192