Editing Die casting (section)

==Mold or tooling==
[[File:Ejector die half.tif|thumb|450px|The ejector die half]]
[[File:Cover die half.tif|thumb|450px|The cover die half]]

Two dies are used in die casting; one is called the "cover die half" and the other the "ejector die half". Where they meet is called the [[parting line]]. The cover die contains the [[sprue (manufacturing)|sprue]] (for hot-chamber machines) or shot hole (for cold-chamber machines), which allows the molten metal to flow into the dies; this feature matches up with the injector nozzle on the hot-chamber machines or the shot chamber in the cold-chamber machines. The ejector die contains the ejector pins and usually the [[runner (casting)|runner]], which is the path from the sprue or shot hole to the mould cavity. The cover die is secured to the stationary, or front, [[platen]] of the casting machine, while the ejector die is attached to the movable platen. The [[mould cavity]] is cut into two ''cavity inserts'', which are separate pieces that can be replaced relatively easily and bolt into the die halves.<ref name="davis251">{{harvnb|Davis|1995|p=251}}.</ref>

The dies are designed so that the finished casting will slide off the cover half of the die and stay in the ejector half as the dies are opened. This assures that the casting will be ejected every cycle because the ejector half contains the ''ejector pins'' to push the casting out of that die half. The ejector pins are driven by an ''ejector pin plate'', which accurately drives all of the pins at the same time and with the same force, so that the casting is not damaged. The ejector pin plate also retracts the pins after ejecting the casting to prepare for the next shot. There must be enough ejector pins to keep the overall force on each pin low, because the casting is still hot and can be damaged by excessive force. The pins still leave a mark, so they must be located in places where these marks will not hamper the casting's purpose.<ref name="davis251"/>

Other die components include ''[[core (manufacturing)|cores]]'' and ''slides''. Cores are components that usually produce holes or opening, but they can be used to create other details as well. There are three types of cores: fixed, movable, and loose. Fixed cores are ones that are oriented parallel to the pull direction of the dies (i.e. the direction the dies open), therefore they are fixed, or permanently attached to the die. Movable cores are ones that are oriented in any other way than parallel to the pull direction. These cores must be removed from the die cavity after the shot solidifies, but before the dies open, using a separate mechanism. Slides are similar to movable cores, except they are used to form [[undercut (manufacturing)|undercut]] surfaces. The use of movable cores and slides greatly increases the cost of the dies.<ref name="davis251"/> Loose cores, also called ''pick-outs'', are used to cast intricate features, such as [[screw thread|threaded holes]]. These loose cores are inserted into the die by hand before each cycle and then ejected with the part at the end of the cycle. The core then must be removed by hand. Loose cores are the most expensive type of core, because of the extra labor and increased cycle time.<ref name=D331>Degarmo, p. 331.</ref> Other features in the dies include water-cooling passages and vents along the [[parting line]]s. These vents are usually wide and thin (approximately {{convert|0.13|mm|in|3|disp=or|abbr=on}}) so that when the molten metal starts filling them the metal quickly solidifies and minimizes scrap. No [[riser (casting)|risers]] are used because the high pressure ensures a continuous feed of metal from the gate.<ref name="degarmo329"/>

The most important material properties for the dies are [[thermal shock]] resistance and softening at elevated temperature; other important properties include [[hardenability]], [[machinability]], heat checking resistance, weldability, availability (especially for larger dies), and cost. The longevity of a die is directly dependent on the temperature of the molten metal and the cycle time.<ref name="davis251"/> The dies used in die casting are usually made out of hardened [[tool steel]]s, because [[cast iron]] cannot withstand the high pressures involved, therefore the dies are very expensive, resulting in high start-up costs.<ref name="degarmo329">Degarmo, p. 329–331.</ref> Metals that are cast at higher temperatures require dies made from higher [[alloy steel]]s.<ref name="davis252">{{harvnb|Davis|1995|p=252}}.</ref>

{| class="wikitable"
|+ Die and component material and hardness for various cast metals
|-
! rowspan=3 | Die component !! colspan=6 | Cast metal
|-
! colspan=2 | Tin, lead & zinc !! colspan=2 | Aluminium & magnesium !! colspan=2 | Copper & brass
|-
! Material !! Hardness !! Material !! Hardness !! Material !! Hardness
|-
| rowspan=3 | Cavity inserts || [[P-grade tool steel|P20]]{{refn|For short-run zinc castings only.|group="note"}} || 290–330 [[Brinell hardness scale|HB]] || H13 || 42–48 [[Rockwell hardness scale|HRC]] || [[Deutsches Institut für Normung|DIN]] 1.2367 || 38–44 HRC
|-
| [[Hot working tool steel|H11]] || 46–50 HRC || H11 || 42–48 HRC || H20, H21, H22 || 44–48 HRC
|-
| H13 || 46–50 HRC || || || ||
|-
| rowspan=2 | Cores || H13 || 46–52 HRC || H13 || 44–48 HRC || DIN 1.2367 || 40–46 HRC
|-
| || || DIN 1.2367 || 42–48 HRC || ||
|-
| Core pins || H13 || 48–52 HRC || DIN 1.2367 [[prehard]] || 37–40 HRC || DIN 1.2367 prehard || 37–40 HRC
|-
| Sprue parts || H13 || 48–52 HRC || H13<br />DIN 1.2367 || 46–48 HRC<br />44–46 HRC || DIN 1.2367 || 42–46 HRC
|-
| Nozzle || [[Stainless steel|420]] || 40–44 HRC || H13 || 42–48 HRC || DIN 1.2367<br />H13 || 40–44 HRC<br />42–48 HRC
|-
| Ejector pins || H13<ref name="nitride" group="note">Nitrided.</ref> || 46–50 HRC || H13<ref name="nitride" group="note"/> || 46–50 HRC || H13<ref name="nitride" group="note"/> || 46–50 HRC
|-
| Plunger shot sleeve || H13<ref name="nitride" group="note"/> || 46–50 HRC || H13<ref name="nitride" group="note"/><br />DIN 1.2367<ref name="nitride" group="note"/> || 42–48 HRC<br />42–48 HRC || DIN 1.2367<ref name="nitride" group="note"/><br />H13<ref name="nitride" group="note"/> || 42–46 HRC<br />42–46 HRC
|-
| Holder block || [[41xx steel|4140 prehard]] || ~300 HB || 4140 prehard || ~300 HB || 4140 prehard || ~300 HB
|}

The main failure mode for die casting dies is [[wear]] or [[erosion]]. Other failure modes are ''heat checking'' and ''thermal fatigue''. Heat checking is when surface cracks occur on the die due to a large temperature change on every cycle. Thermal fatigue is when surface cracks occur on the die due to a large number of cycles.<ref name=D329>Degarmo, p. 329.</ref>

{| class="wikitable"
|+ Typical die temperatures and life for various cast materials<ref>{{Citation |last1= Schrader |first1= George F. |last2= Elshennawy |first2= Ahmad K. |last3= Doyle |first3= Lawrence E. |title= Manufacturing processes and materials |page= 186 |publisher= SME |year= 2000 |edition= 4th |url= https://books.google.com/books?id=Nz2wXvmkAF0C&pg=PT207 |isbn= 978-0-87263-517-3 |postscript= .}}</ref>
|-
! !! Zinc !! Aluminium !! Magnesium !! Brass (leaded yellow)
|-
| Maximum die life [number of cycles] || 1,000,000 || 100,000 || 100,000 || 10,000
|-
| Die temperature [°C (°F)] || 218 (425) || 288 (550) || 260 (500) || 500 (950)
|-
| Casting temperature [°C (°F)] || 400 (760) || 660 (1220) || 760 (1400) || 1090 (2000)
|}