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Basic Considerations For Die Castings

• Dimensional tolerances depend on part configuration. They are dependent on moving die members, the size of the part (projected area), and whether dimensions run across the parting line of the die. Never specify dimensional tolerances closer than are essential and practical to the die cast process.
• When dimensioning part always specify
  A. Amount of draft.
  B. Where dimension is to be held (does dimension increase or decrease because of draft).
• Provide the maximum permissible radii on all corners and try to stay away from sharp corners wherever possible.
• Keep wall sections a uniform thickness.
• Raised engraving on part is desirable and less costly than depressed lettering.
• Minimum machine stock is very important. Over .030 per side could result in opening up porosity.
• Stay away from holes smaller than 4-40 for the following reasons:
  A. Cannot core.
  B. Porosity is a problem in dig drilling and tapping holes this size or smaller. (Minimum hole diameter as a rule is .125 for aluminum and .093 for zinc.)
• Allow a minimum of three (3) times the pitch of thread beyond depth of required tapped hole depth, to allow for tap lead.
• Stay away from undercuts at base of thread.
• Cast threads are possible in class 1 gage limits, allow a flat at 180° if possible for trimming.
• Use roll taps where possible on depth holes. In the case where a thru hole requires a stronger thread, use a roll tap, but hole should have a cast countersink at both ends to prevent bulge.
• Use heli-coils where excessive assembly and disassembly of bolts is required.
• Utilize cast-in inserts for extreme wear areas.
• Close tolerance machined castings should be stress relieved.

Fillets, Ribs, And Corners

FILLETS
Intersecting surfaces forming junctions of metal thickness are properly joined with fillets in order to avoid high stress concentrations in the die castings and to control and facilitate maintenance of otherwise squared edges in the casting die. Fillets projected in a direction normal to the parting plane require draft, but the amount is always governed by the draft of the intersecting surfaces. Draft in corners or fillets projecting in a direction normal to the parting plane have approximately 1.5 the amount of draft of the intersecting walls.

In the sketches above, consideration has been given to the stresses of use and to the stress induced in the die castings of moderate depth. Shallow die castings may have much smaller fillets, while deep pockets and other inside corners may have larger fillets. Sharply squared corners of much length projecting in a direction normal to the parting plane may cause spalled edges in withdrawing the die castings from the die.

RIBS
Ribs are used to increase the stiffness of, or add strength to, a die casting and to aid in making sound die castings. Ribs are something misused and can be a detriment if working stresses are concentrated by their use or if stresses at the edges of the ribs are high.

EXTERNAL CORNERS
Sharply squared corners may be used in many locations if die construction permits. This type of corner is often mandatory at parting line locations and die block intersections. Other than this, corners of die castings should have radii in order to prevent early die failure, to reduce the probability of nicking the edge of the die casting in handling, and to minimize material handling hazards for personnel.

Pressure Tightness

Most die castings can be cast pressure tight. However, in some cases impregnation may be required. Consultation with the die caster in the early design stage is recommended where a requirement for pressure tightness exists in order to take advantage of the basic knowledge of the design and processing factors which will help him to cast pressure tight die casting.

Important considerations relating to the economic production of pressure tight die casting include the following :

DESIGN
Successful casting of pressure tight die castings requires conformance to the principles of good die casting design.
Recommendations concerning fillets, ribs and corners contained in ADCI Product Standard E15 should be followed very carefully.
Sections should be as uniform as possible.
Holes and passage requiring pressure tightness should be cored to reduce the effect of porosity. Ample draft should be allowed in cored holes and passages which are not machined.
Heavy sections should be avoided.
Careful consideration of the factors of good design will aid in the economical casting of pressure tight die castings.

MACHINING
The nature of the die casting process is such that the outer surface of a die casting is usually dense and relatively free from porosity.
A minimum amount of machining stock should be allowed to avoid cutting deeply into a die casting where porosity may be present.
Avoid large draft angles which would require the removal of a large amount of stock from surfaces to be machined, particularly where holes are cored.
Where a large amount of machining must be done, impregnation probably will be required after machining.

Size
Larger die castings are generally more difficult to cast pressure tight and will require pressure testing by the caster to assure adequate process control. Impregnation is more generally required for large die castings.

PRESSURE
Pressure requirements for die castings are generally in order of 5 to 15 psi. Pressure in excess of 100 psi will require special consideration by the die caster.

ALLOY
Certain alloys are better for making pressure tight die castings. Reference is made to ADCI Product Standard M4 for aluminum alloys (in which comparisons are shown for pressure tightness of various aluminum alloys) to aid in the selection of the favorable alloy.

PRESSURE TESTING
Reference is made to the last two paragraphs of ADCI Product Standard C8-56.

Surface Finish, As Cast

General Purpose of Standard on As Cast Surface Finish:
For some applications it is desirable to specify Surface finish requirements. The purpose of this specification is to classify as cast surface finish of die castings into a series of grades so that the type of finish required may be defined in advance. These standards should be used to classify the type of finish only, and final quality. standards should be agreed upon between the die caster and the customer.

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Typical Mechanical Properties Aluminum Alloys

Ingot Alloy Designation Casting Alloy Designation			Temper	Tensile Strength KSI		Elongation % in 2 in.	Hardness, Brinell 500 kg load 10mm ball	Shearing Strength KSI (3)	Endurance Limit (4) KSI	Modules of Elasticity (5) PSI x 106
AA	FORMER	AA		ULTIMATE(2)	YIELD(2)
360.2	360.2	360.0	F	47.0	25	3.0	75	30	19.0	10.3
A360.2	A360	A360.0	F	46.0	24	3.5	75	26	18.0	-
364.2	364	364.0	F	43.0	23	7.5	-	26	18.0	-
380.2	380	380.0	F	48.0	24	3.0	80	31	21.0	10.3
A380.2	A380	A380.0	F	47.0	23	3.5	80	30	20.0	-
B380.2	380	B380.0	F	47.0	24	3.5	80	29	19.0	-
383.2	383	383.0	F	45.0	22	3.5	75	-	-	-
384.2	384	384.0	F	47.0	25	2.5	85	30	19	10.3
A384.2	384Z	A384.0	F	48.0	24	2.5	85	28	19	-
390.2	390	390.0	F	40.5	35	1.0	120	-	20.0	11.9
A413.2	13	413.0	F	42.0	19	3.5	80	25	19.0	10.3
443.2	43	443.0	F	33.0	14	9.0	50	19	17	10.3
A514.2	A214	A514.0	F	40.0	22	10.0	-	26	18.0	-
L514.2	L214	L514.0	F	41.0	-	10.0	-	-	-	-
518.2	218	518.0	F	45.0	27	5.0	80	29	20.0	-

Typical Physical Properties of Aluminum Casting Alloys

Ingot Alloy Designation Casting Alloy Designation			Specific Gravity	Weight LB/CU IN.	Approximate Solidification range of	Electrical Conductivity per cent of I.A.C.S. (4)	Thermal Conductivity at 25oC CGS units (2)	Coefficient of thermal expansion per of X 10-6
AA	FORMER	AA						68-212oF	68-572oF
208.2	108	208.0-F	2.79	0.101	1160-970	31	0.29	12.4	13.4
208.2	108	208.0 Annealed (3)	2.79	0.101	1160-970	38	0.35	-	-
213.1	C113	213.5-F	2.92	0.106	1160-970	30	0.29	12.2	13.3
222.1	122	222.0-F (1)	2.95	0.107	1155-965	34	0.32	12.3	13.1
222.1	122	222.0-T2	2.95	0.107	1155-965	41	0.38	-	-
222.1	122	222.0-T61	2.95	0.107	1155-965	33	0.31	12.3	13.1
238.2A240.1	138	238.0-F (1)	2.95	0.107	1110-945	25	0.25	11.9	12.7
A240.1	A140	A240.0-F	2.79	0.101	1110-950	23	0.23	12.3	13.5
242.2	142	242.2.0-T21	2.81	0.102	1175-990	44	0.40	-	-
242.2	142	242.2.0-T571 (1)	2.81	0.102	1175-990	34	0.32	12.5	13.6
242.2	142	242.2.0-T61 (1)	2.81	0.102	1175-990	33	0.32	12.5	13.6
242.2	142	242.2.0-T77	2.81	0.102	1175-990	38	0.36	12.3	13.1
295.2	195	295.0-T4	2.81	0.102	1190-970	35	0.33	12.7	13.8
295.2	195	295.0-T6	2.81	0.102	1190-970	35	0.34	12.7	13.8
B295.22	B195	B295.0-T4 (1)	2.80	0.101	1170-970	33	0.32	12.2	13.3
B295.2	B195	B295.0-T6 (1)	2.81	0.101	1170-970	33	0.31	12.2	13.3
308.2	A108	308.0 (1)	2.79	0.101	1135-970	37	0.34	11.9	12.7
319.2	319	319.0-F	2.79	0.101	1120-960	27	0.27	11.9	12.7
319.2	319	319.0-F (1)	2.79	0.101	1120-960	28	0.28	-	-
A332.2	A132	A332.0-T551	2.72	0.098	1050-1000	29	0.28	11.0	12.0
F332.2	F132	F332.0-T5 (1)	2.76	0.100	1080-970	26	0.25	11.5	12.4
333.1	333	333.0-F (1)	2.77	0.100	1085-960	26	0.25	11.4	12.4
333.1	333	333.0-T5 (1)	2.77	0.100	1085-960	29	0.29	11.4	12.4
333.1	333	333.0-T6 (1)	2.77	0.100	1085-960	29	0.28	11.4	12.4
333.1	333	333.0-T7 (1)	2.77	0.100	1085-960	35	0.34	11.4	12.4
354.1	354	354.0-T61	2.71	0.098	1105-1000	32	0.30	11.6	12.7
355.2	355	355.0-T51	2.71	0.098	1150-1015	43	0.40	12.4	13.7
355.2	355	355.0-T6 (1)	2.71	0.098	1150-1015	36	0.34	12.4	13.7
355.2	355	355.0-T6	2.71	0.098	1150-1015	39	0.36	12.4	13.7
355.2	355	355.0-T61	2.71	0.098	1150-1015	37	0.35	12.4	13.7
355.2	355	355.0-T62 (1)	2.71	0.098	1150-1015	38	.035	12.4	13.7
355.2	355	355.0-T71	2.71	0.098	1150-1015	39	0.36	12.4	13.7
355.2	355	355.0-T71	2.71	0.098	1150-1015	39	0.36	12.4	13.7
C355.2	C3FF	C355.0-T61	2.71	0.098	1150-1015	39	0.35	12.4	13.7
356.2	356	356.0-T51	2.68	0.097	1135-1035	43	0.40	11.9	12.9
356.2	356	356.0-T6 (1)	2.68	0.097	1135-1035	39	0.36	11.9	12.9
356.2	356	356.0-T6	2.68	0.097	1135-1035	41	0.38	11.9	12.9
356.2	356	356.0-T7	2.68	0.097	1135-1035	40	0.37	11.9	12.9
A356.2	A356.2	A356.2.0-T6	2.69	0.097	1130-1035	40	0.36	11.9	13.0
A356.2	A356.2	A356.2.0-T61	2.67	0.097	1135-1035	39	0.36	11.9	12.9
357.1	357	357.0-F	2.67	0.097	1135-1035	39	0.36	11.9	12.9
357.1	357	357.0-T61	2.68	0.098	1135-1035	39	0.36	11.9	13.0
A357.2	A357	A357.0-T6	2.67	0.098	1125-1030	39	0.36	11.9	12.9
359.2	359	359.0-T6	2.67	0.097	1115-1045	35	0.33	11.6	12.7
360.2	360	360.0-F (1)	2.64	0.095	1105-1035	28	0.27	11.6	12.7
A360	A360	A360.0-F (1)	2.63	0.097	1105-1035	30	0.29	11.7	12.7
364.2	364	364.0-F (1)	2.63	0.095	1115-1035	30	0.29	11.6	12.7
380.2	380	380.0-F (1)	2.72	0.099	1100-1000	23	0.23	11.6	12.5
A380.2	A380	A380.0-F (1)	2.71	0.099	1100-1000	25	0.25	11.7	12.6
B380.2	380Z	B380.0-F (1)	2.76	0.102	1100-1000	23	0.24	11.7	12.6
383.2	-	383.0-F (1)	2.71	0.099	1080-960	23	0.24	11.8	12.7
384.2	384	384.0-F	2.70	0.098	1080-900	23	0.23	11.3	12.3
390.2	390	390.0-F (1)	2.73	0.099	1200-945	25	0.32	10.3	-
390.2	390	390.0-T5 (1)	2.73	0.099	1200-945	25	0.32	10.0	-
413.2	13-F	413.0-F (1)	2.66	0.096	1085-1065	31	0.30	11.5	12.6
A413.2	A13-F	A413.0-F (1)	2.66	0.096	1085-1065	39	0.37	-	-
443.2	43	443.0-F	2.69	0.097	1170-1065	37	0.35	12.3	13.4
443.2	43	443.0 Annealed (3)	2.69	0.097	1170-1065	42	0.39	-	-
A444.2	A344	A444.0-T4	2.68	0.097	1145-1065	41	0.38	12.1	13.2
514.2	214	514.0-F	2.65	0.096	1185-1110	35	0.33	13.3	14.4
514.2	214	514.0 Annealed (3)	2.65	0.096	1185-1110	35	0.33	-	-
A514.2	A214	A514.0-F (1)	2.68	0.097	1180-1075	34	0.32	13.3	14.4
B514.2	B214	B514.0-F	2.65	0.096	1170-1090	38	0.35	12.7	13.8
F514.2	F214	F514.0-F	2.66	0.096	1185-1090	36	0.34	13.1	14.3
518.2	218	518.0-F (1)	2.61	0.091	1150-1005	24	0.24	13.4	14.5
535.2	Almag 35	535.0-F	2.62	0.095	1165-1020	23	0.24	13.1	14.7
A535.1	A218	A535.0-F (1)	2.62	0.092	1150-1020	23	0.24	13.4	14.5
B535.2	B218	B535.0-F	2.62	0.095	1165-1020	24	0.23	13.6	14.7
520.2	220	520.0-T4	2.57	0.093	1120-840	21	0.21	13.7	14.8
705.1	603	705.0-F	2.76	0.100	1180-1105	25	0.25	13.1	14.3
707.1	607	707.0-F	2.77	0.100	1165-1085	25	0.25	13.2	14.4
A712.1	A612	A712.0-F	2.81	0.102	1195-1105	35	0.33	13.4	14.6
C712.1	C612	C712.0-F (1)	2.84	0.103	1190-1120	40	0.38	13.1	14.2
D712.2	D612	D712.0-F	2.82	0.102	1185-1120	40	0.38	13.1	14.2
713.1	613	713.0-F	2.84	0.104	1180-1100	37	0.37	13.3	14.4
850	750	850-T5	2.88	0.104	1200-435	47	0.43	-	-
A850	A750	A850-T5	2.83	0.102	1165-440	43	0.40	12.6	-
B850	B750	B850-T5	2.88	0.104	1175-400	45	0.41	12.9	-

Annealing and Stress Relieving Aluminum Casting

Treatment	Application	Purpose	Temprature oF	Time Hours	Type of Quench
Stress Relieving	Die casting	To reduce internal stresses	350-500	4-6	Cooled in still air
Annealing	Die casting	To increase ductility	500-700	4-6	Furnace cooled or cooled in still air

Characteristics of Aluminum Alloys

Selection of an aluminum allow for die casting required evaluation not only of physical properties, constants, and chemical composition of the alloy, but also of its inherent characteristics and their effect on production of the die casting and in finishing.

The table includes certain casting and other outstanding characteristics which are usually considered in selecting a die casting alloy for a specific application. The characteristics are rated from (1) to (5), (1) being the best and (5) being the least desirable alloy. In applying these ratings, it should be noted that all the alloys have sufficiently good characteristics to be accepted by users and producers of die castings. Hence a rating of (5) indicates a commercial alloy, although in certain cases its application may be limited or its manufacture may be restricted to relatively simple die castings.

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		Die Casting Characteristics						Other Characteristics (k)
Standard
13, A13	1065 - 1080	1	1	1	1	2	4	5	3	5	3	3
380, A380	1000 - 1100	2	2	2	1	4	3	3	1	3	4	3
Special
43	1065 - 1170	3	3	4	4	2	5	4	2	2	2	5
218	995 - 1150	5	5	5	5	1	1	1	5	1	1	4
360, A360	1035 - 1105	1	2	3	2	2	3	3	2	3	3	1
383	960 - 1080	1	2	1	2	3	2	3	1	3	4	2
384	960 - 1080	2	2	1	2	5	3	5	2	4	5	2

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• Ability of alloy to withstand stresses from contraction while cooling through hot- short or brittle temperature range.
• Ability of molten alloy to flow readily in die and fill thin sections.
• Ability of molten alloy to flow without sticking to the die surfaces. Ratings given for antisoldering are based on nominal iron compositions of approximately 1%.
• Based on resistance of alloy in standard type salt spray test.
• Composite rating based on ease of cutting, chip characteristics, quality of finish, and tool life.
• Composite rating based on ease of polishing and quality of finish provided by typical polishing procedure.
• Ability of the die casting to take and hold an electroplate applied by present standard methods.
• Rated on lightness of color, brightness, and uniformity of clear anodized coating applied in sulphuric acid electrolyte. Generally aluminum die castings are unsuitable for light color anodizing where pleasing apperances is required.
• Rated on combined resistance of coating and base alloy to corrosion.
• Rating based on tensile and yield strengths at temperatures up to 500 F (260), after prolonged heating at testing temperature.
• Die casting are not usually solution heat treated. Low temperature aging treatments may be used for stress relief or dimensional stability.
• Die castings are not generally gas or arc welded or brazed.

Note – These data should be used in connection with ADCI-M2 and M3 in determining selection of an aluminum alloy die casting.