1. Home > News >

A brief introduction to die casting process

Time：2024-10-16 09:25:04 / Popularity： / Source：

Basic requirements for die-casting alloys in die-casting production:
Materials used in metal die-casting production are mainly alloy materials composed of aluminum, zinc, magnesium, copper, lead, tin, etc. Among them, aluminum alloys and zinc alloys are widely used, followed by magnesium alloys and copper alloys.
· When superheat temperature is not high, it has good fluidity and is easy to fill complex mold cavities to obtain die castings with good surface quality.
· Small tendency to thermal cracking.
· Crystallization temperature range of die-cast alloys is smaller.
· Die-casting alloys must have as little shrinkage as possible.
· It has high strength at normal temperature to meet needs of production of large thin-walled complex die castings.
· Small tendency to interact chemically with metal cavities to reduce mucosa and mutual alloying.
· Has good processing performance and certain corrosion resistance.
· Die casting alloys have lower melting points.
Die-cast aluminum alloy classification:
Classification Alloy name Alloy series Performance characteristics Sample
Cast aluminum alloy Simple aluminum silicon alloy Al-Si Good casting performance, cannot be heat treated, low mechanical properties AL102
Special aluminum silicon alloy Al-Si-Mg Good casting performance, can be strengthened by heat treatment, and has high mechanical properties AL101
Al-Si-Cu AL107
Al-Si-Mg-Cu AL105
AL110
Al-Si-Mg-Cu-Ni ZL109
Aluminum copper casting alloy Al-Cu Good heat resistance, poor casting performance and corrosion resistance AL201
Aluminum magnesium casting alloy Al-Mg High mechanical properties and good corrosion resistance AL301
Aluminum zinc casting alloy Al-Zn Can be naturally aged and strengthened, suitable for die casting AL401
Aluminum rare earth casting alloy Al-Re Good heat resistance  
Deformed aluminum alloy Aluminum alloys that cannot be heat treated to strengthen Rustproof aluminum Al-Mn Good corrosion resistance, pressure processability and welding performance, suitable for die casting 3A21
Al-Mg
Heat treatable strengthened aluminum alloy Duralumin Al-Cu-Mg 5A05
High mechanical properties 2A11
2A12
Super duralumin Al-Cu-Mg-Zn Highest strength at room temperature 7A04
7A09
Forged aluminum Al-Mg-Si-Cu Good casting performance and good heat resistance 2A14
2A50
Al-Cu-Mg-Fe-Ni 2A70
2A80
Die casting surface quality:
Surface roughness value of die-casting parts is generally two levels lower than roughness value of mold forming surface. New mold can obtain die castings with an Ra value of 0.8μm.
Within normal service life of mold, then: zinc alloy castings Ra=1.6~3.2μm; aluminum and magnesium alloy castings Ra=3.2μm.
Copper alloy castings have the worst surface quality affected by mold cracks. Surface roughness of die castings increases with number of times mold is used.
Die casting wall thickness:
Central layer of thick-walled die-casting parts has larger grains and is prone to defects such as pores and shrinkage cavities, causing its strength and density to decrease as wall thickness increases. Therefore, under premise of ensuring strength and stiffness, wall thickness should be reduced as much as possible. Generally, it is appropriate to not exceed 4.5mm under process conditions.
die casting process  Area at wall thickness a * b/cm * cm zinc alloy aluminum alloy magnesium alloy copper alloy
Wall thickness t
smallest normal smallest normal smallest normal smallest normal
25 0.5 1.5 0.8 2.0 0.8 2.0 0.8 1.5
25-100 1.0 1.8 1.2 2.5 1.2 2.5 1.5 2.0
100-500 1.5 2.2 1.8 3.0 1.8 3.0 2.0 2.5
500 2.0 2.5 2.5 3.5 2.5 3.5 2.5 3.0
At the same time, try to make wall thickness of each section uniform, and use reinforcement ribs in thicker parts to prevent casting defects. It should be noted that if wall thickness of casting is too thin, it will lead to under-casting and cold shut-off.
Die casting stiffeners:
It can improve strength and stiffness of die-casting parts, improve die-casting processability, and smooth flow path of molten alloy. It can also reduce wall thickness and eliminate defects caused by excessive wall thickness.
die casting process 
Structural parameters of reinforcing ribs
Reinforcement of rib and wall structures Illustrate
die casting process  t-casting wall thickness
h - height of reinforcing ribs
t - wall thickness of die casting
b-Root width of rib, b(2/3~3/4)t
R2-Top fillet radius of rib, r2=b/8
R1-Root fillet radius of rib, r1=b/4
a-Slope of rib, a≥3°
Die casting fillet radius:
Rounded corners are designed at connection between walls of die casting, which is beneficial to discharge of gas and flow of molten alloy, prevents stress concentration at sharp corners, and ensures quality of die casting. For mold, it can also avoid stress concentration and cracks at sharp corners and extend life of mold.
Thickness of two connected walls Image Corner radius Illustrate
Equal wall thickness die casting process  r min=Kt
r max=t
R=r+t		 t, t1 - wall thickness of casting
For zinc alloy die castings K=1/4;
For aluminum, magnesium and copper alloy die castings K=1/2
Different wall thickness die casting process  r≥(t+t1)/3
R=r+(t+t1)/2
Die casting thread processing:
For die-cast external threads, when using a threaded ring with a split structure, a machining allowance of 0.2~0.3mm must be considered.
Casting internal threads requires a thread core unscrewing mechanism, and mold structure is complex. Generally, bottom hole is cast first and then processed into a threaded hole. And thread length should not be too long, because a large error will accumulate in length direction when shrinking. Method of processing internal threads can be divided into cutting type and extrusion type.
Die cast gear:
Minimum module of die-cast gear is shown in table below, and draft is selected according to β value of inner surface. For gears with high precision requirements, a machining allowance of 0.2~0.3mm should be left on tooth surface.
die casting process 
Minimum module of die-cast gear (mm)
Alloy type Zinc alloy Aluminum-magnesium alloy Copper alloy
Minimum modulus m 0.3 0.5 1.5
Die cast inserts:
Metal or non-metal parts are embedded in die-casting parts, forming a solid and inseparable whole with die-casting parts. This embedded part is called an insert.
Minimum thickness of metal layer surrounding insert
Die casting outer diameter 2.5 3 6 9 13 16 19 22 25
Insert maximum diameter 0.5 1 3 5 8 11 13 16 18
Minimum thickness of metal layer surrounding the insert 1 1 1.5 2 2.5 2.5 3 3 3.5
 
 
Last article：Moldflow economic benefits and improvement cases Next article：How to design mold for automobile door panels (with mesh)?

Recommended

Related

Go To Top