![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.
Typical die temperatures and life for various cast materials
Zinc Aluminium Magnesium Brass (leadedyellow)
Maximumdie life [numberof cycles] 1,000,000 100,000 100,000 10,000
Die temperature [C°(F°)] 218 (425) 288 (550) 260 (500) 500 (950)
Castingtemperature [C°(F°)] 400 (760) 660 (1220) 760 (1400) 1090 (2000)
Process
The following are the four steps in traditional die casting, also known as high-pressure die
casting, these are also the basis for any of the die casting variations: die preparation, filling,
ejection, and shakeout. The dies are prepared by spraying the mold cavity with lubricant. The
lubricant both helps control the temperature of the die and it also assists in the removal of the
casting. The dies are then closed and molten metal is injected into the dies under high pressure;
between 10 and 175 megapascals (1,500 and 25,400 psi). Once the mold cavity is filled, the
pressure is maintained until the casting solidifies. The dies are then opened and the shot (shots
are different from castings because there can be multiple cavities in a die, yielding multiple
castings per shot) is ejected by the ejector pins. Finally, the shakeout involves separating the
scrap, which includes the gate, runners, sprues and flash, from the shot. This is often done using
a special trim die in a power press or hydraulic press. Other methods of shaking out include
sawing and grinding. A less labor-intensive method is to tumble shots if gates are thin and easily
broken; separation of gates from finished parts must follow. This scrap is recycled by remelting
it.The yield is approximately 67%.
Advantages and disadvantages
Advantages of die casting:
Excellentdimensional accuracy(dependenton castingmaterial,buttypically0.1mmfor the first
2.5 cm (0.005 inch forthe firstinch) and0.02 mm for eachadditional centimeter(0.002 inchfor
each additional inch).
Smoothcast surfaces(Ra1–2.5 micrometresor0.04–0.10 thourms).
Thinnerwallscanbe cast as comparedtosand and permanentmoldcasting(approximately
0.75 mm or 0.030 in).
Insertscan be cast-in(suchas threadedinserts,heatingelements,andhigh strengthbearing
surfaces).](https://image.slidesharecdn.com/assignmentoncasting-160410083122/85/Assignment-on-casting-6-320.jpg)
Assignment on casting
- 1. Assignment on: CASTING Course Code: ME-3302 Course Name: Engineering Materials and Practices Lab Submitted To: Md.Nafeez Tanim Lecturer, Department of Textile Engineering Northern University Bangladesh Submitted By: Mehedi Hasan ID:BTX 130100279 Semester:Summer-2015 Dept. of Textile Engineering Northern University Bangladesh Date of Submission:09.06.2015
- 2. Casting: Casting is a manufacturing process by which a liquid material is usually poured into a mold, which contains a hollow cavity of the desired shape, and then allowed to solidify. The solidified part is also known as a casting, which is ejected or broken out of the mold to complete the process. Types of Casting: 1. Metal 2. Plaster,concrete,or plasticresin Metal: Metal casting is one of the most common casting processes. Metal patterns are more expensive but are more dimensionally stable and durable. Metallic patterns are used where repetitive production of castings is required in large quantities. Plaster, concrete, or plastic resin: Plaster and other chemical curing materials such as concrete and plastic resin may be cast using single-use waste molds as noted above, multiple-use 'piece' molds, or molds made of small rigid pieces or of flexible material such as latex rubber (which is in turn supported by an exterior mold). When casting plaster or concrete, the material surface is flat and lacks transparency. c Different Types of Casting: Molding (process) Sand casting Permanent mold casting Investment casting Lost foam casting Die casting Centrifugal casting Glass casting Slip casting
- 3. Die casting: An engine block with aluminium and magnesium die castings. Die casting is a metal casting process that is characterized by forcing molten metal under high pressure into a mold cavity. The mold cavity is created using two hardened tool steel dies which have been machined into shape and work similarly to an injection mold during the process. Most die castings are made from non-ferrous metals, specifically zinc, copper, aluminium, magnesium, lead, pewter and tin based alloys. Depending on the type of metal being cast, a hot- or cold- chamber machine is used. The casting equipment and the metal dies represent large capital costs and this tends to limit the process to high volume production. Manufacture of parts using die casting is relatively simple, involving only four main steps, which keeps the incremental cost per item low. It is especially suited for a large quantity of small to medium-sized castings, which is why die casting produces more castings than any other casting process. Die castings are characterized by a very good surface finish (by casting standards) and dimensional consistency. Two variants are pore-free die casting, which is used to eliminate gas porosity defects; and direct injection die casting, which is used with zinc castings to reduce scrap and increase yield. History Die casting equipment was invented in 1838 for the purpose of producing movable type for the printing industry. The first die casting-related patent was granted in 1849 for a small hand operated machine for the purpose of mechanized printing type production. In 1885, Otto Mergenthaler invented the linotype machine, an automated type casting device which became the prominent type of equipment in the publishing industry. The Soss die-casting machine, manufactured in Brooklyn, NY was the first machine to be sold in the open market in North America. Other applications grew rapidly, with die casting facilitating the growth of consumer goods and appliances by making affordable the production of intricate parts in high volumes.In 1966,General Motors released the Acurad process.
- 4. Cast metals The main die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is also possible. Specific die casting alloys include: Zamak; zinc aluminium; aluminium to, e.g. The Aluminum Association (AA) standards: AA 380, AA 384, AA 386, AA 390; and AZ91D magnesium.The following is a summary of the advantages of each alloy: Zinc:the easiestmetal tocast;highductility;highimpactstrength;easilyplated;economical for small parts;promoteslongdie life. Aluminium:lightweight;highdimensional stabilityforcomplexshapesandthinwalls;good corrosionresistance;goodmechanical properties;highthermal andelectrical conductivity; retainsstrengthathightemperatures. Magnesium:the easiestmetal tomachine;excellentstrength-to-weightratio;lightestalloy commonlydie cast. Copper:highhardness;highcorrosionresistance;highestmechanical propertiesof alloysdie cast; excellentwearresistance;excellentdimensionalstability;strengthapproachingthatof steel parts. Silicontombac:alloymade of copper,zincandsilicon.Oftenusedasanalternative for investmentcastedsteel parts. Lead andtin: highdensity;extremelyclosedimensionalaccuracy;usedforspecial formsof corrosionresistance.Suchalloysare notusedin foodserviceapplicationsforpublichealth reasons.Type metal,analloyof Lead,Tin andAntimony(withsometimestracesof Copper) is usedforcasting handsettype in letterpressprinting andhotfoil blocking.Traditionallycastin handjerkmouldsnowpredominantlydie castafterthe industrialisationof the type foundries. Around1900 the slugcastingmachines came ontothe marketand addedfurtherautomation withsometimesdozensof castingmachinesatone newspaperoffice. Maximum weight limits for aluminium, brass, magnesium, and zinc castings are approximately 70 pounds (32 kg), 10 lb (4.5 kg), 44 lb (20 kg), and 75 lb (34 kg), respectively. The material used defines the minimum section thickness and minimum draft required for a casting as outlined in the table below. The thickest section should be less than 13 mm (0.5 in), but can be greater. Metal Minimumsection Minimumdraft Aluminiumalloys 0.89 mm (0.035 in) 1:100 (0.6°) Brass and bronze 1.27 mm (0.050 in) 1:80 (0.7°) Magnesiumalloys 1.27 mm (0.050 in) 1:100 (0.6°) Zincalloys 0.63 mm (0.025 in) 1:200 (0.3°)
- 5. Die component Cast metal Tin, lead & zinc Aluminium & magnesium Copper & brass Material Hardness Material Hardness Material Hardness Cavityinserts P20 290–330 HB H13 42–48 HRC DIN 1.2367 38–44 HRC H11 46–50 HRC H11 42–48 HRC H20, H21, H22 44–48 HRC H13 46–50 HRC 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 DIN 1.2367 46–48 HRC 44–46 HRC DIN 1.2367 42–46 HRC Nozzle 420 40–44 HRC H13 42–48 HRC DIN 1.2367 H13 40–44 HRC 42–48 HRC Ejectorpins H13 46–50 HRC H13 46–50 HRC H13 46–50 HRC Plungershot sleeve H13 46–50 HRC H13 DIN 1.2367 42–48 HRC 42–48 HRC DIN 1.2367 H13 42–46 HRC 42–46 HRC Holderblock 4140prehard ~300 HB 4140 prehard ~300 HB 4140 prehard ~300 HB
- 6. 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. Typical die temperatures and life for various cast materials Zinc Aluminium Magnesium Brass (leadedyellow) Maximumdie life [numberof cycles] 1,000,000 100,000 100,000 10,000 Die temperature [C°(F°)] 218 (425) 288 (550) 260 (500) 500 (950) Castingtemperature [C°(F°)] 400 (760) 660 (1220) 760 (1400) 1090 (2000) Process The following are the four steps in traditional die casting, also known as high-pressure die casting, these are also the basis for any of the die casting variations: die preparation, filling, ejection, and shakeout. The dies are prepared by spraying the mold cavity with lubricant. The lubricant both helps control the temperature of the die and it also assists in the removal of the casting. The dies are then closed and molten metal is injected into the dies under high pressure; between 10 and 175 megapascals (1,500 and 25,400 psi). Once the mold cavity is filled, the pressure is maintained until the casting solidifies. The dies are then opened and the shot (shots are different from castings because there can be multiple cavities in a die, yielding multiple castings per shot) is ejected by the ejector pins. Finally, the shakeout involves separating the scrap, which includes the gate, runners, sprues and flash, from the shot. This is often done using a special trim die in a power press or hydraulic press. Other methods of shaking out include sawing and grinding. A less labor-intensive method is to tumble shots if gates are thin and easily broken; separation of gates from finished parts must follow. This scrap is recycled by remelting it.The yield is approximately 67%. Advantages and disadvantages Advantages of die casting: Excellentdimensional accuracy(dependenton castingmaterial,buttypically0.1mmfor the first 2.5 cm (0.005 inch forthe firstinch) and0.02 mm for eachadditional centimeter(0.002 inchfor each additional inch). Smoothcast surfaces(Ra1–2.5 micrometresor0.04–0.10 thourms). Thinnerwallscanbe cast as comparedtosand and permanentmoldcasting(approximately 0.75 mm or 0.030 in). Insertscan be cast-in(suchas threadedinserts,heatingelements,andhigh strengthbearing surfaces).
- 7. Reducesoreliminatessecondarymachiningoperations. Rapidproductionrates. Castingtensile strength ashighas 415 megapascals(60 ksi). Castingof lowfluiditymetals. The main disadvantage to die casting is the very high capital cost. Both the casting equipment required and the dies and related components are very costly, as compared to most other casting processes. Therefore, to make die casting an economic process, a large production volume is needed. Other disadvantages are that the process is limited to high-fluidity metals, and casting weights must be between 30 grams (1 oz) and 10 kg (20 lb). In the standard die casting process the final casting will have a small amount of porosity. This prevents any heat treating or welding, because the heat causes the gas in the pores to expand, which causes micro-cracks inside the part and exfoliation of the surface. Thus a related disadvantage of die casting is that it is only for parts in which softness is acceptable. Parts needing hardening (through hardening or case hardening) and tempering are not cast in dies.