制造技术(中英文课件)

1、lpatterns （模样模样）lMoulding Sand（型砂）（型砂）Lesson 4Review背砂背砂 冒口冒口冷铁冷铁直浇口直浇口横浇道横浇道型芯型芯上砂箱上砂箱下砂箱下砂箱中砂箱中砂箱Backing sandRiserChillSprueRunnerCoreCope-upper moulding flaskDrag-lower moulding flaskCheek-intermediate moulding flaskPatterns materialspattern materials: （模样材料）（模样材料）the usual pattern materials are

2、wood, metal and plasticsThe most commonly usedDisadvantages: absorption of moisture（吸水）（吸水） distortions（变形）、（变形）、dimensional changes（尺寸变化）（尺寸变化） Advantages: the easy availability（易于使用）（易于使用）, the low weight（轻）（轻）, easily shaped（易于成型）（易于成型）, relatively cheap（价格便宜）（价格便宜） (1) woodVarieties of wood: pin

3、e(松树松树), mahogany(桃花心木桃花心木 ), teak( 柚木柚木), walnut(胡桃木胡桃木), deodar(喜马拉雅雪杉喜马拉雅雪杉), plywood board(胶合板胶合板), particle board(刨花板刨花板)Patterns materials(2) Metal patterns:used for large scale casting productionMaterials: cast iron, brass（黄铜）（黄铜）, aluminum, white metal(3) plastics: low weight, easier formabi

4、lity（可成形性好）（可成形性好）,smooth surface（光滑表面）（光滑表面） , durability（耐久力）（耐久力）, dimensionally stable（尺寸稳定）（尺寸稳定） and cleaned easily（易于清洁）（易于清洁）patterns number of castings produced before pattern equipment repair Pattern material Pattern Core Small castings 2000 2000 Hard wood(under 600mm) 6000 6000 Aluminium,

5、 plastic 100,000 100,000 Cast ironMedium castings(600-1,800mm) 1000 750 Hard wood 3000 3000 Aluminium, plastic Large casting(above 1,800mm) 200 150 Soft wood 500 500 Hard wood metal reinforcedType of PatternsType of patterns(模样的类型模样的类型)(1)Single piece pattern（单块模）（单块模）:（2）Split pattern or two piece

6、pattern（分块模）（分块模）Type of Patterns（3）Gated pattern（浇口模）（浇口模） where the gating and runner system are integral with the pattern.(浇口和浇道系统与模样浇口和浇道系统与模样合为一体）合为一体） （4）Cope and drag pattern （两箱造型模）（两箱造型模）Type of Patterns（5）Loose piece pattern （活块模）：（活块模）：is used when withdrawing the pattern from the mould i

7、s not possible.（6）Follow board pattern（成型底板造型）（成型底板造型）Type of Patterns（6）Sweep pattern（刮板模）（刮板模）:used to sweep the complete casting by means of a plane sweep(平面扫描）平面扫描）.This reduces the cost of three dimensional pattern. （7）Skeleton pattern（骨架模）（骨架模）: made of strips of wood, is useful generally for

8、very large casting.Type of PatternsPattern colour code(模样的颜色代码模样的颜色代码)(1)Red or orange on surfaces not to be finished and left as cast;(2)Yellow on surfaces to be machined;(3)Black on core prints for unmachined openings.(4)Yellow stripes on black on core prints for machined openings.(5)Green on seat

9、s of and for loose pieces and loose core prints.(6) Diagonal black strips with clear varnish on to strengthen the weak patterns or shorten a casting.Patterns colour codeMoulding materials are used in manufacturing moulds and cores:Moulding sand (型砂型砂)System sand (系统砂系统砂)Rebonded sand (加粘土回用砂加粘土回用砂)F

10、acing sand (面砂面砂):This sand is used next to the pattern to obtain cleaner and smoother surfaces. Sea coal（煤粉）（煤粉）Slowly burnReducing gases(还原性气体）还原性气体）Create a small gas pressureMolten metal is prevented from entering into the silica grains.Moulding SandPartling sand (分型砂分型砂)：sprinkled(喷洒）喷洒） on the

11、 pattern and to the parting surfaces of the mould halves.Washed silica grainsPrevent the adherence of the moulding sandThis helps in easy withdrawal of the pattern and easier separation of the cope and drag flasks at parting surface.Backing sand (背砂，填充砂背砂，填充砂)：it is contains the burnt facing sand, m

12、oulding sand and clay. The moulding flask is completely filled with backing sand .Moulding SandThe choic of moulding materials is based on their processing properties: (根据工艺性能选择造型材料根据工艺性能选择造型材料)Refractoriness(耐火性能耐火性能): it is the ability of the moulding materials to withstand (抵抗抵抗) the high tempera

13、ture of the molten metal so that it does not cause fusion.Moulding SandGreen strength(湿强度湿强度): the moulding sand that contains moisture is termd as green sand. The green sand should have enough strength so that the constructed mould retains its shape.Dry strength(干强度干强度): when the moisture in the mo

14、ulding sand is completely expelled（排出）（排出）,called dry sand. retain the mould cavity(保持型腔）保持型腔） withstand the metallostatic forces（抵抗金属重力作用）（抵抗金属重力作用）Hot strength(热强性热强性): After all the moisture is eliminated, the sand would reach a high temperature when the metal in the mould is still in the liquid

15、state. hold the shape of mould cavity.(保持型腔的形状）保持型腔的形状）Permeability(透气性透气性):During the solidification of a casting, large amounts of gases are to be expelled from the mould. This gas evolution capability of the moulding sand .（是气体逸出的能力）（是气体逸出的能力）Moulding Sandl Moulding sand compositionSilica sand(含硅

16、砂含硅砂): it is the major portion of the moulding sand (up to 96%)The rest: alumina(Al2O3), Sodium(Na2O+K2O), magnesium oxide (MgO+CaO) (about 2%)Main source: river sandFusion point（熔点）（熔点）: 1450 for Cast iron ; 1550 for steels.Zircon sand(含锆砂含锆砂): it is a zirconium silicate(ZrSiO4).The typical composi

17、tion:ZrO2 66.25%, SiO2 30.96%, Al2O3 -1.92%, Fe2O3-0.74%Fusion point: 2400.Very expensive, low coefficient of thermal expansion, high thermal conductivity, high chilling power, high density.Used to precision investment casting.Moulding SandChromite sand(含铬砂含铬砂):The typical composition:Cr2O3 44%, Fe2

18、O3-28%,SiO2 2.5%, CaO-0.5%,Al2O3+MgO -25%, Fusion point: 1800.It is used to manufacture heavy steel castings. (e.g. austenitic manganese steel castings)Olivine sand(橄榄石砂橄榄石砂):The typical composition: fosterite( Mg2SiO4）, fayalite(Fe2SiO4)It can be used for a range of steels.Moulding SandMoulding San

19、dClay(粘土粘土):binding agents(粘结剂）粘结剂）The most popular clay types are:Kaolinite（高岭石）（高岭石）or fire clay（耐火泥）（耐火泥）and bentonite（膨润土）（膨润土）Al2O3 2SiO2 2H2OAl2O3 4SiO2 H2O nH2O(1)Kaolinite: （高岭石）（高岭石） melting point: 1750 to 1787 . (2)bentonite: （膨润土）（膨润土）melting point: 1250 to 1300 . absorb more waterThere a

20、re two types of bentoniteWestern bentonite(钠基膨润土）钠基膨润土）:with sodium as adsorbed ion. Better swelling properties(较好的膨胀性）较好的膨胀性）Southern bentonite(钙基膨润土）：钙基膨润土）： with calcium ionMoulding SandThe rest: lime(石灰），石灰），alkalies (碱）碱）and other oxides.Water: clay is activated by water ,it develops the necess

21、ary plasticity(可塑性）可塑性） and strength（强度）（强度）.The normal percentages of water: from 2 to 8.Comparative properties of moulding sands with various claysMoulding Sand2.Testing sand propertiesMoisture content(（水含量）（水含量）Sample preparation: a sample of the standard（标准试样）（标准试样）. e.g. (1)Sample of 50gIs drie

22、d105 to110 (2h)The sample is weighed(2) Moisture teller（水分测定仪）:utilise calcium carbide (碳化钙） CaC2+2H2O C2H2+Ca(OH)2Acetylene（乙炔）clay content（粘土含量）（粘土含量）Sample preparation: a sample of the standard（标准试样）（标准试样）. e.g. (1)Sample of 50gIs dried105 to110 (2h)The dried sample475 ml distilled water25ml NaOH

23、Moulding SandSand grain size（砂粒尺寸）采用筛分法测定（砂粒尺寸）采用筛分法测定A sand sample which is devoid(全无）全无）of moisture and clay Placed on the top sieve (筛）筛）of a sieve shaker（振筛机）（振筛机）with gradually decreasing mesh sizes(网格尺寸）网格尺寸）ASTM（标准（标准)（筛号）（筛号）MESHING OPENING(筛孔尺寸）筛孔尺寸）/mm 6 12 20 30 100 200 3.327 1.651 0.833

24、0.589 0.147 0.074Moulding SandSand grain size distribution(筛孔号）筛孔号）Grain Fineness Number(GFN 平均粒度平均粒度)GFN=MinfifiMi=第第i级筛的相乘因素级筛的相乘因素fi =第第i级筛的剩余量级筛的剩余量Moulding SandPermeability（透气性）（透气性）A standard permeability test is to measure time taken by a 2000cm of air at a pressure typically of 980Pa(10g/cm ).,to pass through a standard sa