E-15轴座冲压工艺与模具设计外文翻译资料

 2022-10-16 03:10

Die casting

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.[1] 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.[2] 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.[3] In 1966,[4] General Motors released the Acurad process.[5]

Cast metals

The main die casting alloys are: zinc, aluminium, magnesium, copper, lead, and tin; although uncommon, ferrous die casting is also possible.[6] 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.[7] The following is a summary of the advantages of each alloy:[1]

  • Zinc: the easiest metal to cast; high ductility; high impact strength; easily plated; economical for small parts; promotes long die life.
  • Aluminium: lightweight; high dimensional stability for complex shapes and thin walls; good corrosion resistance; good mechanical properties; high thermal and electrical conductivity; retains strength at high temperatures.
  • Magnesium: the easiest metal to machine; excellent strength-to-weight ratio; lightest alloy commonly die cast.
  • Copper: high hardness; high corrosion resistance; highest mechanical properties of alloys die cast; excellent wear resistance; excellent dimensional stability; strength approaching that of steel parts.
  • Silicon tombac: high strength alloy made of copper, zinc and silicon. Often used as an alternative for investment casted steel parts.
  • Lead and tin: high density; extremely close dimensional accuracy; used for special forms of corrosion resistance. Such alloys are not used in foodservice applications for public health reasons. Type metal, an alloy of Lead, Tin and Antimony (with sometimes traces of Copper) is used for casting hand set type in letterpress printing and hot foil blocking. Traditionally cast in hand jerk moulds now predominantly die cast after the industrialisation of the type foundries. Around 1900 the slug casting machines came onto the market and added further automation with sometimes dozens of casting machines at one newspaper office.

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.[8]

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.[9]

Metal

Minimum section

Minimum draft

Aluminium alloys

0.89 mm (0.035 in)

1:100 (0.6°)

Brass and bronze

1.27 mm (0.050 in)

1:80 (0.7°)

Magnesium alloys

1.27 mm (0.050 in)

1:100 (0.6°)

Zinc alloys

0.63 mm (0.025 in)

1:200 (0.3°)

Equipment

There are two basic types of die casting machines: hot-chamber machines and cold-chamber machines.[10] These are rated by how much clamping force they can apply. Typical ratings are between 400 and 4,000 st (2,500 and 25,400 kg).[1]

Hot-chamber die casting

Hot-chamber die casting, also known as gooseneck machines, rely upon a pool of molten metal to feed the die. At the beginning of the cycle the piston of the machine is retracted, which allows the molten metal to fill the 'gooseneck'. The pneumatic or hydraulic powered piston then forces this metal out of the gooseneck into the die. The advantages of this system include fast cycle times (approximately 15 cycles a minute) and the convenience of melting the metal in the casting machine. The disadvantages of this system are that it is limited to use with low-melting point metals and that aluminium cannot be used because it picks up some of the iron while in the molten pool. Therefore, hot-cham

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压铸

压铸是一个金属铸造工艺,其特征是迫使熔融金属在高压下填充模腔。模腔由两个已被加工成形并且模具注塑过程中工作类似的硬化工具钢组成。大多数压铸件是非铁金属,特别是锌,铜,铝,镁,铅,锡和锡的合金。压铸过程使用热室或冷室压铸机,这取决于被铸造金属的种类。

铸造设备和金属模具象征着很大的资金支出,这往往限制大批量生产。压铸件的制造是相对简单的,仅涉及四个主要步骤,这降低了单件的增量成本。它特别适合于大量的小到中型的铸件,这就是为什么压铸比任何其他铸造过程中产生更多的铸件[ 1 ]。压铸件具有非常好的特征的表面光洁度(通过铸造标准)和尺寸一致性。

两个不同的压铸,一个是无气孔压铸,它被用来消除气孔缺陷 ; 另一个是直接注射压铸,它适用于锌铸件,用以减少废料,提高产量。

历史

压铸设备是在1838年发明的以生产为目的的活字印刷业。第一个与压铸相关的专利是在1849年授予的,以机械化印刷式生产为目的小型手工操作的机器。1885年,奥托·默根特勒发明了Linotype机,即一种自动型铸造设备,它成为了出版业界突出的排字机类型。索斯压铸机,制造于纽约布鲁克林,是第一个在北美公开市场发售的这种类型机器[ 2 ]。压铸通过大批量生产经济实惠的复杂零件促进消费品和家电的增长,使得其他应用快速增长[ 3 ]。在1966年[ 4 ],通用汽车发布了Acurad过程[ 5 ]

铸造金属

主要压铸合金:锌,铝,镁,铜,铅,锡等; 虽然少见,铁压铸也是可能的[ 6 ]。具体压铸合金包括:锌合金 ; 锌铝 ; 铝等。铝业协会(AA)标准:AA 380,AA 384,AA 386,AA 390; 以及AZ91D镁[ 7 ]。以下是每种合金的优点的总结[ 1 ]

  • 锌:最简单的铸造金属; 高延展性; 高冲击强度; 易镀; 成本低; 模具寿命长。
  • 铝:质量轻; 形状复杂和薄壁铸件具有高稳定性; 耐腐蚀性能好; 良好的机械性能; 高导热性和导电性; 高温下强度稳定。
  • 镁:最简单的加工金属; 优良的强度-重量比,最轻的常用压铸合金。
  • 铜:硬度高; 耐腐蚀性高;具有最好机械性能的压铸合金; 优良的耐磨性; 优良的尺寸稳定性;强度近似于钢件。
  • 硅黄铜:由铜,锌和硅组成的高强度合金。常被用作投资铸造钢件的替代品。
  • 铅和锡:高密度; 尺寸精度非常接近; 用于特定的耐腐蚀性场合。这类合金由于公共健康的原因不使用于食品服务行业。铅,锡和锑这些类型的金属合金(有时有微量的铜)是用于铸造手型凸版印刷和烫印箔阻塞。在铸造厂实现工业化之后,传统的手工铸件显著地拖延了现在的压铸模具。1900年左右段塞铸造机进入市场,并进一步自动化,有时在一家报社就有几十铸造机。

铝,黄铜,镁和锌铸件的最大重量限额分别约为70磅(32千克),10磅(4.5千克),44磅(20千克)和75磅(34公斤)[ 8 ]

下面的表概述了不同材料的铸件的最小截面厚度和最低限度的要求。最厚的部分应小于13毫米(0.5英寸),但也可以更大[ 9 ]

金属

最小截面

最低限度

铝合金

0.89毫米(0.035英寸)

1:100(0.6°)

黄铜和青铜

1.27毫米(0.050英寸)

1:80(0.7°)

镁合金

1.27毫米(0.050英寸)

1:100(0.6°)

锌合金

0.63毫米(0.025英寸)

1:200(0.3°)

设备

两种基本类型的压铸机:热室压铸机和冷室压铸机[ 10 ]。这是由它们可以提供夹紧力的大小来确定。典型的额定压力是在400和4000 ST(2500至25400千克)之间[ 1 ]

热室压铸机

热室压铸机,也称为鹅颈机,依靠熔融金属填充型腔。在循环机活塞缩回开始时,熔融金属填充“鹅颈”。在气动或液压动力下的活塞迫使金属流出鹅颈进入模具。该系统的优点包括快速的循环时间(约15个周期),和容易在铸造机熔融金属。这个系统的缺点是,它限制了低熔点金属并且不能使用铝,因为在熔池中掺杂了一些铁杂质。因此,热室压铸机主要用于与锌,锡和铅的合金[ 10 ]

冷室压铸机

这种压铸机用于铸件合金不能在热室压铸机中使用时; 这些合金包括铝,大量铝,镁和铜的锌合金。这些机器加工流程开始时,金属在一个单独炉中熔化[ 11 ]。然后,定量的熔融金属被输送到冷室压铸机,并被送入未加热的注射室(或注射压缸)。然后,该注射室的金属由液压或机械活塞驱动到模具中。这种系统的最大缺点是,熔化的金属从炉到冷室压铸机传送速度较慢,循环时间较长[ 12 ]

模具或工具

两个半模在压铸时使用; 一个被称为“盖半模”,而另一个“顶出半模”。它们重合之处,被称为分型线。盖半模包含直浇道(用于热室压铸机)或喷嘴(用于冷室压铸机),他们的作用是让熔融金属流入模具; 此功能与热室压铸机或冷室压铸机注射室的喷射器喷嘴相匹配。顶出半模包含顶杆和常见的流道,流道是从直浇道或喷嘴到模腔的通道。盖半模被固定前面的铸造机定模板,而顶出半模固定到动模板。模腔被切成两部分,它们是单独的部件,可以相对容易地更换,也便于螺栓插入半模[ 13 ]

该模具设计成这样是为了开模时成品铸件会滑离模具的盖半模,另一半留在顶出半模。这保证了铸件每个周期都可以被顶出,因为顶出半模包含的顶杆会将铸件推出半模。顶杆由卸料板驱动,在同时并以相同的力准确地驱动所有的顶杆,从而使铸件不被损坏。铸件被顶出后,卸料板缩回顶杆,准备下一次顶出。顶杆要足够多以保证整体力对每个顶杆的作用力不大,因为铸件仍然是热的,易被过大的力损坏。顶杆也会留下痕迹,所以他们必须位于特定的地方来确保这些标记不会妨碍铸造的质量[ 13 ]

其它模具组件包括型芯和滑块。型芯通常是用于产生有孔或开口的组件,但它们也可以被用于生产其他元件。有三种类型的型芯:固定的,可动的和松弛的。固定型芯定向平行于模具的拉伸方向(模具开模方向),因此它们是固定的,或永久地附着到模具上。可动型心是在除平行于拉伸方向的任何其他方向定向的。当熔融体固化后这些型芯必须在开模之前,使用一个单独的机构从模腔中取出。滑块类似于可动型心,除了它们被用于形成底切表面之外。利用可动型芯和滑块大大增加了模具的成本[ 13 ]。松散型芯,也称为拾取型芯,用来浇铸复杂的结构,例如螺纹孔。这些松散型芯在每个周期开始之前用手工插入模具中,然后在循环结束时顶出来。型芯必须用手取出。松散型芯是最昂贵型型芯,因为额外的劳动力和延长了的周期时间[ 9 ]。模具的其他特征包括冷却水通道和沿分型线的排气孔。这些排气孔通常宽且薄(大约0.13毫米或0.005英寸),以便当熔融金属开始填充时金属快速凝固,最大限度地减少废料。不使用立管,因为高压确保金属从进口连续进料[ 14 ]

模具材料最重要的特性是耐热冲击性,和在升高的温度下软化的能力; 其它重要性质包括淬透性,可加工性,耐热检查性,焊接性,可用性(特别是对于大型模具)和成本。模具的寿命直接取决于熔融金属的温度和一个周期的时间[ 13 ]。压铸用的模具通常是由硬化工具钢制成,因为铸铁不能承受所需要的高压力,因此模具是非常昂贵的,产生高启动成本[ 14 ]。所以在较高温度下工作的金属模具需要由高合金钢制成[ 15 ]

各种铸造金属模具及零部件的材料和硬度

模具组件

铸造

锡,铅和锌

铝和镁

红铜和黄铜

材料

硬度

材料

硬度

材料

硬度

型腔

嵌件

P20ensp;[注1ensp;]

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

型芯

H13

46-52 HRC

H13

44-48 HRC

DIN 1.2367

40-46 HRC

DIN 1.2367

42-48 HRC

型芯顶杆

H13

48-52 HRC

DIN 1.2367 prehard

37-40 HRC

DIN 1.2367 prehard

37-40 HRC

浇口零件

H13

48-52 HRC

H13
DIN 1.2367

46-48 HRC
44-46 HRC

DIN 1.2367

42-46 HRC

喷嘴

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