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怎么預防壓鑄模具損壞

刮刮乐2000 www.yfrmbf.com.cn 來源:    發布時間:2019-04-08 13:52:53    點擊:

  一、造成壓鑄生產模具損壞的原因:
  1. Causes of die casting die damage:
  在壓鑄生產中,模具損壞比較常見的形式是裂紋、開裂。應力是導致模具損壞的主要原因。熱、機械、化學、操作沖擊都是產生應力之源,包括有機械應力和熱應力,應力產生于:
  In die casting production, the most common form of die damage is cracking. Stress is the main cause of die damage. Thermal, mechanical, chemical and operational shocks are all sources of stress, including mechanical and thermal stresses, which arise from:
 ?。ㄒ唬?在模具加工制造過程中
  (1) In the process of mould manufacturing1、毛坯鍛造質量問題
  1. Quality Problems of Blank Forging
  有些模具只生產了幾百件就出現裂紋,而且裂紋發展很快。有可能是鍛造時只保證了外型尺寸,而鋼材中的樹枝狀晶體、夾雜碳化物、縮孔、氣泡等疏松缺陷沿加工方法被延伸拉長,形成流線,這種流線對以后的然后的淬火變形、開裂、使用過程中的脆裂、失效傾向影響極大。
  Some dies produce only a few hundred pieces, and cracks develop rapidly. It is possible that the forging process only ensures the shape and size, while the dendritic crystals, inclusions of carbides, shrinkage holes, bubbles and other loose defects in steel are stretched along the processing method to form a streamline, which has a great impact on the final quenching deformation, cracking, brittle cracking and failure tendency in the use process.
  2、在車、銑、刨等終加工時產生的切削應力,這種應力可通過中間退火來消除。
  2. The cutting stress produced in turning, milling and planer finishing can be eliminated by intermediate annealing.
  3、淬火鋼磨削時產生磨削應力,磨削時產生摩擦熱,產生軟化層、脫碳層,降低了熱疲勞強度,容易導致熱裂、早期裂紋。對h13鋼在精磨后,可采取加熱至510-570℃,以厚度每25mm保溫一小時進行消除應力退火。
  3. Grinding stress occurs during grinding of quenched steel, friction heat occurs during grinding, softening layer and decarbonization layer occur, which reduces thermal fatigue strength and easily leads to hot cracking and early cracking. After finishing grinding, H13 steel can be heated to 510-570 (?) C and annealed for stress relief with a thickness of 25 mm for one hour.
  4、電火花加工產生應力。模具表面產生一層富集電極元素和電介質元素的白亮層,又硬又脆,這一層本身會有裂紋,有應力。電火花加工時應采用高的頻率,使白亮層減到比較小,必須進行拋光方法去除,并進行回火處理,回火在三級回火溫度進行。
  4. Stress produced by EDM. The die surface produces a white layer enriched with electrode elements and dielectric elements, which is hard and brittle. The layer itself will have cracks and stress. In order to minimize the white layer, the frequency should be used in EDM. The polishing method must be used to remove the white layer, and the tempering process must be carried out at the third tempering temperature.
 ?。ǘ?模具處理過程中
  (2) Mould processing
  熱處理不當,會導致模具開裂而過早報廢,特別是只采用調質,不進行淬火,再進行表面氮化工藝,在壓鑄幾千模次后會出現表面龜裂和開裂。
  Improper heat treatment will lead to die cracking and scrap prematurely. Especially, surface cracking and cracking will occur after thousands of die casting times, when only tempering, quenching and surface nitriding are used.
  鋼淬火時產生應力,是冷卻過程中的熱應力與相變時的組織應力疊加的結果,淬火應力是造成變形、開裂的原因,固必須進行回火來消除應力。
  The stress produced during quenching of steel is the result of superposition of thermal stress in cooling process and microstructural stress in phase transformation. The quenching stress is the cause of deformation and cracking. The stress must be eliminated by tempering.
 ?。ㄈ?在壓鑄生產過程中
  (3) In the process of die casting production1、模溫
  1. Mold temperature
  模具在生產前應預熱到一定的溫度,否則當高溫金屬液充型時產生激冷,導致模具內外層溫度梯度增大,形成熱應力,使模具表面龜裂,甚至開裂。
  Die should be preheated to a certain temperature before production, otherwise, when high temperature liquid metal filling, chilling will occur, leading to the increase of temperature gradient inside and outside the die, forming thermal stress, making the die surface crack, or even crack.
  在生產過程中,模溫不斷升高,當模溫過熱時,容易產生粘模,運動部件失靈而導致模具表面損傷。
  In the process of production, the temperature of the die keeps rising. When the temperature of the die is overheated, it is easy to produce viscous die. The failure of the moving parts results in the surface damage of the die.
  應設置冷卻溫控系統,保持模具工作溫度在一定的范圍內。
  The cooling temperature control system should be set up to keep the working temperature of the die within a certain range.
  2、充型
  2. Filling type
  金屬液以高壓、高速充型,必然會對模具產生激烈的沖擊和沖刷,因而產生機械應力和熱應力。在沖擊過程中,金屬液、雜質、氣體還會與模具表面產生復雜的化學作用,并加速腐蝕和裂紋的產生。當金屬液裹有氣體時,會在型腔中低壓區先膨脹,當氣體壓力升高時,產生內向爆破,扯拉出型腔表面的金屬質點而造成損傷,因氣蝕而產生裂紋。
  The filling of liquid metal at high pressure and high speed will inevitably produce intense impact and erosion on the die, resulting in mechanical stress and thermal stress. In the impact process, the metal liquid, impurities and gases will also have complex chemical interaction with the surface of the die, and accelerate the corrosion and crack generation. When the liquid metal is wrapped with gas, it will expand in the low pressure area of the cavity first. When the gas pressure rises, it will produce inward blasting, pull out the metal particles on the surface of the cavity and cause damage, resulting in cracks due to cavitation.
  3、開模
  3, mold opening
  在抽芯、開模的過程中,當某些元件有形變時,也會產生機械應力。
  In the process of core pulling and die opening, mechanical stress will also occur when some components are deformed.
  4、生產過程
  4. Production process
  在每一個壓鑄件生產過程中,由于模具與金屬液之間的熱交換,使模具表面產生周期性溫度變化,引起周期性的熱膨脹和收縮,產生周期性熱應力。如澆注時模具表面因升溫受到壓應力,而開模頂出鑄件后,模具表面因降溫受到拉應力。當這種交變應力反復循環時,使模具內部積累的應力越來越大,當應力超過材料的疲勞極限時,模具表面產生裂紋。
  In each production process of die casting, due to the heat exchange between the die and liquid metal, periodic temperature changes occur on the die surface, resulting in periodic thermal expansion and contraction, and periodic thermal stress. For example, when casting, the die surface is subjected to compressive stress due to temperature rise, and when the die is ejected from the casting, the die surface is subjected to tensile stress due to temperature drop. When the alternating stress is repeated, the accumulated stress in the die becomes larger and larger. When the stress exceeds the fatigue limit of the material, the surface of the die will crack.
  二、預防模具損傷的措施:
  2. Measures to prevent mould damage:
  1.良好的鑄件結構設計
  1. Good Casting Structure Design
  鑄件壁厚盡可能均勻,避免產生熱節,以減少模具局部熱量集中產生的熱疲勞。鑄件的轉角處應有適當的鑄造圓角,以避免模具上有尖角位導致應力產生。
  The wall thickness of the castings is as uniform as possible to avoid hot spots, so as to reduce the thermal fatigue caused by local heat concentration of the die. Appropriate casting roundness should be provided at the corner of the casting to avoid the stress caused by sharp corners on the die.
  2.合理的模具結構設計
  2. Reasonable die structure design
  1)模具中各元件應有足夠的剛度、強度,以承受壓力而不變形。模具壁厚要足夠,才能減少變形。
  1) Each component in the die should have sufficient stiffness and strength to withstand pressure without deformation. Die wall thickness should be enough to reduce deformation.
  2)澆注系統設計盡量減少對型芯沖擊、沖蝕。
  2) The design of the gating system minimizes the impact and erosion on the core.
  3)正確選擇各元件的公差配合和表面粗糙度。
  3) Correct selection of tolerance fit and surface roughness of each element.
  4)保持模具熱平衡。
  4) Keep the thermal balance of the die.
  3.規范熱處理工藝
  3. Standardize heat treatment process
  通過熱處理可改變材料的金相組織,保證必要的強度、硬度、高溫下尺寸穩定性、抗熱疲勞性能和材料切削性能。
  The metallographic structure of the material can be changed by heat treatment to ensure the necessary strength, hardness, dimensional stability at high temperature, thermal fatigue resistance and cutting performance of the material.
  正確的熱處理工藝,才會得到比較好的模具性能,而鋼材的性能是受到淬火溫度和時間、冷卻速度和回火溫度控制。
  Correct heat treatment process can get the best die performance, and the properties of steel are controlled by quenching temperature and time, cooling speed and tempering temperature.
  4.壓鑄生產過程控制
  4. Control of Die Casting Production Process1)溫度控制:模具的預熱溫度和工作溫度;合金澆注溫度,在保證成型良好前提下,用較低的澆注溫度。
                                         山東模具
  1) Temperature control: preheating temperature and working temperature of the die; casting temperature of the alloy, on the premise of ensuring good moulding, with a lower pouring temperature.
  2)合理的壓鑄工藝:比壓、充填速度。
  2) Rational die casting process: specific pressure and filling speed.
  3)調整機器的鎖模力,使模具受力均勻。注意清掃模具表面的殘削碎片,以免合模時這些多余物使模具表面受力不均勻,引起變形。
  3) Adjust the clamping force of the machine to make the force of the die uniform. Attention should be paid to cleaning the debris on the surface of the die so as not to cause uneven force and deformation on the surface of the die when closing the die.
  4)對合金熔煉嚴格控制,減少金屬液中氣體。
  4) Strict control of alloy smelting and reduction of gas in liquid metal.
  5.模具的維護與保養
  5. Mould Maintenance and Maintenance
  1)定期消除應力
  1) Regular stress relief
  2)模具修補
  2) Die Repair
 
 
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