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    • 铝铸件的常见缺陷及其原因分析与防止方法
    • 本站编辑:杭州宏成精密机械有限公司发布日期:2018-01-22 09:37 浏览次数:
    一、气孔
    1. Stomata
    特征:1.孔壁表面一般比较光滑,带有金属光泽。2.单个或成群或存在于铸件皮下。3.油烟气孔呈油黄色。
    Features: 1. hole wall surface is generally smooth, with metallic luster. 2. single or group or subsurface of the castings. 3. oil and smoke blowholes are oil yellow.
     
    原因分析:1.液体金属浇注时被卷入的气体在合金液凝固后以气孔的形式存在于铸件中。2.金属与铸型反应后在铸件表皮下生成的皮下气孔。3.合金液中的夹渣或氧化皮上附着的气体被混入合金液后形成气孔。
    Reason analysis: 1. the gas involved in the pouring of liquid metal is in the form of the casting in the form of gas hole after the alloy liquid solidifies. 2. subcutaneous pores formed under the epidermis of the castings after the reaction of the metal to the mold. The slag in the 3. alloy liquid or the gas attached to the oxide skin is mixed into the alloy liquid to form a gas hole.
     
    防止方法:1.浇注时防止空气卷入。2.合金液在进入型腔前先经过滤网以除合金液中的夹渣,氧化皮和气泡。3.更换铸型材料或加涂料层防止合金液与铸型发生反应。4.在允许补焊部位将缺陷清理干净后进行补焊。
    Prevention method: prevent air from getting involved in 1. pouring. The 2. alloy liquid is filtered through the filter net before entering the cavity to remove the slag from the alloy liquid, the oxide skin and the bubbles. 3. replace the mold material or coating layer to prevent the alloy liquid from reacting with the mold. 4. when the defects are cleaned and cleaned, the repair welding is carried out.
     
    二、针孔
    Two, pinhole
    特征:1.均匀的分布在铸件的整个断面上的小孔(直径小于1㎜)。2.凝固快的部位孔小数量少,凝固慢的部位孔大数量也多。3.在共晶合金中呈圆形孔洞,在凝固间隔宽的合金中呈长形孔洞。4.在X光底片上呈小黑点在断口上呈互不连续的乳白色小凹点。
    Features: 1. small holes are distributed evenly in the entire section of the casting (diameter less than 1 mm). 2. small number of holes which solidify fast, and the large number of holes which solidify slowly. 3. in eutectic alloy, a circular hole is presented, and a long hole is found in the alloy with wide solidification interval. In 4. X optical film on a small black spots were discrete white pits on the surface.
     
    原因分析:合金在液体状态下熔解的气体(主要为氢),在合金凝固过程中自合金中析出而形成的均布形式的孔洞。
    The reason analysis is that the molten gas (mainly hydrogen) of alloy in liquid state is formed in the solidification process of alloy.
     
    防止方法:1.合金液体状态下彻底精炼除气。2.在凝固过程中加大凝固速度,防止溶解的气体自合金中析出。3.铸件在压力下凝固,防止合金溶解的气体析出。4.炉料、辅助材料及工具应干燥。
    Prevention method: 1. alloy liquid state thoroughly degassing.  2. the solidification rate is increased during the solidification process to prevent the dissolved gas from precipitating from the alloy. 3. the castings are solidified under pressure to prevent the dissolving of the dissolved gases from the alloy.  4. the furnace materials, auxiliary materials and tools should be dry.
     
    三、疏松
    Three, looseness
    特征:1.呈海绵状的不紧密组织,严重时呈缩孔。2.孔的表面呈粗糙的凹坑,晶粒大。3.断口呈灰色或浅黄色,热处理后为灰白、浅黄或黑色。4.多在热节部位产生。5.在X光底片上呈云雾状荧光检查时呈密集的小亮点。
    Characteristics: 1. is a sponge like non tight tissue, in serious case of shrinkage. The surface of the 2. hole is rough and the grain is large. 3. the fracture is gray or light yellow, after heat treatment, it is gray, light yellow or black. More than 4. is produced at the hot spot. 5. a small bright spot was found on the X photo film with cloud - fog - like fluorescence.
     
    原因分析:1.合金液除气不干净形成气体性疏松。2.比较后凝固部位补缩不足。3.铸型局部过热、水分过多、排气不良。
    Reason analysis: 1. alloy liquid degassing is not clean to form a gas loose. 2. the final solidifying part is insufficient. The 3. mold is partially overheated, excessive water and bad exhaust.
     
    防止方法:1.保持合理的凝固顺序和补缩。2.炉料净洁。3.在疏松部位放置冷铁。4.在允许补焊的部位可将缺陷部位清理干净后补焊。
    Prevention methods: 1. maintain a reasonable order of solidification and recontract. 2. charge of cleaning. 3. the cold iron is placed in the loose parts. 4. the defect parts can be cleaned up after the patch is allowed to repair welding.
     
    四、夹杂
    Four, inclusion
    由涂料、造型材料、耐火材料等混入合金液中而形成的铸件表面或内部的与铸件成分不同的质点。
    The surface or inner parts of the castings formed by mixing the coatings, molding materials and refractory materials into the alloy liquid.
     
    原因分析:1.外来物混入液体合金并浇注入铸型。2.精炼效果不良。3.铸型内腔表面的外来物或造型材料剥落。
    The reasons are as follows: 1. foreign materials are mixed into the liquid alloy and poured into the mold. 2. the refining effect is bad. Exfoliation of external objects or molding materials on the surface of the 3. mold cavity.
     
    防止方法:1.仔细精炼并注意扒渣。2.熔炼工具涂料层应附着牢固。3.浇注系统及型腔应清理干净。4.炉料应保持洁净。5.表面夹杂可打磨去除,必要时可进行补焊。
    Prevention method: 1. refine carefully and pay attention to slagging. 2. the coating layer of the melting tool should be firmly attached. 3. the pouring system and the cavity should be cleaned up. 4. the furnace should be kept clean. 5. surface inclusions can be worn and removed, and supplementary welding can be made when necessary.
     
    五、夹渣
    Five, slag inclusion
    特征:1.氧化夹渣以团絮状存在于铸件内部,断口呈黄色或灰白色。2.熔剂夹渣呈暗褐色点状,夹渣清除后呈光滑表面的孔洞。在空气中暴露一段时间后,有时出现腐蚀特征。
    Characteristics: 1. oxidizing slag is formed in the castings, and the fracture is yellow or gray. The slag of the 2. flux is dark brown, and the slag is cleared on a smooth surface after the slag is cleared. After exposure to the air for a period of time, there are sometimes corrosion characteristics.
     
    原因分析:1.精炼变质处理后除渣不干净。2.精炼变质后静置时间不够。3.浇注系统不合理,二次氧化皮卷入合金液中。4.精炼后合金液搅动或被污染。
    The reasons are as follows: 1. the slag is not clean after refining. 2. after refining, the static time is not enough. The 3. pouring system is not reasonable, and the two oxide skin is involved in the alloy liquid. 4. after refining, the alloy liquid is stirred or polluted.
     
    防止方法:1.严格执行精炼变质浇注工艺要求。2.浇注时应使金属液流平稳地注入铸型。3.炉料应保持净洁,回炉料处理及使用量应严格遵守工艺规程。
    Prevention methods: 1. strictly enforce the requirements of refining and casting process. The 2. pouring should make the metal liquid flow smoothly into the mold. The 3. charge should be kept clean, scrap processing and usage shall strictly abide by the procedure.
     
    六、裂纹
    Six. Crack
    特征:1.裂纹呈直线或不规则的曲线。2.热裂纹断面呈氧化特征,无金属光泽,多产生在热节区尖角内侧,厚薄断面交汇处,常和疏松共生。3.断裂金属表面洁净。
    Characteristic: 1. the crack is straight or irregular curve. The 2. hot crack section is characterized by oxidation, without metallic luster, most of which is produced in the inside of the sharp corner of the hot zone, and at the intersection of the thick and thin sections, often and loosely symbiotic. 3. the surface of the broken metal is clean.
     
    原因分析:1.铸件各部分冷却不均匀。2.铸件凝固和冷却过程受到外界阻力而不能自由收缩,内应力超过合金强度而产生裂纹。
    Cause analysis: 1. the cooling of the parts of the casting is not uniform. 2. the solidification and cooling process of castings is subjected to external resistance and can not shrink freely, and the internal stress exceeds the strength of the alloy to produce cracks.
     
    防止方法:1.尽可能保持顺序凝固或同时凝固,减少内应力。2.细化合金组织。3.选择适宜的浇注温度。4.增加铸型的退让性。
    Prevention methods: 1. as much as possible to maintain order to solidify or simultaneously solidify, reduce internal stress. 2. refine the alloy structure. 3. select the appropriate pouring temperature. 4. increase the concession of the mold.
     
    七、偏析
    Seven, segregation
    特征:1.在熔炼过程中坩埚底部和上部的化学成分不均匀。2.铸件的先凝固部位与后凝固部位的化学成分不均匀。
    Characteristics: 1. the chemical composition at the bottom and the upper part of the crucible is not uniform during the melting process. 2. the chemical composition of the first solidification part and the post solidifying part of the castings is not uniform.
     
    原因分析:1.合金凝固时析出相与液相所含溶质浓度不同,多数情况液相溶质富集而又来不及扩散而使先后凝固部分的化学成分不同。2.熔炼过程中某些元素形成的化合物因密度与母液密度不同,在一定温度范围,沿坩埚底部而造成化学成分不均匀。
    Cause analysis: 1. when the alloy solidified, the precipitated phase is different from the solute concentration contained in the liquid phase. In most cases, the solute is enriched in liquid phase but not enough to diffuse, which makes the chemical composition of the solidified part different. 2., during the smelting process, the composition of some elements is different from that of the mother liquor because of the density and the density of the mother liquid. The chemical composition is uneven along the bottom of the crucible at a certain temperature range.
     
    防止方法:1.熔炼过程中加强搅拌并适当的静置。2.适当增加凝固冷却速度。
    Prevention method: 1. in the process of melting, the mixing and proper placement are strengthened. 2. properly increase the cooling rate of solidification.
     
    八、偏析瘤
    Eight. Segregation tumor
    特征:1.在铸件表面上形成瘤状的凸起物。2.金相检查一般为低熔点共晶富集区。
    Features: 1. a nodular protuberance is formed on the surface of the casting. The 2. metallographic examination is generally a low melting point eutectic enrichment area.
     
    原因分析:当铸件中心部位尚未凝固时,铸件表面收缩中心未凝固的液相穿透表面相层渗出而生产。
    Cause analysis: when the central part of the casting is not solidified, the non solidified liquid phase of the shrinkage center of the casting surface penetrates the surface layer and produces.
     
    防止方法:1.适当降低浇注温度。2.适当提高铸型的冷却能力。3.延长开型时间。
    Prevention method: 1. reduce pouring temperature properly. 2. properly improve the cooling capacity of the mold. 3. lengthening the opening time.
     
    九、成分超差
    Nine, component super difference
    特征:化学组元超过上限或低于下限含量,杂质元素超过允许的上限含量。
    Characteristics: the chemical component exceeds the upper limit or lower than the lower limit, and the impurity elements exceed the allowed upper limit content.
     
    原因分析:1.中间合金或预制合金成分不均匀或成分分析误差过大。2.炉料计算或配料称量
    The reasons are as follows: 1. the composition of the intermediate alloy or the prefabricated alloy is not uniform or the error of the component analysis is too large. 2. furnace charge calculation or proportioning weighing