4. pouring should be stable and should pay attention to the slag. After refining, the pre cast alloy liquid should be static for a certain time.
二、气孔、缺陷特征：三铸件壁内气孔一般呈圆形或椭圆形，具有光滑的表面，一般是发亮的氧化皮，有时呈油黄色。表面气孔、气泡可通过喷砂发现，内部气孔、 气泡可通过X光透视或机械加工发现气孔、 气泡在X光底片上呈黑色。
Two, the characteristics of stomata and defects: three, the holes inside the walls are generally round or oval, with smooth surfaces, usually shiny oxide scales and sometimes oil yellow. The surface pores and bubbles can be found by sandblasting. The pores and bubbles can be found through X or mechanical processing. The pores and bubbles are black on the X light negative.
1. cast alloy is not smooth, involved in gas.
The 2. type (core) sand is mixed with organic impurities.
3. mould and sand core have bad ventilation.
4. cold iron surface has a shrinkage cavity, and the design of the pouring system is bad.
1. correctly grasp the casting speed, avoid the gas.
The 2. type (core) sand should not be mixed with organic impurities to reduce the air volume of the molding material.
3. improve the discharge capacity of (core) sand.
4. the correct selection and treatment of cold iron. Improve the design of the gating system.
三、 缩松缺陷特征：铝铸件缩松一般产生在内浇道四周飞冒口根部厚大部位、壁的厚薄转接处和具有大平面的薄壁处。在铸态时断口为灰色，浅黄色经热处理后为灰白浅黄或灰黑色在x光底片上呈云雾状严重的呈丝状缩松可通过X光、荧光低倍 断口等检查方法发现。
Three, shrinkage defect characteristics: aluminum casting shrinkage generally occurs around the internal runner, thick risers, thick parts of the wall, thick walled joints and large flat thin wall. The as cast fracture is gray, light yellow after heat treatment is pale yellow or dark gray clouds in the X-ray film showed serious filamentous shrinkage by X fluorescent light, low power were found fracture.
产生原因：
Cause:
1.冒口补缩作用差。
The effect of 1. risers was poor.
2.炉料含气量太多。
The 2. furnace contains too much gas.
3.内浇道四周过热
3. overheating all around the runner
4.砂型水分过多，砂芯未烘干。
There is too much water in the 4. sand mold and the sand core is not dried.
5.合金晶粒粗大。铸件在铸型中的位置不当 。浇注温度过高，浇注速度太快。
The grain of 5. alloy is coarse. The position of the casting in the mold is improper. The pouring temperature is too high and the pouring speed is too fast.
防止方法：
Prevention methods:
1.从冒口补浇金属液，改进冒口设计。
1. to fill the metal liquid from the riser and improve the riser design.
2.炉料应清洁无腐蚀。
2. the furnace material should be clean and no corrosion.
3.铸件缩松处设置冒口，安放冷铁或冷铁与冒口联用 。
3. the riser in the shrinkage cavity of the castings is set up, and the cold iron or cold iron is put together with the riser.
4.控制型砂水分，和砂芯干燥。
4. control the moisture of the molding sand, and the drying of the sand core.
5.采取细化品粒的措施；改进铸件在铸型中的位置降低浇注温度和浇注速度。
5. the measures of refining the grain are taken, and the position of casting in the mold is improved to reduce the pouring temperature and the casting speed.
四、 裂纹缺陷特征 ：
Four. Characteristics of crack defect:
1.铸造裂纹。沿晶界发展，常伴有偏析，是一种在较高温度下形成的裂纹在体积收缩较大的合金和外形较复杂的铸件轻易出现
1. casting cracks. The development of the grain boundary, often accompanied by segregation, is an easy appearance of a crack formed at a higher temperature in the alloy with larger volume shrinkage and the more complex shape of the casting.
2.热处理裂纹：由于热处理过烧或过热引起，常呈穿晶裂纹。常在产生应力和热膨张系数较大的合金冷却过剧。或存在其他冶金缺陷时产生。
2. heat treatment crack: due to heat treatment or overheating, it often presents a transgranular crack. It is often used to produce alloy cooling plays with greater coefficient of stress and thermal expansion. In the presence of other metallurgical defects.
产生原因：
Cause:
1.铸件结构设计不合理，有尖角，壁的厚薄变化过于悬殊。
1. the structural design of the castings is unreasonable, with a sharp angle, and the thickness of the wall is too large to change.
2.砂型(芯)退让性不良。
2. sand mold (core) is poor.
3.铸型局部过热 。
The 3. mold is partially overheated.
4.浇注温度过高。
4. pouring temperature is too high.
5.自铸型中取出铸件过早；热处理过热或过烧，冷却速度过激。
5. the casting is prematurely taken out of the mold; heat treatment is overheated or overheated, and the cooling speed is excesses.
防止方法:：
Methods of prevention:
1.改进铸件结构设计，避免尖角，壁厚力求均匀，圆滑过渡。
1. improve the design of the casting structure, avoid the sharp angle, the wall thickness strives to be uniform and the smooth transition.
2.采取增大砂型(芯)退让性的措施。
2. measures to increase the concession of the sand mold (core).
3.保证铸件各部分同时凝固或顺序凝固，改进浇注系统设计。
3. ensure that the parts of the castings are solidified at the same time or in order to solidify, and the design of the casting system is improved.
4.适当降低浇注温度。
4. reduce the pouring temperature properly.
5.控制铸型冷却出型时间。
5. control the casting mold cooling out time.
6.铸件变形时采用热校正法；正确控制热处理温度，降低淬火冷却速度。
6. the heat correction method is adopted when the casting is deformed, and the heat treatment temperature is properly controlled to reduce the quenching cooling rate.
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