How the mud core plugging hole product defects are finally eliminated in production?

Canhu’s engineers have summarised the prevention methods of air hole defects

1. Furnace material with high gas content, serious corrosion, more surface grease should be cleaned before use.

2. Strictly control the temperature of liquid iron and pouring temperature. The pouring temperature should not be too low.

3. Cylinder, furnace and liquid iron package should be fully dried, liquid iron package should be fully hot package before use.

4. Balling alloy and inoculant should be fully preheated to reduce the amount of gas brought in by rare earth and ferrosilicon.

5. The setting of pouring system should consider the smooth flow of exhaust gas in the cavity and smooth flow into the cavity.

6. The sand compactness should be even, not too tight.

7. Appropriately reduce the mud content of the core sand to improve air permeability.

8. The sand core should be ventilated smoothly, and the gap between the core head should be sealed to avoid the iron liquid drilling in and blocking the airway.

9. In the casting of the highest place to set the risers or venting holes. Large castings casting attention to lead gas.

10. For large plane castings can be tilted casting, air outlet holes at a slightly higher, in order to facilitate the exhaust.

11. Core support and cold iron must be dry, no rust, no oil.

12. Properly reduce the water in the sand, open the exhaust groove at the parting surface, properly increase the amount of coal powder added.

13. Appropriately reduce the binder, large castings can be attached to increase the permeability of some substances, such as wood chips.

14. Select round sand grains to increase air permeability.

15. Under the premise of ensuring spheroidisation, reduce the amount of residual magnesium appropriately, and try to reduce the sulphur content of the original liquid iron.

16. Control the sand temperature, pouring as soon as possible after closing the box.

17. The sand core is cooled and then used to prevent moisture absorption in the type. Moisture absorption serious sand core can not be used.

18. Spray ingot oil and other carbonaceous materials on the surface of the casting, so that the liquid iron and the casting of the interface between the reducing atmosphere. Liquid iron and casting interface sprinkled with a small amount of cryolite powder or sodium fluorosilicate and other materials can reduce or eliminate subcutaneous porosity.

19. Appropriately increase the pouring temperature in rainy weather.

20. Reduce magnesium sulfide inclusions. Use low-sulfur pig iron or add baking soda to desulfurise appropriately during spheroidising treatment. After the spheroidisation treatment, it is necessary to pick the slag several times and stand still for a few moments, so that the MgS slag floats.

21. Control pouring temperature. Pouring temperature of thin-walled parts shall not be less than 1320 ℃; medium wall thickness castings shall not be less than 1300 ℃; guide disc type thick-walled parts shall not be less than 1280 ℃. Silicon molybdenum cast iron and high nickel austenitic ductile iron temperature is higher.

22. Control sand moisture. Guide plate such large castings, the use of dry casting, usually requires the sand must be drying, modelling, put some grass rope to increase the permeability of the sand and make the wall of the type of gas produced by the smooth discharge outside the type.

23. Casting, iron liquid separation. In the wet sand add coal powder or in the sand surface spraying a layer of dilute lubricant, graphite paint; in the sand surface spraying some of the paraffin suspension containing Fe2O3 fine powder to form a glassy substance, the casting, the separation of liquid iron.

24. The production and prevention of high nickel austenitic ductile iron parts porosity in the "high nickel austenitic ductile iron see defects analysis and countermeasures" article has a special discussion 3).

25. Summer sand water content should be controlled in the process of the upper line, winter should be controlled in the process of the lower line, cloudy and rainy weather moisture is big time are to make appropriate adjustments to the sand water content.

26. The control of sand temperature should not be ignored, the general situation of sand temperature below 35 ℃.

27. Cold core box core making on the resin, triethylamine quality control, sand core brush paint should be dried back to cool after use, to prevent the generation of subcutaneous porosity. Under the premise of meeting the surface quality of castings, try to use coarser sand, reduce the amount of resin, reduce the amount of gas.

28. Only use the film sand core after it cools down, and try to use thicker sand to reduce the amount of resin.