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                                                                      Method for preventing cracking of castings


In the production process of castings, cracks are easily generated near the gate or outer edge of the casting, which leads to an increase in the scrap rate of the casting, which seriously affects the quality of the casting and the economic benefits of the enterprise. So how do you prevent cracks in stainless steel castings?
1. Use of cold iron.
Place cold iron at a local small hot section where cracks are easy to occur (such as the habit of the body and the flange), accelerate the solidification speed at this point, weaken the sequential solidification strength, and achieve a small range of simultaneous solidification, which is beneficial to reduce thermal cracking and shrinkage. Loose defects. It is worth noting that cold iron has the effect of refining grains and improving the local high temperature strength of castings. It is used in the casting production of cast steel three-way valves, which can form a simultaneous solidification principle under the principle of overall sequential solidification, which is beneficial to Prevent hot cracking and shrinkage.
2. Achieve rapid pouring.
Rapid pouring, short filling time, less heat dissipation of molten steel, uniform temperature, is conducive to reducing thermal stress, and inclusions, gases, etc. are also easy to float. In the production of stainless steel castings, the following process plan should be adopted:
(1) Design the cross-sectional area of ​​each component by using large holes to ensure large flow, low speed, smooth and clean filling throughout the casting process;
(2) 2 is filled with a ladle at a low level, and the height of the gate cup (h) is kept proportional to the diameter of the sprue (d) (ie, h>6d) to prevent slag and gas from entering. Cavity
(3) In order to prevent the gas from being caught in the molten steel or bonfire during pouring, it is necessary to sew sufficient vent holes in the upper tank to make the gas in the cavity unimpeded, and the total area of ​​the venting holes should be much larger than the cross section of the sprue. area.

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