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Principles for Selecting Pouring Positions of Large Cast Steel Parts
2020-07-01
Pouring position refers to the position and state of placement within the mold during pouring. Cast steel parts It relates to the internal quality of the cast steel parts, the dimensional accuracy of the casting, and the difficulty of the molding process. Therefore, several schemes often need to be formulated for analysis and comparison to select the best one.
Determining the pouring position of cast steel parts should be comprehensively considered throughout the entire formation process of the cast steel parts.
The control of the filling and solidification process of cast steel parts involves various factors such as alloy type, cast steel part structure, mold conditions, and pouring process. Technical requirements must also be considered and analyzed specifically. For example, thick sections are prone to shrinkage defects during solidification; large flat surfaces tend to have sand inclusions and scabs during pouring; thin-walled areas are prone to misruns and cold shuts. Areas with significant differences in wall thickness are prone to stress concentration and cracking. Additionally, important machining surfaces, heavily stressed areas, and parts mainly subjected to pressure (hydraulic, pneumatic) should be prioritized when determining the pouring position to facilitate process measures that prevent various casting defects and ensure internal quality. Furthermore, the convenience of molding and core setting operations should also be considered. Sometimes conflicts arise, requiring comprehensive analysis to prioritize the main issues while addressing others through auxiliary process measures.
The following principles should be considered when determining the pouring position:
(1) Important parts of the cast steel should be placed as low as possible. The metal in the lower part of the cast steel solidifies under the static pressure of the upper metal and undergoes shrinkage compensation, resulting in a dense structure.
(2) Important machining surfaces should face downward or be in an upright position. Defects such as gas holes and non-metallic inclusions often appear on the upward-facing surfaces of cast steel parts. Therefore, important machining surfaces should face downward or be upright. If certain machining surfaces must face upward, machining allowances should be appropriately increased or riser measures should be taken.
(3) Large flat surfaces of cast steel parts should be placed facing downward to avoid sand inclusions and scab-like defects. For large flat plate cast steel parts, inclined pouring can be used to increase the rising speed of the molten metal surface and prevent sand inclusion and scab defects.
(4) Ensure the cast steel part can be fully filled. For cast steel parts with thin-walled sections, the thin-walled parts should be placed in the lower half or below the internal gating to avoid misruns, cold shuts, and other defects.
(5) Facilitate shrinkage compensation of the cast steel parts. For cast steel parts prone to shrinkage cavities and porosity due to large alloy shrinkage rates or uneven thickness in the structure, the pouring position should prioritize conditions for sequential solidification and facilitate the placement and effectiveness of risers for shrinkage compensation.
(6) Avoid using hanging sand, hanging cores, or cantilever sand cores to facilitate core setting, mold assembly, and inspection. Hanging sand is prone to box stepping during mold assembly and pouring. Installing hanging cores on the upper half mold is inconvenient. Cantilever sand cores are unstable and easily tilt under metal buoyancy, so they should be avoided as much as possible. Additionally, convenience for core setting, mold assembly, and verification should be considered.
(7) The positions of mold assembly, pouring, and cast steel part cooling should be consistent. This avoids flipping the mold after assembly and pouring for cooling. Flipping the mold not only requires significant labor but also easily causes sand core displacement, sand dropping, and even metal penetration defects.
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2026-09-05
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