Smelting And Pouring Of Large Copper Alloy Propellers
| Combined with the large-scale propeller casting process design, consider appropriate process parameters such as shrinkage, deformation, and processing volume; the use of multi-furnace smelting, control of reasonable melting temperature, degassing process, and pouring temperature are prerequisites for ensuring the smooth casting. |
Through the design of the bottom-injection pouring system, and after pouring to the riser 1/3, the high-temperature copper liquid is added to shrink the riser to ensure that the machining castings solidify in sequence, which is the key factor to obtain the internal quality of the castings.
Smelt
Because the paddle gross weight is 57t, two 30t intermediate frequency electric furnaces are used for smelting. The ZCuAl9Fe4Ni4Mn2 material ratio is strictly enforced. The smelting temperature is controlled at 1200 ~ 1250 ℃. Chemical analysis and bending test are performed in the furnace to determine whether the alloy solution meets the requirements. . Once qualified, the furnace can be released.
Since two different sizes of ladle are used for simultaneous pouring, the temperature in each ladle must be controlled. In order to ensure that the final pouring temperature is controlled within the required range, each furnace must be arranged in advance. Time and temperature.
Degassing and gas detection
Because copper alloys are easy to getter, mainly hydrogen, in order to obtain high-quality castings, the bottom-blown nitrogen blowing process is used. The dried nitrogen is blown into the alloy liquid through the bottom-covered bottom.
During the rise of nitrogen bubbles, it is taken away. The hydrogen dissolved in the copper liquid causes the metal inclusions in the alloy liquid to also float up to achieve the purpose of degassing and purifying the alloy liquid.
The gas-containing test of the copper liquid generally controls the air pressure above -0.092 MPa, and the ship propellers is not convex to be regarded as qualified. If the above requirements are not met, nitrogen blowing should continue until it is qualified.
Pouring
After passing the gas, stop blowing nitrogen. For ZCuAl9Fe4Ni4Mn2 alloy, when pouring large castings, the pouring temperature can be 1120 ~ 1140 ℃, usually the line temperature is taken for pouring, which can meet the requirements. When the riser feeding is performed during the pouring, the interval is 40 ~ 60min each time, so as to ensure the order solidification of the casting, improve the feeding effect of the riser, and improve the internal quality of the casting.
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