Search results
Results from the WOW.Com Content Network
Liquid shrinkage is the reduction in volume during the process of solidification (liquid to solid), the liquid shrinkage is accounted for by risers. Solid contraction is the reduction in dimensions during the cooling of the (solid) cast metal. Contraction allowance takes into account only the solid contraction.
A bronze casting showing the sprue and risers. A riser, also known as a feeder, [1] is a reservoir built into a metal casting mold to prevent cavities due to shrinkage.Most metals are less dense as a liquid than as a solid so castings shrink upon cooling, which can leave a void at the last point to solidify.
Directional solidification can be used as a purification process. Since most impurities will be more soluble in the liquid than in the solid phase during solidification, impurities will be "pushed" by the solidification front, causing much of the finished casting to have a lower concentration of impurities than the feedstock material, while the ...
The depth of the mold can range from 0.5 to 2 metres (20 to 79 in), depending on the casting speed and section size. The mold is water-cooled to solidify the hot metal directly in contact with it; this is the primary cooling process. It also oscillates vertically (or in a near vertical curved path) to prevent the metal sticking to the mold walls.
The wax patterns require extreme care for they are not strong enough to withstand forces encountered during the mold making. One advantage of investment casting is that the wax can be reused. [5] The process is suitable for repeatable production of net shape components from a variety of different metals and high performance alloys.
The thermal method involves changing the temperature of the entire part uniformly, either through heating or cooling. When parts are heated for stress relief, the process may also be known as stress relief bake. [13] Cooling parts for stress relief is known as cryogenic stress relief and is relatively uncommon. [citation needed]
Recrystallization may occur during or after deformation (during cooling or subsequent heat treatment, for example). The former is termed dynamic while the latter is termed static . In addition, recrystallization may occur in a discontinuous manner, where distinct new grains form and grow, or a continuous manner, where the microstructure ...
A further possibility is mercerizing, during which the fabric is treated with a caustic soda solution to cause swelling of the fibres. This results in improved luster, strength, and dye affinity. Cotton is mercerized under tension, and all alkali must be washed out before the tension is released or shrinkage will take place. Mercerizing can ...