Research Of Aluminum Silicon Alloy Porosity

This paper studies the affected relationship between the cooling rate and the amount ofhydrogen in aluminum alloys. By the aluminum alloy solidification at atmospheric pressure andthe negative pressure, the relationship between the diffusion rate of hydrogen in the alloy and theouter pressure of the hole was obtained, at the same time,the distribution of hydrogen hole in thealloy, the relationship of hydrogen hole content and the cooling rate, porosity, the affectedrelationship between the mechanical properties of the alloy and hydrogen hole content were alsostudied.Experimental results show that, when the aluminum alloy solidify under negative pressureconditions, hydrogen gas holes more easily spread out, while the greater buoyancy of floatingbubbles, so that the upper portion of the solid aluminum alloy solidified first projection, and thusthe total volume of the alloy becomes large, density becomes small, the alloy is not dense. In thelongitudinal direction of the alloy, gas holes are mainly concentrated in the upper portion, fewergas holes in the lower portion, alloy denser; In the transverse direction, gas holes mainly in theinside, fewer gas holes close to the outer portion, alloy denser.At the same time, the paper through gas content testing of the trapezoidal plate, furtherconfirmed there was a relationship of the aluminum-containing gas and the cooling speed, thefaster cooling speed,the lower gas content. The higher gas containing of aluminum alloy, theeasier stress concentration, which result in lower mechanical properties. For reducing the amountof hydrogen gas hole in aluminum, two mainly propose come out: First, should strengthenmeasures to prevent the blast furnace blast furnace processing is not inough, such as the injectionof purification gas by guns, propellers and others; Second, slow cooling in order to preventaluminum diffusion lead to a lot of solid solution of hydrogen in the alloy is formed out ofhydrogen holes should be accelerated cooling rate of the alloy, such as to appropriately increasecold iron. The experimental studies have shown that, when the thickness is more than30mm, themechanical properties of the casting will not meet production requirements, so the cold iron isneeded.