Understand the use of stainless steel structural parts
Three points of attention for the casting of stainless steel structural parts, stainless steel has been used in construction since the 1920s, and it has a history of about 90 years. Today, stainless steel is used in all aspects of building structures, and its use is growing and its application range is expanding. Since the cooling and solidification rate of stainless steel structural parts in the metal mold is faster than that of the sand mold, and there is no tolerance, the stress generated during casting is greater than that of sand casting, and the tendency to crack is also greater, which is prone to insufficient pouring, cold isolation, Castings and other defects. Generally speaking:
(1) The following structural problems should be paid attention to to prevent under-casting and cold preservation of stainless steel structural parts: a. The shape should be as streamlined as possible to avoid sharp changes in sharp corners and joints, so as to facilitate the flow of molten metal; b. The wall thickness should be appropriate, It should not be too thin, especially when the contour size of the casting is large; c. Large horizontal planes should be avoided, because it makes the molten metal rise slowly during casting, and the area in contact with the air is large, which is easy to be oxidized. At the same time, due to the rapid heat dissipation, the molten metal quickly loses its fluidity, which is likely to cause defects such as insufficient pouring, cold isolation, and slag inclusion.
(2) To prevent cracks in stainless steel castings, the following structural problems should be paid attention to: a. The weak parts of the structure should be reinforced with ribs and bosses to prevent cracks in the castings; b. When reinforcing ribs are arranged on the castings, the effect of shrinkage should also be considered; c. Protruding parts such as bosses, ribs, flanges, etc. What hinders the free shrinkage of castings should be reduced as much as possible; d. Requirements for uniform wall thickness, moderate transition connections between walls, and appropriate rounding at corners. It should be stricter than sand casting; e. Vertically connected walls should be changed to obliquely connected walls.
When designing the basic structural units of stainless steel structural parts and selecting their parameters, the following points should usually be paid attention to: (1) In order to prevent gray cast iron from producing white spots, the wall thickness should not be too thin except for technological measures. (There is information that when the wall thickness exceeds 15mm, the casting of metal mold must be rounded, the rounded corner of aluminum alloy and magnesium alloy metal mold casting must not be less than 3-4m, cast iron, cast steel. (2) Due to the metal mold With the uncompromising nature of the core, in order to take out the casting and the mold, the casting slope of the metal casting should be greater than that of the sand casting, generally 30%-50%. The manufacturer of stainless steel structural parts said that it should be pointed out that the casting slope is not only It is related to the type and height of the alloy, as well as the position of the casting surface.
(3) Due to the fast heat dissipation of the metal mold, the minimum wall thickness of the stainless steel structure should be greater than that of the sand casting, and the minimum wall thickness of various casting alloys and different sizes should be 0.6-0.7 times the thickness of the outer wall; otherwise, due to the slow cooling of the inner wall (rib), cracks are likely to occur at the junction of the inner and outer walls during shrinkage. When designing stainless steel structural parts with complex shapes, if the production process is difficult, the shape should be as simple as possible, and the strength structure should be changed so that the castings can be removed from the metal mold.