Comparison between high pressure casting and low pressure casting?
Thin-walled die casting is the development direction of modern die casting technology, and is the prerequisite for the development of lightweight products. It is important to realize thin-walled die casting in the fields of aerospace, automotive, electronics, etc. High pressure die casting and low pressure die casting all belong to anti-gravity die casting, so what is the difference between them?
High-pressure die casting is what we usually call die-die casting, in which aluminum liquid is poured into a press chamber, filled with mold cavities at high speed by its pressure, and the liquid solidifies under pressure to form aluminum die castings. High-pressure die-die casting: a die casting method in which liquid or semi-solid metal or alloy, or liquid metal or alloy containing enhanced phases, is filled into the cavity of the die-die casting mold at a high speed under high pressure, and the metal or alloy is made to solidify under pressure to form a die casting. Therefore, high pressure and high speed is the fundamental difference between die-die casting method and other die casting methods, and is also an important feature.
1、Good product quality. Because of the die-die casting type fast heat conduction, metal cooling quickly, while crystallization under pressure, die castings with fine grain organization, solid surface, improve the strength and hardness of the die castings, in addition to die casting size stability, good interchangeability, can produce thin-walled complex parts.
2、High productivity, die-die casting mold use more times.
3、Good economic efficiency. The machining allowance of die die casting is small, generally only need finishing and reaming can be used, thus saving a lot of raw materials, processing equipment and man-hours.
1、The mold structure is complex, high manufacturing costs, long preparation cycle, so, only for the mass production of stereotyped products.
2、Die-die casting speed is high, the gas in the cavity is difficult to completely discharge, coupled with the fast solidification of the metal type in the type, the possibility of small shrinkage, resulting in die castings are prone to small pores and shrinkage, the thicker the die casting wall, the more serious this defect, therefore, die-die casting is generally only suitable for wall thickness of 6mm or less die castings.
3、The plasticity of the die die casting is low, not suitable for work under shock load and vibration.
4、In addition, high melting point alloy die-die casting, die casting life is low, affecting the expansion of die-die casting production applications.
1、The product surface finish is good, generally up to Ra6.3 or even up to Ra1.6.
2、No heat treatment.
3、High air tightness, high die casting strength and surface hardness, but low elongation, wall thickness is too thick and easy to produce pores.
4、High mold cost and short service life.
5、High production efficiency.
6、It can produce thin-walled parts with small machining allowance.
7、Can't use special aluminum alloy.
1、Discs, caps, rings, a pump housing casing, bearing retainers, steering wheels, etc;
2、Cylinder class a flange jacket, conduit, shell shape hood cover, upper cover, instrument cover, probe control instrument cover, etc;
3、A multi-hole cylinder body, shell class a cylinder body, cylinder head and oil pump body and other multi-cavity structure of the more complex shell and other power assembly parts;
4、Special shape class a impeller, horn, font by the rib decorative die die casting, etc.
Low-pressure die casting is a die casting method in which liquid metal is under pressure to complete the filling and solidification process to obtain the die casting. It is called low pressure die casting because of the low pressure (generally 20~60kPa). In the sealed crucible (or sealed tank), dry compressed air is introduced and the metal liquid, under the action of gas pressure, enters the straight spruce and rises through the inner spruce and enters the cavity smoothly, keeping the gas pressure on the liquid surface in the crucible. Until the die casting is completely solidified. Then the gas pressure on the liquid surface is released and the unconsolidated metal in the riser flows back to the crucible. The mold is then opened and the die casting is removed. Simply put, low pressure is a compromise between high pressure and gravity.
1、The filling speed can be accurately controlled to obtain the best filling speed, and the liquid metal filling is relatively smooth;
2、Improve the utilization rate of the metal, can reduce the size of the riser or no riser, so it can significantly reduce the material cost and processing time;
3、Low labor intensity, good labor conditions, simple equipment, easy to achieve mechanization and automation, not affected by the operator's proficiency;
4、The use of bottom injection type filling, metal liquid filling smoothly, no splash phenomenon, can avoid the involvement of gas and the scouring of the wall and core, improve the die casting
the qualified rate of the die casting;
5、Easy to form sequential solidification, less internal defects; less involvement of gas and debris; high density of die castings.
1、Small freedom of gating scheme, thus limiting the product;
2、Long die casting cycle, poor productivity, high mold temperature and slow solidification in order to maintain sequential solidification and liquid metal flow.
1、The product surface than die die casting poor stronger than gravity parts
2、Aluminum die castings with few internal pores, can be heat treated.
3、Product air tightness is high, die casting strength and surface hardness is higher than die die casting, but the elongation is lower than gravity.
4、Mold cost is lower and service life is lower.
5、Production efficiency is lower than gravity and much lower than die-die casting.
6、The process is complex and used to produce high requirements and high quality die castings.
7、Low fluidity special aluminum alloy can be used.
Suitable for products with medium wall thickness and high performance requirements, such as wheels and other chassis safety parts.