The core should be made hollow to facilitate venting

Posted by brassbushs on February 22nd, 2020

The cast lead brass has a narrow crystallization temperature range, a large shrinkage rate, and shell-like solidification characteristics. Therefore, shrinkage and loosening are easy to occur in the casting, especially at the hot joints. The use of metal mold casting shell, compact casting structure, good quality, high productivity, high yield, high process yield, is the best method of manufacturing the shell, but because of the poor exhaust capacity of the metal mold, poor concession, often Defects such as porosity cracks and shrinkage are easy to occur in the hot joints of castings, so castings often leak in the hot and cold water partition walls and the inlet holes of the valve core installation holes are shrinking. Riser This article takes the single-control wall shower nozzle 16 shell as an example, analyzes the cause of leakage of the metal mold casting shell, and proposes to solve the leakage of the casting. 1 Analysis of the cause of the leakage 1.1 The material defect is the casting Key 1 for Leakage Use a low grade brass lake. When using a large proportion of raw materials and materials, there are many impurities in the smelted alloy and it is difficult to control the chemical composition. This directly deteriorates the casting properties of the alloy, increases shrinkage, has a high tendency to thermal cracking, and has poor purity. It is easy to produce castings. Cracks are mixed with defects such as coarse crystals, which fundamentally cause casting leakage. 1.2 Micro-shrinkage is the main cause of leakage in castings. The metal mold casting shell is formed by a metal mold on the outside, and the inner cavity is composed of a coated sand core.

After the copper liquid is poured into the metal mold cavity, the outside is rapidly cooled. The tissue is dense and belongs to an exogenous shell-like solidification method, while the cold and hot water partition walls and the shell of the shell are surrounded by a sand core, which has slower cooling and poor exhaust capacity. Intermediate solidification castings are liable to produce intergranular shrinkage and thermal knot shrinkage at this location, causing leakage during the hydraulic test of the casting. 1.3 The defective casting process is the direct cause of casting leakage. When designing the mold, No good replenishment channel is formed, and the replenishment ability of the gate is weak, so the casting is liable to generate thermal shrinkage at this location. During the injection, the copper liquid is not stable enough to enter the cavity, the gas is difficult to be discharged, and the casting is prone to produce porosity defects. The coated sand core is not dried properly, and the sand core has a large amount of gas during casting. The sand core has high strength, poor collapsibility and poor concession properties, and the casting is gear shaft Manufacturers prone to cracks and porosity defects.

The occurrence of these casting defects directly leads to leakage of the casting. 2 Overcoming countermeasures 2.1 When designing the mold design, 1 bubble core seat 1 is provided with 21 deep angular grooves, and 14 thick flat exhaust risers are provided at the upper parting surface of the 14 mold to make the exhaust smooth. According to the characteristics of the casting part biased to the parting surface, when designing the gating system, the gate thickness was intentionally increased to strengthen the shrinkage ability of the gate and prevent thermal knots from loosening. 2.2 Alloy smelting When smelting alloys, higher grade brass ingots and raw materials are used, and the proportion of recycled materials is controlled below 2 cats. And it is necessary to strengthen the refining of the alloy, improve the metallurgical quality of the alloy, and minimize the gas content and inclusions in the alloy. It is required to achieve the charge of the flux. Tools and the like must be fully preheated and dried to eliminate the source of gas generation; and a layer of covering agent 7 deborax 3 and glass breakage are added to the copper liquid surface to prevent the copper liquid from getting inhaled and oxidizing rare earth metals. Metamorphic effect. Therefore, adding 00 to 0.05 mixed rare earth 2.3 to the copper solution process control found in production that appropriately reducing the pouring temperature is an effective measure to reduce the cracking and shrinkage of pores and shrinkage of the casting, so it is more appropriate to control the pouring temperature at 99 spit. Adjust the turning speed of the pouring machine, and control the pouring time to the left and right, so that the metal liquid enters the cavity smoothly, so that the gas can be smoothly discharged. The coated sand core should be dried, and its surface color and lustre should be brown, and the shiny surface should be white with no sand particles falling off. The core should be made hollow to facilitate venting, minimize the gas output of the sand core, and use coated sand with good collapsibility and high strength. Apply 0.0.41. On the sand core of the water inlet cavity forming the clasp, and enjoy the naturally-dried tellurium 1 powder alcohol quick-drying coating to prevent the cleat from loosening. 3 The effect of production application is on the metal mold casting water. After analyzing the cause of the leakage of the nozzle shell and taking corresponding countermeasures, the casting defects were significantly reduced, the casting quality was greatly improved, the casting structure was dense, the pressure resistance was good, the leakage rate was reduced, and the casting yield was increased from 50 to 9 or more. Significant economic benefits.