SU925546A1 - Method and its versions for producing shaped iron castings - Google Patents

Description

After the crystallization is completed in the first stage of cooling, the cooler (water) is supplied to the heat-casting nodes on the layer of molding or core mixture with limited intensity due to the fact that due to the dense packing, the mixture has a reduced water absorption.

After wetting the mixture layer with moisture, increasing the thermal conductivity of the mixture and increasing its throughput, the coolant supply is increased, after it increases the cooling rate of the massive parts, which becomes higher than the cooling rate of the thin sections, and the temperature between the massive and thin parts of the casting is high temperature region (not lower than 700–600 ° C). iB in this case, the chugtun has enough plasticity to relax the resulting thermal stresses.

After equalizing the temperatures of the massive and thin parts of the casting in order to ensure the same cooling rate in the future, the flow rate of the cooler to the thermal units is reduced.

After the casting reaches a temperature of 300-250 ° C, i.e., the temperature range of the elastic state of the iron, when the temperature difference does not affect the formation of additional residual stresses, the flow of the coolant is again increased.

Comparative tests of the proposed method and the prototype method were carried out, for which three single forms of castings of the SMD-B engine crankcase were manufactured. The molds were cast with iron grade СЧ21-40 at 134-0 ° С. After completion of the crystallization process (15 minutes after pouring), water supply to the massed parts of the casting on the core mixture layer began. Water was supplied with an intensity of 430 l / m2 h with pulses of 0.5-0.7 l every 40-45 s.

Further, according to the proposed method, after impregnating the layer of the mixture with moisture (after 25 minutes), the intensity of the cooling charge was doubled.

In the first variant, after equalizing the temperatures (650 ° С - massive part, 630 ° С - thin wall), the intensity of water supply to the massive part was reduced to 70 l / m h.

After reaching the temperature of the massive and thin parts of the casting, respectively, 300 and 280 ° C, the casting was removed from the mold and further, cooling was conducted by supplying a chiller (compressed air) to the entire casting volume with an intensity of 400 mH / m-h.

In the second embodiment, when the temperature of the massive and thin parts of the casting was 650 and 630 ° C, respectively, the casting was removed from the mold and cooled at air pressure for 90 minutes, providing the same cooling rate for the massive and thin parts of the casting by supplying compressed air to the massive parts with an intensity of 80 hours

When the temperature of the massive and thin parts of the casting reached 300 and 280 ° C, respectively, a cooler (compressed air) began to be supplied to the entire volume of the casting with an intensity of 300 hours.

In the casting cooled according to the prototype method, the maximum residual stresses were 7.8 kgf / mm, and in the casting cooled according to the proposed method, 3.4 kgf / mm.

Its general cooling time to 50-60 ° C according to the prototype method was 5 h 20 min, and according to the proposed method - 3 h 20 min.

In order to use the proposed method for the manufacture of shaped castings from cast iron under production conditions, it is recommended to install a differentiated coolant supply to selected parts of the casting in the first casting, determining the cooled areas of each part, controlling the temperature of the cooled parts using thermocouples and determining the flow rate of the cooler. Coolant to the subsequent castings should be supplied according to the flow rate and time set for the first casting.

The proposed method for the manufacture of cast iron castings improves their quality and performance properties by reducing residual stresses and reduces the labor intensity of manufacturing by reducing the duration of heat treatment.

The proposed method for the manufacture of cast iron castings provides (elimination of cold cracks and eliminates artificial aging in order to reduce residual stresses.

Claims (2)

1. Method of making shaped castings from cast iron, including pouring melt into a mold, supplying a coolant to massive parts casting | KI after finishing the crystallization process with an intensity of 1 / m-h, characterized in that in order to reduce the residual stresses in the castings to improve their quality, 15-30 minutes after the start of the supply of the cooler, the intensity of its supply is doubled, after cooling the casting to 700-600 ° C, the flow rate of the cooler is reduced to 50-100 l / m2 h, and at 300-1250 ° C extracted from the mold and all about The cooling is cooled with the flow rate of the cooler 300-400 m3 / m2 h. 2. Method of making shaped castings from cast iron, including pouring the melt into the mold and supplying a cooler to the massive parts of the casting after the end of the crystallization process with an intensity of 400-1000 l / m h, characterized in that in order to reduce the residual stresses castings in order to catch their quality, 16-30 minutes after the start of the supply of the cooler, the intensity of its supply is doubled, after cooling the casting to C, it is removed and the cooler is fed to the massive parts of the casting with an intensity of 80- 130 мз / м2. hours before cooling it to 300-250 ° C with subsequent cooling of the entire casting with a cooling flow rate of 300-400 m3 / m2. n Sources of information taken into account in the examination: 1. For Japan No. 46-17162, cl. B 22 D 33/00, 73. 2. Handbook on cast iron. Ed. N. G. Girshovich. L., “Mechanical Engineering, 1978, p. 698 (prototype).