SU1178540A1 - Method of removing mould cores - Google Patents

Abstract

A METHOD FOR REMOVING CASTING RODS made of self-hardening liquid mixtures from long thin-walled castings, including application of mechanical loads to the casting, characterized in that, in order to reduce the labor intensity by reducing the residual strength of the rod, casting with the rods before casting subjected to heating up to 400-500 0 at a speed of no more than 70 ° C per hour, maintained at this temperature for 5-6 hours and cooled with the furnace to 100-150 ° C.

Description

(L

with

00 SP The invention relates to foundry, in particular, to the removal of cores from extended thin-walled castings. The purpose of the invention is to reduce the labor intensity by reducing the residual strength of the rod. The essence of the method lies in the fact that before removing a rod made of CSH from an extended thin-walled casting, casting with a rod before heating is heated in a heat-treatment furnace up to 400-500 ° C with a heating rate not exceeding 70 ° C per hour This temperature takes 5-6 hours to heat the mixture cores to 400-500 ° C, and the heated casting with the core is cooled with the furnace to 100-150 ° C. The thermal extraction of a thin-walled casting with a core from ZhSS allows one to heat the rod from self-hardening mixes up to 400500С to the full depth. During the heating process from one side, the ZhSS filler - quartz sand expands to 1%, and the other side of the liquid-glass-slag composition gives the mixture and the core strength loses crystallization moisture and shrinks to 4%. As a result, due to the thermal expansion of the rod, cracks appear in the film of the liquid-glass-slag composition, and the film is partially detached from filler grains. The strength of the mixture decreases.

70 70

5 6

is cast from casting

2400

150

The same 100 2370 and the knockout of the core mixture from the casting is improved. PRI me R. Thin-walled casting in the form of a pipe with an outer diameter of 250 mm, a length of 2700 mm and a wall thickness of 20 mm was made using a casting rod from self-hardening liquid mixture on the bonding liquid glass and hardener - ferrochrome slag. The core is reinforced with a skeleton for strength. This casting with a core from the LSS was loaded into a thermal furnace, after which the temperature in the furnace rose to 400-500С at a rate of no more than an hour. The rate of temperature rise of 70 ° C per hour leads to rapid heating of the surface layers of the casting, and at the same time, the internal surfaces lag behind in heating from the surface layers, which ultimately leads to the formation in the casting. . After reaching 400-500 ° C, the furnace was made at a given temperature. 5-6 hours for heating the casting with the core to 400-500С and then cooling the heated casting with the core together with the furnace to 100-150 ° С. After cooling the casting with the core, the core was removed from the internal cavity of the thin-walled casting by hammering out the nq with a percussion tool shh. in tumbling drum, the table shows the test results,

470

570

670

770

5,550

570

570

500

70 The results presented in the table show that the optimal condition for complete heating of the core mixture in the casting and thereby knocking out. Continuation of the table

with easy, but there were cracks in the casting body

200 Mixture knocks out

37 The mixture is knocked out easily.

150

35 The mixture is knocked out easily.

35 The mixture is dislodged120 easily, but the process is extended.

150

35,150

35 same 200

60 The mixture is knocked out easily, there are cracks in the casting.

37 The same capacity of the core from the internal cavity of the casting corresponds to the heating temperature range of 400-500 ° C, the discharge of the casting with the core at a given temperature for complete heating for 6-5 hours, the rate of temperature rise in the furnace not more than 70 ° C and cooling casting with core in the furnace to lOO-ISOC. Lowering the heating temperature of a casting with a core of LHF less than AOOC does not weaken the core mixture and the mixture is not knocked out of the casting. Increasing the rate of temperature rise more and cooling the casting with the core in the furnace to a temperature of 150 ° C leads to a sharp heating and cooling of the casting and this leads to the formation of cracks in the casting. Lowering the casting with a rod of less than 5 hours results in insufficient heating throughout the core, and the mixture is knocked out from the hindrance. Increasing the casting with a core of more than 6 h leads to a lengthening of the process of heat treatment of the casting with a core. Thus, a method for removing a casting rod made of CSH from a thin-walled casting according to the inventive method provides for knocking the rod out of the internal cavity of a casting having a small diameter and a long length. The use of the proposed method of removing casting cores from the GSS from the internal cavity of the casting, in comparison with the known methods, provides the following advantages; it allows to reduce the residual strength of the core mixture of the rod, filling the internal cavity of the extended casting; completely eliminate the formation of the final marriage castings; facilitate the embossing of the core from the internal cavity of the casting and improve the quality of the castings.

Claims (1)

METHOD FOR REMOVING CASTING BARS made of liquid self-hardening mixtures, from long thin-walled castings, including application of mechanical loads to the casting / characterized in that, in order to reduce the complexity by reducing the residual strength of the core, casting with rods before knocking out before subjected to heating to 400-500 ° C at a speed of not more than 70 ° C per hour, kept at this temperature for 5-6 hours and cooled together with the oven to 100-150 ° C.