RU1098128C - Moulding sand for froducing chemical-active metal and alldy castings - Google Patents

Abstract

1o MIXTURE FOR THE PRODUCTION OF CASTING FORMS WHEN RECEIVING CASTINGS FROM CHEMICAL-ACTIVE METALS AND ALLOYS, including refractory filler in the form of magnesite, sodium liquid glass with a silicate module 2.0-3.2, characterized in that, in order to simplify the manufacturing technology by lowering the temperature of their calcination while reducing energy consumption and improving the quality of castings due to increased inertness of the mold to reactive metals and alloys, it additionally contains calcined magnesium oxide in the following the ratio of ingredients, wtD: sodium and liquid glass with silicate module 2.0-3.2 2-30, calcined magnesium oxide 1-12, refractory VT filler in the form of magnesite, the rest. 2 „A mixture according to 1, characterized in that it contains. as calcined oxide (L magnesium is the calcination product of hydrated or chloride, or carbonate magnesium compounds at a temperature of 5001000 ° C

Description

The invention relates to foundry, in particular to compositions of molding compounds for the manufacture of foundry molds for casting reactive metals (Ti, A1, Mg) and alloys based thereon.

Known refractory mass containing distene-sillimanite and zircon powder, water glass and ferrochrome slag, performing the function of hardener (gellant)

The use of this mass as a molding mixture in the preparation of castings of their chemically active metal-j

about y

00

fishing and alloys based on them leads

". to an increase in the layer of increased hardness on castings and, as a consequence, to

00 decrease their service life.

A known mixture for the manufacture of easily removable (leachable) rods and molds containing sodium chloride as a base, liquid glass binder and talc and high calcined magnesia additives. Highly calcined magnesia does not interact with molten glass, therefore the case cannot be expected to obtain highly refractory structures

based on mixed sodium magnesium silicates. In addition, due to the excess of sodium chloride in the composition of this mixture, it is not applicable for the production of castings from titanium alloys, since it does not provide the required high heat resistance of the mold

The closest to the described invention in terms of technical nature and the achieved result is a mixture for the manufacture of casting molds for the production of castings from reactive metals and alloys containing 90-92 wt% refractory napel; Nitel in the form of wetted magnesite powder and 8-10 wtD sodium liquid silicate glass 2.0-3.2,

The curing of this mixture is carried out after filling it with model equipment by blowing carbon dioxide

In order to decompose sodium carbonates formed during the purging, high-temperature (950-1050 0.) burning of the mold is required, which is associated with the delay in the burning furnaces and with significant energy consumption.

In addition, the mold material obtained from the mold mix is not sufficiently inert to the molten chemically active metals and their alloys, which leads to a deterioration in the quality of castings,

{The object of the invention is to simplify the manufacturing technology of molds by lowering the temperature of their calcination while reducing energy consumption and improving the quality of castings by increasing the inertness of the mold to reactive metals and alloys with

To achieve this goal, a mixture for the manufacture of foundry molds for producing castings of their reactive metals and alloys, including a refractory filler in the form of magnesite and sodium liquid glass with a silicate module of 2.0-3.2, additionally contains calcined magnesium oxide in the following ratio of ingredients, May,%: sodium liquid glass with a silicate module 2.0-3.2 2-30, calcined magnesium oxide 1-12, refractory filler in the form of magnesite

The mixture contains calcined magnesium oxide as a product of calcined hydrated or chloride Chr or carbonate magnesium compounds at a temperature of 500-1000 С

The lower limit for the content of calcined magnesium oxide is selected based on the required minimum amount i sufficient to cure the liquid glass in the pressed mixtures, the upper limit is the result of the partial loss of oxide activity during storage and maintaining the constant volume of the molds during heat treatment, as well as taking into account minimum survivability of a freshly prepared mixture with

Magnesium oxides obtained by calcination at temperatures of 500-1000 ° С of hydrated, chloride or carbonate magnesium compounds: magnesium hydroxide obtained from sea water, bischof 1tA - a natural raw material compound based on bpuP are used as calcined (low-volume) 1-penta) magnesium oxide. , magnesite cheese (MgCO) o

The lower limit of the calcination temperature of hydrated, chloride or carbonate magnesium compounds is selected based on the conditions of the bischofite hydrolysis process, the upper limit is determined by the temperature 5 necessary for decarbonization of crude magnesite I

As sodium liquid

glass, it is preferable to use a technical product (GOST 13078-8 with silicate module 2., 2 and a density of 50 g / cm, preferably

The interaction of liquid glass with the indicated parameters of modulus and density and calcined (low-baked) magnesium oxide) leads to the formation of thermally stable and slightly prone to volumetric changes upon heating mixed sodium-magnesium silicate. The completeness of this interaction and the complete removal of volatile products (mainly water vapor) are sufficient 1 is possible at the firing temperature of the Farm 500 to 550 ° C.

The increased / iio chemical inertness of the form also contributes to the formation of calcium silicates, as noted in the free flow of magnesite.

5

Example KB mixing runners load 970 kg (97%) of MLF magnesite powder, 10 kg (1) of low-calcined magnesite obtained from bischofite by calcining at, and 20 kg (2) of a liquid glass solution of 1.35 g / cm with module 2, 0 “The mixture is stirred for 8-12 minutes and used to prepare pressed rods fired at 550570C.

Example 2oV mixing runners load 850 kg (85%) of PMM-1 magnesite powder, 120 kg (2%) of low-baked magnesium oxide obtained from Mg (OH) 2 (precipitated from seawater) by firing at, and 30 kg (3%) liquid glass solution pl, 1.35 g / cm3 (, 0), The mixture is stirred for 8-12 minutes, after which it is used for pressed foundry rods fired at 550 ° C

Example 3B of a concrete mixer load 8lO kg (81%) of MLF magnesite powder, 20 kg (2 low-baked magnesium oxide obtained by calcining MgCO at, and mix for 3-5 minutes, after which an additional 170 kg (17%) of liquid glass is poured pl, 1.25 g / cm3 (, 7) о The mixture is additionally mixed for 5-10 minutes and used for the manufacture of molds by vibration, fired at 520-570 ° С

Example 4oV concrete mixer is charged with 63.0 kg (63%) of finely ground magnesite, 70.0 kg. (7%) of low-boiling magnesium oxide obtained from MgCOj by roasting at 1000 ° С and stirred for 5-7 minutes. Then, 30.0 kg (30%) of liquid glass with a density of 1.25 g / cm (M 3, 2), stirred for 8-10 minutes and used as a coating for molds or for the manufacture of molds and cores of complex configuration, fired at 550-570 ° C

The described molding mixture showed a high inertness to titanium-containing alloys.,

The inertness of the mixture was determined by the indicators of the value of the layer of increased hardness and the maximum and minimum hardness according to Vickers on a PMT-3 device for experimental castings after they were obtained in a vacuum at

28b

 with casting cores of said mixtures. The rods were prepared from the described mixtures by pressing, vibrating and pouring and (for comparison) from the mass of the prototype by manual stuffing about

Test data are given in table „

I

As can be seen from the table, a decrease in the titanium alloy castings of the layer of increased hardness to 0.12 - 0.15 mm and hardness to 305/238 units HV, which had contact with the rods of the proposed mixture, compared with castings that had contact with rods from the prototype mixture (0.8-0.9 mm and 795/255890/296 HV, respectively), testifies to the practical absence of metal interaction with the material of the rods. “At the same time, the survivability of the mixtures was determined by determining the time of their suitability for casting forms and hardening time of mixtures, according to echenii which forms may osvobozhdats of pattern equipment and be directed to the heat treatment Vitality proposed mixtures and mixtures prototype virtually identical, and the solidification of the proposed mixture acceptable for technological cycle of foundry molds at the same time obzhigasnizhena temperature almost twice ,,

The mixture makes it possible to increase the manufacturability of the manufacture of foundry molds and cores through the use of extruded, vibrated and cast self-hardening compositions of mixtures with the exception of the CO process, and also to increase the productivity of moulders by 3-4 times due to the mechanization of laying the moldable mixture in model equipment; reduce the heat treatment temperature on average to, as well as the heat treatment time of molds by 1.5-2.0 times, and reduce energy costs for firing by 60-70%; to improve the quality of castings by reducing the layer of increased hardness and eliminating cracks in the molds and cores, which will increase their working life by 2–3 times. Not only casting molds and cores can be made from the described refractory mixture, but also others

7. 10gBl288

refractory mortars, both unburned with fillers of mageside and gelpys, and roasted with refractory silicate composition BOB „

N and with in the K-honor of the low ovs1zhzhzhennogo oxyl f-iar "ir- b1ali isp / jeovann

1-3 - iigni oxide, populyny facing by Mr, (bischofite) at t-; i850 С; 4-5 - oxide NRNI half-mnir prokzlko MCO at t lOQO C,