RU2015835C1 - Method for manufacture of mold riser - Google Patents

Abstract

FIELD: foundry. SUBSTANCE: method includes manufacture of refractory shell of refractory heat-insulating material, e.g., mullit-silicic material. Shell is open from top and bottom and installed before molding on riser model reduced by 80% in metal capacity as compared with riser standard model. Upper part of shell is overlapped by centering pin on riser model by exothermic rod which consists of iron-aluminium thermit, ferroalloys and other materials which provide for melting steel after its burning similar in chemical composition to that poured into mold. In this case, mass of exothermic rod amounts to 1.4-5.0% of molten steel in riser. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to foundry, in particular to gating systems for pouring molds.

 A known method (ed. St. N 444600, class B 22 D 27/06, 1974) of making a profitable part of the mold, comprising making a refractory shell open to the side of the mold working cavity, filling the cavity of the refractory shell with a mixture of termite with metal, which ensures its combustion, the receipt in profit of liquid metal, similar in chemical composition to be poured into the mold. The disadvantages of this method include the increased complexity of manufacturing a profitable part of the mold and the inability to use it when molding castings on molding machines and automatic molding lines.

 The purpose of the invention is to increase the efficiency of profit, reduce the complexity of manufacturing a profitable part of the mold and expand the scope of this method when molding castings on molding machines and automatic molding lines. The essence of the proposed method lies in the fact that the refractory shell is made of a refractory heat-insulating material, for example, mullite-siliceous material, open from the bottom and top, and a profitable mixture of termite with metal with an additive as a binder liquid glass is used in the form of an exothermic rod.

 The drawing shows a mold that implements the proposed method. To obtain a profitable part of the mold on the model plate "top" above the feed unit 1 set reduced by 80% in volume compared to the usual, profit model 2 with a centering pin 3 in the upper part. Before molding, a refractory heat-insulating shell 4 is installed on the profit model, the upper part of which is overlapped by an exothermal rod 5 on the centering pin. After the molding mixture is compacted and the model is removed, the refractory heat-insulating shell and the exothermal core are held in the upper half-mold due to the reverse bias of the forming surfaces. In the process of pouring the mold, as a result of contact with liquid metal, the exothermic core burns out, producing overheating of the profitable liquid metal. At the same time, when the core is burned, a termite metal is formed in profit, which, mixed with the liquid metal that has entered it, is used to power the casting. Thermite slag floats to the surface of the liquid metal in profit, forming a heat-insulating layer.

 According to practical data, when feeding steel castings using ordinary profits to compensate for shrinkage shells in castings, 10% of liquid steel is consumed from the profit capacity, the rest is used as a heat accumulator.

 The proposed method for manufacturing the profitable part of the mold provides for the replacement of the heat of the molten metal released from the profit with the heat of combustion of the exothermal core while improving the thermal insulation of its surface and 20% of the molten steel is left in the profit for reliable supply of castings (more than two-fold margin from its practical need) .

 Since the proposed exothermic thermally insulated profits are intended to be used instead of the usual closed and open profits calculated by known methods and mastered in production, their calculation is based on data on the mass of ordinary profits.

(T_н-T_к)] /β·S_оп}²= {M_оп[276+0,75(T_н-T_к)/β·S_оп}², (1)
где L_Fe = 276 кДж ˙ кг^-1 - удельная теплота плавления стали;
С_РFe = 0,75 кДж ˙ кг^-1 К^-1 - удельная теплоемкость жидкой стали;
Т_.н. - начальная температура жидкой стали в прибыли, К;
Т_к - температура конца затвердения жидкой стали в прибыли, К;
β = 1,15 кДЖ C^-

кг^-1 К^-1 - коэффициент охлаждающей способности сухой песчаной формы;
S_оп - площадь поверхности обычной закрытой прибыли, м².The duration of the hardening of ordinary closed profits of mass M _op can be determined by the formula
τ _op = {M _op [L _Fe + C

(T _n -T _k )] / β · S _op } ² = {M _op [276 + 0.75 (T _n -T _k ) / β · S _op } ² , (1)
where L _Fe = 276 kJ ˙ kg ^-1 is the specific heat of fusion of steel;
With _РFe = 0.75 kJ ˙ kg ^-1 K ^-1 - specific heat of liquid steel;
_{So called} - initial temperature of liquid steel in profit, K;
T _to - the temperature of the end of the hardening of liquid steel in profit, K;
β = 1.15 kJ C ^-

kg ^-1 K ^-1 - cooling coefficient of the dry sand form;
S _op - the surface area of the ordinary closed profit, m ² .

где Q_эс - теплотворная способность экзотермической смеси, кДж ˙ кг^-1;
m_эс - масса экзотермического стержня в прибыли, кг;
Т_о = 293К - температура окружающей среды;
φ = 0,55 - выход термитной стали в результате сгорания экзотермической смеси;
С

= 1,46кДж ˙ кг^-1 ˙ К^-1 - удельная теплоемкость расплавленного оксида алюминия;
β_т = 0,5-0,6 кДж ˙ С^-1/2 ˙ М^-2 ˙ К^-1 - коэффициент охлаждающей способности муллитокремнеземистого теплоизоляционного материала;
S_этп - площадь поверхности экзотермической теплоизолированной прибыли, м².Duration of solidification of exothermic thermally insulated profit at a flow rate of liquid steel m _ws

where Q _es - calorific value of the exothermic mixture, kJ ˙ kg ^-1 ;
m _es - the mass of the exothermic rod in profit, kg;
T _about = 293K - ambient temperature;
φ = 0.55 — yield of thermite steel as a result of the combustion of an exothermic mixture;
WITH

= 1.46 kJ ˙ kg ^-1 ˙ K ^-1 - specific heat of molten alumina;
β _t = 0.5-0.6 kJ ˙ C ^-1/2 ˙ M ^-2 ˙ K ^-1 - cooling coefficient of mullite-siliceous heat-insulating material;
S _etp - surface area of exothermic heat-insulated profit, m ² .

Based on the condition for the equivalence of the solidification durations of ordinary and exothermic thermally insulated profits of the same purpose, from the expressions (1) and (2) we can compose the following equation
{M _op [276 + 0.75 (T _n -T _k )] / β ˙S _op } ² = = {m _ws [276 + 0.75 (T _n -T _k )] + Q _es ˙ m _es - - 1.07 m _es (T _k - T _o ) / β _t ˙S _etp } ² . (3)
According to experimental data, we take the following average values of conditionally constant values in the equation T _n = 1823 K; T _k = 1723 K; Q _es = 3500 kJ ˙ kg ^-1 ; m _ws = 0.2 M _op and S _etp = 0.5S _op
Transforming equation (3), we derive formulas for calculating the mass of an exothermic rod in an exothermic heat-insulated profit, which, depending on the value of the coefficient of cooling capacity of the heat-insulating material, have the form
when β _t = 0.5 m _es = 0.014 m _s ;
when β _t = 0.6 m _es = 0.05 m _s ;
Thus, according to the above calculation, the mass of an exothermal core in an exothermic heat-insulated profit, depending on the cooling ability of the heat-insulating material, is from 1.4 to 5.0% of the mass of liquid steel in profit.

 METHOD FOR PRODUCING THE PROFITABLE PART OF THE CASTING FORM, including the manufacture of a refractory shell open to the side of the mold working cavity, and the use of a mixture of termite with metal, which, when it is burned, makes it possible to profit in liquid metal that is similar in chemical composition to the casting mold, characterized in that, with the aim of increasing efficiency, reducing the complexity of manufacturing a profitable part of the mold and expanding the scope of application in the molding of castings on molding machines and automatic molds in washing lines, the refractory shell is made of a heat-insulating refractory, for example, mullite-siliceous material, also open at the top, and before molding, it is set to be reduced by 80% in terms of metal consumption compared to the usual profit model, and a rod is made from a mixture of termite with metal, which is installed on the top of the shell, while the mass of the rod is from 1.4 to 5.0% by weight of the liquid steel in profit.

Claims (1)

 METHOD FOR PRODUCING THE PROFITABLE PART OF THE CASTING FORM, including the manufacture of a refractory shell open to the side of the mold working cavity, and the use of a mixture of termite with metal, which, when it is burned, makes it possible to profit in liquid metal that is similar in chemical composition to the casting mold, characterized in that, with the aim of increasing efficiency, reducing the complexity of manufacturing a profitable part of the mold and expanding the scope of application in the molding of castings on molding machines and automatic molds in washing lines, the refractory shell is made of a heat-insulating refractory, for example, mullite-siliceous material, also open at the top, and before molding, it is set to be reduced by 80% in terms of metal consumption compared to the usual profit model, and a rod is made from a mixture of termite with metal, which is installed on the top of the shell, while the mass of the rod is from 1.4 to 5.0% by weight of the liquid steel in profit.

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