SU804200A1 - Exothermic mixture for heating casting heads - Google Patents

Description

(54) EXOTHERMAL MIXTURE FOR HEATING CASTING PROFITS

The invention relates to foundry and ferrous metallurgy, in particular, to compositions of exothermic mixtures for heating casting profits in the production of ingots and large steel castings. A known exothermic mixture for heating casting profits, containing aluminum powder, silicon-magnesium-calcium-aluminum alloy powder, an oxidizer (chrome ore), refractory clay, refractory filler (chamotte), op; ) l. This mixture, under conditions of its use for heating the profits of large steel castings, is characterized by an inadequate duration of combustion and, consequently, a relatively short duration of solidification of profits. Closest to the technical essence and the achieved result to the proposed exothermic mixture for heating foundry profits containing aluminum powder, oxide (chrome ore), combustion catalyst in the form of alkali fluoride alkaline earth metal fluoride, organic burnable additive (sawdust); refractory clay, refractory filler (fireclay) and binder (liquid glass) p. However, the calorific value of this mixture and its heat resistance need further improvement in order. to provide more efficient feeding of molten metal with massive knots of large steel castings and the head part of ingots. The purpose of the invention is to increase the calorific value and heat resistance of the exothermic mixture. This goal is achieved by the fact that an exothermic mixture for heating casting profits, including aluminum powder, oxidizer, burning catalyst in the form of alkali or alkaline earth metal fluoride, organic burnable additive, refractory clay, refractory filler and binder, additionally contains silica powder. magnesium-calcium-cerium (KMKTS) alloy and expanded clay at the following ratio of ingredients, weight. %:

Aluminum Powder Oxidizer Alkali Metal or Alkaline Earth Metal Organic Burnable Supplement Refractory Clay Refractory Filler Binder KMCC Alloy Powder Claydite

TU 48-01-16-70f is manufactured from pig aluminum according to GOST 295-60, lomso and waste alloys.

Don Mine Management

Chrome ore grade DH-1 according to TU 14-9-48-73

Mark 4-1 or 4-2;

Hammer clay

GOST 3226-65

about

Ready fireclay or ground fireclay from bo and waste of fireclay products according to GOST 4385-48 classes - O and A

Mark F-75 or F-85; GOST 7618-55

GOST 962-41; module

lo 2.6-3.0 with beats. 1.43-1.50

Brand LCD {4K-1,. . . , LCG.1K-6; TU-14-5-39-74

TU 956-58 GOST 9759-76

Powder KMKTS - an alloy according to TU 14-5-39-74 has the following chemical composition, in-e.%: Silicon 40-60 Magnesium 6-12 Calcium 4-12 Cerium 1-2 iron Rest

As an oxidant, the proposed mixture contains, in weight. %: chrome ore 20-45, sodium nitrate 2-6. As alkali or alkaline earth metal fluoride, it is preferable to use fluorspar, fire-resistant filler is ground chamotte, and the binder is liquid glass.

Table 1 shows the general characteristics of the materials used in the first exothermic mixture.

Table 1

Amount of aluminum not less than 92% J content of active (non-oxidized) aluminum not less than 85%; 1.6 mm grain; grain fractions smaller than 0.15 mm no more than 15%

Chromium oxide content is at least 48-52; the deviation of the content of chromium oxide to ferrous oxide is not less than 3; grain; 3 mm

Grit 1.6 mm; grain fractions smaller than 0.15 mm no more than 15%

Grain size 4 5 mm; the residue on sieve number 16 according to GOST 3584-53 not more than 30%; pass through the sieve number 0,2 not more than 20%

Grain size 3.0 mm; humidity 8%

E Powder 1.6 mm grit;

sulfur content 0.3%

1.6 mm grit powder: fractions with a grain smaller than 0.15 mm no more than 15%

-61.6 mm grit powder; 5 mm grit size; moisture content 2%

When the content of KMKTSplav powder and expanded clay is higher than the upper and lower lower limits, the required increase in the heat resistance of the mixture is not achieved. Introduction of 2-6% KMKTS-alloy powder ,. as a combustible component, it significantly accelerates combustion due to its content

chemically active elements that are ahead of aluminum in the range of activity of the elements. The introduction of such a powder is most effective in the presence of a mixture of 2-6% sodium nitrate, with which the components of the powder interact when the liquid metal comes into contact with the internal surface of the exothermic insert with heat loss by the following reaction, 4NaN03-5Si. 2Na20 + 5Si02 + 2N2 + Q.

The reactions of the remaining components of the KMCC alloy powder are similar to those given.

Simultaneously introduced into the composition of the mixture at a specified ratio of other components of sodium nitrate, spt., And when heated, envelops the grains of the components of the mixture and thus pseudo-compacts it, excluding areas of local heating and facilitating uniform heating of the entire insert. The latter is an important factor in stabilizing the physical and mechanical properties of the mixture, i.e. the introduction of nitrate in predetermined proportions excludes the formation of TpeuyiH and destruction of exothermic inserts. The simultaneous addition of sodium or potassium nitrate to the mixture allows a 25% reduction in co-refractory filler (chamotte)

Organic Burning Additive (sawdust)

Catalyst (fluorspar)

Binder (liquid glass)

KMKTS-Natriyev alloy saltpeter Keramzit Khromova ore

Properties of mixtures 1-4 are given in table. 3. At the same time, the heat resistance of the mixture is estimated by the number of heating cycles: Up to 700 s and forced cooling to 20 s of cylindrical specimens made from it with a diameter of 20 mm and a height of 50 mm before their destruction or the appearance of cracks.

holding in it chrome ore with,. efficient heating pribyshey. The introduction of 1-8% of expanded clay is due to the need to improve the physical and mechanical properties of the mixture. At the same time, claydite, as a heat insulating material, slows down the burning, ensuring long-term heating of the profits.

The compositions of exothermic mixtures prepared as follows.

0

Sawdust is loaded into displacing runners, water is added and mixed for 4-5 minutes. Then the dry components are introduced in the following sequence: chromium ore, aluminum powder and fluorspar. Time; mixing dry components with sawdust for 4-5 minutes. Then the runners stop and bring in all the missing components.

0 together with liquid glass and mix the mixture again for 3-5 minutes after which it is discharged and used to make exothermic inserts.

For comparison, the optimal composition of the known mixture and the compositions of the proposed mixture are taken, differing in the content of CMC alloy, claydite and oxidant (sodium nitrate), which are listed in Table. 2

table 2

6 2 15

b 6 2 2

15

15.

6

four

b

four

eight

four

44

32

24

From the data in table 3 it follows that the proposed mixture provides a higher

calorific value and heat resistance. The more efficient heat work of profits when using the proposed exothermic mixture is also characterized by the fact that

solidification time

The profits for a 10-ton steel casting are 5-6 hours with a burning time of an exothermic mixture of 20-23 minutes, while using an insert made of a known exothermic mixture, these parameters are respectively 4 hours and 18 minutes.

The higher physicomechanical properties of the proposed mixture allow an increase in the efficiency of heating profits, reducing the possibility of cracking in exothermic

Compressive strength in wet condition, kgf / cm

Compressive strength in dry COCTOHHHIi, KGS / SM

tensile strength in dry. state of

to GS / cm Gas permeability in a dry state, units

Temperature of fire, ° C

Heating capacity kcal / kg

Coefficient of heat conduction, kcal / mc ° C: with joint inserts or their destruction, as well as reduce size.

The proposed exothermic mixture can be used as a material for the manufacture of exothermic inserts for heating profits for castings from steel grades 20-45L / for example castings of support rollers for rotary kilns of the cement industry weighing from 5 to 20 tons with a maximum weight of up to 800 kg.

Table 3

0.96

0.36

16.4 8.6

7,6

3.4

49

32

840

880

2247

1987

580

480

Claims (2)

1. An exothermic mixture for heating casting profits, including aluminum powder, an oxidizing agent, a combustion catalyst in the form of alkali or alkaline earth metal fluoride, an organic burnout additive, refractory clay, refractory filler and a binder, characterized in that, in order to increase its calorific value and heat resistance, it additionally contains a powder of silicon-magnesium-calcium-cerium alloy and expanded clay in the following ratio of ingredients, weight. %: Aluminum Powder Oxidant Silk or alkaline earth metal fluoride 12-25 22-51 0.3-4.0 Organic Burnout Additive 2-10 Refractory Clay 1-15 Refractory filler. 1-15 Binder 10-20 45 Powder of silicon-magnesium-calcium-cerium alloy 2-6 Expanded clay1-8 2. A mixture of pop. 1, the difference is that it contains 20-45 wt.% Chromium ore and 2-6 wt.% Sodium nitrate as an oxidizing agent.