SU1242285A1 - Refractory compound for manufacturing special moulds without firing - Google Patents

Description

one

The invention relates to a foundry, in particular, compositions intended for the manufacture of kiln-free multichannel special forms, mainly when producing sairoTo wok magnets with directional crystallization.

The purpose of the invention is to provide optimal performance characteristics of special forms by increasing their gas permeability, fire resistance and reducing the degree of carbon oxidation in graphite and silicon carbide.

The essence of the invention is as follows.

Aluminum performs the function of anti-oxidant addition, and also contributes to an increase in refractoriness due to the formation of mullite to 2SiOj.

The clay, which acts as a plasticizer, has a significant effect on the physicomechanical properties of the product. The higher the clay content in the mixture, the more plastic the mass and the stronger the special form. However, with the introduction of clay more than 18 wt.% There is a significant sintering of the product during the service. At the same time, optimal service characteristics of the product are not ensured, material is rapidly deteriorated under cyclic temperature loads and shrinkage cracks are formed, which do not allow to produce a magnetic alloy casting due to cracking of the special form. The introduction of clay less than 12 wt.% Leads to a sharp decrease in the molded properties of the mass, reduces the strength properties after manufacture, drying and heat treatment and impairs the surface of the casting.

Silver and / or flake graphite used in the mass has a high thermal conductivity, but at the same time it is a brittle material and has a porosity. A small thermal expansion of graphite in combination with high thermal conductivity and strength at high temperatures make graphite one of the most resistant materials in relation to thermal shock. Chemically, graphite is distinguished by a very low activity, it is not wetted by molten metals and slag, it only slightly interacts with some highly efficient oxides of the type of iron and manganese oxides at high temperatures.

ten

15

20

242285 - 2

With the introduction of graphite more than 14 wt. %

slag resistance and heat resistance of the mass is reduced. The introduction of graphite less than 8 wt.% Does not provide a mass with high slag-resistance and heat resistance.

Silicon carbide (carborundum) -, introduced into the mass, has a high refractoriness, good thermal conductivity. Its introduction allows to increase the total carbon content in the mass. At the same time, carbon loss during service is reduced, since the onset temperature of the carborundum oxidation is significantly higher than the onset temperature of pure carbon.

The oxidation product of silicon carbide is silica, which forms a silica film on the carbide grains, which significantly reduces further oxidation. Besides, . the resulting silica fastens the silicon carbide grains, partially fills the pores, thus increasing the strength: the characteristics of the product. The introduction of silicon carbide less than 8mao.% Does not provide an increase in the density, strength and thermal resistance of the special form, and more than 14 wt.% Leads to an excessive increase in thermal conductivity and from an economic point of view is not advisable.

A / W powder is introduced into the mass in order to reduce oxidation, carbon, and also for refractoriness of the mass. Oxidation of carbon-containing refractories with oxygen occurs not only on the surface, but also inside the pores of the product. At low temperatures, the oxidation on the BOS spirit proceeds very slowly. With an increase in temperature, the degree of oxidation increases. The aluminum introduced into the mass, when molten, forms a protective film on the surface of the carbon component, protecting the carbon from oxidation. Inside the product, aluminum combines with the oxygen contained in the pores, the formation x X participates in the formation of mullite, CACH O -2 Si02, which has high heat resistance, fire resistance and slag resistance.

The aluminum content of less than 0.5 wt.% Does not effectively affect the protection of carbon from oxidation, and its introduction to more than 3.0 wt.% Is impractical from an economic point of view. With the increase in its quantity

thirty

35

40

-"five

50

55

/

cracks are observed during vibropressing of the product, and when the magnetic alloy is poured, the special form is destroyed and metal is lost,

Complex linking is introduced with the purpose of providing service characteristics of the specific forms by increasing gas permeability. It consists of an surface-active substance (surfactant) of class 3 alkyd-aryl sulfonates and a fine sulphite slip. With an increase in the proportion of surfactant in the picker over 0.10 wt.%, The porosity of the product greatly increases, and if the content of AB is less than 0.05 wt.%, It is impossible to reach 15 because of the gas permeability of the special form. As a surfactant of this class, it is preferable to use the product C-TAS-SVTU 31-56) with a density of 1.10 g / cm 3. . 20

The sulphite-yeast mash included in the slurry is used with a density of 1.14-1.18

The introduction of clay into the slip less than 22 wt.% Reduces anti-erosion 25 form stability, and. when the clay content is more than 26 wt. The flow rate of the slip deteriorates, which makes it difficult to distribute in the refractory mass.

The introduction of a complex bond of less than Q 8 wt.% Leads to stratification of the mass in the process of vibropacking, the surface is bad, which affects the quality of the casting, expressed in the formation of gas pockets, and when introduced, more than 12 wt. The filling capacity of the press-forgF liner deteriorates.

As filler in kacce

chamotte is used ..

40

The use of chamotte of the specified grain composition leads to an increase in the heat resistance of the mass, which is achieved due to the closure formed. that porosity. Closed pores prevent the propagation of cracks under cyclic temperature loads of multichannel special forms.

With the introduction of chamotte fraction of more than 1.6 mm, the density of the product decreases, 50 the quality of the casting, magnetic alloy deteriorates. The introduction of chamotte fraction 1.6-1.0 mm less than 28 wt.% Leads to excessive shrinkage of the mass, and more than 32 wt.% Does not allow to obtain a product with the required density. The introduction of chamotte fraction less than 0.4 mm in the amount of less than 38 wt.% Not allowed 35

j you 15 20

five

Q

.

0

0 5

five

It is impossible to obtain a product with the required density, and in the amount of more than 42% by weight it leads to excessive shrinkage of the mass.

Petrographic and X-ray studies of the developed special form allow to establish the presence of mullite, cxc, C, SiC, which together give the product high performance characteristics.

 Example. First, a slip (complex binder) is prepared for which water is poured into the mixer, heated to 50-60 ° C, then a sulphite-yeast brew is poured and the density of the solution is adjusted to 1.14-1. 18 g / cm. From a special bin B, the mixer is fed with a clay refractory hammer and mixed with the mortar. A surfactant (DS-RAS) is supplied to the prepared slip.

The preparation of the mass is carried out in mixing runners in the following order: load the chamotte and moisten with half the required amount of complex binder, mix for 3-5 minutes. Add graphite of GT grade and mix again for 3-5 minutes, add silicon carbide of brand 64C and mix repeat for 3-5 minutes, then powdered aluminum is added and mixed for 3 minutes, then clay is added and mixed for another 3-5 minutes, then the second half of the complex bond is introduced and the whole mass is mixed for 5 minutes.

In tab. 1 shows the compositions of the proposed mixtures 1-9 and 10 according to the known technical solution. .

Properties of mixtures 1-10. Are given in table. 2

The extrusion of multichannel foundry special forms was carried out on a V-18 vibration unit having a vibration frequency of 50 Hz. Drying of the raw material is carried out with a duration of 12-14 hours. Heat treatment of products is carried out in a shaft furnace, with an exposure time of 4 hours for special forms, working in a crystallizer-101, and at 900 ° C with an exposure time of 4 hours for special forms, working in a vacuum furnace - crystallizer firm Leybold-Herarus (Germany).

When testing special forms in the crystallizer-101, the mold is installed on the refrigerator and introduced into the heated mold cavity at a speed of 12 mm / min, and given for 5-10 minutes

to equalize the temperature 1460 - throughout the body of the special form. The 6H14DK25BA split is prepared in a YST-0.06 furnace. The temperature of the alloy when pouring into the special form 1580-1620 ° C. The alloy is poured into a multi-channel special form, after which the shaft is lifted and the magnet crystals are drawn out with a diameter of 4-5 mm / min.

When testing special forms in a vacuum oven-mold of the Leybold-Heracus company (Germany), the special form is placed in a graphite ring, placed on a refrigerator and closed in a vacuum chamber. After a set of vacuum include heating the form. When the special form is heated to 1100-1200 ° C, the alloy is heated. The mold temperature during casting is 1400-1420 ° С, and the temperature of the alloy is 1670-170.0 ° С. After the alloy has been cast, crystals are drawn at a speed of 4 mm / min.

Production tests, as well as laboratory tests (Table 2), show high service characteristics. Mass productivity of clay

Fireclay

Phosphoric acid

ti3, tS 1i3.15 1i3.15 1 (2.8 pg, 8 Ii2.8 2: 3.5 1: 3.5 1i3.5 - 63.55t, 25 39.063.55i.25 39.063.5 51.25 39.0 27.5

--- - 20.0

Note. Mixtures 1–9 were prepared with an average content (0.075 wt.X) of DS-RAS in vikkera (complex sulphite-clay bond) and among the pearl barley of the tanot, i & c.Xt fraction 1.6-1.0 W4 30 Frakda 1,0-0,4 mi 30 Fraction less O, A mm AO

Refractory-mass special forms according to the invention: high strength properties after manufacture, drying and heat treatment, increased gas permeability, and refractoriness, as well as a reduced degree of oxidation of carbon. Special molds are easily destroyed after the casting is removed, the surface of the castings is of satisfactory quality.

The technical and economic efficiency of the invention is that. The proposed refractory mass provides high performance characteristics of casting special forms by increasing their gas permeability, fire resistance and reducing carbon oxidation. The economic efficiency of using the refractory mass according to the invention is to reduce the cost of 1 ton of casting molds and reduce the cost of the cost of 1 ton of magnetic alloy castings. The expected economic effect for the first year of mastering the new technology will be 75,100 rubles.

t a b l and c in 1

,

120

3.7 "5.2

125 125

3.2 L8 14.6 13.7

E.liann Editor

Order 3648/15 Circulation 757 Subscription

VNIIPI USSR State Committee

for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5

Production and printing company, Uzhgorod, Projecto st., 4

Table 2 °

, 915,18,5

12,913,313,69,8 11,712,012,510,6

12,312,613,015,2 1700171017301690

123

125

12,122,124,126

90

3.53.1 2, "3.4 3.2 2.7 5.2

15.0 14.5 14.0 14.9 14.7 13.8 18.0

Compiled by S.Teplov.

Tehred M. Khodanych, Proofreader 0. Lugov

Claims (3)

1. FIRE-RESISTANT MASS FOR THE PRODUCTION OF CASTING STAINLESS SPECIAL FORMS, used mainly in the preparation of preform magnets with directional crystallization, including chamotte, clay, graphite, silicon carbide and a binder, with the aim of ensuring optimal performance characteristics special forms by increasing their gas permeability, refractoriness and reducing the degree of carbon oxidation in graphite and silicon carbide, it additionally contains aluminum powder, and clay as a binder is Too-sulfite liquor based on sulphite-yeast mash and clay in a mass ratio of (2.8 3.5): 1 and a surfactant from the class of alkyl-aryl sulfonates in the following constituents, wt.%: Clay Graphite Silicon Carbide Aluminum Powder Specified Clayne Sulphite Slip Fireclay 2. The mass according to claim 1, n * a, that the ratio com12-18 .8-14 8-14 0.5-3.0 8-12 The rest is distinguished by the clay and o-sulphite slurry has the following composition, May. %: Clay 22-26 Alkyl Aryl Sulfonate Surfactant Sulphite Yeast Mash 3. The mass according to claim 1, 0.05-0.10 The rest is due to the fact that chamotte has the following grain composition, wt.%: SU „„ 1242285 Fraction 1.6-1.0 mm. 28-32 Fraction 1.0-0.4 mm28-32 Fraction less than 0.4 mm38-42 1 1242285