SU916043A1 - Base filler for casting shell mould - Google Patents

Description

The invention relates to investment casting.

A ceramic shell made of investment casting, as a rule, does not withstand the thermal and mechanical stresses that occur when the metal is poured, therefore, the casting mold, in addition to the facing part (ceramic shell), also has an outer support layer. The material of the support layer is, for example, self-hardening self-hardening mixtures - cements, liquid glass, ethyl silicate mixtures [1].

The use of bulk mixtures lengthens the calcination time, requires a significant consumption of binders, complicates the process of knocking out forms.

It is also known to use as the material of the support layer the forms of small steel or cast iron shot, cast iron chips [2] and [3].

The disadvantage of these materials is their rapid oxidation, a large mass, which makes it difficult both to work manually and to mechanize the process, the duration of calcination.

The most common material for the supporting layer are fine-grained dense fire2

refractory materials are quartz sand, fireclay powder, ground fused silica, magnesite, the primary grain size of which is 0.2–0.6 mm, and the maximum does not exceed 2 mm [4].

5 The use of these materials for the manufacture of the support layer has the following disadvantages: a long heating time of the mold (5–9 hours) to 900–1000 ° C; high marriage of castings for clogging with loose material of the supporting layer, which gets into the mold when it is cracked during the process of molding, calcining or pouring the material.

It is also known the use of ceramic-shaped combat with a grain size of 30-40 mm 15 as a reference filler, which is poured into the gap between the shell form and the flask [5].

Such a contractor has a bulk density of 1200 kg / m ³ , which leads to an increase in its ₂₀ heat capacity, and this, in turn, increases the heating time of the form and their

calcination, which is 5 hours

The purpose of the invention is to reduce the time of calcination of molds and marriage castings for clogging.

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This goal is achieved by the use of inorganic materials with a bulk weight of 250-900 kg / m ³ and grain

1-40 mm as a reference filler for the casting shell mold, obtained by investment casting.

Such materials can be attributed to artificial porous materials obtained by swelling during firing or agglomeration: expanded clay gravel, shungizite, agloporites, expanded perlite or vermiculite, slag pumice, industrial waste — porous metallurgical slag, shattered battle of porous refractories, such as powders, materials, waste materials, porous metallurgical slag, crushed battle of porous refractories, such as materials, waste materials, materials, waste materials, porous metallurgical slag, crushed battle of porous refractories, for example, waste materials, materials, waste materials, porous metallurgical slag, crushed battle of porous refractories, for example, waste materials, materials, waste materials, porous metallurgical slag, crushed bout of porous refractory materials, for example powders, porous metallurgical slag, crushed battle of porous refractories, for example powders, materials, waste materials, porous metallurgical slag, crushed battle of porous refractories, for example powders, materials, waste materials, porous metallurgical slag, crushed bout of porous refractory materials, for example powders; , coarse ashes and ash and slag mixtures; natural porous materials ^; - pumice, tuff, volcanic slag.

The heat resistance of the porous material of the support layer must be at least 900 ° C, so that they can withstand the calcination temperature of ethyl silicate forms; Actually, the heat resistance of the materials studied is within 950–2000 ° C, namely, ° C, perlite 950–1100, vermiculite and expanded clay 1100–1200, foam chamfer 1600– 1750, porous slags of ferrochromic production 1400, chromium magnesite production 1700, phosphoses up to 2000.

The drawing shows a graph of the heating time of the form from the bulk mass of the filler. (Bulk weight - the aggregate characteristics of the material, depending on its porosity, grain size, density of the original substance).

An increase in the porosity of the material leads to a decrease in its bulk density and, consequently, to a decrease in heating time (ΐ _Η ). For clay pellets having a porosity of 12 ° / o and a grain size of 30–40 mm, for claydite of the same graininess (raw material is clay) the porosity is 72%. The same when comparing the rubble of chamotte and chamotte lightweight (with the same graininess, the porosity is 14% and 67%, respectively).

At equal porosity material weight, and consequently, T _n, the smaller the coarse grains (compare to LECA grit 0.5-5 mm 30 40 mm).

The materials are much more heat-conducting than quartz and clay — chromo-magnesite; steel shot — they heat up much longer, as they have a high bulk density.

These materials can be monodisperse or be a mixture of fractions in the range of 1-40 mm.

For large FS "rm, which do not have thin pores and small holes, test porous materials with the grain size in

within 10–20, 10–40, 20–30, and 1–40 mm. For more complex and small castings -

1-2.5, 1-5, 1-9, and 5-10 mm. Within the specified limits distribution by fractions can be any.

The reference drive forms the shell shape due to its natural compaction or due to vibration in order to speed up the molding and ensure the filling of voids.

The use of filler granularity of less than 1 mm and a porosity of less than 30% does not allow to obtain a tangible gain in the duration of calcination of the molds, and particles larger than 40 mm make molding difficult and reduce the supporting properties of the material. The upper limit of porosity is limited by the actually achievable values of porosity and the shortest heating time of the forms.

Investigate inorganic materials

having a bulk density of 250–1100 kg / m ³ , a porosity of 30–9O ° / _o, and the following granularity mm: Crushed stone 20-30 Crushed Dynaslegos 10-50 Chamotte foam 1-2.5 Expanded clay 30-40 Expanded clay 10—20 Phosphite 10—15 Expanded clay 0.5-5.0. Hardened TPP ash 1-3, that match with : materials have with a bulk density of> 900 kg / m ³ and a fraction mm: Clay pellets 30-50 Fireclay rubble 20-30 Quartz sand 0.5-0.7 Quartz sand 0.1-0.3 Crushed Chrome Magnetic Zita 0.1-5.0 Steel shot 0.5-0.7

Example 1. Forming the shell support filler [4]. The mold includes the following elements: a ceramic shell made of investment casting; which is installed in the flask, which is a duct, and is molded with a supporting filler, forming a supporting layer. This filler is quartz sand grade KO2 Lyubertsy career (97% · passes through a sieve with a cell of 0.4 mm, the primary particle size of 0.15—0.20 mm).

A thermocouple is mounted in the ceramic shell. The time of heating the casing to the set calcination temperature (920 ° C) is 7 h 20 min. The die is cast by 40L steel. In the course of development, it was found that the casting reject was 4.7%.

Example 2. As a reference filler used battle ceramics bulk density of 1200 kg / m ³ and a particle size of 30— 40 mm [4].

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The time of heating the mold to 920 ° C is 5 h.

Example 3. Analogously to Example 1. Ceramsite gravel is used as the material of the supporting layer. Expanded clay porosity is 63.5%, dispersion,%:

3-5 mm 3-4

6-10 mm 14.6

11-25 mm 63.4

25-40 mm 8-6

The time of heating the mold to 920 ° С is 3 h 20 min. Filling molds with 40 L. steel. Casting blockage is absent.

Example 4. Analogously to example 1; As a reference filler, a battle of lightweight chamotte with a piece size of 10-30 mm is used - 95% and porosity 56%. The time of heating the mold to 920 ° С is 4 h 10 min. The fill is similar to example 2. Marriage on the blockage is absent.

Example 5. Analogously to example I. As the reference filler use agloporite from fly ash of thermal power plants. Grain size 1-3 mm - 94%. The porosity is 68%. The time for heating the mold to 920 ° С is 3 h 45 min. Filling with steel 40 L. Marriage castings on the clog is missing.

Example 6. The calcination of the ceramic shell produced without a support layer. Before the metal is poured, the hot shell is placed in the supporting layer of the filler, which is served by the preheated granulated slag of ferrochrome production. Grain size 2–6 mm - 86% ^ porosity 38%. Marriage on the blockage is missing.

The implementation of the present invention will allow a 40-60% reduction in coolant flow (gas or electricity) used in the calcination of the forms, will lead to heat-resistant steel due to the increased resistance of the flasks, whose residence time at high temperatures will be reduced by 40- 60%. Marriage castings reduced by 25-40%. Preliminary economic calculations showed that the savings would amount to 80- 90 rubles. per 1 ton of castings.

Claims (1)

Claim The use of inorganic materials with a bulk weight of 250–900 kg / m ³ and a grain size of 1–40 mm as a reference filler for a casting shell mold, obtained from investment casting.