SU833352A1 - Mixture for producing casting moulds and cores wirh use of permanent pattern equipment - Google Patents

Description

(54) MIXTURE FOR THE MANUFACTURE OF CASTING FORMS

AND RODS ON CONSTANT MODELING EQUIPMENT

one

The invention relates to a foundry, namely, to a composition of molding sands for the manufacture of stainless steel castings in a shell mold.

The known mixture for shell molds and rods, containing a refractory filler, novolac resin, an aqueous solution of urotropin of 33% concentration and water-waxes dispersion in the following ratio of components, fl, wt.%:

Novolachya resin 3.0-7-, О Water solution of urotropine 33% concentration 1.2-2-2

Water-wax dispersion 0, 02-0.5 Refractory filler Else The specified mixture is characterized by the ability to carburize the surfaces of low-carbon stainless steel castings and form defects on their surface in the form of poly.

Closest to the proposed technical essence and the achieved effect is a mixture for the manufacture of casting molds and cores on a constant model tooling.

including refractory filler, novolac phenol-formaldehyde resin with hexamine and magnesite with the following combination of ingredients .2, wt%:

Phenol-formaldehyde binder (PC-104) 5.0. If5 Acetone

Carbonates (known. Nc, magnesite) 1,5-8,0 Refractory filler. The rest, however, the known mixture does not improve the surface quality of castings from stainless steels (defects on the surface of castings form in the form of bi) and does not eliminate carbonization,

The purpose of the invention is to improve the surface quality, eliminate carburization and enhance the anti-corrosion properties of stainless steel castings.

. This goal is achieved by the fact that this mixture for the manufacture of casting molds and cores according to a constant model equipment, including a refractory filler, novolac phenol-formaldehyde resin with hexamine and magnesite, additionally contains a flotation concentrate

ore, liquid phenol-formaldehyde resin and boric acid in the following ratio of ingredients, wt.%: Flotation concentrate of manganese ore 3,0-10,0

Magnesite1,5-3,0

Novolac phenol-formaldehyde resin with hexylene 1.0-5.0 Borna acid 0,1-о, 15 Phenol-formaldehyde resin 2.0-2.5 Refractory fillerOstal

Manganese ore flotation concentrate is used in powder form with a grain size of 0.050,20 mm, with an active oxygen content of 7-10%, produced by the Marganetsky mining and processing plant in the Dnipropetrovsk region, of the following composition, wt.%: 13.3; A 12.0 1.5; S l, S; MnOx 52.6; MpO 13.4; CaO 1.5; MdO 0.5; Pe, 2.1; other impurities are remaining. .

The amount of manganese ore flotation concentrate is selected on the basis of the content in the .0.50-1.00 mixture of active acid a. When the content of Maganta ore in the flotation concentrate is less than the lower limit, no carburization is formed, and a defect in the form of shrinkage porosity p b is formed on the surface of the castings, and when the content is above the upper limit, the strength of the mixture decreases.

Liquid phenol-formaldehyde resin 180 is introduced to dissolve binder PC-104 and create additional strength for the mixture. The amount of resin 180 is selected on the basis of 50% content of phenol-formaldehyde novolac resin with hexamine (PC-104

When the content of boric acid is less than the lower limit, the heat resistance of the mixture decreases, and when the content is above the upper limit, the strength of the mixture decreases.

 Quartz sand, zircon sand, granular distensillimanite, etc. can be used as a refractory filler. The requirements applied to quartz sand are common for all cases of shell mixtures. Quartz sand 016B of the But .vinsky pit 89.4 84.13 Binder (PC-104) 4.0 4.5

When the shell mold is filled with liquid steel, the phenol-formaldehyde binder is destroyed with the release of a large amount of carbon monoxide CO (25–30%) and a small amount of carbon dioxide C6 5 (1.0–1.5%).

Carbon monoxide reacted with molten iron by reaction

(I)

ЗГе + 2СО.,: + С0, d / saturates the surface of the casting with carbon, which leads to the formation of defects in the form of shrinkable porosity - p bi and reduction of the anticorrosive properties of stainless steel St 12X18H9TL.

5 Introduction of magnesite (MdSO) to the mixture, which decomposes when the mold is poured with steel emitting carbon dioxide (COa) / shifts the reaction (t) to the left, which leads to a reduction in carbonization. However, the complete elimination of carbonization by the introduction of magnesite into the mixture of 1.5-3.0 wt.% Is not achieved. With a further increase in the composition of the mixture of magnesite

f. strength properties are reduced, which leads to the formation of other defects (earth shells, blockages, etc.).

The addition of manganese ore containing active oxygen to the flotation concentrate mixture leads to oxidation of carbon monoxide (co) to carbon dioxide (CO). As a result, reaction (1) does not proceed because of the high (15-25%) CO content and low (10-15%) content

5 in the products of the destruction of a phenol-formaldehyde binder. At the same time, the carburization of the surface of the castings is completely eliminated, defects of castings in the form of bi-bi are eliminated,

0 anti-corrosion properties of steel.

Prepare 3 mixtures by cold cladding. During the preparation of the mixture, the binding agent PC-104, boric acid, manganese ore flotation concentrate, magnesite are introduced into the sand.

 and mix for 1.0-1.5 min, then resin 180 is introduced and stirred for 1.0 min to dissolve binder PK-104, then the mixture is blown with compressed air with continuous mixing for 5-10 min and then poured into the container.

The compositions proposed (1-3) and known (4) mixtures are given in tabl.1.

Table 79,3590,5 5,05,0 5 Ingredients Resin 180 Acetone Flotation concentrate manganese ore Borna acid Magnesite The mixtures are made about the size of 22.4x22 and 4x170 mm, sintered at 550 ° C for .. Name indicators

b,

a / g

s

ur

Carbon content in casting through, mm

0.5

1.0 1.5 2.0 2.5 3.0

7b 29

65 36

72 28

66 31

270

276

290

38.6

41.5

40

42 0.07 0.06 0.05 0.03

Surface-Surface-Surface-Surface is numerical, that is, smooth, clean, has

smooth smooth defects

in the form of p bi

0.18

0.12

.0.11 0.16 0.11 0.11 0.16 0.11 0.11 0.13 0.11 0.11 0.11 0.10 0.11 0.10 0.10 0.10 Table of Contents ingredients, wt.% ,. at ratstsy experiencing on the HVS-1 instrument the arbitrariness of the 20st elements of the NVR. 3 min-, Properties of the mixtures are given in table 2. .. 833352. 6 Continued table. 1 in the mixture :: n :: i: r: i: i: i. 2.0 2.25 2, -5 - - s, 3.0 7.0 10.0 0.1 / 0.12 I ODZ V 1.52.0 3.0 3.0 .--. T a b. LI C a 2; ; Properties of the mixture 1 2 3 I 4.

As follows from the data table. 2, the proposed molding mixture with the addition of a manganese ore flotation concentrate does not reduce the strength properties, at the same time, the quality of the surface of the castings is significantly improved and the carburization of the steel is set.

Carburizing of the surface is determined by the method of layer-by-layer chemical analysis with samples 150x50x20 m in size cast in molds from shell mixtures of steel St 12X18H9TL, GOST 2176-77.

The carbon content in steel St 12X18H9TL according to GOST 2176-77 should be no more than 0.12%. From these tab. 2 shows that the proposed molding mixture improves the quality of the surface, castings, eliminates shrinkage of porous shrinkage - pb and completely eliminates the carburization of the surface of low-carbon stainless castings cast in a shell shape, and the known mixture leads to the formation of cast defects in POREST Bi form and does not eliminate carburization.

The anti-corrosion properties of the steel are determined according to the LM method with provocative heating according to GOST 6032-75 n samples of size 80x20x3 mm, cut from the surface layer of castings. Samples made from castings poured into molds from mixtures 1-3 are not subject to corrosion, and samples from castings from mixture 4 have cracks along the grain boundaries, which indicates unsatisfactory anti-corrosion properties.

From the proposed mixture, the valve bodies and DU40-D.100 valves are made from St 12X18N9TL steel. All castings made using the proposed composition of the mixture

have a clean, smooth surface and no carburized layer.

The composition of the proposed mixture can be used in foundries in the industry in the manufacture of stainless steel castings into shell molds.

Claims (2)

1. USSR Author's Certificate No. 532449, cl. B 22 C 1/22, 1975. 0 2. Foundry production 1977, No. 8, pp.5-8.