SU921662A1 - Lubricant for injection moulds - Google Patents

Description

(H) LUBRICANTS FOR PRESS-FORMS

one

This invention relates to a foundry, in particular, to compositions of lubricants for molds used in injection molding, non-ferrous and aluminum alloys.

Widely known in the foundry industry are a number of mold lubricants for casting non-ferrous alloys under pressure, which mainly contain organic and mineral substances: wax, paraffin, vegetable oil, technical grease, etc., which must form a stable protective film to protect molds from the thermal effect of a liquid metal, reduce friction between the walls of the mold and the metal being poured P.

As refractory fillers, the above lubricants usually contain graphite, carbon black, sulfur. Due to the fact that these lubricants have a high viscosity (thick) I, it is not possible to apply them evenly to the mold,

Having a complex configuration with the presence of protruding parts and recesses. The uneven distribution of lubricant over the surface of the mold does not provide reliable protection against the physical and chemical effects of the liquid metal on the mold; places with abundant lubricant are formed, which leads to a number of casting defects.

When these lubricants are applied in the working temperature range of the molds C and in contact with the liquid metal, they have a high gas-making ability and a low flash point. This leads to pollution of the environment and defects in castings with porosity and gas shells.

Also known lubricant used for casting aluminum alloys under

20 pressure, including the products of polymerization of olefins C and Su, oxidized petrolatum, aluminum powder and flake graphite 12. This

the lubricant has oxidized petrolatum as a base (with a content of hydroxy acids not higher than 1b1).

The closest in technical essence and the achieved result is a lubricant containing black graphite, crude glycerol 40-25, 30; -OH solution KOH-5-10% and drinking water 3.

However, the adhesion ability of the specified lubricant with the mold surface is not high enough, therefore, when Applying this lubricant on the mold surface with high surface finish, there are no conditions for proper adhesion of the lubricant base to the mold surface, adhesion forces sufficient to resist friction forces. moving on the surface of the liquid metal under high specific pressure.

The presence of flake graphite in the lubricant, as solid inclusions, with particle sizes of a micron in diameter, creates a rough microrelief formed after the hardened lubricant film has dried. When the liquid metal moves in the cavity of the molds under pressure, a flushing force of 1-5 kN (100-500 kg) arises pulling out the t-3 protective film 3–10 µm thick protruding graphite particles, which leads to a weakening of the lubricant separation element the possibility of a direct impact of the liquid metal on the mold. Applying such a lubricant on the shaped surface of the mold with different radii of curvature and transitions of the mating surfaces leads to a concentration of stresses in the places of these over-expenditures, formations of cracks hardened protective film and direct metal contact with the mold. These deficiencies include the high gas-releasing capacity of the lubricant, the release of gases into the environment, and surface defects with regard to porosity and gaseous gas. These drawbacks can be eliminated by selecting the composition of the mold lubricant during casting of non-ferrous

alloys under pressure with high heat resistance, adhesive properties, ductility during sintering, low gas-making ability.

The purpose of the invention is to increase the heat resistance of the adhesive ability and plasticity of the lubricant.

This goal is achieved in that the lubricant, including graphite, glycerin and water, additionally contains dimethylsiloxane rubber, polyvinyl alcohol and glycols in the following ratio of ingredients, wt.%:

Graphite

3-7 3-6 Glycerin 6-8 Glycols Dimethylsiloxane 45-50 Polyvini rubber 20-25 "lovy alcohol

Water Use of dimethylsiloxane rubber (SKTN) emulsion in a water composition of polyvinyl alcohol containing silicon in the amount of 17.520) as a lubricant base in the operating temperature range of the mold 250-400C leads to the decomposition of low molecular weight impurities from the release, silicon oxide SiO- As a result, an elastic heat resistance with a high adhesion film of silicone properties and abrasion resistance is formed, and it is able to hold onto the mold for 8-12 filling cycles. The addition to the grease of fatty alcohols (glycols) contributes to the increase of plasticity at high temperatures, as well as by good washing of the working part of the mold, which has protrusions and cavities from the combustion products of the lubricant applied earlier, since glycols are both good plasticizers and solvents oxidation and combustion products, which are formed in the process of pouring metal on the walls of the molds. The compositions and properties of the lubricant are given in tables 1 and 2.

Table 1

Claims (1)

Claim Mixing the components of the lubricant is carried out in a laboratory mixer made on the basis of a tissue grinder RT-1, with a speed of P = 1700 rpm in the following order. An emulsion of dimethylsiloxane rubber in an aqueous composition of polyvinyl alcohol and glycols is poured into the tank (measuring cylinder) of the mixer in the indicated proportions and mixed for 2 minutes, while the impeller rotates at a rotation speed of n = 1700 rpm. GSL-1 grade graphite is poured into a separate container with GOST 6823-54 glycerin and is mixed until a homogeneous mass is obtained. Glycerin mixed with graphite is poured into the mixer tank and mixed for 3 minutes. After mixing, the specific gravity of the lubricant is measured, which is in the range 1.14 1.19 g / cm2 by densimeter. Wherein Lubricant for molds used mainly in injection molding of non-ferrous alloys, including graphite, glycerin and water, characterized in that, in order to increase the heat resistance, adhesion ability and plasticity of the lubricant, it additionally contains dimethylsiloxane rubber, polyvinyl alcohol and glycols, in the following ratio of ingredients, mass. G raffite 3-7 Mr. Litserin 3-6 Whether it is 6-8 Dimethyl siloxano high rubber 45-50 Polyvini alcohol 20-25 Water Rest