CS271785B1 - Method of iron casting etching in cooling space of cast piston - Google Patents

Abstract

Undivided cast pistons from aluminium alloys for combustion engines are for the improvement of the heat outlet equipped with the cooling space, into which the cooling oil is delivered. The refrigerated room is formed by the casting of the iron cast, e.g. of a steel pipe or steel ring, into the aluminium alloy of the pistons. The iron cast in the cooling space is after its setting removed by the 15 to 40 percent water solution of azotic acid at the surrounding temperature, while the amount of acid is 10 to 50 percent greater than the stoichiometric amount that is determined from the weight of the iron cast. The water solution of the azotic acid is mixed mechanically or by air for the acceleration of the removal.

Description

(57) cast-piece aluminum alloy pistons for internal combustion engines is to improve heat dissipation provided with a cooling space ,, that is fed with cooling oil, and ^TEN: a cooling space is formed by casting iron casts, e.g., a steel pipe or the steel ring, in aluminum alloy pistons. After freezing, the iron slag in the cooling chamber is etched with a 15 to 40% aqueous nitric acid solution at ambient temperature, the amount of acid being chosen 10 to 50% higher than the stoichiometric amount determined by the weight of the iron slag. To accelerate etching, the aqueous nitric acid solution is agitated mechanically or by air.

CS 271785 Bl

CS 271785 Bl

The invention relates to a method for etching an iron seal in the cooling chamber of a cast aluminum alloy piston.

It is known to provide the pistons of internal combustion engines, in particular diesel engines, with a cooling chamber to which cooling oil is supplied to improve heat dissipation. The design possibilities of creating a cooling space in the piston body for non-split cast pistons depends on the foundry technology available. The method of cast steel tube or aluminum alloy rings is widespread. Such cooling, to which a steel tube contributes, is described, for example, in DE-OS 34 34 228.

The disadvantages of these embodiments are that the steel grille is not or only incompletely metallicly connected to the aluminum alloy, which reduces heat transfer.

Therefore, using modern technology, this cooling cavity is formed in aluminum pistons by the salt core casting method. However, this technique is dependent on expensive equipment and mastery of such technology. For small series of pistons or small numbers of kues or even developmental designs This technology is difficult to access and entails disproportionate costs. The same is true if the piston is provided inside a cooling chamber with a thermally conductive material, as is apparent, for example, from CS δ. 144 489, or if the cooling cavity is formed within the piston by means of high-porous carbon cores, see for example DE-OS δ. 24 35 377

SUMMARY OF THE INVENTION It is an object of the present invention to alleviate the above-mentioned drawbacks and to allow the production of aluminum alloy pistons with efficient cooling space by simple technology.

The object of the present invention is to provide a 15 to 40% aqueous solution of nitric acid in an amount of 10 to 50% greater than its stoichiometric amount given by the weight of the iron sheet to etch the iron sheet in the cooling space. of a cast aluminum alloy piston at ambient temperature while stirring an aqueous nitric acid solution.

The main advantages of the solution according to the invention reside in the fact that in the case of unmanaged salt-casting technology or inadequate technical production equipment, as well as in the development of new pistons and alternatives easily etched after watering.

The invention is explained in more detail below by way of example.

The steel grippers are melted into the cooling chambers of the non-split cast aluminum alloy pistons to the desired design by any known technology. Then the steel grout is etched with a 28% aqueous solution of nitric acid at ambient temperature. To accelerate the etching, the cell can be mixed with air or mechanically. If stirring is not carried out, etching takes place for a longer time. The amount of nitric acid to be etched is 25% higher than its stoichiometric amount based on the weight of the iron scrap.

The solution according to the invention is useful for etching steel grilles from articles made of aluminum alloys, in particular non-split pistons of internal combustion engines,

Claims (1)

SUBJECT OF THE INVENTION Use of a 15 to 40% aqueous nitric acid solution in an amount of 10 to 50% greater than its stoichiometric amount given by the weight of the iron plug to etch the iron plug in the cooling chamber of the cast aluminum alloy piston at ambient temperature while stirring the aqueous nitric acid solution.