CS214355B1 - Aluminum piston - Google Patents

Abstract

An aluminum piston for combustion engines with cylinders with an aluminum inner surface is provided on the surface with an electrolytically applied coating with a thickness of 5 to 50 f* of a nickel-iron alloy, containing a mass concentration of 20 to 60 t of iron, the remainder nickel.

Description

BACKGROUND OF THE INVENTION The invention relates to an aluminum piston and a nickel-iron alloy coating for internal combustion engine cylinders. It is known to use aluminum alloys in the manufacture of cylinders for internal combustion engines, which has the advantages of reducing weight, improving the thermal regime of the engines, and the possibility of producing cylinders by economical die casting, exhibiting a substantial reduction in labor. Especially preferred is the use of aluminum cylinders in high power motors. When using an aluminum cylinder, however, it is not possible to use an ordinary aluminum piston, as the piston is seized after only a few hours of operation. For this reason, various modifications are made to the active surface of the cylinder or piston in order to limit the friction of homogeneous materials. It is known to use a thin-walled iron alloy cylinder which is stamped into the bore of an aluminum cylinder. Its disadvantage is poor and irregular heat transfer due to inaccuracy of production and dilatations during operation. For aluminum-coated cylinder liners, heat transfer is somewhat better, but aluminum consumption is higher. The electrolytic plating surface of the cylinder is also known by a metal layer having a thickness of 400 to 600, which is machined to about half the thickness after plating. The metallization is usually accomplished with a chromium or silicon carbide dispersion coating. Such coated rollers exhibit somewhat impaired heat transfer, but its main disadvantage is the highly complicated technology, high labor intensity and, in addition, the high power consumption of chrome plating. Therefore, only special purpose motors are used.

Compared to the plating of the active surface of the cylinder, plating of the active surface of the piston has some obvious advantages. Firstly, it is not deteriorated heat transfer through the wall of the cylinder, then considerably smaller thickness of the deposited layer / up to 50 (W) and finally considerably less labor, because in the area of used thicknesses the piston shape .

Two known technologies of piston metallization are known. On the one hand, chromium plating with a thickness of 20 to 40 µm is used. The chromium layer is then covered with an electrodeposited layer of tin of 2-4 [mu] m, which serves as a running-in layer. Due to the thermal stresses, this technology has relatively frequent failures due to the tear-off of the coating at the top of the piston due to differences in the thermal expansion of aluminum and chromium. The second technology is the plating of the piston with a copper - iron - tin coating. This modification shows virtually no defects in quality design. The disadvantage is considerable technological demands, a large number of igředÚpravy and in-process adjustments and high technological discipline.

Disadvantages of the above-mentioned modifications of the aluminum inner surface of the cylinders or the surface of the aluminum pistons are eliminated by the aluminum piston according to the invention, characterized in that it is provided with an electrolytically coated 5 to 50 (W nlkl-iron alloy). The coating according to the invention has better mechanical properties than the coating of pure iron, can be deposited on aluminum alloys without interlayers and the depositing of the coating is technologically undemanding The efficiency of the deposition baths is close to 100%. The build-up layer comprises graphite or tin MoS ₂ .

The invention is illustrated by two examples of metallization of Al-alloy pistons, which are not intended to limit the scope of the invention; not exhausted.

214 355

Example 1

Aluminum alloy piston with Si composition of 19.5 to 22.0; Cu 1.50 to 2.00; NI 0.50 to 1.00;

Mg 0.80 to 1.20; Mn 0.10 to 0.40; % by weight, Al - residue. Activation of the piston in an aqueous solution of 2.5 M nickel chloride and 0.5 M hydrofluoric acid. Rinse the piston in a 5: 1 mixture of concentrated nitric acid and hydrofluoric acid. Piston plating with 80 to 40% nickel alloy and up to 60% iron in an electrolytic bath composition according to AO 169.585. Proudová

Density 5A / dm, 50 C, pH 2.5 to 3, plating time 20 minutes, dual current circuit with separate current control.

Example 2

Aluminum alloy piston with the following composition:

Si 11.5 to 13.0; Cu 0.8 to 1.3; Ni 1.0 to 2.0; Mg 0.85 to 1.3; Mn 0.3 to 0.5% by weight, Al - residue. Piston activated in aqueous solution as in Example 1. Rinse the piston in concentrated nitric acid. Plating of the piston with an alloy of 80 to 40% nickel and 20 to 60% iron in an electrolytic bath of composition according to AO 169.585. Current density 5A / dm ² , t 55 ° C, pH 3.5, plating time 25 minutes, dual current circuit with separate current control. Phosphating the plunger by immersion in a Synfate 1401 solution of the prescribed concentration at 90 ° C for 10 minutes to form a running-in layer of manganese phosphate.

The coated pistons according to the invention are particularly suitable for medium- and high-power two-stroke and four-stroke internal combustion engines equipped with cylinders with an aluminum inner surface. Piston wear decreases by 50 to 70% compared to other modifications. A repaired piston does not require additional corrosion protection. It is advisable to provide a metallized piston with a running-in layer.

Claims (1)

PREVENTION OF THE INVENTION Aluminum piston for internal-combustion cylinders with aluminum inner surface, characterized in that it has an electrolytically coated 5 to 50 nickel-iron alloy coating on the surface, containing 20 to 60% iron by weight, the remainder nickel.