DE1650028C2 - Piston ring made of gray cast iron - Google Patents

Description

0.1 to 1.0% tungsten
0.1 to 0.6% molybdenum
0.05 to 0.5% titanium

contains, the sum of molybdenum, titanium and tungsten being greater than 0.3%.

2. Piston ring according to claim 1, characterized in that that up to 70% of the tungsten has been replaced by equal parts of molybdenum.

3. Piston ring according to claim 1 or 2, characterized in that it contains 0.05 to 0.3% tin.

The subject of the invention is a piston ring made of gray cast iron with the üblii hen contents of carbon, Silicon, manganese and phosphorus, copper, nickel and vanadium, as well as chromium up to 0.7%, of 0.1 to Contains 1.0% tungsten, 0.1 to 0.6% molybdenum and 0.05 to 0.5% titanium, the sum of molybdenum, Titanium and tungsten is greater than 0.3%.

Gray cast iron is known as a piston ring material because of its good wear resistance. According to C. English, Piston Rings, Vol. 1.1958 Springer-Verlag-Vienna, Tables on pages 199 to 244 usually contain gray cast iron for piston rings

2.0 to
0.5 to
0.3 to
0.09 to
0.03 to
0.02 to
0.04 to
0.05 to

4.04%
3.30%
1.27%

1.00%

1.15%
2.50%
2.00%
0.40%

carbon

silicon

manganese

phosphorus

chrome

copper

nickel

Vanadium

as alloy elements. Especially when it contains up to 0.7% chromium, gray cast iron is the malleable cast iron, Nodular cast iron and steel are superior in this regard. However, it makes it difficult due to its low modulus of elasticity the production of piston rings with high tangential force. Also its strength, in particular its heat resistance is sometimes insufficient for a sufficiently long service life. That's why you have Alloyed gray cast iron piston ring materials have already been developed, including molybdenum, vanadium, titanium and copper and nickel, causing a slight increase in Ε modulus and a notable increase in static strength was achieved (cf. German patent specification 1 172 049). Due to the tightened operating conditions the advanced engines, especially those with chrome-plated cylinder liners, but are piston rings with higher tangential force, even higher wear resistance and above all Things with a higher initial hardness and particularly good heat resistance have become necessary.

The invention is now based on the surprising finding that a mere summation effect increase of the described desired properties beyond alloying elements of a gray cast iron piston ring is achieved if the material is carefully weighed in with tungsten A certain concentration is added, which can be modified by adding titanium, and then also one The addition of tin increases the Ε module and the thermal and flexural strength without affecting the piston rings heat-resistant annealed during their production process need to become.

According to the invention, a piston ring of the type mentioned at the beginning contains 0.1 to 1.0% tungsten, 0.1 to 0.6% molybdenum and 0.05 to 0.5% titanium, with the sum of molybdenum, titanium and tungsten being greater

must be than 0.3% in order to prevent the piston ring from solidifying to secure a ncdeÜg-martensitic structure with relatively short graphite lamellae of the cast, whose compact shape contributes to the increase in strength.

So far it is only known that tungsten is very strong carbide former can also be added to stainless steels with 18% Cr and 8% Ni Improve resistance to intergranular corrosion and the formation of weld seam cracks

is prevent taking some chrome-nickel alloy heat-resistant Steels contain up to 3% W to improve the heat resistance. It is also known that ! % W improves the strength of cast iron, but reduces its hardness (see "Alloying elements", Düssel-

Dorf 1962, pp. 71, 74, 83). Because of a weak graphitizing one Effect of tungsten in the cast, a tungsten content of 0.1 to 1% was written as a slight "improvement" of cast iron (cf. "Cast iron" by E. Piwowarsky, 2nd edition 1951, p. 803), but without

on the specific properties of a cast iron intended for piston rings? enter and find that its elasticity and flexural strength when processed into piston rings in internal combustion engines usual cross-section or larger

Cross-sections up to 300 mm ² higher than that of previously known gray cast iron materials and also persists in the operating temperature, whereby it is advisable to closer the tungsten content for larger cross-sections, i.e. also with piston ring liner casting

the upper limit of the specified range and vice versa. While for chilled cast iron rollers and the like. a high-strength cast iron with 0.25 to 10% W in addition to Cr, V and Ni is already known (see British patent specification 421 104), for piston rings only V-Ti-Cu-alloy

In addition to Ni, Co, Cr, Mo and Si, tungsten was indiscriminately developed as a possible alloying element has been mentioned (see British patent specification 507 225). Only for piston rings wound from wire steel alloys with 1 to 10% W are known (cf. German Auslegeschrift 228 067).

In the piston ring according to the invention, as tests have shown, up to 70% of the tungsten can be replaced by equal parts of molybdenum.
A further increase and strength of the bending

fco and heat resistance of the piston ring according to the invention shows up when it contains 0.05 to 0.3% tin.

example
A cast iron that

3.4 to 3.8% C

2.5 to 3.2% Si
0.7 to 1.0% Mn

0.35% P. 0.08% S. 0.4 up to 0.7% Cr contained. became 0.1 up to 0.3% W. 0.3 up to 0.5% Mon 0.1 up to 0.3% Ti 0.15 up to 0.25% Sn

added. The piston ring blanks produced from the cast iron with the dimensions 170.9 / 155.1 X 3.95 mm had a very high Vickers hardness in the as-cast state, so that the tempering temperature could be set at 530 "C. After annealing for 35 minutes at At this temperature and 35 minutes of air cooling, the rings showed a hardness of 414 to 448 kp / mm ^2. The graphite was finely lamellar to dendritic and evenly distributed, the basic structure martensitic-bainitic with finely distributed mixed carbides, the phosphide structure reticulated The machined rings fluctuated between 11 279 to 12 610 kp / mm ² , their flexural strength was between 61.8 and 72.6 kp / mm ² and thus more than 20% higher than with the same rings made of known casting after 4 hours of annealing under voltage at 0 to 300 ° C was 4.0 to 5.3% compared to 27 V ₁ , non-heat-resistant annealed rings of normal assemblies

* ^ Figures show the structure of a piston ring according to the invention (Fig. 1 and 2) and the drop in the tangential force of gray cast iron Kclbennngen at temperatures up to 300 ⁰ C (Fig. 3). In Fig. 1 a 100x and in Fig. 2 a 500 times enlarged Ge ugebild of the piston ring according to the invention is shown -Value applied as Urdinate as a starting point. Curve 1 is that of a known ring that has been heat-resistant annealed, curve L that of the same ring without heat-setting, while curve 3 shows the voltage drop of a KoI-benring according to the invention with a tungsten content in the lower analysis range, curve 4 the one of such a ring with a medium W content and curve 5 that of such a ring with a high W content. The invention therefore makes it possible to save the time-consuming and costly heat-setting process in the manufacture of piston rings.

1 sheet of drawings

Claims (1)

Patent claims: 1. Piston ring made of gray cast iron with the usual contents of carbon, silicon, manganese, phosphorus, Copper, nickel and vanadium, as well as chromium up to 0.7%. Remainder iron and manufacturing-related Impurities, characterized in that he additionally