DE2314729A1 - HEAT-RESISTANT AND WEAR-RESISTANT COMPOUND - Google Patents

Description

March 22, 1973

NIPPON PISTON RING CO., LTD.
Uchisaiwai-cho 2-chome, Cliiyoda-ku,
Tokyo / JAPAM.

■ Heat and tear-resistant sintered alloy.

The invention relates to a heat- and wear-resistant fce iJint erlegiemin.-j.

Such an alloy is used for the valve seat at internal iirennkraffcmmaschinen used, especially for those at which use unleaded gasoline.

It is already known to use sintered metal alloys for various machine parts, but it has been shown that the use of sintered alloys for sliding components is unsatisfactory because they are subjected to difficult operating conditions and. In the case of slidable components ^ mdac * sintered alloy, it must be required that the alloy is highly heat-resistant and wear-resistant. On the other hand, however, the requirement is that the production costs for sliding components should be reduced.

Although it is known to make sintered metals from wear-resistant Produce melts, e.g. using chromium, cobalt, tungsten, molybdenum, titanium and vanadium. However have these metals o a high melting point, so that a high

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Sinterbeniperatür and! Aage Sintorzoit- required wlx-c U Furthermore, their use with various further tangible parts connected xu which, among other things, the early deformation or decrease in Betriebsqualitat include what can be observed in such elmässig Sirifcorerzeu ^ riisseri re _t ".

The invention is based on the above object Avoid disadvantages of the known sintered alloys and specify an improved sintered alloy, in which the heat and wear resistance is significantly increased, but also the The sintering temperature and the sintering time are reduced if a predetermined powder for the alloy is sintered. Furthermore, this alloy should be used for gleiberi.de components, e.g. for Valve seats in internal combustion engines, well suited where one high thermal resistance, but also high resistance against wear is essential.

To solve this problem, according to the invention, a heat and wear-resistant sintered alloy proposed, this being made up of 0.2-2.0 percent by weight of carbon, 2.0-9.9 percent by weight Chromium, 0.3 - 1 »5 percent by weight molybdenum, 3, o - lo, o percent by weight cobalt and 0.5 - 5» ο percent by weight Tungsten, the remainder being essentially iron.

An embodiment of the invention is shown in the drawing and is explained in more detail below; Show it:

Fig »1 shows the results of the encryption test, with curve a the alloy according to the invention, curve b

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din iioclicli.roTiihnlt: i.gof3 GuRsoi; .jnn mi · ¹ . · ΊΑο i.un-vo c a well-known Viisonisi.vfcei ^ lo-Tioxnm ^ called,

Pi-T. 2 the dependence on others; in flor a \ i f for the sintered alloy according to the invention, -;

the liiirven incline the Andorunyen to preclileissiaenge or the iindei-imjjen li with regard to dor 'il'drtc.

The inventive sintered alloy, the liocliverschlexssfest is produced by the formation and sintering of a powder formation, which is composed in percent by weight as follows:

Carbon - o, 2 - 2, ο <β>

Chrome - 2, ο - 9.9 f °

Holybden - o, 3 - Io f>

¥ olfrara - o, 5 - 5 f>

iiest - to yield Ioο ^ j, im

essential iron «,

In detail, the sintered alloy according to the invention can thereby Make sure that you have 1, & - 25 parts by weight of alloy powder mixes, which has the following composition in percent by weight:

Carbon - o, 2 - 3 f>,

Chrome - 2ο - Jo ^r jo _f

¥ olfraπι - 5 - 3ο f _3f and

Cobalt - l, o - ho <, j

with 99iO - 75s ο weight part of base powder made of iron, carbon, Holybden and cobalt, so that the powder mixture obtained

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in percent by weight - consists of the following:

Carbon - ο, 2 - 2, ο f> chromium - 2, ο - 9.9 ^ molybdenum - ο, 3 - 1.5 $ cobalt - 3, ο -.JLo, ρ ^ tungsten - o, 5 - 5, ο $

with residual metal to make up 100 percent by weight, essentially Iron is, according to which the powder mixture obtained through

3-7 tons per cm of pressure compressed into a compact mass and this compact mixture at looo - 12oo C 3o - 6o min. is sintered for a long time.

The amount of each powder component of the alloy is limited for the following reasons:

If there is less than 0.2 fa carbon, it cannot completely form carbides with the other elements, so that a sintered metal alloy of low hardness is produced as a result; the formation of metal carbides is accelerated by increasing the carbon content up to 3 f> , but if more than 3/3 carbon is present, this is of no use in terms of carbide formation.

Chromium, together with carbon and tungsten, forms carbides, in the range of 2o - Jo ¹ Jo, to increase the hardness of the sintered alloy, but if more than 7 ο fa- chromium is used, the hardness is not increased, but the alloy becomes brittle. On the other hand, if less than 20% chromium is used, effective carbide formation cannot occur.

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Tungsten forms complex carbides together with other elements to increase the hardness of the obtained alloy. However, more than $ 30 tungsten increases the melting point of the alloy and adversely affects solubility. If there is less than 5 $ tungsten, this proportion is not effective or not conducive to carbide formation «

Cobalt increases the solubility of the alloy in order to increase the mutual alloyability, forms a tough basic structure and stabilizes the hardness, but these advantageous effects practically do not occur below 1.0 $ . Be used more than ko "fa cobalt, the solvability is inadvertently accelerated and the hardness decreases.

The amount of each component in the final resulting pul- Mixing is limited for the following reasons: If there is less than 0.2 $ S carbon, a ferrite-rich matrix is created made that is not too hard to withstand high wear resistance to ensure »If there is more than 2 $ £ of carbon, a basic structure with a high cementite content is created and high hardness, but the alloy obtained is brittle. An excessive addition of carbon is also disadvantageous for the machinability and the consistent quality of the product.

Molybdenum contributes to the solidification and the increased toughness of the Alloy with, i.e. increases the impact strength and the resistance to permanent fatigue and stabilizes the sintered structure,

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however, these effects occur outside the I3ereich.es o, 3 1,5 not usually bulky or not a ψ. . ..-; '..

Cobalt, which is used to stabilize the sintered structure at elevated temperatures, in a manner known per se, is intended to serve as a kind of bridging material between the alloy powder and the base powders and is used to increase the resistance to heat and wear in the sintered alloy obtained; however, if there is more than Io 'p cobalt, the machinability of the metal is reduced. But if you have less than $ 3, this element does not contribute to the improvement of the heat and wear resistance.

The amounts of chromium and tungsten are in those indicated above Areas with regard to the structure and properties of the sintered product are limited.

An addition of 0.5-5 'p nickel or copper is advantageous for stabilization as well as for monitoring the accuracy of the sintered product obtained, as results from experiments.

Nickel serves to contract the sintered product and, on the contrary, the sintered product is stretched by copper in the aforementioned limited area. If there is less than 0.5 / 3 nickel or copper, these elements have no effect on the volume effect. But if there is more than 5 ίο nickel or copper, a boil-like martensitic

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table structure, whereby the uniformity and hardness of the Structure is influenced subsequently.

Preferred embodiments of the invention are based on Examples explained below:

example 1

0.65 percent by weight of graphite powder (- 3 ^ 5 mesh size), 0.5 percent by weight of ferromolybdene powder (- I50 I pocket size) in percent by weight molybdenum, 6 percent by weight cobal powder (- 325 hook size), 5 percent by weight alloy powder (- 150 hash size), which in weight percent from $ 3 Carbon, öo 5S chromium, 25 /> Tungsten and 12 7 'cobalt consists essentially of the remainder to make up for uri loo ^ j reduced iron powder (- loo bottle size) were mixed, to make a powder as a starting point. This powder— initial mix was 1 weight percent zinc stearate added in the form of powder as a lubricant, the so obtained

2 A powder mixture was applied at a pressure of + tons per cm compressed into a compact mixture and then subsequently at l.loo - 1,2oo C 3 ° - 6 ° min, long in a disintegrated Sintered ammonia gas atmosphere.

The sintered alloy thereby obtained was, in weight percent, of 0.78 ^ j carbon, 2.99 'p chromium, o, h7 £> molybdenum, 5>ol', 1.23 'p tungsten y> cobalt, balance essentially iron to make 100% by weight and has a density of 6.1 g / cm "* and a Rockwell hardness of 92.5.

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Example 2

1.05 percent by weight of graphite powder, 1.0 percent by weight of ferro-molybdenum powder in percent by weight of molybdenum, 6.2 percent by weight of kotalt powder, 15.0 percent by weight of alloy powder with the remainder, to make up loo fo , of essentially reduced iron powder (these components had the same grain sizes and compositions as indicated in Example 1) were mixed to make an initial powder mix. One weight percent zinc stearate was added to this mixture as an initial lubricant. The powder mixture obtained in this way was compressed at a pressure of 6 tons per cm and sintered in a decomposed ammonia gas atmosphere at 1,000-1,200 C for 30-60 minutes.

The sintered alloy obtained consisted of, in percent by weight: 1.46% carbon, 8.93% chromium, 0.95% molybdenum, 7.91% Cobalt, 3 »7 ^ / o tungsten, the remainder essentially iron, about 100 percent by weight and shows a density of 6.68 g / cm. and a Rockwell B hardness of 96 »5 ·

Example 3

Under the same conditions as given in Example 2, · a powder mixture is made with the same composition as in Example 2, with the exception that it has 5 Weight percent contains nickel and another powdery Mixture which has the same composition as in Example 2, with the exception that this contains 5 percent by weight of copper

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and this mixture is compressed into a compact mixture and sintered. This nickel-containing sintered alloy exhibits a density of 6.71 g / cm and a Rockwell B hardness of 97 »5 and the sintered alloy containing copper shows a density of 6.72 g / cm and a hardness of 97, o.

The curves a bzxtf. b and c in Fig. 1 each show experimental values on the size of the wear resistance loss of the sintered alloy according to the invention or for a cast iron with a high chromium content or for a known sintered iron alloy. The curves χ and y or ζ in Fig. 2 show measured values by which the hardness changes depending on the duration, once for the sintered alloy according to the invention, then for the known cast iron containing chromium or for the known sintered iron alloy. Both tests were carried out using an apparatus that tests the wear on the valve seat. . (Test temperature 4oo C, number of revolutions 3,000 per minute, spring pressure 35 kg »valve speed in the closing interval 0.5 m per second, width of the valve contact surface 1 mm, number of individual tests in the test series 8 χ Io, associated counter alloy JIS SUII 31 B - steel).

It can be seen from FIGS. 1 and 2 that the loss of wear resistance in the sintered alloy according to the invention is extremely low and that, on the other hand, the inventive

A common, proper sintered alloy has the property that its

associated hardness steep relative to the duration (Io - 2o hours)

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increases. This illustrates that from the inventive Alloy made valve seats after going into the Kotor built-in and at the usual temperature on the cylinder head, about 4oo ° C, is operated depending on the length of time slowly gets a greater hardness, regardless of its initially relatively low hardness and that furthermore accordingly the drop in wear resistance is reduced. Thus, when the alloy according to the invention is used as a valve seat the fatigue strength of the latter is considerably increased.

The test specimen in the valve seat abrasion test was ring-shaped with an outer diameter of 4o, o well, one Inside diameter of 28.0 mm and a height of Io.0 mm.

The well-known high-chromium cast iron and the well-known Sintered iron alloy, to which reference was made above for comparison, had the following composition or. Hardness:

High chromium cast iron;

Composition, weight percent: 1.61 $ carbon, -13 » Chromium, 0.47 / 6 molybdenum, the remainder essentially iron. Rockwell B hardness: 102

Well-known ferrous sintered alloy:

Composition, weight percentages: $ 1.02 carbon, 2.7653 chromium, the remainder essentially iron.
Rockwell B hardness: 9h

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Venn also the subject matter of the invention based on the advantageous Embodiments is explained, so are, depending on the individual case, modifications or within the scope of the inventive Deviations from teaching are possible.

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Claims (2)

March 22, 1973 IG / NIPPON PISTON RING CO0, LTD. Patent claims: 1. Heat and wear-resistant sintered alloy, in particular for components of internal combustion engines with sliding or abutting surfaces, z, Bt for valve seats of motor vehicle engines, characterized in that this alloy, in percent by weight, 0.2 - 2.0 $ carbon, 2.0 - 9.9 $ chromium, 0.3 - 1.5 $ Contains molybdenum, $ 3.0-10.0 cobalt and $ 0.5-5.0 tungsten, the remainder being iron, 2. A method for producing a sintered alloy according to claim 1, characterized in that a first mixture is first produced which contains 1.0-25 parts by weight of an alloy in powder form, which alloy, in percent by weight, consists of 0.2-3 $ carbon , 20 - 70 $ chromium, 5 - 30 $ tungsten and 1,, 0- 40 $ cobalt, then this mixture is added to a second mixture which has 99.0 75 powdery parts by weight of iron, carbon, molybdenum and / or cobalt that the two mixtures are compressed together or subjected to a pressure and then such a mixture is sintered. 309841/0860 Le e rs e ι τ e