KR20050000840A - Wear resist sintering alloy for valve seat and method for manufacturing the same - Google Patents

Abstract

PURPOSE: To provide a wear resistant sintered alloy for valve seat and a method for manufacturing the same, wherein an abrasion amount of the sintered alloy is reduced as a whole by simultaneously performing sintering and copper infiltration on powder compact properly comprising Fe, Cr, Co, C, Mn, W and V and tempering the sintered and copper infiltrated alloy. CONSTITUTION: The wear resistant sintered alloy for valve seat comprises 100 wt.% of powder compact containing iron as a main component, 0.8 to 1.2 wt.% of carbon, 15.0 to 20.0 wt.% of chromium, 0.3 to 0.6 wt.% of manganese, 25.0 to 30.0 wt.% of cobalt, 5.0 to 7.0 wt.% of tungsten and 2.0 to 4.0 wt.% of vanadium; and 20 to 30 wt.% of copper for the powder compact. The method for manufacturing the wear resistant sintered alloy for valve seat comprises first step of blending iron powder as a main component with 0.8 to 1.2 wt.% of carbon powder, 15.0 to 20.0 wt.% of chromium powder, 0.3 to 0.6 wt.% of manganese powder, 25.0 to 30.0 wt.% of cobalt powder, 5.0 to 7.0 wt.% of tungsten powder and 2.0 to 4.0 wt.% of vanadium powder and press forming the blend by a surface pressure of 5 to 8 ton/cm¬2; second step of air cooling the sintered and copper infiltrated alloy after simultaneously sintering powder compact passing through the first step and infiltrating 20 to 30 wt.% of copper for 100 wt.% of the powder compact into the powder compact in a temperature range of 1,140 to 1,180 deg.C; and third step of tempering the air cooled alloy in a temperature range of 450 to 550 deg.C.

Description

Wear-resistant sintered alloy for valve seats and its manufacturing method {Wear resist sintering alloy for valve seat and method for manufacturing the same}

The present invention relates to a wear-resistant small alloy for valve seats and a method of manufacturing the same, comprising a large amount of chromium and cobalt containing iron as a main component, and a large amount in powder compacts in which carbon, manganese, tungsten and vanadium are appropriately controlled. By sintering copper and sintering at the same time and then manufacturing it by heat treatment, the valve seat can be improved in matching with the valve seat when the valve seat is applied with similar physical properties with the valve material as a counterpart, and the overall amount of wear can be reduced. It relates to a wear-resistant small binder and a method for producing the same.

In general, the valve seat is a part that keeps the airtightness of the combustion chamber in close contact with the valve surface, and repeatedly performs shocking work against the valve surface. It should be made to have hardness.

Conventionally used wear-resistant small alloys for valve seats have iron as a main component, and carbon is 0.4 to 1.0% by weight, silicon is 0.1 to 1.0% by weight, chromium 0.5 to 2.0% by weight, molybdenum 6.0 to 10.0% by weight, and cobalt 6.0 to It contains 15.0 weight% and 6.0-18.0 weight% of lead, and is manufactured through the following process.

First, metal powders other than lead in the composition are mixed, and then molded by adding a surface pressure of 4 to 8 ton / cm 3.

Thereafter, preliminary sintering is carried out at 750 to 800 ° C. for 40 minutes in a reducing atmosphere, and then forged under a surface pressure of 7 to 10 ton / cm 3.

Subsequently, main sintering was carried out at 1,110 to 1,140 ° C. for 30 to 50 minutes under hydrogen atmosphere, and then impregnated with lead at 400 to 450 ° C. for 10 to 30 minutes to give self-lubricating activity. To produce a wear-resistant small alloy for the valve seat.

However, the small-alloy for valve seat prepared with the composition and content exhibits microstructure characteristics in which large metal particles are dispersed in the matrix structure, and the large metal particles cause cracks due to external impacts, thereby degrading impact resistance. .

In addition, when the conventional small alloy for valve seat is applied, the wear resistance is easily lowered, and there is a fear that the compressed gas in the cylinder leaks along with the drop of the wear-face metal particles, and the workability is also poor, and there is a need for improvement.

In addition, in the conventional wear-resistant small-alloy for valve seats, harmful lead is used to impart self-lubrication, and thus it is unlikely to be used environmentally, and an improvement is urgent in that lead is used as a pollutant.

Therefore, the present invention has been invented to solve the above problems, and the iron powder as a main component containing a large amount of chromium and cobalt, and in addition to the conventionally formed powder compacts with appropriate control of the content of carbon, manganese, tungsten and vanadium By sintering and sintering a large amount of copper at the same time as lead instead of lead, it is produced by heat treatment. As a result, similarity with the valve material as a counterpart can increase the matching with the valve when the valve seat is applied. It is an object of the present invention to provide a non-lead-impregnated sintered alloy for a valve seat and a method of manufacturing the same.

Hereinafter, the present invention will be described in detail.

In the small alloy for engine valve seat, the main component is iron, which is 0.8 to 1.2% by weight, 15.0 to 20.0% by weight of chromium, 0.3 to 0.6% by weight of manganese, 25.0 to 30.0% by weight of cobalt, and 5.0 to tungsten. It is characterized by containing 20-30 weight% copper with respect to 100 weight% of powder compacts containing 7.0 weight% and 2.0-4.0 weight% of vanadium.

In addition, the present invention is a method for producing a small alloy for engine valve seat, the main component is iron 0.8 to 1.2% by weight, chromium 15.0 to 20.0% by weight, manganese 0.3 to 0.6% by weight, cobalt 25.0 to 30.0 weight %, Tungsten 5.0 to 7.0% by weight and vanadium powder 2.0 to 4.0% by weight of the first step to form a pressure of 5 to 8 ton / cm 3; A second step of sintering the powder compacts subjected to the first step at a temperature of 1,140 to 1,180 ° C., infiltrating 20-30% by weight of copper with respect to 100% by weight of the powder compacts, and then air-cooling the powder compacts; Then it is characterized in that it comprises a third step of heat treatment at a temperature of 450 ~ 550 ° C.

Referring to the wear-resistant small-alloy for valve seat and the manufacturing method of the present invention having such a feature in more detail as follows.

The present invention relates to a wear-resistant small alloy for automobile valve seats that are burned in a dry atmosphere, such as LPG vehicles and diesel engine vehicles, and a method for manufacturing the same. The composition range of each alloy steel element is suitably used to improve wear resistance and hardness based on iron. Set.

Particularly, in the present invention, in order to improve wear resistance in a dry atmosphere, matchability with a valve, and self-lubrication, a large amount of chromium and cobalt is contained, and in addition, carbon, manganese, tungsten, and vanadium are appropriately contained. It is manufactured with properties similar to those of valves, and also by infiltration of a large amount of copper during sintering instead of lead for self-lubrication.

First, in the first step, iron is the main component, and carbon is 0.8 to 1.2% by weight, chromium 15.0 to 20.0% by weight, manganese 0.3 to 0.6% by weight, cobalt 25.0 to 30.0% by weight, tungsten 5.0 to 7.0% by weight and 2.0 to 4.0 weight% of vanadium is mix | blended and pressure-molded by surface pressure 5-8 ton / cm <3>.

Abrasion resistant small alloys for valve seats vary significantly in mechanical properties as high speed steel depending on the amount of carbon (C) added.

In the present invention, carbon is added at 0.8 to 1.2% by weight based on the total composition of the metal powder in the first step.

If the content of carbon is less than 0.8% by weight, the strength and hardness are insufficient, and if the content of carbon is more than 1.2% by weight, the tensile strength and the hardness are reduced, which is not preferable.

Chromium (Cr) used in the present invention is added to increase wear resistance, heat resistance, and self-lubrication as high-speed steel, and the content is added in an amount of 15.0 to 20.0% by weight based on the total composition of the metal powder in the first step. .

If the content of chromium is less than 15.0% by weight, the effects of wear resistance, heat resistance, and self-lubrication are not maximized.

Manganese (Mn) used in the present invention is added to combine with a trace amount of sulfur present in iron to form MnS, the content is added in an amount of 0.3 to 0.6% by weight relative to the total composition of the metal powder of the first step. .

If the content of manganese is less than 0.3% by weight, it is difficult to have self-lubrication obtained through MnS formation, which is not preferable.

Cobalt (Co) used in the present invention is added to increase the strength, heat resistance and self-lubrication, the content is added in 25.0 to 30.0% by weight based on the total composition of the metal powder of the first step.

If the cobalt content is less than 25.0% by weight, it is difficult to obtain similar properties with the valve, and the effect of increasing heat resistance and self-lubrication is not maximized.

Tungsten (W) used in the present invention is added to increase the high temperature tensile strength and hardness as the high speed steel, the content is added in 5.0 to 7.0% by weight relative to the total composition of the metal powder of the first step.

If the content of tungsten is less than 5.0% by weight, the amount of carbide formed is small and wear resistance is lowered.

Vanadium (V) used in the present invention is added to control grains as high-speed steel, and the content is added at 2.0 to 4.0% by weight based on the total composition of the metal powder in the first step.

If the content of vanadium is less than 2.0% by weight, it is not preferable because huge crystal grains are formed to cause cracks.

Next, in the second step process, the powder compact through the first step process is air cooled after sintering for 30 to 50 minutes at a temperature of 1,140 to 1,180 ° C.

In this process, when sintered below 1,140 ° C., the powder particles are not diffused well and the matrix structure is weakened. If the temperature is higher than 1,180 ° C., grains are coarsened and mechanical properties are deteriorated.

Here, the copper powder or the copper molded product is placed on the powder molded product subjected to the first step process and subjected to copper sintering at the same time as the sintering process. At this time, 20 to 30% by weight based on 100% by weight of the powder molded product subjected to the first step process Infiltrate copper.

Here, when the amount of copper to be infiltrated is used less than 20% by weight, it is not preferable because of the large number of micropores which are present due to the inadequate amount of copper penetrating into the powder compact.

In addition, when the amount of copper is more than 30% by weight, there is a problem, such as the need for post-treatment processing to be removed because the remaining copper is infiltrated over the powder molded body is present is not preferable.

Next, in the third step, tempering the base alloy by tempering 60-90 minutes at a temperature of 450-550 ° C. after cooling copper sintering as described above, imparts toughness to the matrix structure, and then processes some processing steps. The completion of the small bond of the present invention.

Here, when considered below 450 ° C, it is difficult to achieve the purpose of imparting toughness, and when considered at a temperature higher than 550 ° C, it is not preferable in terms of hardness of the final sintered alloy.

The non-lead-impregnated wear-resistant low-alloy alloy for valve seat manufactured through the above process has properties similar to that of the valve material as a counterpart by the use of high alloy metal powder. Of course, it has the advantage that the overall amount of wear is reduced.

In addition, the self-lubrication function is performed with copper acupuncture bar, which can cope with dry atmosphere fuel (eg LPG), which was possible only with existing lead-containing materials, and prevents environmental problems due to the inclusion of lead by eliminating the existing lead impregnation method There are advantages to it.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the Examples.

Examples and Comparative Examples

As an example, the metal powder blended according to the composition and content shown in Table 1 was molded at a pressure of 7 ton / cm 3, and then the powder compact was sintered and co-cooled at 1,170 ° C. for 40 minutes, whereby the powder compact 100 25 wt% copper was used relative to wt%.

Subsequently, after boiling for 70 minutes at 500 ° C., a small alloy was manufactured through some processing steps, and the amount of wear was measured after a single piece test on the valve seat to which the small alloy was applied and the valve seat manufactured according to the existing process (Comparative Example). The results are shown in Table 1 together with the measurement results of density and hardness.

[Test Methods]

Abrasion (mm) measurement: The simulation Rig Tester was used under the following test conditions.

-Rotation speed of cam: 2000rpm

Temperature: 350 ℃

-Time: 10 hours

Fuel used: LPG

As a result of the measurement, as shown in Table 1, it was found that the comparative example has a relatively low hardness, and the example has a high hardness equivalent to that of the valve.

In addition, from the results of the wear measurement, it was found that the wear amount for the valve seat small alloy according to the embodiment of the present invention is reduced by about 25% compared to the comparative example.

In this way, in the present invention, it is possible to obtain a small alloy for valve seats having improved wear resistance and hardness. Accordingly, when the small alloy according to the present invention is applied as a material for valve seats for automobile engines, matching properties with valves of relative sliding products are obtained. And it is possible to obtain the effect that the self-lubrication is further improved.

The present invention is widely applicable to the manufacture of valve seats for automobile engines that are burned in a dry atmosphere such as LPG vehicles.

As described above, according to the wear-resistant small alloy for valve seats according to the present invention and a method for manufacturing the same, iron is used as a main component to contain a large amount of chromium and cobalt, and the content of carbon, manganese, tungsten, and vanadium is appropriate. By sintering and sintering a large amount of copper in the controlled powder compact at the same time, it is produced by heat treatment, which has the following effects.

1) By using high alloy metal powder, the physical properties such as strength are similar to those of the counterpart material, so that the valve seat can be matched with the valve and the overall wear is reduced.

2) Enhance the self-lubrication role by containing a large amount of copper during sintering, and can be applied to dry fuel (eg LPG) that was only available by impregnating harmful lead.

3) Non-lead impregnated sintered alloy, which excludes the existing lead impregnation method to prevent the occurrence of environmental problems caused by the inclusion of lead.

Claims (2)

In the small alloy for engine valve seat, Iron is the main component and contains 0.8 to 1.2% by weight of carbon, 15.0 to 20.0% by weight of chromium, 0.3 to 0.6% by weight of manganese, 25.0 to 30.0% by weight of cobalt, 5.0 to 7.0% by weight of tungsten and 2.0 to 4.0% by weight of vanadium. 20 to 30% by weight of copper, based on 100% by weight of the powdered compacts. In the method for producing a small alloy for engine valve seat, Mainly iron, 0.8-1.2 wt% carbon, 15.0-20.0 wt% chromium, 0.3-0.6 wt% manganese, 25.0-30.0 wt% cobalt, 5.0-7.0 wt% tungsten, 2.0-4.0 wt% vanadium A first step of blending and pressing under a surface pressure of 5 to 8 ton / cm 3; A second step of sintering the powder compacts subjected to the first step at a temperature of 1,140 to 1,180 ° C., infiltrating 20-30% by weight of copper with respect to 100% by weight of the powder compacts, and then air-cooling the powder compacts; A third step of heat treatment at a temperature of 450 to 550 ° C. thereafter; Method for producing a wear-resistant small alloy for valve seat comprising a.