Specialized metallurgical processes – compositions for use therei – Compositions – Consolidated metal powder compositions
Reexamination Certificate
2000-11-27
2002-02-19
Mai, Ngoclan (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Compositions
Consolidated metal powder compositions
C075S246000, C419S026000, C419S027000, C419S029000
Reexamination Certificate
active
06348079
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
The present invention relates to a sintered alloy having an excellent wear resistance for a valve seat and a method of producing the same. More particularly, the present invention relates to a sintered alloy having an excellent wear resistance for a valve seat, which is produced by a sub-zero treatment for a metal powder containing Fe(iron) as a main component, C(carbon), Si (silicon), Cr(chromium), Mo(molybdenum), Co(cobalt), Mn(manganese), Pb(lead), V(vanadium) and W(tungsten) so that amount of metallic particles separated from a base matrix decreases and a size of the separated metallic particle becomes small when an abrasion of the sintered alloy is in proceed, thereupon a wear resistance and impact resistance are improved and a self-lubricity and a machinability is enhanced, and a method of producing the same.
2. Description of the Prior Art
A conventional sintered alloy having a wear resistance used for a valve seat comprises Fe as a main component, C of from 0.4 to 1.2% by weight, Si of from 0.1 to 1.0% by weight, Cr of from 0.5 to 2.0% by weight, Mo of from 6.0 to 10.0% by weight, Co of from 6.0 to 15.0% by weight and Pb of from 0.4 to 1.2% by weight.
The processes as follow produce such a sintered alloy having an excellent wear resistance used for a valve seat.
First of all, a metal powder as above except Pb is mixed and then a surface pressure of from 4 to 8 ton/cm
2
is applied to the mixed metal powder. Under a reducing atmosphere, a preliminary sinter process is performed at a temperature of from 750 to 800° C. for 40 minutes and then a forging process is performed at surface pressure of 7 to 10 ton/cm
2
. Thereafter, a main sinter process is performed at a temperature of from 1,110 to 1,140° C. for from 30 to 40 minutes under hydrogen atmosphere and then Pb is impregnated at a temperature of from 400 to 450° C. for from 10 to 30 minutes so as to give a self-lubricity, and then a barrel process is performed at same temperature for from 80 to 110 minutes, the sintered alloy having an excellent wear resistance for a valve seat is produced.
However, the sintered allov having components and content as described above has a microstructure characteristic in which giant metal particles are dispersed in the base matrix. Such giant metal particles cause a crack when an external impact is applied so that an impact resistance is deteriorated. Therefore, the wear resistance will be deteriorated so that the metal particles are fallen away from the abrasive surface. Further, there is a problem that a compressed gas in a cylinder is leaked, therefore, there is an urgent need to improve such problems.
SUMMARY OF THE INVENTION
As described above, a productivity for producing a conventional sintered alloy having a wear resistance for a valve seat is decreased due to a great deal of process and a impact resistance and a wear resistance are deteriorated by giant particles dispersed within a base matrix. And further a leakage of a compressed air can be occurred.
Therefore, it is an object of the present invention to provide a sintered alloy having an improved wear resistance and a machinability for a valve seat by containing Fe(iron) as a main component, C(carbon), Cr(chromium) Mo(molybdenuni), V(vanadium), W(tungsten), Si(silicon), Co(cobalt), Mn(manganese) and Pb(lead) and to provide a method of producing the same.
For fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is characterized by a sintered alloy having a wear resistance for a valve seat comprising Fe(iron) as a main component, C(carbon) of from 0.8 to 1.2% by weight, Cr(chromium) of from 2.0 to 4.0% by weight, Mo(molybdenum) of from 2.0 to 4.0% by weight, V(vanadium) of from 2.0 to 4.0% by weight, W(tungsten) of from 7.0 to 10.0% by weight, Si(silicon) of from 0.2 to 0.6% by weight, Co(cobalt) of from 3.0 to 5.0% by weight, Mn(manganese) of from 0.2 to 0.5% by weight, Pb(lead) of from 10.0 to 15.0% by weight.
The present invention is also characterized by a method thereof comprising;
the first step of mixing Fe as a main component, C of from 0.8 to 1.2% by weight, Cr of from 2.0 to 4.0% by weight, Mo of from 2.0 to 4.0% by weight, V of from 2.0 to 4.0% by weight, T of from 7.0 to 10.0% by weight, Si of from 0.2 to 0.6% by weight, Co of from 3.0 to 5.0% by weight, Mn of from 0.2 to 0.5% by weight and applying a surface pressure of from 5 to 8 ton/cm
2
;
the second step of sintering at a temperature of from 1140 to 1180° C. and then cooling by air;
the third step of performing the sub-zero treatment at a temperature of from −200 to −160° C.;
the fourth step of impregnating Pb at a temperature of from 450 to 550° C.; and
the fifth step of performing the barrel process at the same temperature.
The present invention is described in detail hereunder.
In the present invention, Fe is a main component and a content of each alloy steel component is limited in order to improve a wear resistance and machinability. In particular, a metal powder of a high speed steel such as C, Cr, Mo, V and W is used to increase a cutting ability and improve a surface property.
First, Fe as a main component, C of from 0.8 to 1.2% by weight, Cr of from 2.0 to 4.0% by weight, Mo of from 2.0 to 4.0% by weight, V of from 2.0 to 4.0% by weight, W of from 7.0 to 10.0% by weight, Si of from 0.2 to 0.6% by weight, Co of from 3.0 to 5.0% by weight, Mn of from 0.2 to 0.5% by weight are mixed and then a surface pressure of from 5 to 8 ton/cm
2
is applied;
A mechanical property of the sintered alloy varies significantly with a content of C. A content of C is used in the range of from 0.8 to 1.2% by weight against the total weight of the composition of the sintered alloy. If the content of C is less than 0.8% by weight, a strength and hardness are insufficient. In contrast, if the content of C is more than 1.2% by weight, a tensile strength and a hardness are decreased, therefore it is not desirable.
Cr used in the present invention is added in order to increase a wear resistance and a cutting ability. Cr is used in the range of from 1.0 to 2.5% by weight against the total weight of the composition of the sintered alloy. If the content of Cr is less than 1.0% by weight, an improvement of the wear resistance and the cutting ability cannot be obtained. On the other hand, if the content of Cr is more than 2.5% by weight, a physical property is not increased any more.
Mo used in the present invention is added in order to increase a cutting ability, a tensile strength at a high temperature and a hardness. Mo is used in the range of from 0.1 to 0.3% by weight against the total weight of the composition of the sintered alloy. If the content of Mo is less or more than the above range, strength and hardness are not increased.
V used in the present invention is added in order to adjust a grain. V is used in the range of from 2.0 to 4.0% by weight against the total weight of the composition of the sintered alloy. If the content of V is less than 2.0% by weight, giant grain that causes a crack is produced, therefore, it is not desirable.
W used in the present invention is added in order to increase a tensile strength at a high temperature and hardness. W of the invention is used in the range of from 7.0 to 10.0% by weight against the total weight of the composition of the sintered alloy. If the content of W is less than 7.0% by weight, a small quantity of carbide is formed so that a wear resistance becomes lowered. If the content of W is more than 10.0% by weight, a physical property is not increased any more.
Also, Si used in the present invention is added as a de-oxidizer. Si prevents grain carbides from precipitating from grain boundaries during manufacturing process and, at same time, Si plays a role for decreasing a grain oxide layer. On the other hand, there is a trend that Si makes segregation in the alloy, and also becomes a silicon oxide which exists in the steel and
Hyundai Motor Company
Mai Ngoclan
LandOfFree
Sintered alloy having a wear resistance for a valve seat and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Sintered alloy having a wear resistance for a valve seat and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Sintered alloy having a wear resistance for a valve seat and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2960979