KR950014348B1 - Process for making sintering alloy and article made thereby - Google Patents

Abstract

The abrasion resistance iron based sintered alloy is manufactured by (a) mixing 77.0 wt% Fe-Cr-Mo-W-V-C based alloy powder, 11.5 wt% Fe-Cr-Mo-Ni based alloy powder, 10.0 wt% Fe-Cr-Mo-W-Co-C based alloy powder, 1.0 wt% graphite powder and 0.5 wt% MnS powder, (b) pressing the mixture under 5-8 ton/cm2, (c) sintering the molded body at 1,120-1,220 deg.C in vacuum to make the framework body for impregnation, (d) impregnation green compact, pressed with 3-6 ton/cm2 and composed of Cu impregnation agent and MoS2 powder, on the framework body at the atmosphere of decomposition ammonia gas or mixture gas of nitrogen and hydrogen, at 1,080-1,150 deg.C for 30-60 min., (e) annealing the impregnation framework body at 1,000-1,200 deg.C for 1-3 hrs. in salt bath furnace or vacuum furnace, (f) tempering it at 540-600 deg.C for 1-2 hrs. in nonoxidative atmosphere.

Description

Abrasion resistant small bond alloy and its manufacturing method

The present invention relates to an iron base alloy for valve seat having excellent abrasion resistance and corrosion resistance, and more particularly, to a wear resistant iron base alloy having excellent corrosion resistance and abrasion resistance of an engine operated using LPG as fuel.

In general, the valve seat has a severe wear condition among the engine parts, and especially in an engine using LPG as fuel, the wear fatigue is more severe, which is a lubricant that offsets friction when using LPG. Since the operating conditions are much harsher than that of an internal combustion engine that uses gasoline or diesel as fuel, the lubrication is not good and the valve seat is cut off due to engine operation in a dry state. The wear resistance of the valve sheet is severely treated, and thus the wear resistance of the valve seat is particularly required.

Conventional valve seats of internal combustion engines using LPG as a fuel have been mainly manufactured by Pb impregnation method. This is due to the low melting point of Pb. There is a problem of environmental pollution, and in particular, Pb impregnation at a temperature of 400-500 ℃ lowered the base material hardness of the product was poor performance.

In addition, although a valve seat in which Cu is infiltrated using Fe-Cr-Mo-W-V alloy powder has been conventionally used as a gasoline engine valve seat, it has not been well suited for LPG, which is a more severe condition.

Accordingly, an object of the present invention is to provide a wear-resistant iron-based alloy of a new composition having excellent corrosion resistance and wear resistance to an engine operated using LPG as a fuel.

In the production of iron-based small alloys, Fe-Cr-Mo-WVC-based alloy powder, Fe-Cr-Mo-W-Co-C-based alloy powder, Fe-Cr-Mo-Ni-based alloy powder, Put graphite powder and MnS powder together with Zn-stearic acid in V-cone mixer, and do not cause segregation and do not degrade the lubricant by excessive mixing. After mixing, the molded body is not sintered at room temperature and is molded by applying a pressure of 5-8 ton / cm 2, which is a pressure range in which no mold breakage occurs due to excessive pressure. Vacuum sintering of -6) × 10 ^-3 Torr does not occur and grain growth does not occur, and vacuum sintering is carried out at a temperature of 1,120-1,220 ° C. to make a infiltration skeleton.

Here, the Fe-Cr-Mo-Ni-based alloy powder is used to supply each element in a pre-alloy state.

In addition, the Cu injector and MsO ₂ powder are mixed in a predetermined composition so that the molded product is not broken, and the molded product is formed into a desired shape by applying a pressure of about 3-6 ton / cm 2, which does not damage the mold, and then forms a green compact. Putting the above-mentioned green powder on the sieve, 30- at a temperature of 1080-1150 ℃ which is a temperature and time range in which microparticles do not occur and particle growth does not occur significantly in the decomposition ammonia gas or mixed gas (N ₂ / H ₂ ) atmosphere. Heated for 60 minutes, infiltrated (Cu + MoS ₂ ) to make the infiltrated skeleton, and then in a salt bath or vacuum furnace to ensure a sufficient hardness, and 1 to a temperature of 1,000-1,200 ℃ range that does not occur in the industry growth It is quenched after holding for 3 hours, and the brittleness of the hard tissue is suppressed to the maximum in an oxidizing atmosphere, and the soaking is carried out twice at a temperature of 540-600 ° C. in which hardness decrease does not occur.

The final composition range of the iron-based alloy obtained by the above production method is 1.0-3.5wt% C, 8.0-15.0wt% Cr, 1.0-3.0wt% Co, 2,5-5.0wt% Mo, 0.5 -3.0 wt% Ni, 3.5-7.5 wt% W, 0.5-3.0 wt% V, 8.0-18.0 wt% Cu, 0.2-1.0 wt% MnS, 0.1-1.5 wt% MoS ₂ , remaining amount This is made of Fe.

Looking at the influence of the elements consisting of the additive component of the present invention. Cr reacts with C to form carbides to improve wear resistance and at the same time to improve heat resistance, and to form Fe-Cr-Mo-W-C based carbide in hard spots to improve hardness and high temperature wear resistance. However, if less than 8%, the effect is reduced, if more than 15% formability is a problem and machinability is reduced.

Mo is partly employed in the base structure to enhance the employment of the base, while some form Fe-Cr-Mo-WC-based carbide to improve wear resistance, but less than 2.5% is not satisfactory, 5.0% If it is abnormal, economy and machinability will be inferior.

Co is employed in the base structure to improve strength and heat resistance. If it is 1.0% or less, it is ineffective, and if it is 3.0% or more, the price is increased to become economical.

Ni is dissolved in the matrix structure to improve the strength, toughness and heat resistance, but Ni is not effective at 0.5% or less, and at 30% or more, the economy is inferior.

W is partly employed in the base organization to strengthen the employment, while some form a complex carbide to act to further improve wear resistance. If the added amount is 3.5% or less, the effect of the desired wear resistance is inferior. If the added amount is 7.5% or more, the counterpart member is significantly worn out, so that the added amount thereof is 3.5-7.5%.

V mainly forms complex carbides with Fe, Cr, Mo, C and the like, but itself forms carbides to maintain high hardness to improve wear resistance. However, if it is 0.5% or less, the effect of improving the desired hardness is inferior, and if it is 3.0% or more, the relative member wears remarkably due to the increase of single carbide, so that the addition amount is made 0.5-3.0%.

Cu fills pores existing in the sintered body of the iron system by copper infiltration to improve density and hardness, and also has excellent work conductivity, thereby improving thermal conductivity and preventing high temperature corrosion.

If the amount is 8.0% or less, only some pores are filled, so the Cu infiltration effect is lowered. If the amount is more than 18%, the amount of the product is excessively excessive, resulting in deterioration of the shape of the product and outflow to the surface of the product.

MoS ₂ has the effect of improving the self-lubricating property and machinability of the alloy sintered body, 0.1% or less is ineffective, 1.5% or more is less economical, and because of the effect of lowering the strength due to a decrease in sinterability, the addition amount is 0.1-1.5 Should be%

MnS has an effect of improving machinability. If the amount is 0.2% or less, the effect is not effective. If MnS is 1.0% or more, the economy is inferior. Therefore, the amount is preferably 0.2-1.0%.

The present invention uses the Fe-Cr-Mo-WVC alloy powder as a base powder to strengthen the matrix structure, Fe-Cr-Mo-W-Co-C alloy powder and Fe-Cr-Mo-Ni alloy powder was turned improve the wear resistance by using, also by infiltration of the pores caused by inevitable manufacturing products by powder metallurgy as a Cu sikyeotgo also improve the wear resistance help days, by the addition of a solid lubricant MoS ₂ stylized further improve the wear resistance In addition, MnS was added to improve the workability of the small alloy.

Hereinafter, an embodiment according to the composition of the iron-based alloy of the present invention will be described.

EXAMPLE

The raw material powder was mixed according to the composition ratio shown in Table 1 below, and then the mixed powder was molded at a pressure of 6ton / cm 2, and the molding agent was vacuum sintered at a vacuum of 2 × 10 ⁻³ Torr and a temperature of 1,170 ° C. Make an infiltration skeleton.

Then, Cu injector and MoS ₂ powder were mixed in a weight ratio of 30: 1, and the green compact formed at a pressure of 5ton / cm 2 was placed on the skeletal agent, and heated and infiltrated at a temperature of 1,120 ° C. in a reducing atmosphere. After making the prepared skeletal body, the mixture was kept in a vacuum furnace at a temperature of 1,100 ° C. for 60 minutes, and then quenched twice at a temperature of 550 ° C.

The small bonds prepared by the above manufacturing process had a density of 7.8 g / cm 3 and a hardness of HRA 76.

TABLE 1

The durability test was performed on the valve seat obtained by the manufacturing process of the above example using a dedicated abrasion tester. The test conditions and test results are shown in Table 2, in which the relative valves were reheated using SUH36, a heat-resistant forged steel.

TABLE 2

Table 3 shows the component composition range of the iron base alloy for valve seat of the present invention obtained by the production method of the above embodiment compared with the conventional small alloy.

TABLE 3

As described above, as a result of the durability test in the engine operating the valve seat according to the embodiment of the present invention to LPG, the wear resistance of the valve seat of the embodiment is significantly improved compared to the conventional example, therefore, the sintered valve seat of the present invention is LPG It is excellent material for valve seat of small engine used as fuel.

Claims (2)

1.0-3.5 wt% C, 8.0-15.0 wt% Cr, 1.0-3.0 wt% Co, 2.5-5.0 wt% Mo, 0.5-3.0 wt% Ni, 3.5-7.5 wt% W, 0.5- Wear-resistant iron-based alloy, characterized in that the 3.0 wt% V, 8.0-18.0wt% Cu, 0.1-1.5wt% MoS ₂ , 0.2-1.0wt% MnS, the remaining amount is made of Fe. 77.0 wt% Fe-Cr-Mo-WVC alloy powder, 11.5 wt% Fe-Cr-Mo-Ni alloy powder, 10.0 wt% Fe-Cr-Mo-W-Co-C alloy powder, 1.0 Mixing wt% flammable powder, 0.5wt% MnS powder, and applying a pressure of 5-8ton / cm 2 to make a molded body, and vacuum-sintering the molded body at a temperature of 1,120-1,220 ° C. to form a infiltrating skeleton. ; and infiltrant and MoS ₂ powder mixed 3-6ton / ㎠ place the green compact molded by a pressure put on the skeleton body for immersion decomposed ammonia gas or a mixed gas for Cu (N ₂ / H ₂₎ in the atmosphere of 1080 - The step of infiltration by heating for 30-60 minutes at a temperature of 1150 ℃, and quenched by maintaining the infiltrated skeleton at a temperature of 1,000-1,200 ℃ 1-3 hours in a salt bath or vacuum furnace, and then the temperature of 540-600 ℃ Method for producing a wear-resistant iron-based alloy, characterized in that the source is soaked in an oxygen-free atmosphere for 1-2 hours.