KR19990035469A - Highly abrasion resistant engine valve-sheet material - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material for an engine valve seat of a vehicle having excellent wear resistance and a method for manufacturing the same, wherein a Cr and Mo-based compound is uniform in a structure in which sorbite, bainite, and martensite are mixed. The engine valve seat material of the present invention has a highly distributed structure and has a high self-lubrication property using a solid lubricant. As a result, the engine valve seat material of the present invention is not only excellent in wear resistance but also localized of the material as compared to a conventional engine valve seat material. It is economically and usefully used as a material for valve sheets for newly developed engines.

Description

Highly abrasion resistant engine valve-sheet material

The present invention relates to a material for an engine valve seat of a motor vehicle and a method for manufacturing the same. More specifically, Cr and Mo compounds are uniformly distributed in a structure in which sorbite, bainite, and martensite are mixed. The present invention relates to a material for high wear resistance engine valve sheet which has increased wear resistance by increasing self-lubrication property.

Valve seats for automobile engines are engine parts that play an important role in improving the combustion chamber's thermal efficiency by maintaining airtightness with the valves when opening and closing the intake and exhaust valves. They must withstand contact with the valves, friction and exposure to exhaust gases, etc. Therefore, heat resistance, abrasion resistance, impact resistance and corrosion resistance to a temperature of about 400 to 700 ° C. are required.

On the other hand, valve sheet manufacturing method for automobile engine is divided into infiltration method, hard metal addition method and alloy composition control method.

In the infiltration method, Cu or P, which is an infiltration material, is infiltrated into the pores of the sintered body, and a small amount of solid lubricants, such as Pb, MnS, CaF ₂ , and ZnO, are lubricated by the infiltration material and solid lubricant added to the valve sheet surface when the valve is rotated. Increase the effect

In the light metal addition method, a sintered compact is prepared by adding a hard Fe-Mo, Co-Ni-WC composite carbide having a size of 300 µm into the sintered compact matrix. The abrasion resistance is improved by allowing the dispersed carbide to be transmitted through the hard carbide having excellent abrasion resistance. Such a composite carbide has a disadvantage in that the contribution to wear resistance is great, but the workability is poor, and manufacturing cost is increased by using a large amount of expensive Co, Ni, and W.

On the other hand, the method of manufacturing a sintered body by mixing in an elemental powder state by controlling the alloy composition has the advantage that the raw material is cheap and can be easily manufactured, but it is difficult to obtain a uniform sintered structure There are Co, Ni, Mo, Cr, W, V, etc. The mainly used elements are expensive Co mainly added to improve the heat resistance.

Existing engine valve seat materials include 1.0-1.6 wt% C, 1.3-3.0 wt% Ni, 5.0-8.0 wt% Cr, 0.3-0.8 wt% Mo, 5.0-8.0 wt% Co, 1.5-3.0 wt% W, 11.0 to 18.0% by weight Cu, 1% by weight or less of the rest of the material and the remainder are composed of Fe, the density is 7.4 to 8.0 g / cm ³ , the compressive load is 250 kgf or more, and the hardness (H _v10 ) is 300 to 390. This material has a structure in which Cr and Co-based compounds are uniformly distributed in a sorbite matrix. However, these conventional materials have a disadvantage that they are not economical because they use expensive Co.

Meanwhile, 0.2-0.8 g / gallon tetraethyl lead contained in conventional gasoline for automobile engines increases the octane number and is used as an antiknocking agent. Pb oxide or Pb compound has been formed to form a lubricating film on the surface of the valve or valve sheet, thereby reducing the wear of the valve sheet.

However, due to the pollution problem of lead with carbon monoxide, nitrogen oxide gas, etc., in recent years, the use of unleaded gasoline with less than 0.004 g / gallon of tetraethyl lead in gasoline is mandatory, so the valve seats for automobiles are much more wear-resistant than conventional ones. Excellent new materials are required.

Therefore, the inventors of the present invention have been trying to manufacture a valve sheet material to cope with the trend of high power, high rotation, and low fuel consumption, and a structure in which Cr, Mo compounds are mixed with sorbite, bainite, and martensite. The iron base alloy dispersed in the present invention was found to be a material for an engine valve sheet having excellent wear resistance, thus completing the present invention.

An object of the present invention is to provide an engine valve sheet material having excellent wear resistance and a method of manufacturing the same.

In order to achieve the above object, the present invention provides an iron base alloy for engine valve sheet in which Cr, Mo-based compounds are uniformly dispersed in a structure in which sorbite, bainite and martensite are mixed, and a method of manufacturing the same.

Hereinafter, the present invention will be described in detail.

The material for the engine valve seat of the present invention is 0.5 to 1.5 wt% C, 1.0 to 3.0 wt% Ni, 2.0 to 6.0 wt% Cr, 3.0 to 6.5 wt% Mo, 0.5 to 2.0 wt% Co, 9.0 to 20.0 wt% Cu Up to 2% by weight of other materials, including 0.1 to 0.6% by weight Ca, small amounts of W and Mn, and the remainder consisting of Fe, in particular 1.1% by weight C, 1.5% by weight Ni, 3.8% by weight Cr, 5.0% by weight Mo, 1.2 wt% Co, 12.0 wt% Cu, 0.25 wt% Ca, up to 2 wt% other materials and the remainder consisting of Fe (Fe-1.1C-1.5Ni-3.8Cr-5.0Mo-1.2Co-12Cu-0.25Ca) The material is preferred.

Among the materials of the present invention, C has an effect of strengthening the matrix structure and forming carbides, and improving wear resistance by depositing a hard phase in combination with Cr or Mo. If the content of C is less than 0.5% by weight, the effect is hardly obtained, and if the content of C is more than 1.5% by weight, the material is brittle.

Ni enhances the matrix phase to prevent carbides from falling off, improves sinterability and improves initial taming with counterparts. In addition, it improves the heat treatment effect during heat treatment to improve the hardenability and toughness. However, if the content is less than 1.0% by weight, it is difficult to expect the above effect. If the content exceeds 3.0% by weight, a large amount of retained austenite is present, thereby reducing wear resistance.

Cr is partially dissolved in the base to improve hardenability and corrosion resistance at the same time, and combines with C to form hard carbide to improve wear resistance. However, if the addition amount is less than 2.0% by weight, it is difficult to expect a predetermined effect. If the addition amount is more than 6.0% by weight, the sinterability is lowered, and the strength of the part is impaired due to the large amount of hard carbide and wear of the counterpart material.

Mo not only strengthens the matrix as Cr, but also reacts with C to form hard carbide to improve wear resistance. However, if the added amount is less than 3.0% by weight, it is difficult to expect a predetermined effect. If the amount is more than 6.5% by weight, the sinterability is lowered, and a large amount of hard carbide causes brittleness of the parts, which leads to a decrease in strength and accelerated wear of the counterpart. Let's do it.

Co is employed in the base to improve strength and corrosion resistance, and also contribute to strength. However, if the added amount is less than 0.5% by weight, it is difficult to expect a predetermined effect. When the added amount is more than 2.0% by weight, the raw material is expensive, so that the cost of the product is increased and the diffusivity of the hard ingredient is promoted.

W forms carbide which is excellent in wear resistance.

Mn is added as MnS to improve solid lubrication and S to improve processability.

Ca is a solid lubricant that can be dissolved at a constant temperature to improve solid lubricity, thereby improving wear resistance. If it is added in excess of 0.6% by weight, a large amount is distributed in the matrix, which increases the brittleness of the material and lowers the thermal conductivity.

Cu fills the pores of the matrix to improve the thermal conductivity and strength of the material. If the added amount is less than 9.0% by weight, pores are present. If the added amount is more than 20.0% by weight, the amount of the solid solution is too high, causing a decrease in strength and a cost increase, and an increase in the amount of retained austenite.

The material of the present invention has a density of 7.4 to 8.0 g / cm ³ , a rolling load of 250 kgf or more, and a hardness (H _v10 ) of 250 to 400, and a Cr, Mo system in a mixed structure of sorbite, bainite, and martensite. The compound has a uniformly distributed tissue.

Existing mainly used for the valve valve material is Cr, Co-based compounds as hard particles, while the material of the present invention can be more economically produced engine valve sheet by using Cr, Mo-based compounds, solid lubricants It is characterized by improving the wear resistance by adding Ca to increase self-lubrication.

The engine valve sheet material of the present invention is mixed with a powder having a component ratio of the present invention, molded, sintered at a constant temperature, infiltrated and then quenched at a constant temperature for a predetermined time, and tempering. Manufactured through the process.

The powder mixing during the manufacturing process is carried out for 50 minutes, the density during molding is 6.8 ± 0.2 g / cm ³ and sintering is carried out for 30 to 100 minutes at a temperature of 1150 ± 30 ℃, quenching at 900 ± 50 ℃ temperature For 50-120 minutes, sourcing is performed for 100-200 minutes at a temperature of 650 ± 50 ° C.

Hereinafter, the present invention will be described in detail with reference to Examples. The following examples are merely illustrative of the present invention, and the content of the present invention is not limited by the examples.

EXAMPLES AND COMPARATIVE EXAMPLES Production of Highly Abrasion Resistant Engine Valve Sheet Materials

The metal powder was mixed for a certain time so that the final component of the small alloy for the engine valve sheet to be produced may have the composition shown in Table 1 below, and then molded into a press at a density of 6.8 ± 0.2 g / cm ³ and then 1150 ± 30 ° C. It was sintered for a certain time under temperature and simultaneously infiltrated. Then, the sintered alloy of the present invention was prepared by performing quenching and consideration at a constant temperature and time.

An engine valve seat single wear test and an engine durability test were performed with the sintered alloy prepared as described above, and the results are shown in Tables 2 and 3 below.

division Development Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Chemical composition wt% C 1.1 1.0 0.9 1.1 0.9 1.0 0.8 0.8 1.0 Ni 1.3 1.8 1.5 1.5 0.6 0.9 1.5 0.7 - Cr 3.8 4.7 4.8 2.0 3.8 2.4 - 5.0 2.1 Mo 5.0 6.0 3.0 5.5 3.4 2.2 2.8 1.0 2.1 Co 1.7 2.5 3.0 0.8 15.0 13.0 - 8.0 - W a very small amount a very small amount 1.8 1.3 3.0 1.7 11.0 0.4 3.8 Nb - - - - 0.5 0.6 - 0.2 - Mn a very small amount a very small amount - - - - 0.5 - - Ca 0.25 0.5 0.5 0.4 - - - - - Cu 13.5 14.0 12.7 14.1 13.8 13.5 - - 16.5 S - - - - - - 0.94 - - V - - - - - - - - 1.4

Engine valve seat single wear test result division Development Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Test 1 53 62 65 59 62 55 51 65 54 Test 2 42 57 59 62 49 44 40 51 35

Engine durability test results division Development Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 1.8 L ◎ ○ ◎ ○ - ◎ 2.0 L ◎ - ◎ ○ △ △ 2.0 L ◎ - ○ - - - * ◎: Good, ○: Normal, △: Under

As described above, the material for the engine valve seat of the present invention is comparable to other materials having excellent efficacy such as abrasion resistance and other highly effective materials currently used as the material for the engine valve sheet, and the existing material is Cr, Co-based. Compared with the use of a compound, the use of Cr and Mo compounds which are inexpensive is more economical and can be usefully used as a material for the engine valve sheet that is becoming more efficient, and is also a very desirable material in that localization of the material can be achieved. have.

Claims (3)

0.5 to 1.5 wt% C, 1.0 to 3.0 wt% Ni, 2.0 to 6.0 wt% Cr, 3.0 to 6.5 wt% Mo, 0.5 to 2.0 wt% Co, 9.0 to 20.0 wt% Cu, 0.1 to 0.6 wt% Ca, small amount Other materials, including W and Mn of 2 wt% or less and the remainder consisting of Fe The method of claim 1, wherein 1.1 wt% C, 1.5 wt% Ni, 3.8 wt% Cr, 5.0 wt% Mo, 1.2 wt% Co, 12.0 wt% Cu, 0.25 wt% Ca, up to 2 wt% of other materials and the remainder are Material for engine valve seat of automobile composed of Fe The powder is mixed to form the composition of claim 1, and then molded and sintered at a temperature of 1150 ± 30 ° C. for 30 to 100 minutes, infiltrated, quenched at 900 ± 50 ° C. for 50 to 120 minutes, and 650 ±. A method for producing the material for an engine valve seat according to claim 1, which is tempered at a temperature of 50 ° C. for 100 to 120 minutes.