KR840001096B1 - A hot forging powder material - Google Patents

Abstract

This method produces a powder-forged material contg.(%) 1.4-3.5 Si, 0.2-0.9 Mn, 1.0-2.0 C balance Fe. The swarf of an FCD cast-iron mother material is pulverised and the graphite microparticles sepd. to give a material with a C content of 1.0-2.5%. The powder is then performed to a density of 80-85% and lubricant is applied before heating in a non-carburising atm. at a temp. above the material melting point but below 1300 deg. C for 10-900 secs. before cooling to give a surface temp. of 1000-1100 deg. C. The material is then forged in a die under pressure, such that its specific gravity is 100-110 % of the mother material.

Description

Powder Hot Forging Material

1 is a view showing the wear test results of the forging body according to an embodiment of the present invention.

Test material: S-55C (HV-270)

Pressure: 10kg / ㎠

Distance: 500m

No grease

Solid line indicates S55C, dotted line FC-25 and dashed line indicates the present invention, respectively.

2 is a diagram showing tissue by 100 times micrograph.

3 is a diagram showing tissue by 400 times micrograph.

The present invention relates to a high strength powder hot forging material having excellent wear resisting slidability.

Powder hot forging parts are gradually replaced by general forging parts or cutting parts due to the excellent economy of powder metallurgy, that is, good material recovery rate, omission of machining process such as cutting, and excellent material uniformity.

However, powder hot forged products do not balance product prices (ie raw material costs and processing costs) and performance at the stage of industrialization.

Powder hot forging is mainly used in the field of mechanical parts such as gears, cams, etc. of steel products, the characteristics of the material required for such parts are high tensile strength, compressive strength and toughness.

Also important are the hardness and the appropriate slipperiness necessary for wear resistance. In particular, the slipperiness is not simply a property obtained from hardness or toughness, but is realized as a ratio by an appropriate situation of a fine metal structure. In addition, since the properties of these materials must be satisfied at the same time, in the case of the conventional materials, there are various problems in economy and technology. For example, the cast iron material has excellent wear resistance and sliding resistance due to the action of the contained black particles (flakes or spherical particles), but the strength and toughness of the cast iron material decrease due to the brittleness of the contained graphite particles and the cavity of the grain boundary. Therefore, cast iron metal is not suitable as a mechanical component material because it cannot solve the nonuniformity or segregation of the structure. In addition, in the case of carbon steel or low alloy steel, strength and toughness can be satisfied by proper heat treatment, but since the wear resistance is reduced, special surface treatment such as nitriding is required. In addition, the mild steel material has non-metallic inclusions that are not removed in the steelmaking step, and furthermore, the directionality of the material produced by forging or rolling may impair the uniformity of component strength.

In addition, the conventional powder hot forging parts also have the same problems as above, it was not possible to obtain a material of high strength and excellent wear resistance slip.

In the present invention, a combination of a technique for producing a composite tissue alloy, which is difficult or impossible to manufacture by a smelting method, which is a characteristic of powder metallurgy, and a technique for producing a high density, defect-free material, which is a feature of powder hot forging technology. By this, a new high performance component material which has not been seen in the past can be obtained.

The most important component of the material of the present invention is fine graphite particles uniformly dispersed and precipitated in the matrix. Cast iron is conventionally known as a spray-precipitated graphite material, and spherical graphite cast iron is particularly excellent in dispersing spherical graphite particles. However, the strength and toughness of the material are not good because the size of the graphite particles is relatively large as 10-100㎛. It is also difficult to finely control the graphite particles by the casting method, and it is difficult to significantly change the carbon content because it causes hard cementite phase precipitation. However, in the powder metallurgy method of the present application, it was found that raw material powders can be selected and appropriately dispersed and precipitated evenly with fine graphite particles. The composition selected for this is the graphitization element of carbon, Si is the most important element of the iron alloy reinforcement, the selection range of 2-3% is most suitable. Since the graphitization effect is not effective below the lower limit and hardening proceeds excessively and becomes brittle above the upper limit, the present range was selected. Another essential element is 0.2-0.9% of Mn, which is effective in improving hardenability and is a reinforcing element of seven alloys.

Mn is an element effective for stably presenting graphite.

As with Si, the upper and lower limits of Mn are simply determined by the effective range and the harmful range. Needless to say, C is an element which becomes graphite and an element which is indispensable in order to become steel at the same time. As described above, the presence of a large number of granulated graphite particles adversely affects the strength and toughness, and on the contrary, when too small, the wear resistance and slippage effect is reduced. In addition, the solid solubility should contain about 0.8% since carbon is an essential element for strengthening the matrix into vacant steel.

The most suitable carbon amount required for the graphite particles is 1-2% as the total carbon amount, and preferably 1.4-1.8%. Other elements such as P.S.O and the like are present as unavoidable impurities. However, when the amount is 0.3% or less, there is no effect. Therefore, there is no particular restriction on the extent of inclusion of impurities as impurities. In addition, as a mixture from a raw material, there is no effect as long as it exists only as an impurity in some elements, such as a trace amount of Mg, Al, SnMo, Cr, Cu, and it does not need to define the range in particular.

By heat-treating the material of this invention, it is possible to harden an apparatus phase, to raise strength and to improve abrasion resistance.

In this case, the hardness of the known phase is most preferably 400-600 mHV. In order to avoid embrittlement due to excessive hardening and to enhance the effect, the upper and lower limits are set.

Example

The powders of Fe: 2.6%, Si: 0.8% and Mn: 1.7% were hot forged to obtain a forging having a specific gravity of 7.6.cc. Again, the forging was quenched after being quenched at 900 ° C. A cross-sectional photograph of each material is shown in FIGS. 2 and 3. Clearly fine graphite particles are uniformly dispersed and precipitated in the figure. Table 1 shows a comparative example of the mechanical properties of the Valyo. The results of the mam test are shown in FIG. From the above results, the material of the present invention is a useful material which has excellent properties that are suitable for mechanical structural products, and is widely used as a powder hot forging material, compared with conventional materials.

TABLE 1

Claims (1)

In powder hot forging material, Si2-3%, Mn0.2-0.9%, C1.0-2.0%, and the balance are iron, and 0.5-1.2% of the carbon content is 0.5-2.0㎛ Powder hot forging material, characterized in that uniformly dispersed precipitated as fine graphite particles.

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