KR100641064B1 - Treat method of surface for blade and blade - Google Patents

Abstract

A blade surface treatment method which improve wear resistance and corrosion resistance of the blade by diffusion infiltration of boron into the surface of a blade, prolongs the life of the blade by enhancing surface hardness of the blade, and enables the boride hardening layer to be formed on the tool steels regardless of types of tool steels by removing an alpha-ferrite layer during formation of a boride hardening layer, and a blade of which surface is treated by the same are provided. A blade surface treatment method comprises: a pretreatment process of removing organic matters, inorganic matters and the like adhered to the surface of a blade manufactured using STD61 steel and SKH9 steel; an injection process of loading a blade into a heat resistant sealed container containing a boride powder preparation mixed with B4C, KBF4 and the like, and closing a cover of the sealed container; a heating process of heating the heat resistant sealed container to a temperature of 900 to 950 deg.C at a heating rate of 5 deg.C/min in an inert atmosphere, holding the blade at the same temperature for 30 to 180 minutes, and subjecting the blade to furnace cooling; a diffusion process of holding the boronized blade at a temperature of 990 to 1,100 deg.C for 120 minutes, and rapidly cooling the blade to obtain quenching effect and diffuse Si accumulated in an alpha-ferrite layer into a subject; and a tempering process of tempering a blade formed through the diffusion process.

Description

Surface method of blade and its blade {Treat method of surface for blade and blade}

1 is a front view showing a typical blade,

Figure 2 is a detailed view showing the boride cured layer produced through the surface treatment method of the blade to which the present invention is applied,

3 is a graph showing the thickness change of the boride hardened layer formed on the surface of the blade with the boration treatment temperature and time in the surface treatment method of the blade to which the present invention is applied,

Figure 4 is a graph showing the hardness distribution of the cross section according to the depth of the boride hardened layer according to the surface treatment method of the blade to which the present invention is applied,

Figure 5 is a graph showing the hardness distribution of the cross-section according to the depth of the boride hardened layer according to the surface treatment method of the blade to which the present invention is applied (before diffusion heat treatment),

Figure 6 is a graph showing the hardness distribution of the cross-section according to the depth of the boride hardened layer according to the surface treatment method of the blade to which the present invention is applied (after diffusion hardening heat treatment).

* Description of the symbols used in the main parts of the drawings *

A, A1; Boride hardened layer

B; Blade

The present invention relates to a surface treatment method of the blade and to the blade in more detail in the surface treatment method of forming a boride hardened layer such as FeB, Fe2B by diffusion penetration of boron (element symbol; B) on the surface of the blade; The blade is to improve the surface treatment method to remove the α-ferrite layer generated when the Si content is high during the surface treatment to enable the surface treatment irrespective of the material.

In general, blades of various shapes and structures are applied to cutting paper, wood, metal, etc., and these blades are carburized, nitrided, titanium nitride, etc. Surface treatment has been performed.

Among them, carburizing and nitriding have surface hardness of about HV1200, and the problem of thickness control of the hardened layer of the surface treatment, breakage of the blade in the process of processing the blade after diffusion penetration, and carburizing and nitriding treatment There was a problem that the material of the blade that can be used in order to be limited.

In the case of titanium nitride coating, the surface hardness of HV2500 is high, but in terms of price, since the processing cost is high and the blade must be completely processed, the surface has to be dulled.

Among the materials used for manufacturing the blade, a material of a tool steel type (11 STD, 61 STD, 2 SKH, 9 SKH, etc.) is used.

It is known that when boronizing boron (boron; B) with a slightly higher Si content (about 0.5%) among these tool steels, an unusual phenomenon is not seen in other steels.

That is, when the boride hardened layer is formed from the austenite phase on the surface of the tool steel during the boring process, the Si component is not dissolved in the boride hardened layer due to the redistribution of alloying elements between the boride hardened layer and the object phase. If it accumulates near the subject under the cargo hardening layer and exceeds a certain amount, the α-ferrite layer is formed.

This layer is called α-ferrite layer because Si is a ferrite stabilizing element and the layer forms a ferrite structure. The α-ferrite layer has a low hardness value not only for the boride hardened layer but also for the subject.

Therefore, when a load is applied to the surface of the borated material, the α-ferrite layer may not properly support the boride cured layer on the surface, but rather the boride hardened layer may penetrate into the α-ferrite layer. have.

This phenomenon is called the "eggshell effect" phenomenon.

Therefore, it was difficult to apply the boride treatment to the tool steel with Si content of more than 0.5% due to this phenomenon in the boring treatment for the tool steel.

Accordingly, the present invention was created to solve the above problems, by diffusing and penetrating boron on the surface of the blade, to form a boride hardened layer to improve the wear resistance and corrosion resistance, as well as to increase the surface hardness to extend the life of the blade Furthermore, boride hardened layer can be formed irrespective of the type of tool steel by removing the α-ferrite layer even when the boron hardened layer is formed even in the tool steel having a Si content of 0.5% or more through diffusion penetration of boron. The purpose.

Hereinafter, the configuration and operation of the present invention will be described with reference to the accompanying drawings.

Figure 2 is a detailed view showing a boride hardened layer produced by the surface treatment method of the blade to which the present invention is applied, Figure 3 is formed on the blade surface according to the boride treatment temperature and time in the surface treatment method of the blade to which the present invention is applied 4 is a graph showing the change in thickness of the boride hardened layer, Figure 4 is a graph showing the hardness distribution of the cross-section according to the depth of the boride hardened layer according to the surface treatment method of the blade to which the present invention is applied, Figure 5 is applied to the present invention Graph showing the hardness distribution of the cross-section according to the depth of the boride hardened layer according to the surface treatment method of the blade (before diffusion heat treatment), Figure 6 is a depth of the boride hardened layer according to the surface treatment method of the blade to which the present invention is applied The hardness distribution of the cross section according to the present invention will be described together as a graph (after diffusion hardening heat treatment).

Surface treatment method of the blade of the present invention for achieving the above object,

First, a blade is manufactured by using 61 STDs and SKH9 species having a Si content of 0.91%, which are frequently used as materials of the blades for carrying out the present invention.

A pretreatment step of removing organic matter, inorganic matter, etc. adhered to the blade surface manufactured using the STD61 species and the SKH9 species;

A charging step of placing a blade in a sealed container in which a mixed boride material powder such as B4C and KBF4 is added, and then covering the sealed container to prepare a lid;

A step of charging the blade into a boride material powder and then heating the heat-resistant airtight container at 5 ° C./min to 900 ° C.-950 ° C. in an inert atmosphere for 30 to 180 minutes, followed by a furnace cooling process;

A diffusion process of maintaining the borated blade again at a temperature of 990 ° C.-1100 ° C. for 120 minutes and quenching to diffuse the quenching effect and Si accumulated in the α-ferrite layer to a subject;

A tempering process of tempering the blade generated through the diffusion process;

Through the above process is made of a post-treatment process of grinding and processing the blade.

The boriding method of diffusing the boron to form a boride hardened layer may include a pack boriding method, a face boring method, an electroless salt bath boring, an electrolytic salt bath boring, a gas boring, and a plasma beam Various techniques such as riding are known.

Among them, the most widely used method is the pack-boarding method applied to the present invention, and it is possible to work by a relatively simple technology without a separate dedicated equipment, and can be applied to products of various shapes. And since foreign matters are not attached to the blade surface, there is an advantage that a relatively clean surface can be obtained.

In the pack-riding method, B4C, Ferroboron (Fe-B), amorphous boron, etc. are used as boron sources, but Ferroboron (Fe-B), amorphous boron, etc. are known to use B4C a lot because of their relatively high price.

In addition, the boration treatment to which the present invention is applied includes inhibitors for controlling the boration reaction not to be very active, among which B4C is used as a boron source, Al2O3 / SiC is used as a diluent, and KBF4 is boron released from the specimen surface. The sanctions used to form cargoes are used as commercial sanctions.

During the high temperature boration process, KBF4 is evaporated to decompose while releasing boron from the surface of the specimen. At this time, the reaction is continuously controlled by the reaction of K and F atoms with B4C to produce KBF4.

Therefore, the sanctions used in the pack-boarding method are not used for single use and can be reused several times by mixing with the new sanctions.

Looking at the present invention through the following specific examples.

<Example 1>

SKH9 type (Example for the boride hardened layer of a blade)

Heating temperature Heating time Cured layer thickness Quenching and Quenching Tempering after cooling Hardness 950 ℃ 300 minutes About 50㎛ Air cooling (1150 ℃) Air cooling (530 ℃) HRC 59-62 950 ℃ 180 minutes About 37㎛ Air cooling (1150 ℃) Air cooling (530 ℃) HRC 59-62

In this case, cracks occur during cooling, and as shown in FIG. 2 (a), the hardened layer A at the end portion of the blade B is thick and broken.

In addition, partial heat treatment of the boride hardened layer occurred through hardening heat treatment at 1150 ° C., resulting in a decrease in blade surface roughness. This is because the solid boride hardened layer is partially melted in the liquid phase because the process reaction temperature of pure Fe-B is 1149 ° C.

Thus, it was confirmed that there is a limitation in the heat treatment temperature during the curing heat treatment after the thickness of the boride hardened layer and the boride treatment.

<Example 1-1>

SKH9 type (Example for the boride hardened layer of a blade)

Heating temperature Heating time Cured layer thickness Quenching and Quenching Tempering after cooling Hardness 950 ℃ 60 minutes About 25㎛ Air cooling (1050 ℃) Air cooling (530 ℃) HRC 58-60 950 ℃ 30 minutes About 16㎛ Air cooling (1050 ℃) Air cooling (530 ℃) HRC 58-60

In this case, as shown in FIG. 2 (b), the hardened layer A1 is uniformly distributed along the surface of the blade B, thereby solving the problem of breaking the end of the blade, thus forming a boride hardened layer to be formed on the surface of the blade. It can be seen that the preferred thickness of is about 5-25 μm.

In addition, the problem of surface roughness of the boride hardened layer also set the quenching temperature to 1050 ℃ to solve the problem of melting the solid boride hardened layer to solve the problems such as surface roughness degradation.

<Example 2>

SKH9 type (Example for the boride hardened layer of a blade)

The thickness change of the boride hardened layer formed according to the boride treatment temperature and time for SKH9 species is shown in FIG. 3. Looking at this, if the boration treatment temperature is set to 900-950 ℃ and heated for 40-60 minutes (50-60s ⁿ : n = 1/2) to obtain a desired thickness of the cured layer of about 20㎛.

4 shows the surface hardness of the boride hardened layer according to Example 2 as a graph, and it can be seen that the surface hardness of the boride hardened layer is Hv1500 or more.

<Example 3>

STD61 species (Example regarding the α-ferrite layer)

Heating temperature Heating time Cured layer thickness α-ferrite layer thickness Cooling after quenching Cooling after tempering Hardness 900 ℃ 180 minutes About 50㎛ About 21㎛ Air cooling (1020 ℃) Air cooling (530 ℃) HRC 50-52

The thickness of the boride hardened layer of the specimen subjected to boration treatment at 900 ° C. for 180 minutes is about 50 μm. At this time, the thickness of the α-ferrite layer formed is about 21 μm.

In FIG. 5, the hardness value Hv410 is lower than the hardness value Hv530 of the subject under the boride hardened layer.

In order to remove the α-ferrite layer under the boride hardened layer, diffusion hardening heat treatment was performed, and the experiment was performed at different temperatures and holding times.

First, no change in the α-ferrite layer was observed when the temperature was maintained at about 980 ° C. for 60 minutes and 120 minutes.

Therefore, if the temperature was raised to about 1020 ℃ and the diffusion hardening heat treatment time was maintained the same, no change was observed when 60 minutes were maintained.

When it is maintained for 120 minutes, it can be seen that the α-ferrite layer is transformed into martensite structure and the hardness is increased to Hv530.

This phenomenon occurs because Si accumulated in the α-ferrite layer diffuses into the object layer, and the concentration of this portion decreases from about 3.2% to about 2.15%. Thus, the α-ferrite layer undergoes phase transformation into austenite, and Change to martensite.

This change in hardness can be confirmed through FIG. 6.

In order to confirm the performance of the blade according to the present invention, the experimental results of the conventional blades are shown in Table 1.

TABLE 1

Comparison of Mechanical Properties of Blades

Conventional blade Surface Hardening Blades Hardness Deep Hardness (Rockwell) HRC 62 HRC 62 Surface Hardness (Microviscus) HRC 62 HRC 68 or higher (Hv1532) Friction Coefficient (500-3600S) 4.63 1.38 = Weight loss Cycles (a: 10800, b: 21600) a: 1.9mg b: 2.4mg a: 0.5mg b: 0.8mg Corrosion resistance (immersion solution = 3.5% HCl, after 120 hours 4.98% reduction 0.25% reduction

As shown in the experimental results of Table 1, the blade according to the present invention has a low surface hardness and a low coefficient of friction, abrasion resistance, excellent wear resistance, and corrosion resistance.

The surface treatment method of the blade of the present invention as described above and the resulting blade is not only to improve the wear resistance, machinability, corrosion resistance, etc., compared to the existing blade by forming a boride hardened layer on the surface, the surface hardness to increase the blade Has the effect of prolonging its lifespan.

In addition, it is a useful invention to remove the α-ferrite layer generated during the surface hardening treatment even in tool steels with a Si content of 0.5% or more to enable surface hardening treatment regardless of the type of tool steel.

Claims (3)

In the surface treatment method of the blade; The surface treatment method of the blade, A pretreatment step of removing organic matter, inorganic matter, etc. adhered to the blade surface manufactured using STD61 species and SKH9 species; A charging step of placing a blade in a sealed container in which a mixed boride material powder such as B4C and KBF4 is added, and then covering the sealed container to prepare a lid; A step of charging the blade into a boride material powder and then heating the heat-resistant airtight container at 5 ° C./min to 900 ° C.-950 ° C. in an inert atmosphere for 30 to 180 minutes, followed by a furnace cooling process; A diffusion process of maintaining the borated blade again at a temperature of 990 ° C.-1100 ° C. for 120 minutes and quenching to diffuse the quenching effect and Si accumulated in the α-ferrite layer to a subject; A tempering process of tempering the blade generated through the diffusion process; The surface treatment method of the blade, characterized in that consisting of a post-treatment step of polishing and processing the blade through the above process. delete delete

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