KR20190060437A - Fan impeller and weling method thereof, welded structure - Google Patents

Abstract

Disclosed is a fan impeller, comprising: a body comprising a plurality of end plates and blades; a first welding unit located on a first connection unit formed between the end plates and the blades; and a second welding unit located on the first welding unit. Hardness of the first welding unit is higher than that of the first connection unit and lower than that of the second welding unit.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a fan impeller, a fan impeller,

The present invention relates to a fan impeller joined through welding and a welding method thereof.

The conventional blower having a high-speed impeller rotates at a high speed in most cases, so that the high-speed impeller receives a very large centrifugal force. The impeller subjected to centrifugal force is abraded, and the impeller having high abrasion resistance is made of abrasion resistant material by welding the connection parts between the parts.

Particularly, in the case of the gas circulation fan impeller of the coke dry type fire extinguishing system (CDQ), the glow coke (950 to 1100 ° C) is exhausted from the closed furnace to the circulating gas. At this time, the sensible heat of the heated gas is recovered as energy, The fan impeller rotates at a high speed of 1300 rpm or more.

In this process, the end plates and the blades of the fan impeller come into contact with iron oxide, fine dust, and COG (coke oven gas), and can be abraded and corroded due to friction, impact,

This has led to the problem that COG of high temperature can not be discharged and circulated, and thus it can not be used as heat generated by steam generated by the next process.

The present invention provides a fan impeller having a multi-layer welded portion, wherein the first welded portion of the lower layer has a relatively high ductility and the second welded portion of the upper layer has a relatively high hardness to maximize corrosion resistance and wear resistance.

A fan impeller according to the present invention includes: a body made of a plurality of hard disks and blades; A first weld positioned on a first connection formed between the hard plate and the blade; And a second welding portion positioned on the first welding portion, wherein a hardness of the first welding portion is higher than that of the first connecting portion, and lower than that of the second welding portion.

The ductility of the first weld may be higher than that of the second weld.

A weld heat affected zone is formed below the second weld and around the first joint, and the area fraction of the martensite structure of the weld heat affected zone may be 18% or less.

Wherein the main body is made of an alloy material containing carbon (C) having a content of 0.3% or less based on 100% of the total weight, and the first weld portion is a first weld material having a higher content of carbon (C) than the alloy And the second welded portion may be made of a second welded material having a higher content of carbon (C) than the first welded material.

The first welding material and the second welding material each include chromium (Cr), and the chromium (Cr) content of the second welding material may be higher than the chromium (Cr) content of the first welding material.

Wherein the first welding material comprises 0.08 to 0.10% of carbon (C), 14 to 20% of chromium (Cr), 6 to 10% of nickel (Ni), 0.3 to 0.6% of silicon (Si) , Manganese (Mn): 4 to 8%, iron (Fe), and other unavoidable impurities.

Wherein the second welding material comprises 0.3 to 0.6% of carbon (C), 22 to 28% of chromium (Cr), 1 to 4% of manganese (Mn), 0.5 to 1.5% of molybdenum (Mo) , 1.5 to 3.0% of niobium (Nb), the balance iron (Fe), and other unavoidable impurities.

The hardness of the first weld may be between 30 and 33 HRC, and the hardness of the second weld may be between 55 and 62 HRC.

A boss which passes through the through hole formed in the main body and is connected to the end plate to form a second connection portion; A third weld positioned on the second connection; And a fourth welded portion positioned on the third welded portion, wherein a hardness of the third welded portion is higher than that of the second connected portion and lower than that of the fourth welded portion.

A welding structure according to the present invention includes a structure composed of a plurality of members; A first weld layer located at the joint formed between the members; And a second weld layer positioned on the first weld layer, wherein the hardness of the first weld layer is higher than the joint and lower than the second weld layer.

The ductility of the first weld layer may be higher than the second weld layer.

A method of welding a fan impeller according to the present invention includes positioning a first welded portion using a first welded material on a first connecting portion formed between a hard plate and a blade among a plurality of hard plates and a blade, And positioning a second welded portion on the first welded portion using a second welded material, wherein a hardness of the first welded portion is higher than that of the first connection portion and lower than that of the second welded portion.

The method may further include, before the step of positioning the first weld, performing a work hardening treatment on the surface of the first connection part.

Before the step of positioning the first weld, preheating the body may be further included.

In the preheating step, it may be preheated at a temperature of 100 to 200 DEG C for 0.5 to 1 hour.

Placing the boss in a through hole formed in the body so as to form the hard plate and the second connection portion; Positioning the third weld on the second connection using the first weld; And positioning a fourth welded portion on the third welded portion using the second welded material, wherein the hardness of the third welded portion is higher than that of the second connected portion and lower than that of the fourth welded portion .

According to the fan impeller of the present invention, the multi-layer welded portion is formed, the first welded portion of the lower layer has a relatively high ductility and the second welded portion of the upper layer has a relatively high hardness so that the fan impeller is used for CDQ gas circulation, The corrosion and abrasion of the end plate and the blade can be suppressed to the utmost, and the occurrence of perforations can be prevented.

In addition, it is possible to maximize corrosion resistance and abrasion resistance, and thereby, it is possible to manufacture a welded structure with high durability by preventing facility defects.

1 is a view showing a body made of a hard plate and a blade in a fan impeller according to the present invention.
2 is a view showing a state where a first welding portion and a second welding portion are disposed on a first connecting portion formed by a hard plate and a blade in a fan impeller according to the present invention.
3 is a view showing a welding heat affected portion formed by the first welding portion and the second welding portion in the fan impeller according to the present invention.
4 is a view showing a state where a third welding part and a fourth welding part are located on a second connecting part formed by a boss and a hard plate in a fan impeller according to the present invention.
5 is a cross-sectional view of a fan impeller according to the present invention.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly illustrate the present invention, parts not related to the description are omitted, and the same or similar components are denoted by the same reference numerals throughout the specification.

In addition, since the sizes and thicknesses of the respective components shown in the drawings are arbitrarily shown for convenience of explanation, the present invention is not necessarily limited to those shown in the drawings. In the drawings, the thickness is enlarged to clearly represent the layers and regions. In the drawings, for the convenience of explanation, the thicknesses of some layers and regions are exaggerated.

Also, when a portion such as a layer, a film, an area, a plate, etc. is referred to as being "on" or "on" another portion, this includes not only the case where the other portion is "directly on" . Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. Also, to be "on" or "on" the reference portion is located above or below the reference portion and does not necessarily mean "above" or "above" toward the opposite direction of gravity .

Also, throughout the specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

Also, in the entire specification, when it is referred to as " planar ", it means that the object portion is viewed from above, and when it is called " sectional image, " this means that the object portion is viewed from the side.

Pan Impeller

1 and 2, a fan impeller according to the present invention includes a main body 100 including a plurality of end plates 110 and blades 120, a blade 110, 1 hardness of the first welding portion 200 is higher than that of the connecting portion and lower than that of the second welding portion 300. The second welding portion 300 is located on the first welding portion 200 and the first welding portion 200.

The main body 100 is formed of a plurality of blades 120 arranged between a plurality of upper and lower hard plates 110 and 110 arranged vertically. The rigid plate 110 and the blade 120 constituting the main body 100 may be formed of an inner material, specifically, an alloy material. More specifically, it may be composed of rolled steel for general structure or HT steel (HT 50, 60, 70, etc.).

The first welding portion 200 is positioned in such a manner as to surround the surface of the connection portion on the connection portion where the plurality of hard plates 110 and the blades 120 are connected to each other. The second welding portion 300 is positioned on the first welding portion 200 so as to surround the surface of the first welding portion 200.

The first welding portion 200 and the second welding portion 300 form a multi-layered pass and are positioned on the connecting portion to weld the hard plate 110 and the blade 120 by welding.

In the case of the first weld portion 200 abutting the connection portion, the first weld portion 200 may be formed of a material having excellent corrosion resistance and wear resistance to serve as a corrosion prevention layer and stabilize the metal structure of the connection portion.

The first welding portion 300 is made of a material having a hardness higher than that of the main body 100 and a hardness lower than that of the second welding portion 300 so that the hardness difference between the connecting portion of the main body 100 and the second welding portion 300 is mitigated. Lt; / RTI >

The second welding portion 300 contacting the first welding portion 200 may be made of a material having a higher corrosion resistance and wear resistance than the first welding portion 200 as a portion exposed to the outside air. Further, it may be formed of a material having a hardness higher than that of the main body 100 and the first welding portion 200.

Accordingly, even if the fan impeller according to the present invention is repeatedly used for CDQ gas circulation at a high speed of 1300 rpm or more in a high-temperature atmosphere, corrosion and wear of the hard plate 110 and the blade 120 can be suppressed to the utmost, Can be prevented.

As described above, since the fan impeller has a structure in which the hardness increases from the main body 100 to the first welding portion 200 and the second welding portion 300, corrosion resistance and wear resistance can be maximized, It is possible to manufacture a welded structure having high durability.

In the fan impeller according to the present invention, the ductility of the first welded part 200 may be higher than that of the second welded part 300.

In addition, the weld heat affected zone 400 is formed below the second weld zone 300 and around the joint, and the area fraction of the martensite structure of the weld heat affected zone 400 may be less than 18%.

As shown in FIG. 3, when the joint is welded, a heat affected zone (HAZ) 400 is formed around the first joint by welding heat. Since the weld heat affected zone 400 is subjected to a high temperature of about 1300 DEG C or higher during the welding process, crystal grains of the austenite structure grow.

After cooling, at least a portion of the austenite structure may be transformed into a martensitic structure. Since such a martensite structure has high brittleness, cracks may occur, and the martensite structure may be detached in the form of a piece, resulting in facility defects.

When the welded portion is formed by a multi-layered pass as in the fan impeller according to the present invention, the first heat affected portion 410 is formed around the first jointed portion in the process of welding the first welded portion 200 to the first jointed portion . The second heat affected part 420 may be formed below the second welded part 300 and around the first jointed part in the process of welding the second welded part 300 onto the first welded part 200.

The first heat affected portion 410 and the second heat affected portion 420 may overlap each other and the welding heat affected portion 400 may have a first heat affected portion 410 and a second heat affected portion 420 may be included.

In the process of forming the second welded part 300 on the first welded part 200, the first welded part 200 may be reheated to increase the brittleness.

Accordingly, in order to prevent the microstructure of the weld heat affected zone 400 including the first heat affected zone 410 and the second heated zone 420 from being transformed into martensite during the welding process, It can be formed of a material having a relatively low hardness but a high ductility.

Accordingly, the first welding portion 200 can function as a buffer region to mitigate the hardness deviation between the first connecting portion of the main body 100 and the second welding portion 300.

On the other hand, the area fraction of the martensite structure of the weld heat affected zone 400 may be 18% or less based on 100% of the total volume. If the martensite structure fraction exceeds 18%, the brittleness may be increased.

In the fan impeller according to the present invention, the main body 100 is made of an alloy material containing carbon (C) having a content of 0.3% or less based on 100% of the total weight. The first weld portion 200 is made of carbon And the second welding portion 300 may be made of a second welding material having a higher content of carbon (C) than the first welding material.

Carbon (C) is generally added to the alloy to serve to increase the strength and hardness of the alloy. The alloy forming the main body 100 may be a ferritic carbon steel containing 0.3% or less of carbon (C).

Specifically, the alloy contains 0.1 to 0.3% of carbon (C), 0.35% or less of silicon (Si), 0.8% or less of manganese (Mn), 0.04% or less of phosphorus (P) , The balance iron (Fe), and other unavoidable impurities.

The ferritic carbon steel may further include 0.004 to 0.035% of titanium (Ti) to improve the strength and toughness, and the embrittlement region of the weld heat affected zone (HAZ).

The carbon content of the first welded material forming the first welded portion 200 is higher than the carbon content of the alloy forming the main body 100 and the carbon content of the second welded material forming the second welded portion 300 (C) content of the first welding material is higher than the carbon (C) content of the first welding material, the hardness of the first welding material 200 and the second welding material 300 increases from the main body 100 to the first welding material 200 and the second welding material 300.

Meanwhile, the first welding material and the second welding material each include chromium (Cr), and the chromium (Cr) content of the second welding material may be higher than the chromium (Cr) content of the first welding material.

Cr (Cr) is added as an alloying element to the first welding material and the second welding material to improve the high-temperature oxidation characteristic, thereby contributing to strengthening of corrosion resistance. However, if it is contained in an excessive amount, the elongation may be lowered and the hot workability may be impaired.

Therefore, the chromium (Cr) content of the second weld material is higher than the chromium (Cr) content of the first weld material, so that the hardness of the second weld material 300 may be higher than that of the first weld material 200. On the other hand, the ductility of the first welded part 200 may be higher than that of the second welded part 300.

Specifically, the first weld material preferably contains 0.08 to 0.10% of carbon (C), 14 to 20% of chromium (Cr), 6 to 10% of nickel (Ni), 0.3 to 0.6 %, Manganese (Mn): 4 to 8%, the balance iron (Fe) and other unavoidable impurities.

The first welding material is an austenitic material, and may be an age hardening material having a low hardness in the welding process but a high hardness due to even distribution of the precipitates with time.

The first weld portion 200 may have a hardness of 30 to 33 HRC, an elongation of 40 to 43, and a thickness of 7 to 12 mm.

When the content of carbon (C) is less than 0.08%, the formability is deteriorated and the strength and hardness are decreased. When the content of carbon (C) is more than 0.10%, the strength and hardness are increased, It may be difficult to serve as a buffer zone.

Chromium (Cr) is an important element for enhancing corrosion resistance, and improves high temperature oxidation characteristics. If it is added in an excess amount, the high temperature strength is lowered, the hot workability at high temperature is impaired, and the elongation rate may be lowered. If the content of chromium (Cr) is less than 14%, the effect of high-temperature oxidation characteristics is insignificant. If the content exceeds 20%, high-temperature strength and elongation may be decreased and hot workability may be impaired.

If the content of nickel (Ni) is less than 6%, the toughness may decrease, and if it exceeds 8%, the diffusion of carbon (C) or nitrogen (N) may be slowed.

Silicon (Si) is a very effective element in improving the high-temperature oxidation characteristics. If the content of silicon (Si) is less than 0.3%, the effect of improving sag resistance, phase stability, high-temperature oxidation characteristics and elongation is insignificant, and if it exceeds 0.6%, the elongation can be drastically reduced.

Although manganese (Mn) is advantageous in terms of sag resistance, high temperature oxidation resistance and phase stability, if it is added excessively, moldability may be deteriorated due to decrease in elongation. When the content of manganese (Mn) is less than 4%, the effect of improving the sag resistance, phase stability, high-temperature oxidation characteristics and elongation is insignificant, and if it exceeds 8%, the elongation can be drastically reduced.

Specifically, the second welding material may contain 0.3 to 0.6% of carbon (C), 22 to 28% of chromium (Cr), 1 to 4% of manganese (Mn), 0.5 to 1.5% of molybdenum %, Niobium (Nb): 1.5 to 3.0%, the balance iron (Fe) and other unavoidable impurities.

Second Welding Material Like the first welding material, it may be an austenitic material, an age-hardening material having a low hardness in the welding process but a high degree of distribution of precipitates evenly over time. It may also be a surface hardening material.

The second weld 300 may have a hardness of 55 to 62 HRC, an elongation of 18 to 23, and a thickness of 7 to 12 mm.

If the content of carbon (C) is less than 0.3%, the hardness may be lower than that of the first weld portion 200, and if it exceeds 0.6%, the strength and hardness may be excessively increased.

If the content of chromium (Cr) is less than 22%, the hardness may be lower than that of the first weld portion 200, and if it exceeds 28%, the manufacturing cost may increase and the high temperature strength and elongation may be sharply lowered.

When the content of manganese (Mn) is less than 1%, the effect of improving sag resistance, phase stability, high-temperature oxidation characteristics and elongation is insignificant, and if it exceeds 4%, the elongation can be drastically reduced.

If the content of molybdenum (Mo) is less than 0.5%, the quenchability and heat resistance may be deteriorated, and if it exceeds 1.5%, the curing ability may be excessively high.

If the content of niobium (Nb) is less than 1.5%, the bonding with carbon (C) may be restricted, and if it exceeds 3.0%, the hardness may be lowered.

4 and 5, the fan impeller according to an embodiment of the present invention includes a boss 500 passing through a through hole formed in the main body 100 and connected to the hard plate 110 to form a second connection portion, The second welding portion 600 and the fourth welding portion 700 positioned on the second welding portion 600 and the fourth welding portion 700 positioned on the second welding portion 600. The hardness of the third welding portion 600 is higher than that of the second welding portion 600, 4 welded portion 700 of FIG.

The boss 500 passes through the through hole formed in the main body 100 and is connected to the end plate 110. Specifically, the plurality of rigid plates 110 constituting the main body 100 are divided into one rigid plate 111, a middle rigid plate 112, and another rigid rigid plate 113. Through holes are formed in the respective end plates 110 and connected to each other through a plurality of blades 120 disposed between the end plates 110 to form the main body 100. The boss 500 is disposed in the through hole formed in the one end plate 111, the center end plate 112 and the other end plate 113 and forms the second connection portion with the central end plate 112.

When the fan impeller is repeatedly used for CDQ gas circulation at a high speed of 1300 rpm or more in a high temperature atmosphere, the first connection part, which is the connection part between the hard plate 110 and the blade 120, as well as the first connection part between the boss 500 and the hard plate 110 The second connection portion, which is the connection portion, is also vulnerable to corrosion due to wear. Therefore, a third welding portion 600 that can act as a buffer region on the second connection portion is formed, and a fourth welding portion 700 having a hardness higher than that of the third welding portion 600 is formed on the third welding portion 600, And the abrasion resistance can be improved.

The description of the third welding part 600 and the fourth welding part 700 is the same as that of the first welding part 200 and the second welding part 300 and therefore the first welding part 200 and the second welding part 300 I will substitute it for explanation.

Welded structure

The weld structure according to the present invention comprises a structure comprising a plurality of members, a first weld layer located at the joint formed between the members, and a second weld layer located over the first weld layer, wherein the hardness of the first weld layer is Higher than the joint and lower than the second weld layer.

The ductility of the first weld layer may be higher than the second weld layer.

It is required to have excellent corrosion resistance and abrasion resistance because it is used in a high temperature environment and the structure connected by welding is not limited to the fan impeller for CDQ gas circulation.

Accordingly, when the member is connected through welding, the first welding layer having a higher hardness than the member and the second welding portion 300 having a hardness higher than that of the first welding layer are applied, Welded structures can be expected.

The description related to the first welding layer and the second welding layer will be described instead of the above description of the fan impeller.

Pan Impeller  welding method

The fan impeller welding method according to the present invention uses a first welding material on a first connecting portion formed between a hard plate 110 and a blade 120 among a plurality of hard plates 110 and a blade 120, And positioning the second welded portion 300 using the second welded material on the first welded portion 200. The hardness of the first welded portion 200 is determined by the following equation: Is higher than the first connecting portion and lower than the second welding portion (300).

First, a first welding material is welded on a first connection part formed by the hard plate 110 and the blade 120 to form a first welding part 200.

After forming the first welding portion 200, the second welding portion 300 is formed by welding the second welding material on the first welding portion 200.

Thus, the hard plate 110 and the blade 120 are connected to each other through a welded portion forming a multi-layered path. The description of the first welding portion 200 and the second welding portion 300 will be described with reference to the above description of the fan impeller.

The method of welding the fan impeller according to the present invention can be applied to the manufacturing process of the fan impeller and can be applied to the repair process of the fan impeller which is already in use.

When the fan impeller is being used in the repair process, the end plate 110 and the blade 120 may be connected through a conventional welding material. Accordingly, the first welded portion 200 can be formed on the existing welded portion.

Before the step of positioning the first welding portion 200, it may further include a process of hardening the surface of the first connection portion. The surface of the first connection portion may be processed by a method such as shot peening to improve the hardness.

Prior to the step of positioning the first welded portion 200, the step of preheating the main body 100 may further include the step of preheating the main body 100. In the heat-treating step, it may be preheated at a temperature of 100 to 300 ° C for 0.5 to 1 hour.

The purpose of the preheating may be to remove the internal stress of the main body 100 to secure toughness and ductility. Therefore, before welding, the main body 100 can be preheated at a temperature of 100 to 300 占 폚.

The method for welding a fan impeller according to an embodiment of the present invention includes disposing the boss 500 in the through hole formed in the main body 100 to position the end plate 110 and the second connection portion Positioning the third welding portion 600 on the second connecting portion using the first welding material and placing the fourth welding portion 700 on the third welding portion 600 using the second welding material And the hardness of the third weld is higher than that of the second weld and may be lower than that of the fourth weld.

The description of the boss 500, the third welding portion 600, and the fourth welding portion 700 will be described with reference to the above description of the fan impeller.

Hereinafter, specific examples of the present invention will be described. However, the following examples are only a concrete example of the present invention, and the present invention is not limited to the following examples.

Example  And Comparative Example

[Preparation of Test Specimens]

Specimens 1 to 5 were prepared by welding weld materials satisfying the following Table 1.

In the case of specimen 1, the specimen is made of an alloy satisfying the composition of the first weld material in the fan impeller according to the present invention, and in the case of specimen 2, made of an alloy satisfying the composition of the second weld material.

Specimens 3 to 5 are specimens made of an austenitic material or an alloy that does not satisfy the composition range of the first weld material or the second weld material.

division C
(weight%) Cr
(weight%) Ni
(weight%) Si
(weight%) Mn
(weight%) Mo
(weight%) Nb
(weight%) Psalm 1 0.10 18.5 8.6 0.41 6.7 - - Psalm 2 0.4 25 - - 2.0 0.7 1.5 Psalm 3 0.07 21 7.5 0.2 3.0 - - Psalm 4 0.08 23 6.5 0.3 2.0 - - Psalm 5 0.15 13 6.0 0.2 1.5 - -

After preparing the specimens 1 to 5 satisfying the composition shown in Table 1, the abrasion resistance, the hardness and the elongation were respectively tested and evaluated.

Abrasion resistance (KS M ISO5407), hardness (ASTM E18) and elongation (ASTM A370) were measured by the test method according to the respective standard specifications.

The measurement results are shown in Table 2 below.

Wear rate
¹ x ^{10 -13} m ³ / m Hardness (HRC) Elongation (%) Psalm 1 640 32 41 Psalm 2 80 60 20 Psalm 3 790 29 34 Psalm 4 790 29 33 Psalm 5 490 34 30

Meanwhile, in order to compare the effect of the welded portion of the fan impeller according to the present invention in the case where the welded portion is made of a multi-layered path and the hardness is increased toward the upper layer and the ductility is low, Examples and Comparative Examples were prepared under the following conditions.

In the embodiment, the same welding material as the specimen 1 was welded on the HT 50 steel plate, and then the same welding material as the specimen 2 was welded.

In Comparative Example 1, a weld material having the same composition as that of Specimen 2 was welded on the HT50 steel plate, and the same welding material as that of the specimen 1 was welded.

In Comparative Example 2, the same welding material as the specimen 3 was welded on the HT 50 steel plate.

In Comparative Example 3, the same welding material as the specimen 4 was welded on the HT 50 steel plate.

In Comparative Example 4, the same welding material as the specimen 5 was welded on the HT 50 steel plate.

Weld configuration Weld thickness Welding Heat Affecting Organization
Martensite area fraction (%) Example Specimen 1 (first layer) /
Sample 2 (second layer) 15mm A + F + M mixed tissue
A: austenite, F: ferrite, M: martensite
Martensite area fraction: 18% Comparative Example 1 Specimen 3 (single layer) 15mm A + F + M mixed tissue
A: austenite, F: ferrite, M: martensite
Martensite area fraction: 20% Comparative Example 2 Specimen 4 (single layer) 15mm A + F + M mixed tissue
A: austenite, F: ferrite, M: martensite
Martensite area fraction: 20% Comparative Example 3 Specimen 5 (single layer) 15mm A + F + M mixed tissue
A: austenite, F: ferrite, M: martensite
Martensite area fraction: 23%

The area fraction of martensite is the result of analyzing the specimen using Electron Back Scattered Diffraction (EBSD).

As can be seen from the above Table 3, in the case of the two-layered embodiment, the martensite area fraction was 18%, but in the case of Comparative Examples 1 to 3, it exceeded 18%. In the case of the example, it is confirmed that since the specimen 2 is formed on the outermost layer, the abrasion resistance is the most excellent and the durability is superior to those of Comparative Examples 1 to 3. [

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims and their equivalents. It will be understood that the invention may be embodied in other specific forms without departing from the spirit or scope of the invention. It is therefore to be understood that the embodiments and / or the examples described above are illustrative in all aspects and not restrictive.

100: main body 110: hard plate
111: one side plate 112:
113: the other end plate 120: the blade
200: first welding portion 300: second welding portion
400: welding heat affected part 410: first heat affected part
420: second heat affected part 500: boss
600: third welding part 700: fourth welding part

Claims (16)

A body made of a plurality of hard disks and blades;
A first weld positioned on a first connection formed between the hard plate and the blade; And
And a second weld portion positioned on the first weld portion,
Wherein the hardness of the first weld is higher than that of the first weld and lower than that of the second weld. The method according to claim 1,
Wherein the ductility of the first weld is higher than that of the second weld. The method according to claim 1,
A welding heat affected part is formed below the second welding part and around the first connection part,
And the area fraction of the martensite structure of the weld heat affected zone is 18% or less. The method according to claim 1,
The main body is made of an alloy material containing carbon (C) having a content of 0.3% or less based on 100% of the total weight,
Wherein the first welding portion is made of a first welding material having a higher content of carbon (C) than the alloy,
And the second welding portion is made of a second welding material having a higher content of carbon (C) than the first welding material. 5. The method of claim 4,
Wherein the first welding material and the second welding material each contain chromium (Cr)
Wherein the chromium (Cr) content of the second weld bead is greater than the chromium (Cr) content of the first weld bead. 5. The method of claim 4,
Wherein the first welding material comprises:
(Cr): 14 to 20%, nickel (Ni): 6 to 10%, silicon (Si): 0.3 to 0.6%, manganese (Mn): 0.08 to 0.10% 4 to 8%, balance iron (Fe) and other inevitable impurities. 5. The method of claim 4,
The second welding material may be formed,
(Ni): 0.5 to 1.5% of molybdenum (Mo), 0.5 to 1.5% of molybdenum (Mo), and 1 to 4% of chromium (Cr) 1.5 to 3.0%, balance iron (Fe) and other inevitable impurities. The method according to claim 1,
Wherein the hardness of the first weld is 30 to 33 HRC and the hardness of the second weld is 55 to 62 HRC. The method according to claim 1,
A boss which passes through the through hole formed in the main body and is connected to the end plate to form a second connection portion;
A third weld positioned on the second connection; And
And a fourth weld located on the third weld,
Wherein the hardness of the third weld is higher than that of the second joint and lower than that of the fourth weld. A structure made up of a plurality of members;
A first weld layer located at the joint formed between the members; And
And a second weld layer positioned on the first weld layer,
Wherein the hardness of the first weld layer is higher than the joint and lower than the second weld layer. 11. The method of claim 10,
Wherein the ductility of the first weld layer is higher than the second weld layer. Positioning a first welded portion using a first welded material on a first connection portion formed between the hard plate and the blade among a plurality of hard plates and blades; And
Positioning the second weld on the first weld using a second weld,
Wherein the hardness of the first weld is higher than that of the first weld, and the hardness of the first weld is lower than that of the second weld. 13. The method of claim 12,
Before the step of positioning the first weld,
Further comprising: machining the surface of the first connection portion. 13. The method of claim 12,
Before the step of positioning the first weld,
And preheating the body. ≪ Desc / Clms Page number 16 > The method according to claim 14,
In the preheating step,
Wherein the preheating is carried out at a temperature of 100 to 200 DEG C for 0.5 to 1 hour. 13. The method according to claim 12,
After the step of positioning the second weld,
Placing a boss in a through-hole formed in the body to form the end plate and the second connection portion;
Positioning the third weld on the second connection using the first weld; And
And positioning the fourth weld on the third weld using the second weld,
Wherein the hardness of the third weld is higher than that of the second weld, and the hardness of the third weld is lower than that of the fourth weld.

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