JP6965794B2 - Manufacturing method of locally reinforced parts and locally reinforced parts - Google Patents

Description

The present invention relates to a method for manufacturing a locally reinforced part and a locally reinforced part.

Laser quenching technology for increasing the strength of steel materials is known. In this technology, the structure is transformed by the heat input by the laser to strengthen the strength of the steel material.
Further, as a laser quenching technique, _{there is disclosed a technique of quenching a workpiece subjected to MoS 2} film treatment with a laser to increase the surface hardness and improve the wear resistance (see, for example, Patent Document 1).
A carburizing and quenching technique for increasing the strength of steel materials is also known. In this technique, a steel material is exposed to a carbon atmosphere, carbon is diffused from the surface of the steel material to increase the carbon concentration in the surface layer, and quenching is performed in this state to improve the strength of the steel material.

Japanese Unexamined Patent Publication No. 7-242931

However, the laser quenching technique has a problem that it is difficult to improve the strength in the depth direction because the heat input range is only the surface layer of a steel material or the like.
Further, the carburizing and quenching technique has a problem that since carbon is diffused from the surface, it is difficult for carbon to diffuse to the inside and it takes a long time to carburize.
The present invention has been made in view of the above circumstances, and is a method for manufacturing a locally reinforced part that can be reinforced to a position deeper than the surface of a part made of steel in a short time, and a locally reinforced locally to a deep position. The purpose is to provide reinforced parts. The present invention can be realized as the following forms.

[1] A coating step of applying a reinforcing element-containing substance containing an element that enhances the strength of the steel to at least a part of the surface of a part made of steel.
A method for manufacturing a locally reinforced part, comprising a melting step of melting a portion coated with the reinforced element-containing material together with the reinforced element-containing material.
A method for manufacturing a locally reinforced part, which comprises locally increasing the strength of the portion coated with the reinforcing element-containing substance.

[2] The reinforcing element-containing material is characterized by containing one or more elements selected from the group consisting of C, Si, Mn, Cr, Mo, V, W, Ni, Co, B, and Ti. , [1]. The method for manufacturing a locally reinforced component.

[3] The method for manufacturing a locally reinforced component according to [1] or [2], wherein the melting step is a step of utilizing laser light irradiation or a step of utilizing arc discharge.

[4] The method for manufacturing a locally reinforced part according to any one of [1] to [3], wherein the steel is a low carbon steel.

[5] The element is C.
The method for manufacturing a locally reinforced component according to any one of [1] to [4], wherein the strength-enhanced portion is substantially composed of only martensite structure.

[6] A locally reinforced part made of steel.
Reinforcing parts extending in the thickness direction from the surface layer to the inside are locally formed.
The strengthened portion is stronger than the peripheral portion of the strengthened portion, and is also strengthened.
The reinforced portion is a locally reinforced component characterized in that the content of an element that enhances the strength of the steel is larger than that of the peripheral portion.

[7] The element is one or more selected from the group consisting of C, Si, Mn, Cr, Mo, V, W, Ni, Co, B, and Ti, according to [6]. Described locally reinforced parts.

[8] The locally reinforced component according to [6] or [7], wherein the steel is a low carbon steel.

[9] The element is C.
The locally reinforced component according to any one of [6] to [8], wherein the reinforced portion is substantially composed of only martensite structure.

<Effect of manufacturing method>
According to the method for manufacturing a locally reinforced part of the present invention, since the reinforced element-containing material is applied and the applied portion is melted together with the reinforced element-containing material, it can be reinforced to a position deeper than the surface of the steel part. .. Further, since the reinforcing element-containing material is not diffused from the surface but the applied portion is melted together with the reinforcing element-containing material, it can be strengthened in a short time.
When the reinforcing element-containing material contains one or more elements selected from the group consisting of C, Si, Mn, Cr, Mo, V, W, Ni, Co, B, and Ti, a remarkable strength improving effect is achieved. Is obtained.
When the melting step is a step using laser light irradiation or a step using arc discharge, the step is not complicated and is advantageous in terms of cost.
When the steel is low carbon steel, it remains low carbon steel except for the reinforced portion, so that general welding can be performed at this portion.
When the element is C and the strength-enhanced portion is substantially composed of only the martensite structure, a remarkable strength-improving effect can be obtained.

<Effect of locally reinforced parts>
When a strengthening portion extending from the surface layer to the inside in the thickness direction is formed, and the content of the element to be strengthened in the strengthening portion is larger than that in the peripheral portion, a remarkable strength improving effect is obtained as compared with the strengthening of only the surface layer. can get.
When the reinforcing element-containing material contains one or more elements selected from the group consisting of C, Si, Mn, Cr, Mo, V, W, Ni, Co, B, and Ti, a remarkable strength improving effect is achieved. Is obtained.
When the steel is low carbon steel, it remains low carbon steel except for the reinforced portion, so that general welding can be performed at this portion.
When the element is C and the strength-enhanced portion is substantially composed of only the martensite structure, a remarkable strength-improving effect can be obtained.

The present invention will be further described in the following detailed description with reference to the plurality of references mentioned, with reference to non-limiting examples of typical embodiments according to the invention.
It is a schematic diagram explaining the manufacturing method of the locally reinforced part. It is a schematic diagram explaining the manufacturing method of the locally reinforced part. It is sectional drawing which shows the measurement point of the hardness distribution of the comparative example 1. FIG. It is sectional drawing which shows the measurement point of the hardness distribution of Example 1. FIG. It is a comparison result of hardness distribution. It is a comparison result of carbon content distribution. It is sectional drawing which shows the measurement point of the hardness distribution of the comparative example 1. FIG. The region surrounded by the alternate long and short dash line in this figure is the carbon content distribution measurement region (2.0 mm × 0.5 mm). It is sectional drawing which shows the measurement point of the hardness distribution of Example 1. FIG. The region surrounded by the alternate long and short dash line in this figure is the carbon content distribution measurement region (2.0 mm × 0.5 mm). It is a measurement result of the hardness distribution of Comparative Example 1. It is a measurement result of the hardness distribution of Example 1. It is a measurement result of the carbon content distribution of Comparative Example 1. It is a measurement result of the carbon content distribution of Example 1. It is a structure photograph of a steel plate not irradiated with a laser. It is a tissue photograph of the strengthening part of Comparative Example 1. It is an organization photograph of the strengthening part of Example 1. It is a top view which shows the gear component (sector gear) which is an example of a locally strengthening component. The shaded area is the locally reinforced reinforced part.

The matters shown here are for exemplifying and exemplifying embodiments of the present invention, and are considered to be the most effective and effortless explanations for understanding the principles and conceptual features of the present invention. It is stated for the purpose of providing what seems to be. In this regard, it is not intended to show structural details of the invention beyond a certain degree necessary for a fundamental understanding of the invention, and some embodiments of the invention are provided by description in conjunction with the drawings. It is intended to clarify to those skilled in the art how it is actually realized.

Hereinafter, embodiments of the present invention will be described in detail. In this specification, the description using "~" for the numerical range shall include the lower limit value and the upper limit value unless otherwise specified. For example, in the description of "10 to 20", both the lower limit value "10" and the upper limit value "20" are included. That is, "10 to 20" has the same meaning as "10 or more and 20 or less".

1. 1. Manufacturing Method of Locally Reinforced Parts The manufacturing method of locally strengthened parts of the present invention includes a coating step of applying a reinforcing element-containing substance containing an element that strengthens the strength of steel to at least a part of the surface of a part made of steel. It is provided with a melting step of melting the portion coated with the reinforcing element-containing material together with the reinforcing element-containing material. Then, the method for producing a locally reinforced component of the present invention locally increases the strength of the portion coated with the reinforcing element-containing substance.

The "steel" is not particularly limited, but low carbon steel and alloy steel are preferably used. For example, it is composed of cold-rolled steel sheet (JISG3141), hot-rolled steel sheet (JISG3131), processed high-strength steel sheet for automobiles (JISG3134 / 3135), carbon steel for machine structure (JISG4051), and alloy steel for machine structure (JISG4053). At least one selected from the group can be mentioned as a suitable example.

The "parts" are not particularly limited. The shape and size of the parts are appropriately selected according to the application. Examples of the parts include frame parts such as side back frames, rail parts for sliding seats, gear parts such as sector gears (see FIG. 16), and the like. There is a desire to locally increase the strength of these parts. For example, there is a request to locally increase the strength of the tooth portion of the gear component (see the shaded portion in FIG. 16) and the edge portion of the frame component and the rail component. The edges of frame parts and rail parts are non-welded parts, and by strengthening the edges, they function as reinforcing parts.
As the parts, a part in which a steel plate is processed can be preferably exemplified. The thickness of the steel plate at this time is not particularly limited, but is, for example, 0.6 mm to 6 mm. The processing method is not particularly limited, and for example, press processing, bending processing, spinning processing, and the like are preferably exemplified.

The "reinforcing element-containing substance" is not particularly limited as long as it is a substance containing an element that reinforces the strength of steel, and a wide range of substances can be used.
Reinforcing element-containing substances are C (carbon), Si (silicon), Mn (manganese), Cr (chromium), Mo (molybdenum), V (vanadium), W (tungsten), Ni (nickel), Co (cobalt). , B (boron), and Ti (tungsten), preferably containing one or more elements selected from the group.
As the reinforcing element-containing material, a carbon-containing material and an intermetallic compound are preferable.
Grease and press oil are preferably exemplified as the carbon-containing material. Grease is a base oil with a thickener added. Examples of the base oil include paraffin-based mineral oil, naphthen-based mineral oil, ester-based synthetic oil, ether-based synthetic oil, hydrocarbon-based synthetic oil, and the like. These can be used alone or as a mixed oil. Examples of the thickener include soaps such as lithium soap, lithium complex soap, calcium soap, calcium complex soap, aluminum soap and aluminum complex soap, and urea compounds such as diurea compounds and polyurea compounds, but are particularly limited. It's not a thing.
As the grease, for example, a grease having a boiling point of 300 to 500 ° C. is preferably used.

In the coating step, the area to which the reinforcing element-containing material is applied is not particularly limited. The amount of the reinforcing element-containing material applied is also not particularly limited. The coating amount is preferably 0.01 mg to 1 g / mm ² , more preferably 0.05 mg to 0.5 mg / mm ² , and further preferably 0.1 mg to 0.3 mg / mm ² . Within this range, the strength can be strengthened not only on the surface of the component but also on the inside.

In the melting step, the portion coated with the reinforcing element-containing material is melted together with the reinforcing element-containing material. The method for dissolving is not particularly limited. For melting, laser light irradiation or arc discharge can be preferably used. Therefore, the melting step is preferably a step of utilizing laser light irradiation or a step of utilizing arc discharge. The step of utilizing the irradiation of laser light is particularly preferable because it is similar to laser welding and can strengthen the local area in a short time. In the step of using the irradiation of the laser beam, the depth of enhancement can be controlled by adjusting the intensity of the laser beam and the irradiation time.

The structure of the portion where the strength is strengthened is not particularly limited. It is preferable that the element for enhancing the strength of the steel is C (carbon), and the portion for which the strength is enhanced is substantially composed of only the martensite structure. In this form, the strength of the reinforced portion is extremely high.
Here, "substantially only martensite tissue" means that the volume fraction other than the martensite tissue is 5% or less. The metal structure is observed with an optical microscope and a scanning electron microscope. For structure observation, a cross-sectional tissue photograph (magnification: 400 to 1000 times) is obtained, and the phase fraction (volume fraction) is measured using an image analyzer.

Here, an estimation mechanism in which the strength of the component is locally increased by using one embodiment of the present manufacturing method will be described with reference to FIGS. 1 and 2. This form is an example in which a step of utilizing laser light irradiation is adopted as the melting step.
First, as shown in FIGS. 1A and 1B, the reinforcing element-containing substance 3 is applied to the surface of the steel component 1.
Subsequently, as shown in FIGS. 2C to 2E, the portion to be strengthened is irradiated with the laser beam 5.
Then, the laser beam 5 is absorbed by the reinforcing element-containing material 3 and the component 1 made of steel, and the temperature rises (see FIG. 2C). At this time, it is presumed that the reinforcing element-containing substance 3 is decomposed to reduce the molecular weight. At this time, a part of the reinforcing element-containing substance 3 may evaporate (vaporize) (see FIG. 2 (D)). In FIG. 2D, a part of the reinforcing element-containing substance 3 is shown to have evaporated.
Then, the steel component 1 begins to melt and the molten pool 7 is formed (see FIG. 2E). At this time, convection occurs in the molten pool 7 and the inside of the molten pool 7 is agitated. By this stirring, an element (for example, carbon) derived from the reinforcing element-containing material 3 is involved in the molten pool 7, and as a result, this element and steel are mixed.
Subsequently, the molten pool 7 containing the element derived from the reinforcing element-containing substance 3 releases heat around it and solidifies (see FIG. 2 (F)). Since the molten pool 7 is rapidly cooled during solidification, it is considered that the strength of the molten portion 9 derived from the molten pool 7 is improved. In this manufacturing method, the elements derived from the reinforcing element-containing substance 3 are dispersed in the entire molten portion 9, and the entire molten portion 9 is strengthened.
In this description, FIGS. 1 (A) and 1 (B) correspond to the coating process, and FIGS. 2 (C) to 2 (E) correspond to the melting process.

2. Locally reinforced parts Locally reinforced parts are made of steel. In the locally reinforced component, a reinforced portion extending in the thickness direction from the surface layer to the inside is locally formed. The strength of the reinforced portion is stronger than that of the peripheral portion of the reinforced portion. Further, the strengthened portion has a higher content of the element for strengthening the strength of the steel than the peripheral portion.

As for "steel", the description of "steel" in "1. Manufacturing method of locally reinforced parts" can be applied as it is.
As for "parts", the description of "parts" in "1. Manufacturing method of locally reinforced parts" can be applied as it is.
The "reinforced portion" is formed so as to extend in the thickness direction from the surface layer of the locally reinforced component to the inside, and the depth thereof is not particularly limited. In the case of a part in which a steel plate is processed, the depth of the reinforced portion is preferably the depth of the entire plate thickness rather than a part of the plate thickness. By forming the reinforced portion for the entire plate thickness, the strength as a part can be improved. Here, the strengthening of the entire plate thickness means the strengthening of the locally strengthened part over the entire thickness direction from one surface (front surface) to the other surface (back surface).
The reinforced portion is locally formed, but here, "locally formed" means that the reinforced portion is formed not all but a limited part of the locally reinforced part. The local area is appropriately adjusted depending on the use and type of the part.

It can be confirmed, for example, that the reinforced portion is strengthened more than the peripheral portion of the reinforced portion by comparing the Vickers hardness of the reinforced portion with the Vickers hardness of the unreinforced peripheral portion.
For example, a case where the Vickers hardness of the reinforced portion is 350 to 550 Hv higher than the Vickers hardness of the peripheral portion can be exemplified. The Vickers hardness is measured in accordance with JIS Z2244 (measurement load 300 g). The measurement position of the sample is pushed in with a Vickers indenter with a specified load (300 g), and the Vickers hardness is obtained from the size of the formed square depression (two diagonal lengths) by the following formula.

Further, for example, when the steel is low carbon steel, the Vickers hardness of the reinforced portion can be set to, for example, 500 to 700 Hv. When the steel is low carbon steel, the Vickers hardness of the unreinforced peripheral portion is 150 to 170 Hv.

The strengthened portion contains a larger amount of elements that strengthen the strength of the steel than the peripheral portion. "Elements that enhance the strength of steel" are C (carbon), Si (silicon), Mn (manganese), Cr (chromium), Mo (molybdenum), V (vanadium), W (tungsten), Ni (nickel). , Co (cobalt), B (boron), and Ti (tungsten), and one or more elements selected from the group are preferable.
The content of the element that strengthens the strength of the steel in the strengthened portion differs depending on the type of the element and the like. When the element is C (carbon), the content in the strengthening portion is preferably 0.2 to 0.5% by mass.

The structure of the portion where the strength is strengthened is not particularly limited. It is preferable that the element for enhancing the strength of the steel is C (carbon), and the portion for which the strength is enhanced is substantially composed of only the martensite structure. In this form, the strength of the reinforced portion is extremely high.
Here, "substantially only martensite tissue" means that the volume fraction other than the martensite tissue is 5% or less. The metal structure is observed with an optical microscope and a scanning electron microscope. For structure observation, a cross-sectional tissue photograph (magnification: 400 to 1000 times) is obtained, and the phase fraction (volume fraction) is measured using an image analyzer.

1. 1. Sample preparation (Example 1)
A steel plate having a thickness of 1 mm made of low carbon steel was used. Grease (mineral oil) was applied to the surface of the steel sheet. Then, the grease-coated portion was irradiated with a YAG laser. The output of the YAG laser was 4 kW. The boiling point of the grease was 300 to 500 ° C.
(Comparative Example 1)
A sample was prepared in the same manner as in Example 1 except that no grease was applied.

2. Comparison of hardness distribution (1) Measurement method The Vickers hardness was measured in the cross section of the sample of Comparative Example 1 shown in FIG. The measurement point was on the line indicated by the arrow in FIG. That is, it is the center in the thickness direction in the sample cross section, and the center position where the YAG laser is irradiated is set as 0 point, and the measurement points are set at substantially equal intervals from this 0 point to the minus side (left side). For example, "-1 mm" means a measurement point 1 mm away from the 0 point on the left side.
In the case of the sample of Example 1, as shown in FIG. 4, the measurement points were set in the same manner as the sample of Comparative Example 1.

(2) Measurement results Fig. 5 shows the measurement results. The region described as "strengthening portion" in FIG. 5 means a portion melted by being irradiated with a YAG laser. That is, the "strengthening part" is synonymous with the melting part. The region described as "HAZ portion" means a region that has not been irradiated with the YAG laser but has been affected by heat. HAZ is an abbreviation for Heat Affected Zone. The region described as "peripheral portion" means a portion that is not irradiated with the YAG laser and is hardly affected by heat. The "peripheral part" is the material itself of low carbon steel, and is the part where the properties of the material have not changed substantially. That is, the "peripheral part" is synonymous with the material part. In addition, "reinforcing part", "HAZ part", and "peripheral part" have the same meanings below.
Looking at FIG. 5, it can be seen that the Vickers hardness of the reinforced portion of Example 1 is much higher than the Vickers hardness of the reinforced portion of Comparative Example 1.
Further, from FIG. 5, it was confirmed that in Example 1, the Vickers hardness of the reinforced portion was much higher than that of the peripheral portion. On the other hand, in Comparative Example 1, it was confirmed that the Vickers hardness of the reinforced portion was only slightly higher than that of the peripheral portion.

3. 3. Comparison of carbon content distribution (1) Measurement method An electron probe microanalyzer (EPMA) was used to analyze the carbon content distribution (quantitative) of the cross section of the sample. The measurement conditions are as follows.

Pressurized voltage: 15V
Beam size: 2 μm
Current: 0.15 μA
The measurement points were the same as in "2. Comparison of hardness distribution".

(2) Measurement results Fig. 6 shows the measurement results.
From the results of FIG. 6, it was confirmed that in Example 1, the carbon content of the reinforced portion was higher than that of the peripheral portion. On the other hand, in Comparative Example 1, it was confirmed that the carbon content of the reinforced portion was equivalent to that of the peripheral portion.

4. Comparison of hardness distribution (analysis in the thickness direction)
(1) Measurement method The Vickers hardness was measured in the cross section of the sample of Comparative Example 1 shown in FIG. The measurement points were on the three lines indicated by the arrows in FIG. That is, at three depths in the sample cross section in the thickness direction, near the front surface (upper arrow), in the center (center arrow), and near the back surface (lower arrow), the center position where the YAG laser is irradiated is set as 0 point. Measurement points were set at approximately equal intervals from this 0 point to the minus side (left side).
In the case of the sample of Example 1, as shown in FIG. 8, the measurement points were set in the same manner as the sample of Comparative Example 1.

(2) Measurement result FIG. 9 shows the measurement result of Comparative Example 1. The description "front surface" in FIG. 9 means "near the front surface", and the description "back surface" means "near the back surface".
In Comparative Example 1, it was confirmed that the Vickers hardness of the reinforced portion was only slightly higher than that of the peripheral portion in any of the vicinity of the front surface, the center, and the vicinity of the back surface.
FIG. 10 shows the measurement results of Example 1. In Example 1, it was confirmed that the Vickers hardness of the reinforced portion was much higher than that of the peripheral portion in any of the vicinity of the front surface, the center, and the vicinity of the back surface.

5. Comparison of carbon content distribution (analysis in the thickness direction)
(1) Measurement method An electron probe microanalyzer (EPMA) was used to analyze the carbon content distribution (quantitative) of the cross section of the sample. The measurement conditions are as follows.

Pressurized voltage: 15V
Beam size: 2 μm
Current: 0.15 μA

(2) Measurement result FIG. 11 shows the measurement result of Comparative Example 1. FIG. 11 shows the carbon content distribution in the region (2.0 mm × 0.5 mm) surrounded by the alternate long and short dash line in FIG. 7. The front side of FIG. 11 is the front side, and the back side is the back side. The higher the mountain, the higher the carbon content. In Comparative Example 1, the height of the mountain is substantially the same at any location in the measurement area. From this, it was confirmed that in Comparative Example 1, the carbon content of the reinforced portion was equivalent to that of the peripheral portion.
FIG. 12 shows the measurement results of Example 1. FIG. 12 shows the carbon content distribution in the region (2.0 mm × 0.5 mm) surrounded by the alternate long and short dash line in FIG. The front side of FIG. 12 is the front side, and the back side is the back side. The higher the mountain, the higher the carbon content. In the first embodiment, the height of the mountain of the strengthening portion is large. From this, it was confirmed that in Example 1, the carbon content of the reinforced portion was higher than that of the peripheral portion. Further, in FIG. 12, the height of the mountain of the strengthening portion is increased from the front side to the back side. From this, it was confirmed that in Example 1, the carbon content of the reinforced portion was high in all of the vicinity of the front surface, the center, and the vicinity of the back surface.

6. Observation of metal structure (1) Measurement method The metal structure was observed with an optical microscope. The structures of the steel sheet (material) not irradiated with the laser, the strengthened portion of Comparative Example 1, and the strengthened portion of Example 1 were confirmed.
(2) Measurement result FIG. 13 shows a photograph of a steel plate not irradiated with a laser. The left side is a 400x photo and the right side is a 1000x photo. From these photographs, it was found that the steel sheet not irradiated with the laser had a pearlite structure. The pearlite structure consists of a ferrite structure that appears white in the photograph and a cementite structure that appears black.
FIG. 14 shows a photograph of the strengthened portion of Comparative Example 1. The left side is a 400x photo and the right side is a 1000x photo. From these photographs, it was confirmed that the strengthened portion of Comparative Example 1 had a martensite structure and a ferrite structure.
FIG. 15 shows a photograph of the strengthened portion of Example 1. The left side is a 400x photo and the right side is a 1000x photo. From these photographs, it was confirmed that the strengthening part of Example 1 consisted only of martensite tissue.

7. Summary It was confirmed that when grease is applied to the surface of the steel sheet and the applied part is irradiated with a laser, it can be strengthened to a position deeper than the surface of the steel sheet. It was also confirmed that the carbon content of the reinforced portion was higher than that of the peripheral portion. It was also found that the strengthening department consisted only of martensite organization.
According to this embodiment, the required parts of the parts made of weldable low carbon steel can be selectively strengthened.
In addition, since not only the surface layer of the part but also the inside can be strengthened, the strength can be ensured even if the wall thickness is thinner than that of the conventional part, so that the weight reduction effect can be expected.

The above examples are for illustration purposes only and are not to be construed as limiting the invention. Although the present invention has been described with reference to typical embodiments, the language used in the description and illustration of the invention is understood to be descriptive and exemplary rather than restrictive. As described in detail here, modifications can be made within the scope of the appended claims without departing from the scope or nature of the invention in that form. Although specific structures, materials and examples have been referred to herein in detail of the invention, it is not intended to limit the invention to the disclosures herein, but rather the invention is claimed in the accompanying claims. It shall cover all functionally equivalent structures, methods and uses within the scope.

The present invention is not limited to the embodiments detailed above, and various modifications or modifications can be made within the scope of the claims of the present invention.

1 ... Parts 3 ... Reinforcing element-containing material 5 ... Laser light 7 ... Melting pond 9 ... Melting part

Claims (7)

A coating step of applying a reinforcing element-containing substance containing an element that enhances the strength of the steel to at least a part of the surface of a steel component.
A method for manufacturing a locally reinforced part, comprising a melting step of melting a portion coated with the reinforced element-containing material together with the reinforced element-containing material.
The reinforcing element-containing material is selected from the group consisting of grease and press oil.
Locally increase the strength of the portion coated with the reinforcing element-containing substance ,
The strength-enhanced portion consists essentially of martensite structure only.
Said part, the volume fraction of non-martensitic structure is characterized in der Rukoto 5%, the production method of the local reinforced component. The coating amount of the reinforcing element-containing material is 0.01 mg to 1 g / mm. ² The method for manufacturing a locally reinforced component according to claim 1. The method for manufacturing a locally reinforced component according to claim 1 or 2, wherein the melting step is a step using irradiation of laser light or a step using arc discharge. The method for manufacturing a locally reinforced part according to any one of claims 1 to 3, wherein the steel is a low carbon steel. A locally reinforced part made of steel
Reinforcing parts extending in the thickness direction from the surface layer to the inside are locally formed.
The strengthened portion is stronger than the peripheral portion of the strengthened portion, and is also strengthened.
The reinforcing portion, the content of elements to enhance the strength of the steel much larger than the said peripheral portion,
The strengthening part consists substantially only of martensite structure.
The reinforcing portion, the volume fraction of non-martensitic structure is characterized in der Rukoto 5%, local reinforced component. The locally reinforced component according to claim 5 , wherein the element is C. The locally reinforced component according to claim 5 or 6 , wherein the steel is a low carbon steel.

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