JP2004018882A - Method for producing wear-resistant low carbon steel boss member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simply and easily produce a boss member excellent in the wear resistance and the weldability. <P>SOLUTION: High frequency induction-heating is discontinuously applied to a plurality of positions in the end surfaces of the boss member composed of a low carbon steel, and the partial hardened boss member is produced by performing air-cooling to these heated parts. In the high frequency induction-heating and hardening, these parts are heated under condition of 10 to 50 kHz frequency, ≥ 16kW output of the electric source and ≤ 1 sec heating time, and it is desirable to set the length of each partial hardening part to be 5 to 30 mm, the width of each partial hardening part to be 3 to 7 mm, and the distance between the nearest portions in respective hardened parts to be ≥ 1 mm. <P>COPYRIGHT: (C)2004,JPO

Description

【００４６】
表１より明らかなように、本発明によれば、断続的に高周波焼入を行っているため、低炭素鋼であっても所定の硬さに焼入することができる。
【００４７】
【発明の効果】
本発明によれば、焼入性に劣る低炭素鋼からなるボス部材を焼入するに際して高周波誘導加熱及び空冷という焼入しにくい条件を採用しても、非連続的に焼入しているため、焼入硬化することができる。そのため耐摩耗性と溶接性に優れたボス部材を簡便に製造できる。また耐摩耗層が剥離する虞も少ない。
【図面の簡単な説明】
【図１】図１は作業機械の一例を示す概略側面図である。
【図２】図２はボス部材の一例を示す概略断面図である。
【図３】図３はボス部材端面の焼入方法を説明するための概略斜視図である。
【図４】図４はボス部材端面の焼入パターンの一例を示す概略正面図である。
【図５】図５はボス部材端面の焼入パターンの他の例を示す概略正面図である。
【図６】図６はボス部材端面の焼入パターンのさらに他の例を示す概略正面図である。
【図７】図７はボス部材端面の焼入パターンの別の例を示す概略正面図である。
【符号の説明】
１０ａ　ボス部材
１３ａ，１３ｂ　端面
１６ａ〜１６ｆ　部分焼入部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method of manufacturing a boss member useful for rotatably connecting two parts.
[0002]
[Prior art]
As the boss member, for example, a substantially cylindrical boss member used for connection between an arm and a bucket in a construction machine such as a hydraulic shovel is used. The boss member is attached to the distal end side of the arm by welding, and both ends thereof are sandwiched by a pair of bracket portions extending from the bucket. Then, the bucket is pivotally attached to the tip of the arm by penetrating the boss member and the bracket portion with the connecting pin.
[0003]
The boss member has an end surface which is in contact with the bracket and is formed to be protruded. When a thrust load acting on the boss portion or the bracket portion is received by the end surface, the thrust direction of the bracket portion with respect to the boss portion (axial direction of the connection pin) ) To prevent rattling.
[0004]
In such a hydraulic excavator, a can-made structure using a rolled steel plate for a welding structure such as SMC490 (JIS G3160) is used as the arm, while the boss member fixed to the end of the arm by welding is used. In general, a low-carbon steel material represented by S30C is used for the purpose of welding to the arm, that is, for the purpose of welding without preheating.
[0005]
However, since the bucket handles a large amount of earth and sand, earth and sand or the like frequently intrudes into a small gap between the end surface of the boss and the bracket. Since the boss member made of a low carbon steel material such as S30C has poor hardenability, that is, it is not possible to increase the hardness so much even when heat treatment is performed by air cooling, so that the end face of the boss portion is significantly worn. If the end face of the boss part is worn, the gap in the thrust direction between the boss part and the bracket part becomes large, causing rattling. Will encourage.
[0006]
As a method for enhancing the wear resistance of the sliding material, not the end face, for example, in Japanese Patent Application Laid-Open No. Hei 2-173212, a sliding surface (outer peripheral surface) of a shaft-like member is conveyed by a converged high-density heat source (laser beam , An electron beam, a TIG arc, a plasma arc, etc.) to locally heat and quench and harden, and remove the uncured portion to form a hard convex portion and a non-hard concave portion on the sliding surface (outer peripheral surface). It is disclosed. Although the concentrated high-density heat source is a useful technique for quenching low-hardenability low-carbon steel, it can only be heated in a pinpoint manner. It is necessary to continue heating for a long time while shifting the heating unit, and the productivity is extremely low, and practical application is difficult.
[0007]
On the other hand, a method of curing the end face of the boss member is disclosed in, for example, JP-A-9-184518 and JP-A-2001-329356. In these publications, it is proposed to leave quenching in order to actually increase the wear properties of low carbon steel with low hardenability. That is, it discloses that a wear-resistant material such as a cemented carbide material or a ceramic material is sprayed on the end surface of the boss portion to form a wear-resistant layer. However, in this method, since it takes time to melt the cemented carbide material or the ceramic material for thermal spraying, the productivity is still insufficient. Further, since the wear-resistant layer has poor impact resistance, it may be cracked or partially peeled off. Furthermore, skill is required to form a uniform wear-resistant layer, and the cost of materials and incidental equipment including thermal spraying equipment becomes expensive, which is a major factor in cost increase.
[0008]
Therefore, a technique for easily producing a boss member having excellent wear resistance and weldability has not yet been established.
[0009]
[Problems to be solved by the invention]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for easily manufacturing a boss member having excellent wear resistance and weldability.
[0010]
Another object of the present invention is to provide a method for manufacturing a boss member that can achieve both weldability and wear resistance and that does not peel off the wear-resistant layer.
[0011]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the inventors of the present invention, in the course of intensive research, first use a boss member of low carbon steel to secure weldability, and improve the wear resistance of this low carbon steel. For this reason, we focused on induction hardening. This is because induction hardening does not require a large-scale quenching device and is excellent in work efficiency, and is considered to be useful for easily increasing the wear resistance of the low carbon steel boss member. In particular, if the cooling condition of the induction hardening is air-cooled, it is considered to be extremely useful because water cooling equipment is not required and the high-frequency power supply capacity can be reduced. However, it has been considered that low-carbon steel cannot be quenched by a combination of high-frequency induction heating and air cooling. The inventors of the present invention also cannot quench hardening when induction hardening is performed entirely, and harden continuously (for example, in a spiral shape) even when partially induction hardening. In this case, it was confirmed that quenching could not be performed to a high hardness. However, it has been found that when quenching is discontinuous (for example, intermittently), even in induction quenching, quenching with high hardness is found contrary to the common technical knowledge, and the present invention has been completed.
[0012]
That is, the method for manufacturing a wear-resistant low-carbon steel boss member according to the present invention includes the steps of discontinuing the end face of a boss member made of low-carbon steel (for example, low-carbon steel having a carbon content of about 0.4% by mass or less). The present invention has a gist in that high-frequency induction heating is performed over a plurality of locations and the heating part is air-cooled, and a partially quenched boss member is manufactured. When performing partial quenching discontinuously, for example, the following steps 1 to 4 may be repeated a plurality of times in this order.
[0013]
1: A high-frequency coil having a heating conductor portion having an area substantially equal to the area of the part to be partially quenched is brought close to the end surface of the boss member. 2: The boss member is partially induction-heated by energizing the high-frequency coil. 3: Stop the energization of the high-frequency coil to cool down the air 4: Allow the high-frequency coil to move relatively to the vicinity of another part to be partially quenched while stopping the energization May form a discontinuous pattern, and a method of discontinuously forming a high-frequency partial quenched portion by bringing the combination coil close to the end face may be adopted. In the high frequency partial quenching, heating is performed under the conditions of a frequency of 10 to 50 kHz, a power output of 16 kW or more, and a heating time of 1 second or less, the length of each partial quenched portion is 5 to 30 mm, and the width of each partial quenched portion is 3 to 7 mm. It is desirable to make the distance between the re-adjacent portions of the quenched portions 1 mm or more.
[0014]
In addition, in this specification, the term "air cooling" is used to include natural cooling at room temperature. In the present specification, the hardness (HRC) of the quenched portion means a value obtained by rounding off the first decimal place (excluding the column of Examples).
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be specifically described with reference to the drawings as appropriate. However, the present invention is not necessarily limited to the illustrated examples, and may be appropriately modified within a range that can conform to the purpose of the preceding and following descriptions. The present invention can be implemented, and all of them are included in the technical scope of the present invention. In the illustrated example, the same components are denoted by the same reference numerals, and redundant description will be avoided.
[0016]
FIG. 1 is a schematic side view of a hydraulic excavator having a boss member obtained by the present invention at an arm tip, and FIG. 2 is an enlarged sectional view of the arm tip. In this excavator 1, a boom 3 extending from a vehicle body 2, an arm 4 rotatably connected to a tip of the boom 3, a rotatably connected to a tip of the arm 4, and processing of earth and sand. The working part 6 is constituted by a bucket 5 for operating the boom 3, the arm 4, and the bucket 5, which are organically movable by telescopic hydraulic cylinders 7 a, 7 b, and 7 c connected to each other. Earth and sand can be processed freely.
[0017]
In such a hydraulic excavator 1, the connection between the bucket 5 and the arm 4 is made by connecting a boss 10 a formed at the tip of the arm and a pair of brackets 8 a and 8 b formed at the rear end of the bucket 5. This is done by supporting the through-hole at 20 (see FIG. 2). More specifically, the boss portion 10a includes a pair of boss side bracket portions 11a and 11b welded to both side portions on the arm tip side, and a tubular portion 12 connecting the boss side bracket portions 11a and 11b. Both ends 13a, 13b of the boss 10a are sandwiched between the pair of brackets 8a, 8b. The boss 10a (the boss-side brackets 11a and 11b) and the bucket-side brackets 8a and 8b are formed with through-holes having substantially the same diameter. Can be pivotally attached to the arm 4.
[0018]
In this example, the support plates 21a and 21b are fixed to the inner surfaces of the brackets 8a and 8b by welding to reinforce the brackets 8a and 8b. Further, in this example, a line 30 for supplying a lubricant such as grease is attached to the cylindrical portion 12 constituting the boss 10a, and a lubricant supply port 31 is provided at the other end of the line 30. Connected. By supplying the lubricant from the lubricant supply port 31, the inside 32 of the cylindrical portion 12 can be used as a lubricant retaining portion. The lubricant in the retaining portion 32 is used to enhance the slidability between the boss member 10a and the connecting pin 20. Further, lubricant is supplied to both end surfaces 13a and 13b of the boss 10a through a flow path (not shown), and the slidability between the boss 10a and the brackets 8a and 8b is also enhanced.
[0019]
In such a hydraulic excavator 1, since the boss 10a is sandwiched between the brackets 8a and 8b as described above, a thrust load acts on the boss 10a. Therefore, even when the lubricant is supplied to both end surfaces 13a and 13b of the boss 10a, the end surfaces 13a and 13b are in a state of being easily worn. In particular, the space between the boss 10a and the brackets 8a and 8b (more precisely, between the boss 10a and the bracket support plates 21a and 21b in this example) is used despite being protected by the oil seal 18. Due to severe conditions, earth and sand may enter during this time. In particular, in the case of a shovel, a work attachment such as a bucket may be replaced at a work site according to the purpose, and the boss end faces 13a and 13b are exposed at the time of replacement work, and soil and the like easily adhere to the boss. Moreover, in the excavator of the present invention, the boss 10a is made of low carbon steel in consideration of weldability. For these reasons, the end faces 13a and 13b are in a state of being more easily worn.
[0020]
Therefore, in the present invention, the end faces 13a and 13b of the boss member 10a made of low-carbon steel are partially and discontinuously subjected to high-frequency induction heating over a plurality of locations, and the heating portion is air-cooled, thereby cooling the boss member 10a. Has increased wear resistance. The reason why the wear resistance is enhanced by induction hardening is that there is no fear of peeling of the wear resistant layer (hardened hardened layer). The reason for utilizing high-frequency induction heating for quenching is that a large-scale quenching device is not required and the work efficiency is excellent. The reason for performing air cooling is that water cooling requires an extra water cooling facility, and also requires an increase in the high-frequency power supply capacity (for example, 200 kW or more), which increases equipment costs and running costs. By the way, as described above, it is difficult to quench low-carbon steel by high-frequency dielectric heating and air cooling. Therefore, in the present invention, induction hardening is partially performed discontinuously so that low-carbon steel can be hardened. When the high frequency partial quenching is performed discontinuously, there are also the following advantages. That is, since the inner peripheral portion (boss hole) of the boss member 10a is finish-cut, if the entire end surface is hardened, the finish cutting becomes extremely difficult. Is extremely short and the productivity is inferior. On the other hand, if induction hardening is partially discontinuously applied, such a problem does not occur. Even if the entire boss member including the outer peripheral surface is quenched, severe wear is likely to occur only on the end surface, resulting in waste. There is no. The present invention does not deny tempering the entire boss member.
[0021]
Hereinafter, the induction hardening method will be described in more detail with reference to the schematic perspective view of FIG. In the induction hardening, the high-frequency coil 30 having a heating conductor portion (heating surface) 31 substantially equal to the area (shape) of the partial quenching portion 16 is brought close to the boss member, and the boss member is partially energized by energizing the high-frequency coil 30. Then, the energization of the high-frequency coil 30 is stopped, and cooling (air cooling) is performed to perform quenching. When the energized high-frequency coil is brought close to the part to be quenched, only that part is rapidly heated locally by induction heating, and when the energization is stopped, rapid cooling occurs due to heat conduction around the heated part. Transforms and hardens by quenching. Since the cooling rate during this quenching is governed by heat conduction, it is important that the quenched portions are not continuous but arranged discontinuously (eg, intermittently) at appropriate intervals.
[0022]
The method of high-frequency induction heating is not particularly limited as long as the end surface of the boss member can be partially and continuously quenched. When the high-frequency coil 30 is used alone, or when a plurality of high-frequency coils are used in combination. It is convenient to heat according to the following.
[0023]
(1) When using the high-frequency coil alone The following steps 1 to 4 are repeated a plurality of times in this order.
[0024]
1: A high-frequency coil having a heating conductor portion having an area (shape) substantially equal to the area (shape) of the part to be partially quenched is brought close to the end face of the boss member. 2: The boss member is energized by energizing the high-frequency coil. Partial induction heating 3: Stop the energization of the high-frequency coil and air-cool it. 4: Move the high-frequency coil relatively to the vicinity of the part to be partially quenched while stopping the energization. For relative movement of the high-frequency coil, the high-frequency coil may be moved, or the boss member may be moved (for example, rotated).
[0025]
(2) When a plurality of high-frequency coils are used in combination, a plurality of high-frequency coils are combined to form a discontinuous pattern in the coil portion, and the high-frequency quenched portion is discontinuous by bringing the combination coil close to the end face. It is formed.
[0026]
In any of the above cases, if the coil portion is too large, the area to be heated at one time becomes too large, so that it becomes difficult to burn. Therefore, in the present invention, it is desirable to use a sufficiently small coil. In the above example, it is assumed that a high-frequency coil having a heating conductor portion having a length and a width (diameter) substantially equal to the portion to be partially quenched is used. I have.
[0027]
When quenching is performed as described above, the end surface of the boss member is partially quenched in various patterns. FIG. 4 is a schematic front view showing an example of the boss end face 13 subjected to the high frequency partial quenching. In FIG. 4, the high-frequency partially quenched portion is painted black (note that the painting is for convenience of explanation of the invention, and the actual end faces 13a and 13b of the boss portion are painted black. Do not mean). In the illustrated example, a plurality of high-frequency hardened portions 16a are formed at substantially equal intervals, and are formed so as to be radial as a whole. Even in such a case, since the high-frequency partial quenching is discontinuously performed, it is possible to quench the steel with sufficiently high hardness even with a low carbon steel, and to sufficiently enhance the wear resistance of the end faces 13a and 13b. Can be. In the present invention, since the high hardness portion (hardened portion) is partially formed, the soft portion 15 remains. The soft portion 15 is useful for preventing the propagation of cracks when cracks occur in the quenched portion (hardened portion) 16a. It is useful to function as. In addition, in the present invention, since the worn portion also functions as a retreat place for earth and sand, the slidability of the end faces 13a and 13b can be further improved.
[0028]
When forming the high-frequency partial quenching portion 16a radially, each partial quenching portion 16a may be formed along the radial direction as shown in FIG. 4 or may be formed so as to be inclined toward the circumferential direction. . FIG. 5 is a schematic front view of the end faces 13a and 13b in which the partially quenched portions 16b inclined in the circumferential direction are formed. In this example, the partially quenched portions 16b are both inclined at substantially equal angles.
[0029]
It is also desirable to form the partially quenched portion along the circumferential direction. 6 and 7 are schematic front views of such end faces 13a and 13b. In the example of FIG. 6, a plurality of partial quenched portions 16c are formed in a line along the circumferential direction (to form a circle as a whole). A row of the second partial quenching portions 16d is also formed inside the row of the partial quenching portions 16c, and these two rows (circles) are formed concentrically. In the example of FIG. 6, the partially quenched portion 16c forming the outer first row (circle) and the partially quenched portion 16d forming the inner second row (circle) are aligned in the radial direction. It is formed as follows. On the other hand, the example of FIG. 7 is the same as FIG. 6 in that the rows of the outer partial quenching portions 16e and the rows of the inner partial quenching portions 16f are formed concentrically. 6 is different from that in FIG. 6 in that the inner quenched portion 16f and the inner partial quenched portion 16f are formed alternately when viewed in the circumferential direction. When the outer partial quenched portion and the inner partial quenched portion are alternately formed, quenching and hardening are facilitated, and further, the lubricant is easily retained in the worn soft portion 15. The number of the rows (circles) is not limited to two, but may be one or three or more.
[0030]
As long as the high-frequency partial quenching portions 16 are formed discontinuously (for example, intermittently) on the end surfaces 13a and 13b, the number and locations of the high-frequency partial quenching portions 16 are not particularly limited, but it is preferable to form a plurality of them at substantially equal intervals. By forming them at substantially equal intervals, the wear resistance of the end faces 13a and 13b can be substantially uniformly increased, and the soft portion 15 can also be left almost uniformly, so that the slidability of the end faces 13a and 13b can be improved. Can be increased substantially evenly. The high-frequency hardened portions 16a to 16f may be formed on both end surfaces 13a and 13b in the same pattern or in different patterns.
[0031]
In the present invention, since cooling after high-frequency induction heating is performed by air cooling (heat conduction), as described above, quenching is not continuous but quenched discontinuously (for example, intermittently) at appropriate intervals. It is important that the partial quenched portions are often arranged at substantially equal intervals. It is desirable that the interval between the partially quenched portions is such that the distance between the nearest quenched portions is 1 mm or more, for example. The upper limit of the distance is not particularly limited as long as no rattling occurs when the non-quenched portion is worn, but usually, about half (based on area) of the entire end face is partially quenched. Often the same as the width of the quenched part.
[0032]
The partially quenched portion is often an anisotropic shape such as a substantially rectangular shape or a substantially elliptical shape, the length (the length of the long axis) is, for example, about 5 to 30 mm, and the width (the length of the short axis). Length) is, for example, about 3 to 7 mm.
[0033]
In the present invention, it is desirable to set the conditions for high-frequency induction heating as follows.
[0034]
(1) Frequency If the frequency is too high, the quenching depth becomes too shallow, so that sufficient wear resistance cannot be obtained. Therefore, the frequency is set to 10 kHz or more, preferably 20 kHz or more. On the other hand, if the frequency is too low, the material is heated to a deep part too much, so that the cooling rate during air cooling becomes too slow, and sufficient quench hardening cannot be obtained. Therefore, the frequency is set to 50 kHz or less, preferably 30 kHz or less. A particularly preferable frequency is a level necessary to make the quenching depth about 1 to 2 mm, and is about 23 to 27 kHz (particularly about 25 kHz) when quenching steel described later.
[0035]
(2) Quenching time (heating time)
The lower limit of the quenching time is not particularly limited as long as the steel can be made martensite and / or bainite. However, if the quenching time is too short, it becomes difficult to perform ON-OFF control of energizing the high-frequency coil. Is desirably, for example, 0.2 seconds or more. On the other hand, if the quenching time is too long, the temperature will be too high, and the cooling rate during air cooling will be too slow, so that sufficient quench hardening cannot be obtained. Further, the working efficiency is reduced. Therefore, the quenching time is set to 1 second or less, preferably 0.5 second or less.
[0036]
(3) Power supply output The power supply output can be appropriately set according to the hardenability, quenching area, etc. of the steel, and is, for example, 16 kW or more (preferably 20 kW or more, more preferably 24 kW or more). The larger the quenching area, the greater the power output required. If the quenching area is too large, sufficient quenching and hardening cannot be obtained. Therefore, the upper limit of the power output is selected from the range in which quench hardening is possible. The power output is usually about 100 kW or less.
[0037]
The amount of heat input to the quenching part is determined by the quenching time and the power output. However, as long as a predetermined quench hardness can be achieved, the smaller the amount of heat input, the better. When the amount of heat input is reduced, the occurrence of thermal deformation and thermal distortion of the boss member can be reduced, and dimensional accuracy can be maintained.
[0038]
When the high-frequency coil is used alone, the relative moving speed of the high-frequency coil is, for example, about 5 to 13 mm / sec.
[0039]
In the present invention, the boss member 10a is manufactured from low carbon steel. The reason for using low-carbon steel is that it is not necessary to preheat the boss member 10a when welding it to the arm 4, and that the weldability is excellent. In addition, when low-carbon steel is used, the manufacturing cost can be reduced as compared with the case where medium-high carbon steel is used. The carbon content of the low carbon steel is, for example, 0.4% by mass or less, preferably 0.35% by mass or less. If the carbon content is too small, it is difficult to achieve a predetermined hardness even if high-frequency partial quenching is performed. Therefore, the carbon content is, for example, 0.25% by mass or more, preferably 0.30% by mass. % Or more. B may be added to the low carbon steel. When B is added, the hardenability can be increased, and the toughness of the weld heat affected zone (HAZ zone) can be increased. The content of B is, for example, 0.0005% by mass or more, and 0.003% by mass or less (preferably 0.002% by mass or less).
[0040]
The hardness (HRC) of the partially quenched portion of the end face is 45 or more, preferably 48 or more, and more preferably 50 or more. In the present invention, even when low-hardness steel having low hardenability is used, high-frequency partial quenching is performed discontinuously, so that a predetermined hardness or more can be achieved even with air cooling. On the other hand, the hardness of the quenched portion is usually 65 or less, often 60 or less. The hardness of the non-quenched portion (Brinell hardness HB) is usually about 130 to 200.
[0041]
The boss member according to the present invention includes, in addition to a shovel, a work attachment for handling earth and sand (buckets such as a slope work bucket, an excavation bucket, and a snow removal bucket), and an arm member for pivotally supporting the work attachment. Can be applied to various work machines (such as a machine for civil engineering work or construction work), and can be applied to various work machines such as a wheel loader and a snow blower. .
[0042]
【Example】
Hereinafter, the present invention will be described more specifically with reference to Examples. However, the present invention is not limited to the following Examples, and may be appropriately modified within a range that can be adapted to the purpose of the preceding and the following. It is of course possible to carry out them, and all of them are included in the technical scope of the present invention.
[0043]
Experimental example 1
The end face of a boss member (manufactured by S30C) having a boss having a diameter of 170 mm and a boss hole having a diameter of 109 mm was subjected to high-frequency partial quenching so as to have a pattern shown in FIG. More specifically, after the high-frequency coil [area of the heating conductor portion = 6 mm × 19 mm (substantially rectangular)] is brought into proximity with the boss member and energized for 0.5 seconds (frequency 25 kHz) for induction heating, the energization is stopped. By repeating the operation of sliding the high-frequency coil for about 0.5 seconds, conducting electricity again for 0.5 seconds and inducing induction heating, 48 parts were hardened uniformly on one side so that the pattern shown in FIG. 4 was obtained. The size of each quenched part was about 4 mm × about 17 mm.
[0044]
The power output is selected at seven levels from the range of 16 to 25 kW. In each case, after the end face of the boss member is quenched at 48 places by the above-mentioned repetitive operation, six partial hardened parts are evenly selected. The Rockwell hardness of the quenched part was measured, and it was confirmed whether or not induction hardening of a predetermined hardness or more was performed. Table 1 shows the results.
[0045]
[Table 1]

[0046]
As is clear from Table 1, according to the present invention, since induction hardening is performed intermittently, even a low-carbon steel can be hardened to a predetermined hardness.
[0047]
【The invention's effect】
According to the present invention, when quenching a boss member made of low carbon steel having poor hardenability, even if the hard-hardening conditions of high-frequency induction heating and air cooling are adopted, the quenching is discontinuous. Can be quenched and hardened. Therefore, a boss member excellent in wear resistance and weldability can be easily manufactured. Moreover, there is little possibility that the wear-resistant layer is peeled off.
[Brief description of the drawings]
FIG. 1 is a schematic side view showing an example of a work machine.
FIG. 2 is a schematic sectional view showing an example of a boss member.
FIG. 3 is a schematic perspective view for explaining a method of quenching the end surface of the boss member.
FIG. 4 is a schematic front view showing an example of a quenching pattern on the end face of the boss member.
FIG. 5 is a schematic front view showing another example of the quenching pattern on the end face of the boss member.
FIG. 6 is a schematic front view showing still another example of the quenching pattern on the end face of the boss member.
FIG. 7 is a schematic front view showing another example of the quenching pattern on the end face of the boss member.
[Explanation of symbols]
10a Boss members 13a, 13b End faces 16a to 16f Partially quenched part

Claims (5)

Production of a partially quenched wear-resistant low-carbon steel boss member characterized in that the end face of the boss member made of low-carbon steel is discontinuously high-frequency induction-heated at a plurality of locations and the heated portion is air-cooled. Method. The method for manufacturing a wear-resistant low-carbon steel boss member according to claim 1, wherein the high-frequency partial quenching portion is formed discontinuously at a plurality of positions by repeating the following steps 1 to 4 a plurality of times in this order.
1: A high-frequency coil having a heating conductor portion having an area substantially equal to the area of the part to be partially quenched is brought close to the end surface of the boss member. 2: The boss member is partially induction-heated by energizing the high-frequency coil. 3: Stop the energization of the high-frequency coil and cool down by air. 4: With the energization stopped, relatively move the high-frequency coil to the vicinity of another part to be hardened. The wear resistance according to claim 1, wherein the coil portion forms a discontinuous pattern by combining a plurality of high-frequency coils, and the high-frequency partial quenching portion is discontinuously formed by bringing the combined coil close to the end face. Method of manufacturing a boss member of a conductive low carbon steel. High frequency partial quenching is performed under the conditions of a frequency of 10 to 50 kHz, a power output of 16 kW or more, and a heating time of 1 second or less, the length of each partial quenched part is 5 to 30 mm, the width of each partial quenched part is 3 to 7 mm, The method for producing a wear-resistant low-carbon steel boss member according to any one of claims 1 to 3, wherein a distance between the re-adjacent portions of the quenched portions is 1 mm or more. The method for producing a wear-resistant low-carbon steel boss member according to any one of claims 1 to 4, wherein low-carbon steel having a carbon content of 0.4 mass% or less is subjected to high-frequency partial quenching.

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