JP2008133523A

JP2008133523A - Ohmic heating method

Info

Publication number: JP2008133523A
Application number: JP2006321734A
Authority: JP
Inventors: Fumiaki Ikuta; 文昭生田; Morio Tomita; 盛男富田; Tsunetaka Takeuchi; 恒孝竹内
Original assignee: Neturen Co Ltd
Current assignee: Neturen Co Ltd
Priority date: 2006-11-29
Filing date: 2006-11-29
Publication date: 2008-06-12
Anticipated expiration: 2026-11-29
Also published as: JP5088929B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ohmic heating method of a work, by which a part that needs to be heated can be sufficiently and securely heated by avoiding insufficient heating caused by variation in sheet thickness and width. <P>SOLUTION: In an ohmic heating method, the work 1 to be heat-treatmented is contacted with a pair of electrodes 7a and 7b which are placed at a certain distance from each other, and an electric current is applied to the electrodes 7a and 7b to heat the work 1. The length W1 of the cross section of a prescribed part (a narrow part 4) of the work 1 placed between the electrodes 7a and 7b is made smaller than the design standard W0, and the heating temperature is locally increased at the prescribed part (the narrow part 4) when applying the electric current. The parts that particularly need to be heated are made narrow to make cross sections smaller than those of parts that do not need to be heated, so that heating is concentrated on the narrow parts. This enables application of a large electric current to the work by direct current heating and rapid heating of the work. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

この発明は、対の電極を介してワークに通電をして抵抗加熱によりワークの加熱処理を行う通電加熱方法に関するものである。 The present invention relates to an energization heating method for energizing a work through a pair of electrodes and performing heat treatment of the work by resistance heating.

ワークを加熱して焼き入れ熱処理などの加熱処理を行う際には、加熱炉などを用いて加熱する他、ワークに通電をして抵抗加熱する通電加熱の方法も用いられている（例えば特許文献１参照）。通電加熱は、急速加熱が可能でＣＯ_２の排出のないクリーンなエネルギーのため、熱処理や熱間プレスの加熱手段として広く使われている。その原理は通電電流Ｉと被加熱物の抵抗ＲによるＩ^２×Ｒで表されるジュール発熱によるものであり、被加熱ワークの両端を電極でクランプし、その電極間に電圧をかけ商用周波もしくは高周波の電流を流すことで加熱を行う。
特開平５−１４４９０９号公報 When performing heat treatment such as quenching heat treatment by heating the workpiece, in addition to heating using a heating furnace or the like, an electric heating method is also used in which the workpiece is energized and subjected to resistance heating (for example, patent document). 1). Current heating is widely used as a heating means for heat treatment and hot pressing because of its clean energy that allows rapid heating and does not emit CO ₂ . The principle is based on Joule heating represented by I ² × R due to the energization current I and the resistance R of the object to be heated. Both ends of the workpiece to be heated are clamped with electrodes, and a voltage is applied between the electrodes to commercial frequency or Heating is performed by applying a high-frequency current.
JP-A-5-144909

ところで、板材プレス成形品の熱処理や板材の熱間プレス成形のために通電加熱を行う場合、プレス成形時の加工量の違いにより、プレス品では板厚変化およびカット幅のばらつきが生じる。しかし、通電加熱に供するワークにおいて、通電方向と直交する方向の断面積が通電方向で一定でないと抵抗Ｒが変わってくるため発熱量が変わり、加熱温度も変わってくる。このため、板材のスリット幅の僅かな違いや冷間プレス時の加工量の違いによる板厚や板幅の変化があると、通電加熱時に板幅の狭い部位や肉厚の薄い部位の温度が高くなる。温度の高くなった部分は抵抗がより高くなり、ますます発熱量が多くなり温度がさらに高くなる。また、大電流を流す場合は電極の締め付け力の不均一により接触抵抗によるオーバーヒートも発生しやすい。その結果、ワークの目的とする部位の温度を十分に上げることができず、熱処理や熱間加工のための加熱が不十分になり、所望とする特性が得られなかったり、不均一になるという問題がある。 By the way, when conducting heating for heat treatment of a plate material press-formed product or hot press forming of a plate material, due to a difference in processing amount at the time of press forming, a plate thickness change and a variation in cut width occur in the press product. However, in a work to be subjected to energization heating, if the cross-sectional area in the direction orthogonal to the energization direction is not constant in the energization direction, the resistance R changes, so the amount of heat generation changes and the heating temperature also changes. For this reason, if there is a change in the plate thickness or the plate width due to a slight difference in the slit width of the plate material or a difference in the amount of processing during cold pressing, the temperature of the narrow or thin portion during energization heating will Get higher. In the part where the temperature is high, the resistance becomes higher, the amount of heat generation becomes larger and the temperature becomes higher. In addition, when a large current flows, overheating due to contact resistance is likely to occur due to non-uniformity of the electrode clamping force. As a result, the temperature of the target part of the workpiece cannot be raised sufficiently, heating for heat treatment or hot working becomes insufficient, and desired properties cannot be obtained or become non-uniform. There's a problem.

本発明は、上記事情を背景としてなされたものであり、ワークの所望部位を確実かつ十分に加熱することができる通電加熱方法を提供することを目的とする。 The present invention has been made against the background of the above circumstances, and an object thereof is to provide an energization heating method capable of reliably and sufficiently heating a desired portion of a workpiece.

すなわち、本発明の通電方法のうち、第１の発明は、加熱処理を施すワークに、互いに距離を隔てた対の電極を接触させ、該電極への通電によって該ワークを加熱する通電加熱方法において、前記電極間のワークの所定部位の横断面長さを設計基準寸法よりも小さくして前記通電に際し該所定部位の加熱温度を部分的に高めることを特徴とする。 That is, among the energization methods of the present invention, the first invention is an energization heating method in which a pair of electrodes spaced apart from each other is brought into contact with a workpiece to be heat-treated, and the workpiece is heated by energization of the electrodes. The cross-sectional length of a predetermined portion of the work between the electrodes is made smaller than a design reference dimension, and the heating temperature of the predetermined portion is partially increased during the energization.

第２の通電方法の発明は、第１の発明において、前記ワークは、設計基準寸法において横断面形状が連続して一定であることを特徴とする。 The invention of a second energization method is characterized in that, in the first invention, the workpiece has a continuously constant cross-sectional shape in a design standard dimension.

第３の通電方法の発明は、加熱処理を施すワークに、互いに距離を隔てた対の電極を接触させ、該電極への通電によって該ワークを加熱する通電加熱方法において、前記ワークは、設計基準寸法において横断面形状が連続して一定である形状を有し、前記電極間のワークの所定部位の横断面長さを前記電極が接触する部位の横断面長さよりも小さくして前記通電に際し該所定部位の加熱温度を部分的に高めることを特徴とする。 The invention of a third energization method is an energization heating method in which a pair of electrodes spaced apart from each other is brought into contact with a workpiece to be heat-treated, and the workpiece is heated by energization of the electrodes. The cross-sectional shape has a shape in which the cross-sectional shape is continuously constant in dimension, and the cross-sectional length of a predetermined part of the workpiece between the electrodes is made smaller than the cross-sectional length of the part in contact with the electrode, The heating temperature of the predetermined part is partially increased.

第４の通電方法の発明は、第１〜第３の発明のいずれかにおいて、前記ワークは、周囲に加工代を有する粗形材であり該加工代量を部分的に小さくすることで前記所定部位の横断面長さを設計寸法よりも小さくすることを特徴とする。 In a fourth energization method according to any one of the first to third inventions, the workpiece is a rough shape having a machining allowance around it and the machining allowance is partially reduced to reduce the predetermined amount. The cross-sectional length of the part is made smaller than the design dimension.

第５の通電方法の発明は、第１〜第４の発明のいずれかにおいて、前記ワークは最終形状品であり、前記所定の部位に対する他の部位の横断面長さを前記設計基準寸法よりも大きくすることで前記所定部位の横断面長さを相対的に小さくすることを特徴とする。 According to a fifth energization method of the present invention, in any one of the first to fourth inventions, the work is a final shape product, and a cross-sectional length of another part with respect to the predetermined part is larger than the design reference dimension. The cross section length of the predetermined portion is relatively reduced by increasing the length.

第６の通電方法の発明は、第１〜第５の発明のいずれかにおいて、前記横断面長さの減少率が２％以上であることを特徴とする。 An invention of a sixth energization method according to any one of the first to fifth inventions is characterized in that a reduction rate of the cross-sectional length is 2% or more.

第７の通電方法の発明は、第１〜第６の発明のいずれかにおいて、前記横断面長さを小さくした所定部位が、電極の接触位置から、減少した横断面長さに対し０．５倍以上の距離を隔てていることを特徴とする。 In a seventh energization method according to any one of the first to sixth inventions, the predetermined portion with the reduced cross-sectional length is 0.5% from the contact position of the electrode with respect to the reduced cross-sectional length. It is characterized by a distance of more than double.

すなわち本発明によれば、電極間に通電することでワークに電流が流れ、設計基準寸法よりも横断面長さを小さくした所定部位で電流密度が増し、該部位を設計基準寸法のものよりも高温に加熱することができる。この結果、所定の部位における加熱処理を確実かつ十分に行うことができ、ワークの肉厚や幅にばらつきがある場合にも所定の部位の加熱が不十分になるのを回避することができる。そして、電極が接触する位置から離れた位置の横断面長さを小さくすることにより、もともと接触抵抗のばらつきで温度が不安定になり易い電極接触部近傍の横断面長さが相対的に大きくなり温度上昇を抑えることができる。ワークの加熱処理においては中央部の強度を必要とされる場合が多く、両端の電極接触部近傍の温度は低くて良い場合が多い。また熱間プレスの場合は電極で挟む両端部は切代とされるので温度も少なくて良く、どちらの場合も電極接触部近傍に高い温度を必要としないので好都合である。 That is, according to the present invention, a current flows through the workpiece by energizing between the electrodes, and the current density increases at a predetermined portion whose transverse section length is smaller than the design reference dimension. Can be heated to high temperatures. As a result, the heat treatment at the predetermined portion can be reliably and sufficiently performed, and it is possible to avoid insufficient heating of the predetermined portion even when the thickness and width of the workpiece vary. And by reducing the cross-sectional length at a position away from the position where the electrode contacts, the cross-sectional length in the vicinity of the electrode contact portion where the temperature tends to become unstable due to variations in contact resistance is relatively increased. Temperature rise can be suppressed. In the heat treatment of the workpiece, the strength at the center is often required, and the temperature in the vicinity of the electrode contact portions at both ends may be low. In the case of hot pressing, both ends sandwiched by the electrodes are used as cutting allowances, so that the temperature may be small. In either case, a high temperature is not required in the vicinity of the electrode contact portion, which is convenient.

なお、加熱処理の対象となるワークは、特に用途などが限定をされるものではなく、加熱処理が必要とされる種々のワークを処理対象にすることができる。例えば、内側の部位で特に発熱を集中させて高強度化をしたいドアインパクトビームなどに好適である。
該ワークは、好適には設計基準寸法において横断面が連続して一定のものが挙げられる。ただし、本発明としてはこれに限定されず、異形横断面形状のものであってもよい。
また、ワークは板形状のものが代表的に挙げられるが、この他に、断面形状として屈曲形状や湾曲形状を含むものが例示され、さらには、筒形状を有するものが挙げられる。これらワークにおける横断面長さとしては、ワーク断面形状における合計長さで示すことができる。したがって湾曲部や屈曲部は湾曲形状や屈曲形状に沿った横断面長さを有し、筒形状では、周長で示される。なお、横断面とは、電極間方向に対し直交する方向に沿った断面を意味している。通常は、ワークの長尺方向に対し横断する断面が横断面となる。 In addition, the workpiece | work used as the object of heat processing does not specifically limit a use etc., The various workpiece | work which requires heat processing can be made into processing object. For example, it is suitable for a door impact beam or the like where it is desired to increase the strength by concentrating heat generation particularly at the inner part.
The workpiece preferably includes a workpiece having a constant cross section in a design standard dimension. However, the present invention is not limited to this, and may have an irregular cross-sectional shape.
In addition, the workpiece is typically a plate-like one, but in addition to this, one including a bent shape or a curved shape as a cross-sectional shape is exemplified, and further, one having a cylindrical shape is exemplified. The cross sectional length of these workpieces can be represented by the total length in the workpiece cross sectional shape. Therefore, the curved portion or the bent portion has a cross-sectional length along the curved shape or the bent shape, and is indicated by a circumferential length in the cylindrical shape. In addition, a cross section means the cross section along the direction orthogonal to the direction between electrodes. Usually, the cross section which crosses with respect to the longitudinal direction of a workpiece | work becomes a cross section.

また、前記設計基準寸法は通電加熱時の設計基準となるものであり、所定部位の横断面長さを小さくする前の形状に対するものである。粗形材においてはバリなどの加工代を含む寸法として与えられるものであり、最終製品形状に加工代量を含めたものが設計基準寸法となる。加工代量は、加工方法によってその量が異なってくるが、通常は、同一方向、例えば横方向両側では連続して同一の加工代量とし、縦方向両側でも連続して同一の加工代量とする。例えば、ワークの横断面が連続して一定の形状を有していれば、加工代を含む粗形材形状も通常は横断面が連続して一定の形状となるので、上記所定部位のバリ量を小さくすることで、該所定部位の横断面長さを電極が接触する部位よりも横断面長さを小さくすることができる。 Moreover, the said design reference | standard dimension becomes a design reference | standard at the time of energization heating, and is with respect to the shape before making the cross-sectional length of a predetermined part small. The rough shape material is given as a dimension including a machining allowance such as a burr, and the final product shape including the machining allowance is a design reference dimension. The machining allowance varies depending on the machining method, but usually the same machining allowance is made continuously in the same direction, for example, both sides in the horizontal direction, and the same machining allowance is made continuously in both sides in the longitudinal direction. To do. For example, if the cross section of the workpiece has a constant shape, the shape of the rough shape including the machining allowance is usually a constant shape with a continuous cross section. By reducing the cross sectional length of the predetermined portion, the cross sectional length can be made smaller than that of the portion in contact with the electrode.

また、加熱処理の対象となるワークが最終形状品である場合、所定の部位の横断面長さが相対的に小さくなるように、他の部位の横断面長さを設計基準寸法よりも大きくすることができる。ワークの横断面形状が連続して同一である場合は、前記のように電極が接触する部位の横断面長さを所定の部位の横断面長さよりも大きくすればよい。 In addition, when the workpiece to be heat-treated is a final shape product, the cross-sectional length of the other part is made larger than the design reference dimension so that the cross-sectional length of the predetermined part becomes relatively small. be able to. When the cross-sectional shape of the workpiece is continuously the same, the cross-sectional length of the portion that contacts the electrode may be made larger than the cross-sectional length of the predetermined portion as described above.

前記した横断面長さを小さくして加熱温度を部分的に上げる「所定の部位」は、電極間において適宜の領域を選定することができるが、通常は、電極が接触する部位およびこの近傍を除いた領域で横断面長さを小さくする。
なお、横断面長さの減少率は、小さな減少率でも効果は認められるが、２％以上の減少率において明らかな効果が認められる。より望ましくは３％以上である。これにより横断面長さを小さくした所定の部位は、他の部位に比べて顕著に通電加熱効果が向上し、横断面を減少させる前に比べて、通電時に確実に、発熱を集中させることができる。なお、減少率を０．２％以上としたが、横断面長さを無制限に減幅しても、電極部を設置する部位における電流集中が起き、均一な温度が得られなくなるため、最大１５％以下を限度とするのが望ましい。
また、横断面長さを減少させる所定の部位は、電極の直近に設けないのが望ましい。これは電極部の近くは、接触抵抗のばらつきにより温度が不安定になりやすいので、その温度上昇を助長するのが好ましくないためである。このため、横断面長さを小さくする所定の部位は、設計基準寸法に対し、０．５倍以上の距離で電極の接触部位と離れているのが望ましい。また、上限としては１．０倍が好ましい。これは、電極接触部位の面積が広くなるに従いワークの温度の均一が得られなくなるためである。 As for the “predetermined part” in which the heating temperature is partially increased by reducing the length of the cross section described above, an appropriate region can be selected between the electrodes. Reduce the cross-sectional length in the excluded area.
The reduction rate of the cross-sectional length is effective even when the reduction rate is small, but an obvious effect is observed when the reduction rate is 2% or more. More desirably, it is 3% or more. As a result, the predetermined part with the reduced cross-sectional length has a significantly improved energization heating effect compared to other parts, and it can concentrate heat generation more reliably during energization than before reducing the cross-section. it can. Although the reduction rate is 0.2% or more, even if the width of the cross section is reduced without limit, current concentration occurs in the portion where the electrode portion is installed, and a uniform temperature cannot be obtained. It is desirable to limit it to less than%.
Moreover, it is desirable not to provide the predetermined site | part which reduces cross-sectional length in the immediate vicinity of an electrode. This is because the temperature tends to become unstable near the electrode portion due to variations in contact resistance, and it is not preferable to promote the temperature rise. For this reason, it is desirable that the predetermined part for reducing the cross-sectional length is separated from the contact part of the electrode by a distance of 0.5 times or more with respect to the design reference dimension. Further, the upper limit is preferably 1.0 times. This is because the temperature of the workpiece cannot be made uniform as the area of the electrode contact area increases.

以上説明したように、本発明の通電加熱方法によれば、加熱処理を施すワークに、互いに距離を隔てた対の電極を接触させ、該電極への通電によって該ワークを加熱する通電加熱方法において、前記電極間のワークの所定部位の横断面長さを設計基準寸法よりも小さくして前記通電に際し該所定部位の加熱温度を部分的に高めるので、ワークを特に加熱したい部位の幅を狭くし、加熱が不必要な部位の断面積より小さくして発熱が幅の狭い部位に集中させることができる。この結果、ワークに対し直通加熱による大電流、急速加熱を可能にし、ワークに対し効率的かつ効果的に加熱処理を施すことができる。 As described above, according to the energization heating method of the present invention, in the energization heating method in which a pair of electrodes spaced apart from each other are brought into contact with the workpiece to be heat-treated, and the workpiece is heated by energization of the electrodes. The cross-sectional length of a predetermined part of the workpiece between the electrodes is made smaller than the design reference dimension, and the heating temperature of the predetermined part is partially increased during the energization. Further, the heat generation can be concentrated on a narrow portion by making it smaller than the cross-sectional area of the portion that does not require heating. As a result, the workpiece can be subjected to a large current and rapid heating by direct heating, and the workpiece can be efficiently and effectively subjected to heat treatment.

以下に、本発明の一実施形態を図１に基づいて説明する。
この実施形態では、ワーク１は鋼製で長板形状を有し、設計基準寸法からなる設計基準形状１ａにおいて横断面長さが長尺方向において一定になっている。
該ワーク１は、長尺方向両端側が電極７ａ、７ｂの接触する部位とその近傍の幅広部２ａ、２ｂからなり、幅広部２ａ、２ｂ間が減幅境界部３ａ、３ｂを介して横断面長さを小さくした減幅部４となっており、該減幅部４は本発明の所定部位に相当する。幅広部２ａ、２ｂと減幅部４との間は、幅が次第に変化して幅広部２ａ、２ｂと減幅部４とが連なる減幅テーパ部３ａ、３ｂとなっている。 Below, one Embodiment of this invention is described based on FIG.
In this embodiment, the workpiece 1 is made of steel and has a long plate shape, and the cross-sectional length is constant in the longitudinal direction in the design reference shape 1a having the design reference dimensions.
The workpiece 1 is composed of a portion where the electrodes 7a and 7b are in contact with each other at both ends in the longitudinal direction and the wide portions 2a and 2b in the vicinity thereof. A reduced width portion 4 is formed, and the reduced width portion 4 corresponds to a predetermined portion of the present invention. Between the wide portions 2a and 2b and the reduced portion 4, there are reduced taper portions 3a and 3b in which the width gradually changes and the wide portions 2a and 2b and the reduced portion 4 are continuous.

なお、この実施形態では上記減幅部３ａ、３ｂは、設計基準形状１ａの寸法（横断面長さＷ_０）に対し、好適には３％以上で横断面長さＷ_１（この実施形態では幅）が減少されている。また、減幅テーパ部３ａ、３ｂは、設計基準形状１ａの幅Ｗ_０に対し、０．５倍以上の長さで電極７ａ、７ｂが接触する部位から離れており、この結果、減幅部３ａ、３ｂの両端も電極７ａ、７ｂが接触する部位から設計基準形状１ａの幅に対し０．５倍以上の長さＬで離れている。
また、上記ワーク１の両側に接触させる電極７ａ、７ｂは、通電加熱に際しては、適宜の固定手段（図示しない）によってワーク１の両端部に取り付け固定される。電極７ａ、７ｂは、変圧器６の二次側に接続されており、変圧器６の一次側に交流電源５が接続されている。 In this embodiment, the width-decreasing portions 3a and 3b are preferably 3% or more with respect to the dimension of the design reference shape 1a (cross-sectional length W ₀ ), and the cross-sectional length W ₁ (in this embodiment). Width) has been reduced. Alternatively, the reduced width tapered portions 3a, 3b, compared width _{W 0} of the design reference shape 1a, is away from the site where the electrodes 7a, 7b are contacted with a length of 0.5 times or more, as a result, reduced width portion Both ends of 3a and 3b are also separated by a length L of 0.5 times or more with respect to the width of the design reference shape 1a from the portion where the electrodes 7a and 7b contact.
The electrodes 7a and 7b brought into contact with both sides of the workpiece 1 are fixedly attached to both ends of the workpiece 1 by appropriate fixing means (not shown) during energization heating. The electrodes 7 a and 7 b are connected to the secondary side of the transformer 6, and the AC power supply 5 is connected to the primary side of the transformer 6.

次に、この実施形態の作用について説明する。
交流電源５により変圧器６に通電を行うと、変圧比による二次電圧が得られ、電極７ａ、７ｂ間に通電される。なお、該通電においては、定電圧、定電流、または電圧制御、電流制御のいずれによってなされるものであってもよい。
上記通電によって電極７ａ、７ｂ間で、幅広部２ａ、減幅テーパ部３ａ、減幅部４、減幅テーパ部３ｂ、幅広部２ｂを通して電流が流れる。この際に、減幅部４では横断面長さが他部よりも小さくなっているため、電流密度が大きくなり、発熱が集中して他部よりも温度が高くなる。一方、電極７ａ、７ｂに近い幅広部２ａ、２ｂでは、電流密度が相対的に小さくなり発熱が抑えられる。これにより大電流による加熱処理においても所望の部位（この実施形態では減幅部４）を確実に加熱昇温させることができ、また温度が不安定になりやすい電極接触部分の近傍の発熱を抑制することができる。 Next, the operation of this embodiment will be described.
When the transformer 6 is energized by the AC power source 5, a secondary voltage is obtained by the transformation ratio and is energized between the electrodes 7a and 7b. Note that the energization may be performed by constant voltage, constant current, voltage control, or current control.
The current flows between the electrodes 7a and 7b through the wide portion 2a, the reduced taper portion 3a, the reduced width portion 4, the reduced taper portion 3b, and the wide portion 2b. At this time, since the cross-sectional length of the reduced width portion 4 is smaller than that of the other portion, the current density increases, heat generation is concentrated, and the temperature becomes higher than that of the other portion. On the other hand, in the wide portions 2a and 2b close to the electrodes 7a and 7b, the current density is relatively small and heat generation is suppressed. As a result, even in a heat treatment with a large current, a desired portion (in this embodiment, the reduced width portion 4) can be reliably heated and heated, and heat generation near the electrode contact portion where the temperature tends to become unstable can be suppressed. can do.

上記実施形態では、平板の長尺形状のワークを加熱処理の対象として説明をした。ただし、本発明のワーク形状が平板状のものに限定されないことは前記したとおりであり、その他の形状の例を図２に示す。なお、図２は、各ワークの横断面形状を示すものである。
ワーク１０は、前記したワーク１と同様に平板状の形状を有するものであり、ワーク１に対しやや小さい横断面長さを有している。該ワーク１０では、設計基準寸法における横幅断面長さＷ_１０に対し、減幅部の横断面長さＷ_１１を小さくしている。
ワーク２０は、屈曲形状により断面門型で下端に外側に屈曲した屈曲片を有している。該ワーク２０では、設計基準寸法における横断面長さＷ_２０は、門型部と両側の屈曲片に至る長さを示すものである。減幅部を設ける場合、例えば屈曲片の横断面長さを小さくして全体の横断面長さＷ_２１を減少させることができる。 In the said embodiment, the elongate workpiece of the flat plate was demonstrated as the object of heat processing. However, as described above, the workpiece shape of the present invention is not limited to a flat plate shape. Examples of other shapes are shown in FIG. FIG. 2 shows the cross-sectional shape of each workpiece.
The workpiece 10 has a flat shape like the workpiece 1 described above, and has a slightly smaller cross-sectional length than the workpiece 1. In the work 10 with respect to the width cross-sectional length W ₁₀ in the design reference dimension, which reduces the cross-sectional length W ₁₁ of the reduced width portion.
The workpiece 20 has a gate shape in cross section with a bent shape and a bent piece bent outward at the lower end. In the workpiece 20, the cross-sectional length W ₂₀ in the design standard dimension indicates a length that reaches the portal portion and the bent pieces on both sides. When providing a reduced width portion, it is possible to reduce the overall cross-sectional length W ₂₁ for example by reducing the cross section length of the bent piece.

ワーク３０は、断面矩形に屈曲させ、その一終端を内側に折り曲げて断面日型形状としたものである。このワーク３０では、矩形部から内側折り曲げ部に至る長さが横断面長さにおける設計基準寸法Ｗ_３０として与えられる。一方、横断面長さを小さくする場合、例えば屈曲部と折り曲げ部のそれぞれの端部を短くすることで横断面長さＷ_３１を小さくすることができる。
ワーク４０は、断面矩形の筒形状を有するものであり、設計基準寸法となる横断面長さＷ_４０は周長により示される。そして横断面長さを小さくする場合、筒幅や筒高さを小さくすることで周長である横断面長さＷ_４１を小さくすることができる。なお、上記各形状のワークにおいて、横断面長さの減少が上記の減少方法に限定されるものではない。
以上、本発明について上記実施形態に基づいて説明を行ったが、本発明は上記実施形態の内容に限定をされるものではなく、本発明の範囲を逸脱しない範囲で適宜の変更が可能である。 The work 30 is bent into a rectangular cross section, and one end thereof is bent inward to form a cross-sectional shape. In this work 30, a length extending from the rectangular portion inwardly bent portion is given as a design reference dimension W ₃₀ in cross-section length. On the other hand, if to reduce the cross-sectional length, it is possible to reduce the cross-sectional length W ₃₁ by for example shortening the respective ends of the bent portion bend.
The workpiece 40 has a cylindrical shape with a rectangular cross section, and a transverse cross section length W ₄₀ that is a design reference dimension is indicated by a peripheral length. The case of decreasing the cross-sectional length, it is possible to reduce the cross-sectional length W ₄₁ is a circumferential length by reducing the cylinder width and cylinder height. In addition, in the workpieces of the above shapes, the reduction in the cross-sectional length is not limited to the above-described reduction method.
As described above, the present invention has been described based on the above embodiment, but the present invention is not limited to the content of the above embodiment, and appropriate modifications can be made without departing from the scope of the present invention. .

以下に、本発明の実施例を説明する。
ワーク１として長さ１２００ｍｍ、幅１００ｍｍ、厚さ１．６ｍｍの平板状の鋼板を用意し、長手方向中央部で長さ７００ｍｍに亘って減幅部４を設けた。なお、所定の部位（幅１００ｍｍ）に対する減幅部４の横断面長さの減少率（以下減幅率という）を変えたもの（減幅率１％、２％、３％、４％、５％）をそれぞれ供試材（Ｎｏ．１〜５）とした。
上記供試材の両端側に電極７ａ、７ｂを接触するように固定し、幅広部２ａ、２ｂの長さをそれぞれ１４０ｍｍとした。減幅テーパ部３ａ、３ｂは、その結果、１０ｍｍ長さとなった。 Examples of the present invention will be described below.
A flat steel plate having a length of 1200 mm, a width of 100 mm, and a thickness of 1.6 mm was prepared as the workpiece 1, and the reduced width portion 4 was provided over a length of 700 mm at the central portion in the longitudinal direction. In addition, what changed the reduction rate (henceforth a reduction rate) of the cross-sectional length of the width reduction part 4 with respect to a predetermined | prescribed site | part (width 100mm) (a reduction rate 1%, 2%, 3%, 4%, 5) %) Were used as test materials (Nos. 1 to 5).
The electrodes 7a and 7b were fixed so as to be in contact with both ends of the test material, and the lengths of the wide portions 2a and 2b were 140 mm. As a result, the reduced taper portions 3a and 3b have a length of 10 mm.

上記供試材において以下の条件で通電加熱を行った。
（加熱条件）
通電電圧９〜２０Ｖ（最大２５．６Ｖ）
通電電流２７００〜５７００Ａ（最大９８００Ａ）
加熱時間１０秒 The sample material was energized and heated under the following conditions.
(Heating conditions)
Energizing voltage 9 to 20V (maximum 25.6V)
Energizing current 2700-5700A (maximum 9800A)
Heating time 10 seconds

上記通電加熱に際し、図３（ａ）に示すように、ワークの幅中央において、電極７ｂから７５ｍｍ距離のＡ点、減幅部４の長手方向中央のＢ点、電極７ａと減幅テーパ部３ａとの境界にあって電極７ａから１４０ｍｍ距離のＣ点について、加熱温度を測定した。最高加熱温度を表１に示し、供試材の一部について加熱温度の変化を図４〜図６に示した。
表１および図から明らかなように、減幅に従って減幅部での発熱が集中しやすくなっており、供試材Ｎｏ．２（減幅率２％）〜供試材Ｎｏ．５（減幅率５％）で減幅部に発熱が集中し、供試材Ｎｏ．３（減幅率３％）〜供試材Ｎｏ．５で減幅部への集中が顕著になっている。 3A, at the center of the width of the workpiece, the point A at a distance of 75 mm from the electrode 7b, the point B at the center in the longitudinal direction of the width reduction portion 4, the electrode 7a and the width reduction taper portion 3a, as shown in FIG. The heating temperature was measured at point C at a distance of 140 mm from the electrode 7a. The maximum heating temperature is shown in Table 1, and changes in the heating temperature for some of the test materials are shown in FIGS.
As is apparent from Table 1 and the figure, the heat generation at the reduced portion tends to concentrate as the width decreases. 2 (width reduction rate 2%) to specimen No. 5 (attenuation rate 5%), heat generation was concentrated in the reduced part. 3 (attenuation rate 3%) to specimen No. 5, the concentration on the reduced part is remarkable.

次に、上記ワーク１において５％の減幅によって長さ７００ｍｍ、幅９５ｍｍの減幅部４を設け、該減幅部４の両側に電極間距離が８５５ｍｍとなるように電極７ａ、７ｂを配置した。そして、幅広部２ａ、２ｂはそれぞれ７２．５ｍｍ長、減幅テーパ部３ａ、３ｂは５ｍｍ長とした。
上記ワークにおける電極の配置位置を、電極間距離を一定にして長尺方向に所定量ずらした供試材をそれぞれ用意し、図３（ｂ）に示すように、ワークの幅中央において、減幅テーパ部３ｂの長手方向中央をＡ１点、減幅部４の長手方向中央をＢ１点、減幅テーパ部３ａの長手方向中央をＣ１点とした。これら各点の位置は、Ａ１、Ｂ１点においては電極２ｂからの距離とし、Ｃ１点は電極２ａからの距離とした。 Next, the workpiece 1 is provided with a reduced portion 4 having a length of 700 mm and a width of 95 mm by 5% reduction, and electrodes 7a and 7b are arranged on both sides of the reduced portion 4 so that the distance between the electrodes is 855 mm. did. The wide portions 2a and 2b are 72.5 mm long, and the reduced taper portions 3a and 3b are 5 mm long.
Prepare specimens in which the electrode placement positions in the workpiece are shifted by a predetermined amount in the longitudinal direction with a constant distance between the electrodes. As shown in FIG. The center in the longitudinal direction of the taper portion 3b is A1 point, the center in the longitudinal direction of the reduced width portion 4 is point B1, and the center in the longitudinal direction of the reduced width taper portion 3a is C1 point. The positions of these points were the distance from the electrode 2b at the points A1 and B1, and the distance from the electrode 2a at the point C1.

この供試材に対し、前記と同じ通電条件で加熱を行い、各点での温度を測定した。最大加熱温度を表２に示し、加熱温度の変化を図７〜図１０に示した。
表２および図から明らかなように、板幅減少位置を電極に接近させると、境界部の温度が上昇し、電極から離れた減幅部の中央部の温度が次第に低下する。これは表面積の多い方に熱を奪われるためである。減幅部が、設計基準寸法の横断面長さに対し、０．５倍未満の距離で電極に近接していると、減幅部と電極近傍との温度差が僅かになってしまう。したがって、減幅部を過度に電極に接近させるのは望ましくないことが分かる。 The specimen was heated under the same energizing conditions as described above, and the temperature at each point was measured. The maximum heating temperature is shown in Table 2, and the change in heating temperature is shown in FIGS.
As is apparent from Table 2 and the figure, when the plate width reduction position is brought closer to the electrode, the temperature of the boundary portion increases, and the temperature of the central portion of the reduced width portion away from the electrode gradually decreases. This is because heat is taken away by the one with a larger surface area. If the reduced width portion is close to the electrode at a distance of less than 0.5 times the cross sectional length of the design standard dimension, the temperature difference between the reduced width portion and the vicinity of the electrode becomes slight. Thus, it can be seen that it is not desirable to have the reduced width portion too close to the electrode.

本発明の一実施形態におけるワークへの通電状態を示す図である。It is a figure which shows the electricity supply state to the workpiece | work in one Embodiment of this invention. 同じく、ワークの変更例を示す図である。Similarly, it is a figure which shows the example of a change of a workpiece | work. 本発明の実施例におけるワークおよび温度測定位置を示す図である。It is a figure which shows the workpiece | work and temperature measurement position in the Example of this invention. 同じく、通電時の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the test material at the time of electricity supply. 同じく、通電時の他の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the other test material at the time of electricity supply. 同じく、通電時のさらに他の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the other test material at the time of electricity supply. 同じく、通電時のさらに他の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the other test material at the time of electricity supply. 同じく、通電時のさらに他の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the other test material at the time of electricity supply. 同じく、通電時のさらに他の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the other test material at the time of electricity supply. 同じく、通電時のさらに他の供試材の温度変化を示す図である。Similarly, it is a figure which shows the temperature change of the other test material at the time of electricity supply.

符号の説明Explanation of symbols

１ワーク
２ａ幅広部
２ｂ幅広部
３ａ減幅テーパ部
３ｂ減幅テーパ部
４減幅部
５交流電源
７ａ電極
７ｂ電極
１０、２０、３０、４０ワーク DESCRIPTION OF SYMBOLS 1 Work 2a Wide part 2b Wide part 3a Decreasing taper part 3b Decreasing taper part 4 Decreasing part 5 AC power source 7a Electrode 7b Electrode 10, 20, 30, 40 Workpiece

Claims

加熱処理を施すワークに、互いに距離を隔てた対の電極を接触させ、該電極への通電によって該ワークを加熱する通電加熱方法において、前記電極間のワークの所定部位の横断面長さを設計基準寸法よりも小さくして前記通電に際し該所定部位の加熱温度を部分的に高めることを特徴とする通電加熱方法。 In a current heating method in which a pair of electrodes spaced apart from each other are brought into contact with a workpiece to be heat-treated, and the workpiece is heated by energizing the electrodes, the cross-sectional length of a predetermined portion of the workpiece between the electrodes is designed An energization heating method characterized in that the heating temperature of the predetermined portion is partially increased during energization by making it smaller than a reference dimension.

前記ワークは、設計基準寸法において横断面形状が連続して一定であることを特徴とする請求項１記載の通電加熱方法。 2. The energization heating method according to claim 1, wherein the workpiece has a continuously constant cross-sectional shape in a design standard dimension.

加熱処理を施すワークに、互いに距離を隔てた対の電極を接触させ、該電極への通電によって該ワークを加熱する通電加熱方法において、前記ワークは、設計基準寸法において横断面形状が連続して一定である形状を有し、前記電極間のワークの所定部位の横断面長さを前記電極が接触する部位の横断面長さよりも小さくして前記通電に際し該所定部位の加熱温度を部分的に高めることを特徴とする通電加熱方法。 In the energization heating method in which a pair of electrodes spaced apart from each other are brought into contact with a workpiece to be heat-treated, and the workpiece is heated by energizing the electrodes, the workpiece has a continuous cross-sectional shape in a design reference dimension. The cross section length of the predetermined portion of the workpiece between the electrodes is smaller than the cross sectional length of the portion in contact with the electrode, and the heating temperature of the predetermined portion is partially set during the energization. An electric heating method characterized by increasing.

前記ワークは、周囲に加工代を有する粗形材であり該加工代量を部分的に小さくすることで前記所定部位の横断面長さを設計寸法よりも小さくすることを特徴とする請求項１〜３のいずれかに記載の通電加熱方法。 The workpiece is a rough shape having a machining allowance around it, and the cross-sectional length of the predetermined portion is made smaller than the design dimension by partially reducing the machining allowance. The energization heating method in any one of -3.

前記ワークは最終形状品であり、前記所定の部位に対する他の部位の横断面長さを前記設計基準寸法よりも大きくすることで前記所定部位の横断面長さを相対的に小さくすることを特徴とする請求項１〜４のいずれかに記載の通電加熱方法。 The workpiece is a final shape product, and the cross-sectional length of the predetermined part is relatively reduced by making the cross-sectional length of the other part with respect to the predetermined part larger than the design reference dimension. The energization heating method according to any one of claims 1 to 4.

前記横断面長さの減少率が２％以上であることを特徴とする請求項１〜５のいずれかに記載の通電加熱方法。 6. The energization heating method according to claim 1, wherein a reduction rate of the cross-sectional length is 2% or more.

前記横断面長さを小さくした所定部位が、電極の接触位置から、減少した横断面長さに対し０．５倍以上の距離を隔てていることを特徴とする請求項１〜６のいずれかに記載の通電加熱方法。 The predetermined portion with the reduced cross-sectional length is separated from the contact position of the electrode by a distance of 0.5 times or more with respect to the reduced cross-sectional length. The energization heating method according to 1.