JP2020190516A - Tensile test method and device for metal material - Google Patents
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- 238000009864 tensile test Methods 0.000 title claims abstract description 76
- 238000000034 method Methods 0.000 title claims abstract description 51
- 239000007769 metal material Substances 0.000 title claims abstract description 42
- 238000012360 testing method Methods 0.000 claims abstract description 236
- 238000010438 heat treatment Methods 0.000 claims abstract description 110
- 230000006698 induction Effects 0.000 claims abstract description 67
- 238000001816 cooling Methods 0.000 claims description 21
- 238000002347 injection Methods 0.000 claims description 16
- 239000007924 injection Substances 0.000 claims description 16
- 239000000112 cooling gas Substances 0.000 claims description 13
- 238000007664 blowing Methods 0.000 claims description 3
- 238000005259 measurement Methods 0.000 abstract description 8
- 238000003754 machining Methods 0.000 abstract description 3
- 229910000831 Steel Inorganic materials 0.000 description 17
- 239000010959 steel Substances 0.000 description 17
- 238000012545 processing Methods 0.000 description 9
- 238000006073 displacement reaction Methods 0.000 description 6
- 238000003780 insertion Methods 0.000 description 5
- 230000037431 insertion Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000001939 inductive effect Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 239000003779 heat-resistant material Substances 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910001026 inconel Inorganic materials 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
- 238000002791 soaking Methods 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
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Abstract
Description
本発明は、薄板金属材料の加熱状態での加工特性を測定するための引張試験方法及び装置に関するものであり、特に高強度鋼板の引張試験に好適な引張試験技術である。 The present invention relates to a tensile test method and apparatus for measuring the processing characteristics of a thin metal material in a heated state, and is a tensile test technique particularly suitable for a tensile test of a high-strength steel sheet.
近年、自動車分野において、衝突安全性の確保と車体軽量化による燃費向上を目的として、ハイテン材、超ハイテン材と呼ばれるような高い強度を有する鋼板（高強度鋼板）の使用比率が増加している。
一方、車体などの自動車部品の成形に関しては、近年、従来の冷間でのプレス成形に代わり、いわゆるホットスタンプが適用される比率が増している。このホットスタンプは、加熱した高強度鋼板を型で急冷しながら成形することで、焼き入れされた高強度で高精度な部品を製作することができる利点がある。
In recent years, in the automobile field, the ratio of high-strength steel sheets (high-strength steel sheets) called high-tensile steels and ultra-high-tensile steel sheets has been increasing for the purpose of ensuring collision safety and improving fuel efficiency by reducing the weight of the vehicle body. ..
On the other hand, with regard to the molding of automobile parts such as car bodies, the ratio of so-called hot stamping is increasing in recent years instead of the conventional cold press molding. This hot stamp has an advantage that a hardened high-strength and high-precision part can be manufactured by molding a heated high-strength steel sheet while quenching it with a mold.
このような背景から、加熱状態の高強度鋼板の加工特性を正確に把握する必要性が生じており、高強度鋼板の薄板試験片の温間・熱間引張試験技術の確立が求められている。
従来、温間や熱間で丸棒などの引張試験を行う装置が知られており（例えば、特許文献１）、試験片の加熱方式としては、試験片を誘導加熱コイル内に挿通して高周波誘導加熱する方式と、試験片の両端を電極に接続して直接通電加熱する方式がある。
Against this background, it is necessary to accurately grasp the processing characteristics of high-strength steel sheets in a heated state, and it is required to establish a warm / hot tensile test technique for thin sheet test pieces of high-strength steel sheets. ..
Conventionally, a device for performing a tensile test of a round bar or the like in a warm or hot state has been known (for example, Patent Document 1), and as a heating method for a test piece, the test piece is inserted into an induction heating coil to obtain a high frequency. There is a method of induction heating and a method of directly energizing and heating by connecting both ends of the test piece to electrodes.
しかし、温間や熱間で丸棒などの引張試験を行う従来の引張試験装置を薄板試験片の引張試験に適用した場合、以下のような問題がある。
まず、試験片を高周波誘導加熱する方式の装置は、薄板試験片の温度コントロールが容易であるという利点があるが、薄板試験片に伸び計を取り付けることができないという問題がある。すなわち、薄板試験片の引張試験では、材料の加工特性を正確に把握するために、標点間の伸び量を測定することが好ましい。その場合、伸び計の固定具を薄板試験片の標点位置に取り付ける必要があるが、高周波誘導加熱方式の装置では、薄板試験片の主要部分が誘導加熱コイル内に置かれるため、この誘導加熱コイルが邪魔になって伸び計の固定具を試験片に取り付けることができない。したがって、従来のような高周波誘導加熱方式の装置は、薄板試験片の引張試験には適用できない。
However, when a conventional tensile test device that performs a tensile test of a round bar or the like warmly or hotly is applied to a tensile test of a thin plate test piece, there are the following problems.
First, the device of the type of high-frequency induction heating of the test piece has an advantage that the temperature of the thin plate test piece can be easily controlled, but there is a problem that an extensometer cannot be attached to the thin plate test piece. That is, in the tensile test of the thin plate test piece, it is preferable to measure the amount of elongation between the gauge points in order to accurately grasp the processing characteristics of the material. In that case, it is necessary to attach the fixture of the extensometer to the reference point position of the thin plate test piece, but in the high frequency induction heating type device, the main part of the thin plate test piece is placed in the induction heating coil, so this induction heating The coil is in the way and the extensometer fixture cannot be attached to the test piece. Therefore, the conventional high-frequency induction heating type device cannot be applied to the tensile test of the thin plate test piece.
一方、試験片を直接通電加熱する方式の装置は、薄板試験片を広範囲に加熱できる利点はあるが、薄板試験片の長手方向を均一に加熱することができない（温度勾配が生じる）という問題がある。試験片を直接通電加熱する方式の装置では、試験片の両端をチャックで把持し、このチャックを電極として試験片を通電加熱するものであるが、チャックを保持する部材が冷却機構（水冷などによる冷却機構）を備え、この冷却機構でチャックが冷却されているため、チャックを通じて薄板試験片からの抜熱が生じる。このため薄板試験片長手方向で大きな温度勾配が生じ、例えば、薄板試験片長手方向の中心点から２０ｍｍ程度離れた位置では、中心点よりも１００℃以上低い温度となる。このため伸び計を用いたとしても、薄板試験片の加工特性を正確に測定することができない。
したがって本発明の目的は、以上のような従来技術の課題を解決し、高強度鋼板などの薄板金属材料の加熱状態での加工特性を正確に測定することができる引張試験方法及び装置を提供することにある。
On the other hand, a device that directly energizes and heats a test piece has an advantage that the thin plate test piece can be heated in a wide range, but has a problem that the longitudinal direction of the thin plate test piece cannot be uniformly heated (a temperature gradient is generated). is there. In a device that directly energizes and heats a test piece, both ends of the test piece are gripped by a chuck, and the test piece is energized and heated using this chuck as an electrode. The member holding the chuck is a cooling mechanism (water cooling or the like). A cooling mechanism) is provided, and since the chuck is cooled by this cooling mechanism, heat is removed from the thin plate test piece through the chuck. Therefore, a large temperature gradient occurs in the longitudinal direction of the thin plate test piece, and for example, at a position about 20 mm away from the center point in the longitudinal direction of the thin plate test piece, the temperature becomes 100 ° C. or more lower than the center point. Therefore, even if an extensometer is used, the processing characteristics of the thin plate test piece cannot be accurately measured.
Therefore, an object of the present invention is to provide a tensile test method and an apparatus capable of solving the above-mentioned problems of the prior art and accurately measuring the processing characteristics of a thin metal material such as a high-strength steel plate in a heated state. There is.
本発明者らは、上記課題を解決するために検討を重ねた結果、両端をチャックで把持された薄板試験片を、両チャックを電極として直接通電加熱するとともに、薄板試験片両端側の部位（両チャック寄りの部位）のみを誘導加熱コイルにより部分的に高周波誘導加熱し、チャックを通じた抜熱分を補償することにより、薄板試験片長手方向での均熱性（温度勾配が小さいこと）を飛躍的に高めることができ、伸び計による測定範囲の温度勾配をほぼ解消できることが判った。
本発明は、このような知見に基づきなされたもので、以下を要旨とするものである。
As a result of repeated studies to solve the above problems, the present inventors directly energize and heat the thin plate test piece whose both ends are gripped by chucks using both chucks as electrodes, and the parts on both ends of the thin plate test piece ( By partially inducing and heating only the part near both chucks with an induction heating coil to compensate for the heat removal through the chucks, the heat equalization property (small temperature gradient) in the longitudinal direction of the thin plate test piece is dramatically improved. It was found that the temperature gradient in the measurement range of the extensometer can be almost eliminated.
The present invention has been made based on such findings, and has the following gist.
［1］両端をチャック（１）で把持された薄板試験片（Ａ）を加熱状態とし、この加熱状態の薄板試験片（Ａ）に引張荷重を負荷する金属材料の引張試験方法であって、
両チャック（１）を電極として薄板試験片（Ａ）を直接通電加熱するとともに、薄板試験片（Ａ）の長手方向のうちの両端側の部位のみを誘導加熱コイル（２）で部分的に高周波誘導加熱することを特徴とする金属材料の引張試験方法。
［2］上記［1］の引張試験方法において、薄板試験片長手方向の中央位置（p）と各チャック（１）間の距離をＬとした場合、誘導加熱コイル（２）が、薄板試験片長手方向において各チャック（１）からの距離がＬ／２の点（p１）と当該チャック（１）間の範囲内に配置されることを特徴とする金属材料の引張試験方法。
［3］上記［2］の引張試験方法において、誘導加熱コイル（２）が、薄板試験片長手方向において各チャック（１）からの距離がＬ／２の点（p１）とＬ／１５の点（p２）間の範囲内に配置されることを特徴とする金属材料の引張試験方法。
[1] A tensile test method for a metal material in which a thin plate test piece (A) whose both ends are gripped by a chuck (1) is heated and a tensile load is applied to the heated thin plate test piece (A).
The thin plate test piece (A) is directly energized and heated by using both chucks (1) as electrodes, and only the portions on both ends of the longitudinal direction of the thin plate test piece (A) are partially high-frequency by the induction heating coil (2). A method for tensile testing a metal material, which comprises induction heating.
[2] In the tensile test method of [1] above, when the distance between the central position (p) in the longitudinal direction of the thin plate test piece and each chuck (1) is L, the induction heating coil (2) has the length of the thin plate test piece. A method for tensile testing a metal material, wherein the distance from each chuck (1) in the manual direction is arranged within a range between the point (p 1 ) of L / 2 and the chuck (1).
[3] In the tensile test method of [2] above, the induction heating coil (2) has a distance of L / 2 from each chuck (1) in the longitudinal direction of the thin plate test piece (p 1 ) and L / 15. A method for tensile testing a metallic material, characterized in that it is arranged within a range between points (p 2 ).
［4］上記［1］〜［3］のいずれかの引張試験方法において、伸び計（３）により薄板試験片（Ａ）の標点間の伸び量を測定することを特徴とする金属材料の引張試験方法。
［5］上記［4］の引張試験方法において、薄板試験片（Ａ）を所定の熱履歴で加熱又は加熱−冷却し、その熱履歴中の任意の時点で引張試験を行って薄板試験片（Ａ）の標点間の伸び量を測定することを特徴とする金属材料の引張試験方法。
［6］上記［5］の引張試験方法において、薄板試験片（Ａ）を所定の熱履歴で加熱−冷却する際の冷却工程では、薄板試験片（Ａ）に噴射ノズル（４）から冷却ガスを吹き付けることを特徴とする金属材料の引張試験方法。
[4] In any of the above-mentioned tensile test methods [1] to [3], the amount of elongation between the gauge points of the thin plate test piece (A) is measured by the extensometer (3). Tensile test method.
[5] In the tensile test method of [4] above, the thin plate test piece (A) is heated or heated-cooled with a predetermined heat history, and a tensile test is performed at any time in the heat history to perform the thin plate test piece ( A) A method for tensile testing a metal material, which comprises measuring the amount of elongation between reference points.
[6] In the tensile test method of the above [5], in the cooling step when the thin plate test piece (A) is heated and cooled with a predetermined heat history, the thin plate test piece (A) is subjected to the cooling gas from the injection nozzle (4). A tensile test method for a metallic material, which comprises spraying.
［7］両端をチャック（１）で把持された薄板試験片（Ａ）を加熱状態とし、この加熱状態の薄板試験片（Ａ）に引張荷重を負荷する金属材料の引張試験装置であって、
両チャック（１）が、薄板試験片（Ａ）を直接通電加熱するための電極を構成するとともに、薄板試験片（Ａ）の長手方向のうちの両端側の部位のみを部分的に高周波誘導加熱する誘導加熱コイル（２）を備えることを特徴とする金属材料の引張試験装置。
［8］上記［7］の引張試験装置において、薄板試験片長手方向の中央位置（p）と各チャック（１）間の距離をＬとした場合、誘導加熱コイル（２）が、薄板試験片長手方向において各チャック（１）からの距離がＬ／２の点（p１）と当該チャック（１）間の範囲内に配置されることを特徴とする金属材料の引張試験装置。
[7] A tensile test device for a metal material in which a thin plate test piece (A) whose both ends are gripped by a chuck (1) is heated and a tensile load is applied to the heated thin plate test piece (A).
Both chucks (1) form electrodes for directly energizing and heating the thin plate test piece (A), and only partially high-frequency induction heating is performed on both ends of the thin plate test piece (A) in the longitudinal direction. A tensile test device for a metal material, which comprises an induction heating coil (2).
[8] In the tensile test apparatus of [7] above, when the distance between the central position (p) in the longitudinal direction of the thin plate test piece and each chuck (1) is L, the induction heating coil (2) has the length of the thin plate test piece. A tensile test device for a metallic material, characterized in that the distance from each chuck (1) in the manual direction is within the range between the point (p 1 ) of L / 2 and the chuck (1).
［9］上記［8］の引張試験装置において、誘導加熱コイル（２）が、薄板試験片長手方向において各チャック（１）からの距離がＬ／２の点（p１）とＬ／１５の点（p２）間の範囲内に配置されることを特徴とする金属材料の引張試験装置。
［10］上記［7］〜［9］のいずれかの引張試験装置において、薄板試験片（Ａ）の標点間の伸び量を測定する伸び計（３）を備えることを特徴とする金属材料の引張試験装置。
［11］上記［7］〜［10］のいずれかの引張試験装置において、薄板試験片（Ａ）に冷却ガスを吹き付ける噴射ノズル（４）を備えることを特徴とする金属材料の引張試験装置。
[9] In the tensile test apparatus of [8] above, the induction heating coil (2) has a distance of L / 2 from each chuck (1) in the longitudinal direction of the thin plate test piece (p 1 ) and L / 15. tensile testing device for a metallic material being disposed within the range between the point (p 2).
[10] The tensile test apparatus according to any one of [7] to [9] above, characterized in that it includes an extensometer (3) for measuring the amount of elongation between the gauge points of the thin plate test piece (A). Tensile test equipment.
[11] The tensile test apparatus for a metal material according to any one of the above [7] to [10], comprising an injection nozzle (4) for blowing a cooling gas onto the thin plate test piece (A).
［12］上記［7］〜［11］のいずれかの引張試験装置を用い、金属材料の薄板試験片に所定の熱履歴を付与する方法（但し、薄板試験片の引張試験を行う方法を除く。）であって、
両端をチャック（１）で把持された薄板試験片（Ａ）を所定の熱履歴で加熱又は加熱−冷却することを特徴とする、金属材料の薄板試験片に対する熱履歴付与方法。
［13］上記［12］の熱履歴付与方法において、薄板試験片（Ａ）を所定の熱履歴で加熱−冷却する際の冷却工程では、薄板試験片（Ａ）に噴射ノズル（４）から冷却ガスを吹き付けることを特徴とする、金属材料の薄板試験片に対する熱履歴付与方法。
[12] A method of imparting a predetermined thermal history to a thin plate test piece of a metal material using the tensile test apparatus according to any one of the above [7] to [11] (however, the method of performing a tensile test of the thin plate test piece is excluded. .) And
A method for imparting a heat history to a thin plate test piece made of a metal material, which comprises heating or heating-cooling a thin plate test piece (A) whose both ends are gripped by a chuck (1) with a predetermined heat history.
[13] In the cooling step of heating-cooling the thin plate test piece (A) with a predetermined heat history in the heat history imparting method of the above [12], the thin plate test piece (A) is cooled from the injection nozzle (4). A method for imparting a heat history to a thin plate test piece of a metal material, which comprises blowing gas.
本発明によれば、加熱状態にある薄板試験片の引張試験において、薄板試験片長手方向での均熱性（温度勾配が小さいこと）を飛躍的に高めることができ、このため高強度鋼板などの薄板金属材料の加熱状態での加工特性を正確に測定することができる。 According to the present invention, in the tensile test of a thin plate test piece in a heated state, the heat equalization property (the temperature gradient is small) in the longitudinal direction of the thin plate test piece can be dramatically improved, and therefore, a high-strength steel plate or the like can be used. It is possible to accurately measure the processing characteristics of a thin metal material in a heated state.
本発明は、両端をチャック１で把持された薄板試験片Ａを加熱状態とし、この加熱状態の薄板試験片Ａに引張荷重を負荷する金属材料の引張試験方法であり、両チャック１を電極として薄板試験片Ａを直接通電加熱するとともに、薄板試験片Ａの長手方向のうちの両端側の部位のみを誘導加熱コイル２で部分的に高周波誘導加熱することにより、チャックを通じた抜熱分を熱補償し、薄板試験片長手方向での均熱性（温度勾配が小さいこと）を高めるものである。これにより、試験片中央部での伸び計による測定範囲（標点間位置）の温度を均一にすることができる。
なお、本発明の引張試験方法の対象となる薄板とは、一般に厚さが６ｍｍ以下の板状金属材料を指す。
The present invention is a tensile test method for a metal material in which a thin plate test piece A whose both ends are gripped by a chuck 1 is heated and a tensile load is applied to the heated thin plate test piece A, and both chucks 1 are used as electrodes. The thin plate test piece A is directly energized and heated, and only the portions on both ends of the longitudinal direction of the thin plate test piece A are partially high-frequency induction heated by the induction heating coil 2 to heat the heat removed through the chuck. It compensates and enhances the soaking property (small temperature gradient) in the longitudinal direction of the thin plate test piece. As a result, the temperature in the measurement range (position between the gauge points) measured by the extensometer at the center of the test piece can be made uniform.
The thin plate to which the tensile test method of the present invention is applied generally refers to a plate-shaped metal material having a thickness of 6 mm or less.
図１（斜視図）は、本発明の一実施形態における薄板試験片Ａの引張試験部を示しており、薄板試験片Ａは、その長手方向が上下方向となるようにして、両端（上下端）をチャック１x，１yで把持される。本実施形態では、チャック１xが可動側、チャック１yが固定側であり、引張試験時には、チャック１x，１yが薄板試験片Ａの両端を把持した状態で、図示しない駆動機構（アクチュエータなどによる駆動機構）によりチャック１xが移動（上昇）することにより、薄板試験片Ａに引張荷重が負荷される。また、通常、引張荷重は可動側（チャック１xの支持部材）に設けられるロードセルなどで検出される。 FIG. 1 (perspective view) shows a tensile test portion of the thin plate test piece A according to the embodiment of the present invention, and both ends (upper and lower ends) of the thin plate test piece A so that the longitudinal direction thereof is the vertical direction. ) Is gripped by the chucks 1x and 1y. In the present embodiment, the chuck 1x is on the movable side and the chuck 1y is on the fixed side. During the tensile test, the chucks 1x and 1y hold both ends of the thin plate test piece A, and a drive mechanism (drive mechanism by an actuator or the like) (not shown) is used. ) Moves (rises) the chuck 1x, so that a tensile load is applied to the thin plate test piece A. Further, the tensile load is usually detected by a load cell or the like provided on the movable side (support member of the chuck 1x).
本発明では、薄板試験片Ａの主たる加熱を直接通電加熱で行い、補助的な局部加熱を高周波誘導加熱で行うものであり、このため、両チャック１x，１yが、薄板試験片Ａを直接通電加熱するための電極を構成するとともに、薄板試験片Ａの長手方向のうちの両端側の部位ａのみを部分的に高周波誘導加熱する誘導加熱コイル２x，２yが設けられる。
本発明の引張試験方法で使用される薄板試験片Ａの形状に特別な制限はないが、通常は、図２（ア）に示すような細長矩形の平面形状を有するものや、図２（イ）に示すようなＪＩＳ５号試験片（この例はＪＩＳ５号ハーフ試験片）が使用される。図２（ア），（イ）は薄板試験片Ａの平面形状を示している。薄板試験片Ａの長手方向両端部には、チャック１x，１yに対してボルト締めするための複数のボルト挿通孔ｅが貫設されている。このように複数のボルト挿通孔ｅにボルトを通してボルト締めすることにより、薄板試験片Ａをチャック１x，１yにしっかりと固定することができる。
薄板試験片Ａのサイズも特に制限はないが、通常、幅が３０〜５０ｍｍ程度（図２（イ）に示すＪＩＳ５号試験片の場合は両端部分の幅）、全長が１００〜２００ｍｍ程度、チャック１ｘ，１ｙ間の薄板試験片長さが５０〜１５０ｍｍ程度、板厚が０．１〜５ｍｍ程度である。
In the present invention, the main heating of the thin plate test piece A is performed by direct energization heating, and the auxiliary local heating is performed by high frequency induction heating. Therefore, both chucks 1x and 1y directly energize the thin plate test piece A. In addition to forming an electrode for heating, induction heating coils 2x and 2y are provided to partially heat only the portions a on both ends of the longitudinal direction of the thin plate test piece A at high frequencies.
The shape of the thin plate test piece A used in the tensile test method of the present invention is not particularly limited, but usually, one having an elongated rectangular planar shape as shown in FIG. 2 (a) or FIG. 2 (a). ) Is used as shown in the JIS No. 5 test piece (in this example, the JIS No. 5 half test piece). FIGS. 2A and 2B show the planar shape of the thin plate test piece A. A plurality of bolt insertion holes e for bolting the chucks 1x and 1y are provided at both ends of the thin plate test piece A in the longitudinal direction. By passing bolts through the plurality of bolt insertion holes e and tightening the bolts in this way, the thin plate test piece A can be firmly fixed to the chucks 1x and 1y.
The size of the thin plate test piece A is also not particularly limited, but usually the width is about 30 to 50 mm (in the case of the JIS No. 5 test piece shown in FIG. 2 (a), the width of both ends), the total length is about 100 to 200 mm, and the chuck. The length of the thin plate test piece between 1x and 1y is about 50 to 150 mm, and the plate thickness is about 0.1 to 5 mm.
チャック１x，１yは、それぞれ、薄板試験片Ａのボルト挿通孔ｅと対応するボルト挿通孔（図示せず）を有する１対のチャック構成部材５を有し、この１対のチャック構成部材５で薄板試験片両端部を両側から挟み、ボルト（ボルト６）締めすることにより、薄板試験片Ａの両端を把持する。
チャック１x，１yは、それぞれ支持部材（図示せず）などを介して装置本体に支持されており、チャック１xの支持部材は、上述したように駆動機構（アクチュエータなどによる駆動機構）に連結され、移動（上下昇降）可能である。チャック１x，１yは、薄板試験片Ａを直接通電加熱するための電極を構成するものであるため、それらの支持部材などを介して直接通電加熱用電源（図示せず）に接続される。また、通電加熱による発熱からチャック１x，１yを保護するため、それらの支持部材は水冷などの冷却機構を備え、この冷却機構でチャック１x，１yを冷却する。
The chucks 1x and 1y each have a pair of chuck constituent members 5 having a bolt insertion hole e corresponding to the bolt insertion hole e of the thin plate test piece A (not shown), and the pair of chuck constituent members 5 Both ends of the thin plate test piece A are gripped by sandwiching both ends of the thin plate test piece from both sides and tightening bolts (bolts 6).
The chucks 1x and 1y are supported by the device main body via support members (not shown), respectively, and the support members of the chuck 1x are connected to a drive mechanism (drive mechanism by an actuator or the like) as described above. It can be moved (up and down). Since the chucks 1x and 1y form electrodes for directly energizing and heating the thin plate test piece A, they are directly connected to a power source for energizing and heating (not shown) via their support members and the like. Further, in order to protect the chucks 1x and 1y from heat generated by energization heating, their support members are provided with a cooling mechanism such as water cooling, and the chucks 1x and 1y are cooled by this cooling mechanism.
誘導加熱コイル２x，２yは、薄板試験片Ａの長手方向のうちの両端側の部位ａのみを部分的に高周波誘導加熱するものであるので、このような局部加熱に適したコイル厚（図３に示す薄板試験片長手方向でのコイル厚ｔ）に構成されるとともに、両チャック１x，１yに近い位置に配置される。
誘導加熱コイル２x，２yは、それぞれチャック１x，１yとの位置関係が一定に維持される必要があるので、誘導加熱コイル２xは、チャック１xの支持部材（可動側の支持部材）に支持され、引張試験時にはチャック１xと一体に移動する。一方、誘導加熱コイル２yは、チャック１yの支持部材などのような固定側の支持部材に支持される。なお、誘導加熱コイル２x，２yのチャック１x，１yに対する位置関係を微調整するための機構を付設してもよい。
Since the induction heating coils 2x and 2y partially perform high-frequency induction heating only at the portions a on both ends in the longitudinal direction of the thin plate test piece A, the coil thickness is suitable for such local heating (FIG. 3). The coil thickness is t) in the longitudinal direction of the thin plate test piece shown in (1), and both chucks are arranged at positions close to 1x and 1y.
Since the induction heating coils 2x and 2y need to maintain a constant positional relationship with the chucks 1x and 1y, respectively, the induction heating coils 2x are supported by the support member (support member on the movable side) of the chuck 1x. During the tensile test, it moves integrally with the chuck 1x. On the other hand, the induction heating coil 2y is supported by a support member on the fixed side such as a support member of the chuck 1y. A mechanism for finely adjusting the positional relationship between the induction heating coils 2x and 2y with respect to the chucks 1x and 1y may be provided.
誘導加熱コイル２x，２yは、薄板試験片長手方向のうちの両端側の部位ａの幅方向を均一に加熱できるものであれば、その構成や形状などに特別な制限はない。本実施形態の誘導加熱コイル２x，２yは、薄板試験片幅方向に沿って対向する１対のコイル部２０と、両コイル部２０をそれらの一端側で連結するコイル２１からなる平面コ字状の構成を有し、両コイル部２０間に薄板試験片Ａが位置し、部位ａの幅方向を均一に加熱できるようにしている。 The induction heating coils 2x and 2y are not particularly limited in their configuration and shape as long as they can uniformly heat the width direction of the portions a on both ends in the longitudinal direction of the thin plate test piece. The induction heating coils 2x and 2y of the present embodiment have a flat U-shape composed of a pair of coil portions 20 facing each other along the width direction of the sheet test piece and a coil 21 connecting both coil portions 20 on one end side thereof. The thin plate test piece A is located between the two coil portions 20 so that the width direction of the portion a can be uniformly heated.
誘導加熱コイル２x，２yは、各チャック１x，１yにあまり近すぎると、電極であるチャック１x，１y（上述したように支持部材の冷却機構で冷却されている）を加熱してしまい、直接通電加熱に支障を生じるおそれがある。一方、誘導加熱コイル２x，２yが各チャック１x，１yから離れすぎると、電極（チャック１x，１y）からの抜熱分を熱補償することによる均熱性の確保ができなくなるおそれがあるとともに、後述するような伸び計による測定範囲を狭めてしまうため好ましくない。
引張試験の試験片としては、丸棒形状のものがあるが、丸棒試験片は表面積が小さく、しかも薄板試験片とは異なり幅方向での端部が存在しないため、熱が逃げにくく、このため長手方向での温度分布が生じにくい。これに対して本発明が試験対象とする薄板試験片は、丸棒試験片に較べて表面積が大きく、しかも幅方向での端部が存在するため、熱の放射（抜熱）により熱が逃げやすく、このため長手方向において温度分布が生じやすい。このような点からも、本発明では誘導加熱コイル２x，２yを配置する位置を最適化することが好ましい。
If the induction heating coils 2x and 2y are too close to the chucks 1x and 1y, the electrodes chucks 1x and 1y (cooled by the cooling mechanism of the support member as described above) are heated and the induction heating coils 2x and 2y are directly energized. It may interfere with heating. On the other hand, if the induction heating coils 2x and 2y are too far from the chucks 1x and 1y, the heat equalization may not be ensured by thermally compensating for the heat removed from the electrodes (chuck 1x and 1y). This is not preferable because it narrows the measurement range with an extensometer.
There is a round bar-shaped test piece for the tensile test, but the round bar test piece has a small surface area, and unlike the thin plate test piece, there is no end in the width direction, so heat does not easily escape. Therefore, the temperature distribution in the longitudinal direction is unlikely to occur. On the other hand, the thin plate test piece to be tested by the present invention has a larger surface area than the round bar test piece and has an end in the width direction, so that heat escapes due to heat radiation (extraction). Therefore, a temperature distribution is likely to occur in the longitudinal direction. From this point of view, it is preferable to optimize the positions of the induction heating coils 2x and 2y in the present invention.
図３は、薄板試験片Ａ及びチャック１x，１yに対する誘導加熱コイル２x，２yの位置関係を示したものであり、pは薄板試験片長手方向の中央位置、Ｌはその中央位置pと各チャック１x，１y間の距離である。ここで、上述したような観点から、誘導加熱コイル２x，２yは、薄板試験片長手方向の中央位置pと各チャック１x，１y間におけるチャック寄りの位置、すなわち、薄板試験片長手方向において各チャック１x，１yからの距離がＬ／２の点p１と当該チャック１x，１y間の範囲内に配置されることが好ましい。また、さらに好ましい条件としては、誘導加熱コイル２x，２yは、薄板試験片長手方向において各チャック１x，１yからの距離がＬ／２の点p１とＬ／１５の点p２間の範囲S1（薄板試験片長手方向での範囲）内に配置されることが好ましい。また、より好ましい条件としては、誘導加熱コイル２x，２yが、薄板試験片長手方向において各チャック１x，１yからの距離がＬ／２．５の点p３とＬ／１２の点p４間の範囲S2（薄板試験片長手方向での範囲）内に配置されることが好ましく、また、薄板試験片長手方向において各チャック１x，１yからの距離がＬ／３の点p５とＬ／１０の点p６間の範囲S3（薄板試験片長手方向での範囲）内に配置されることが特に好ましい。 FIG. 3 shows the positional relationship of the induction heating coils 2x and 2y with respect to the thin plate test piece A and the chucks 1x and 1y. P is the central position in the longitudinal direction of the thin plate test piece, L is the central position p and each chuck. It is the distance between 1x and 1y. Here, from the viewpoint as described above, the induction heating coils 2x and 2y are located at the center position p in the longitudinal direction of the thin plate test piece and the positions closer to the chucks between the chucks 1x and 1y, that is, each chuck in the longitudinal direction of the thin plate test piece. 1x, the distance from 1y is L / 2 point p 1 and the chuck 1x, it is preferably located within a range of between 1y. As the more preferable conditions, the induction heating coil 2x, 2y, each chuck 1x in thin specimens longitudinally range distance from 1y is between point p 2 of p 1 and L / 15 in terms of L / 2 S1 It is preferably arranged within (the range in the longitudinal direction of the thin plate test piece). Further, a more preferable condition, the induction heating coil 2x, 2y is, the chucks 1x in thin specimens longitudinally from 1y distance between points p 3 and L / 12 point p 4 of the L / 2.5 it is preferably disposed within S2 (ranging from a thin plate specimen longitudinal direction), and each chuck 1x in thin specimens longitudinal distance from 1y is a point p 5 and L / 10 of L / 3 It is placed within S3 in between the points p 6 (range in thin specimen longitudinal direction) is particularly preferred.
以上のような条件を満たす位置に配置された誘導加熱コイル２x，２yで薄板試験片Ａを部分的に高周波誘導加熱することにより、その熱がチャック１x，１yに及んでチャックの機能が害されるようなことが避けられ、且つ伸び計による測定範囲が狭められるようなこともなく、薄板試験片長手方向の均熱性を高めることができる。
また、誘導加熱コイル２のコイル厚ｔ（薄板試験片長手方向でのコイル厚）は、必要とされる範囲を局所的に誘導加熱するために３〜１０ｍｍ程度とすることが好ましい。また、誘導加熱コイル２と薄板試験片Ａの間隔ｃは、小さすぎると誘導加熱コイル２が試験片からの放射熱を強く受けるため好ましくなく、一方、遠すぎると高周波誘導加熱による加熱能力が低下するので、５〜１０ｍｍ程度とすることが好ましい。
なお、図３では、範囲S1〜S3、コイル厚t及び間隔cを、一つの誘導加熱コイル２x，２yについてのみ示しているが、他の誘導加熱コイル２x，２yについても同様である。
By partially high-frequency induction heating of the thin plate test piece A with the induction heating coils 2x and 2y arranged at positions satisfying the above conditions, the heat extends to the chucks 1x and 1y and the function of the chuck is impaired. Such a situation can be avoided, and the measurement range by the extensometer is not narrowed, and the heat equalizing property in the longitudinal direction of the thin plate test piece can be improved.
Further, the coil thickness t (coil thickness in the longitudinal direction of the thin plate test piece) of the induction heating coil 2 is preferably about 3 to 10 mm for locally inducing heating in a required range. Further, if the distance c between the induction heating coil 2 and the thin plate test piece A is too small, the induction heating coil 2 receives strong radiant heat from the test piece, which is not preferable. On the other hand, if it is too far, the heating capacity due to high frequency induction heating decreases. Therefore, it is preferably about 5 to 10 mm.
In FIG. 3, the range S1 to S3, the coil thickness t, and the interval c are shown only for one induction heating coil 2x, 2y, but the same applies to the other induction heating coils 2x, 2y.
また、直接通電加熱による薄板試験片Ａの加熱温度を制御するため、薄板試験片長手方向の中央位置p（中央位置pの幅方向中央）に熱電対７が取り付けられ、この熱電対７で中央位置pの試験片温度が測定される。この中央位置pの試験片温度を直接通電加熱の制御温度とし、測定された試験片温度に基づく直接通電加熱電源のフィードバック制御などにより温度制御が行われる。
また、図示しないが、誘導加熱コイル２x，２yで加熱される薄板試験片Ａの部位ａ（部位ａの幅方向中央）にも熱電対が取り付けられ、この熱電対で部位ａの試験片温度が測定され、この測定された試験片温度に基づく高周波誘導加熱電源のフィードバック制御などにより部位ａの温度制御が行われる。
Further, in order to control the heating temperature of the thin plate test piece A by direct energization heating, a thermocouple 7 is attached at the center position p in the longitudinal direction of the thin plate test piece (center in the width direction of the center position p), and the thermocouple 7 is at the center. The temperature of the test piece at position p is measured. The temperature of the test piece at the central position p is set as the control temperature for direct energization heating, and the temperature is controlled by feedback control of the direct energization heating power source based on the measured test piece temperature.
Further, although not shown, a thermocouple is also attached to a portion a (center in the width direction of the portion a) of the thin plate test piece A heated by the induction heating coils 2x and 2y, and the temperature of the test piece of the portion a is measured by this thermocouple. It is measured, and the temperature of the part a is controlled by feedback control of a high frequency induction heating power source based on the measured temperature of the test piece.
本発明の引張試験方法では、通常、伸び計３により薄板試験片Ａの標点間の伸び量を測定する。これによりクロスヘッド間（試験片全体）で伸び量を測定するよりも、薄板試験片Ａの加工特性をより的確に把握することができる。
図４（斜視図）及び図５（正面図）は、図１の実施形態において、伸び計３により薄板試験片Ａの標点間の伸び量を測定している状況を示している（なお、図４では熱電対７の図示を省略してある）。伸び計３は、薄板試験片Ａの長手方向で間隔をおいた２点（標点b１，b２）において、薄板試験片Ａの厚み方向を両側から挟んで拘束する２つの固定具８x，８yと、この２つの固定具８x，８yの相対変位を検出する変位検出器（図示せず）を備えている。この変位検出器は、例えば、差動トランス式検出器などで構成することができる。
In the tensile test method of the present invention, the amount of elongation between the reference points of the thin plate test piece A is usually measured by the extensometer 3. As a result, the processing characteristics of the thin plate test piece A can be grasped more accurately than measuring the elongation amount between the crossheads (the entire test piece).
FIG. 4 (perspective view) and FIG. 5 (front view) show a situation in which the elongation amount between the reference points of the thin plate test piece A is measured by the extensometer 3 in the embodiment of FIG. In FIG. 4, the thermocouple 7 is not shown). The extensometer 3 has two fixtures 8x, which restrain the thin plate test piece A by sandwiching the thickness direction of the thin plate test piece A from both sides at two points (marking points b 1 and b 2 ) spaced apart from each other in the longitudinal direction. It is equipped with a displacement detector (not shown) that detects the relative displacement of the 8y and the two fixtures 8x and 8y. This displacement detector can be configured by, for example, a differential transformer type detector.
各固定具８x，８yは、薄板試験片Ａを両側から一定の圧力で挟むための１対のアーム９を備え、各アーム９は、尖った先端部を有する接触子１０を備えている。各固定具８x，８yは、薄板試験片Ａの両側から接触子１０を試験片表面に一定の圧力で押し付け、試験片表面に食い込ませることにより、薄板試験片Ａにしっかりと固定することができる。このため薄板試験片Ａを速い引張速度（例えば最大１００ｍｍ／ｓ）で引っ張っても試験片に適切に追従することができる。 Each fixture 8x, 8y includes a pair of arms 9 for sandwiching the thin plate test piece A from both sides with a constant pressure, and each arm 9 includes a contactor 10 having a sharp tip. Each of the fixtures 8x and 8y can be firmly fixed to the thin plate test piece A by pressing the contacts 10 against the surface of the test piece A with a constant pressure from both sides of the thin plate test piece A and letting them bite into the surface of the test piece. .. Therefore, even if the thin plate test piece A is pulled at a high tensile speed (for example, a maximum of 100 mm / s), it can appropriately follow the test piece.
各固定具８x，８yは、１対のアーム９（及び接触子１０）で薄板試験片Ａを両側から一定の圧力で挟むための機構を有している。この機構は公知のものでよく、例えば、１対のアーム９を回転ネジ軸などで機械的に連動させて接近・離間できるようにした機構などが適用できる。
本発明では、薄板試験片Ａが直接通電加熱により高温に加熱されるため、接触子１０は高い耐熱性と耐摩耗性を有するとともに、導電性と熱伝導性が低い材料で構成することが好ましく、特に窒化珪素などで構成することが好ましい。また、アーム９も耐熱材（例えば、インコネルなど）で構成することが好ましい。
Each fixture 8x, 8y has a mechanism for sandwiching the thin plate test piece A from both sides with a constant pressure by a pair of arms 9 (and contacts 10). This mechanism may be a known one, and for example, a mechanism in which a pair of arms 9 are mechanically interlocked with a rotating screw shaft or the like so that they can approach and separate from each other can be applied.
In the present invention, since the thin plate test piece A is heated to a high temperature by direct energization heating, the contact 10 is preferably made of a material having high heat resistance and abrasion resistance and low conductivity and thermal conductivity. In particular, it is preferably composed of silicon nitride or the like. Further, it is preferable that the arm 9 is also made of a heat-resistant material (for example, Inconel).
本発明の引張試験方法では、両端をチャック１x，１yで把持された薄板試験片Ａを、両チャック１x，１yを電極として直接通電加熱するとともに、薄板試験片Ａの長手方向のうちの両端側の部位ａのみを誘導加熱コイル２x，２yで部分的に高周波誘導加熱し、その際の薄板試験片Ａの伸び量を測定する。通常、この伸び量の測定は、図４及び図５に示すように伸び計３を用いて行われ、伸び計３の２つの固定具８x，８yを薄板試験片Ａの長手方向で間隔をおいた標点b１，b２にそれぞれ固定し（接触子１０で薄板試験片Ａを両側から挟んで固定する）、変位検出器でこの２つの固定具８x，８yの相対変位を検出することにより、薄板試験片Ａの標点b１，b２間の伸び量を測定することができる。
なお、標点間の伸び量の測定は、伸び計３の代わりに非接触のレーザー式や光学式などの変位計を用いて行ってもよい。
In the tensile test method of the present invention, the thin plate test piece A whose both ends are gripped by the chucks 1x and 1y is directly energized and heated by using both chucks 1x and 1y as electrodes, and both ends of the thin plate test piece A in the longitudinal direction. Only the portion a of the above is partially high-frequency induction heated by the induction heating coils 2x and 2y, and the elongation amount of the thin plate test piece A at that time is measured. Normally, the amount of elongation is measured using an extensometer 3 as shown in FIGS. 4 and 5, and the two fixtures 8x and 8y of the extensometer 3 are spaced apart in the longitudinal direction of the sheet steel test piece A. By fixing to the existing reference points b 1 and b 2 respectively (fixing the thin plate test piece A by sandwiching the thin plate test piece A from both sides with the contactor 10), and detecting the relative displacement of these two fixtures 8x and 8y with the displacement detector. , The amount of elongation between the reference points b 1 and b 2 of the thin plate test piece A can be measured.
The extension amount between the gauge points may be measured by using a non-contact laser type or optical type displacement meter instead of the extension meter 3.
本発明では、薄板試験片Ａの主たる加熱が直接通電加熱で行われるとともに、チャック１x，１yを通じた抜熱分が誘導加熱コイル２x，２yによる補助的な加熱（部位ａの加熱）により熱補償されるので、薄板試験片長手方向での均熱性（温度勾配が小さいこと）が高められる。特に、薄板試験片Ａに対して図３に示すような条件で配置された加熱コイル２x，２yによって、薄板試験片Ａの長手方向のうちの両端側の部位ａを部分的に高周波誘導加熱することにより、伸び計による測定範囲（標点b１，b２間の距離）を十分に確保しつつ、薄板試験片長手方向での均熱性を格段に高めることができ、その結果、伸び計３による標点b１，b２間の測定範囲の温度勾配をほぼ解消することができる。 In the present invention, the main heating of the thin plate test piece A is performed by direct energization heating, and the heat removal component through the chucks 1x and 1y is compensated by the auxiliary heating (heating of the portion a) by the induction heating coils 2x and 2y. Therefore, the heat equalizing property (small temperature gradient) in the longitudinal direction of the thin plate test piece is enhanced. In particular, the heating coils 2x and 2y arranged on the thin plate test piece A under the conditions shown in FIG. 3 partially induce and heat the portions a on both ends of the thin plate test piece A in the longitudinal direction. As a result, the heat equalizing property in the longitudinal direction of the thin plate test piece can be remarkably improved while sufficiently securing the measurement range (distance between the reference points b 1 and b 2 ) by the extensometer, and as a result, the extensometer 3 temperature gradients of the measurement range between the reference points b 1, b 2 by can be almost completely eliminated the.
図６は、上下のチャックで把持された薄板試験片（板厚１ｍｍ）を直接通電加熱のみで加熱した場合（図６（ア）の場合）と、本発明法のように薄板試験片を直接通電加熱するとともに、上下の加熱コイルにより、薄板試験片の長手方向のうちの両端側（上部側・下部側）の部位ａを部分的に高周波誘導加熱した場合（図６（イ）の場合）について、薄板試験片の各部位の温度とデジタルカメラによる薄板試験片の画像を示したものである。この試験では、両チャック間での薄板試験片の長さを８０ｍｍとし、標点間距離を３０ｍｍとした仮想の標点b１，b２（薄板試験片長手方向の中央位置pと各標点b１，b２間の距離：１５ｍｍ）を設定し、薄板試験片長手方向の中央位置pと各標点b１，b２に熱電対を取り付け、温度測定を行った。また、図６（イ）の場合は、図３に示すように、薄板試験片長手方向の中央位置pと各チャック１x，１y間の距離をＬとした場合、各チャック１x，１yからの距離がＬ／３の点p５とＬ／１０の点p６間の範囲S3に配置された加熱コイル２x，２yにより、薄板試験片Ａの長手方向のうちの両端側の部位ａを部分的に高周波誘導加熱した。 FIG. 6 shows a case where the thin plate test piece (plate thickness 1 mm) gripped by the upper and lower chucks is heated only by direct energization heating (in the case of FIG. 6A), and a case where the thin plate test piece is directly heated as in the method of the present invention. In the case of energizing heating and partially high-frequency induction heating of the portions a on both ends (upper side / lower side) of the longitudinal direction of the thin plate test piece by the upper and lower heating coils (in the case of FIG. 6 (a)). The temperature of each part of the thin plate test piece and the image of the thin plate test piece by the digital camera are shown. In this test, the length of the thin plate test piece between the two chucks was 80 mm, and the distance between the gauge points was 30 mm. Virtual gauge points b 1 , b 2 (center position p in the longitudinal direction of the thin plate test piece and each gauge point). The distance between b 1 and b 2 (15 mm) was set, and thermocouples were attached to the center position p in the longitudinal direction of the thin plate test piece and each reference point b 1 and b 2 , and the temperature was measured. Further, in the case of FIG. 6A, as shown in FIG. 3, when the distance between the central position p in the longitudinal direction of the thin plate test piece and the chucks 1x and 1y is L, the distance from the chucks 1x and 1y. There L / 3 points p 5 and L / 10 heating coils 2x disposed range S3 in between p 6 points, by 2y, the site a of both ends of the longitudinal direction of the thin plate specimen a partially High frequency induction heating was performed.
図６（ア）の場合、図６（イ）の場合ともに、加熱速度１０℃／secとし、中央位置pに取り付けた熱電対の測定温度に基づくフィードバック制御により、薄板試験片長手方向の中央位置pでの制御温度を９００℃として直接通電加熱を行った。この直接通電加熱による温度制御では、中央位置pが加熱開始から約１００sec後に制御温度である９００℃まで昇温し、それ以降は９００℃に保持されるようにした。また、図６（イ）の場合には、上記のような温度制御に加えて、加熱コイル２x，２yによる高周波誘導加熱を行った。この加熱コイル２x，２yによる高周波誘導加熱では、各標点b１，b２に取り付けた熱電対の測定温度に基づく手動によるフィードバック制御を行うとともに、各標点b１，b２の温度が制御温度（９００℃）と同等の温度に達する直前で手動による調整を行い、制御温度（９００℃）と同等の一定温度に保持されるようにした。 In the case of FIG. 6A and FIG. 6B, the heating rate is set to 10 ° C./sec, and the center position in the longitudinal direction of the thin plate test piece is controlled by feedback control based on the measurement temperature of the thermocouple attached to the center position p. Direct energization heating was performed with the control temperature at p set to 900 ° C. In this temperature control by direct energization heating, the central position p was raised to the control temperature of 900 ° C. about 100 seconds after the start of heating, and was maintained at 900 ° C. thereafter. Further, in the case of FIG. 6A, in addition to the temperature control as described above, high frequency induction heating was performed by the heating coils 2x and 2y. The heating coils 2x, high-frequency induction heating by the 2y, performs feedback control by manually based on the temperature measured by the thermocouple attached to the gauge b 1, b 2, the temperature of the gauge b 1, b 2 is controlled Just before reaching the temperature equivalent to the temperature (900 ° C), manual adjustment was performed so that the temperature was maintained at a constant temperature equivalent to the control temperature (900 ° C).
図６（ア）の場合には、薄板試験片の中央位置ｐの温度に較べて標点b１，b２の温度は５０℃以上低くなっており、画像を見ても中央位置ｐと標点b１，b２の明るさには大きな違いがある。この図６（ア）の場合と同じく薄板試験片を直接通電加熱のみで加熱した場合（但し、図６（ア）の場合とは若干異なる試験条件で直接通電加熱した）について、中央位置ｐからの距離と試験片温度との関係を調べた。その結果を図７に示すが、薄板試験片長手方向に大きな熱勾配が生じていることが分かる。
図６（ア）の場合に対して、本発明例に相当する図６（イ）の場合には、薄板試験片の中央位置ｐと標点b１，b２は温度差が殆どなく、標点内の均熱性が確保されていることが分かる。
In the case of FIG. 6 (A), the temperature of the gage b 1, b 2 as compared to the temperature of the center p of the thin plate specimen is lower than 50 ° C., the center position p and targets be viewed images There is a big difference in the brightness of points b 1 and b 2 . As in the case of FIG. 6 (a), when the thin plate test piece is heated only by direct energization heating (however, the thin plate test piece is directly energized and heated under slightly different test conditions from the case of FIG. 6 (a)), from the center position p. The relationship between the distance and the temperature of the test piece was investigated. The results are shown in FIG. 7, and it can be seen that a large thermal gradient is generated in the longitudinal direction of the thin plate test piece.
In the case of FIG. 6 (a), which corresponds to the example of the present invention, as opposed to the case of FIG. 6 (a), there is almost no temperature difference between the center position p of the thin plate test piece and the reference points b 1 and b 2. It can be seen that the heat equalization within the point is ensured.
上述したように、本発明法の引張試験方法では、クロスヘッド間（試験片全体）で伸び量を測定するよりも、伸び計３により薄板試験片Ａの標点間の伸び量を測定した方が薄板試験片Ａの加工特性をより的確に把握することができる。
図８は、本発明法においてクロスヘッド間（薄板試験片全体）で伸び量を測定して得られた応力−歪曲線と、伸び計３により薄板試験片Ａの標点間の伸び量を測定して得られた応力−歪曲線を示しており、両者の違いが分かる。
As described above, in the tensile test method of the present invention, the amount of elongation between the gauge points of the thin plate test piece A is measured by the extensometer 3 rather than the amount of elongation between the crossheads (the entire test piece). Can more accurately grasp the processing characteristics of the thin plate test piece A.
FIG. 8 shows the stress-strain curve obtained by measuring the amount of elongation between the crossheads (the entire thin plate test piece) in the method of the present invention, and the amount of elongation between the gauge points of the thin plate test piece A using the extensometer 3. The stress-strain curve obtained is shown, and the difference between the two can be seen.
本発明の引張試験方法の好ましい実施形態では、薄板試験片Ａを所定の熱履歴で加熱又は加熱−冷却し、その熱履歴中の任意の時点で引張試験を行って薄板試験片Ａの標点間の伸び量を測定する。この場合に薄板試験片Ａに付与される熱履歴は、例えば、高強度鋼板をホットスタンプする際の熱履歴を模擬したものである。
この実施形態において、薄板試験片Ａを所定の熱履歴で加熱−冷却する際の冷却工程では、薄板試験片Ａに噴射ノズル４から冷却ガスを吹き付けることが好ましい。図９（斜視図）は、薄板試験片Ａに噴射ノズル４から冷却ガスを吹き付ける場合の実施状況の一例を示しており、薄板試験片Ａの長手方向の両端寄りの薄板試験片Ａの両側位置に噴射ノズル４が配置され、各噴射ノズル４から薄板試験片Ａの両面に冷却ガスが吹き付けられる。各噴射ノズル４からの冷却ガスの噴射方向は、薄板試験片の板面に垂直の方向に対して薄板試験片長手方向の中央位置p側に傾きを持たせており、冷却ガスが薄板試験片Ａの板面全体に当たり、薄板試験片Ａを効率的に冷却できるようにしている。冷却ガス（通常、常温ガス）としては、例えば、Ｎ２、Ａｒ、Ｈｅなどを使用できる。
In a preferred embodiment of the tensile test method of the present invention, the thin plate test piece A is heated or heated-cooled with a predetermined heat history, and a tensile test is performed at any time in the heat history to perform a tensile test at a reference point of the thin plate test piece A. Measure the amount of elongation between. In this case, the heat history given to the thin plate test piece A is, for example, simulating the heat history when hot stamping a high-strength steel sheet.
In this embodiment, in the cooling step when the thin plate test piece A is heated and cooled with a predetermined heat history, it is preferable to blow the cooling gas from the injection nozzle 4 onto the thin plate test piece A. FIG. 9 (perspective view) shows an example of an implementation situation in which cooling gas is sprayed from the injection nozzle 4 onto the thin plate test piece A, and the positions on both sides of the thin plate test piece A near both ends in the longitudinal direction of the thin plate test piece A. The injection nozzles 4 are arranged in the sheet, and cooling gas is sprayed from each injection nozzle 4 on both sides of the thin plate test piece A. The injection direction of the cooling gas from each injection nozzle 4 is inclined toward the center position p side in the longitudinal direction of the thin plate test piece with respect to the direction perpendicular to the plate surface of the thin plate test piece, and the cooling gas is the thin plate test piece. It hits the entire plate surface of A so that the thin plate test piece A can be efficiently cooled. As the cooling gas (usually normal temperature gas), for example, N 2 , Ar, He, or the like can be used.
図１０は、薄板試験片Ａに付与される熱履歴の一例を示しており、この例では、９００℃に加熱・保持した後、６００〜３００℃まで冷却し、その温度に一定時間保持されている間に薄板試験片Ａに引張荷重が負荷され、加工特性が測定される。
本発明では、上述したように直接通電加熱と高周波誘導加熱を組合わせた加熱手段を用いることにより薄板試験片Ａの均熱性を高めることができ、しかも、上記のような冷却手段（噴射ノズル４）を有することにより、薄板試験片Ａを任意の熱履歴で正確に加熱又は加熱−冷却することができ、例えば、高強度鋼板をホットスタンプする際の鋼板の加工特性を正確に把握することが可能となる。図１１は、本発明例に相当する図６（イ）と同様の条件で薄板試験片を加熱−冷却した場合の熱履歴を示しており、薄板試験片Ａの標点間を所定の熱履歴で正確に加熱又は加熱−冷却できることが分かる。
FIG. 10 shows an example of the heat history applied to the thin plate test piece A. In this example, after heating and holding at 900 ° C., it is cooled to 600 to 300 ° C. and held at that temperature for a certain period of time. During this time, a tensile load is applied to the thin plate test piece A, and the machining characteristics are measured.
In the present invention, the heat equalizing property of the thin plate test piece A can be improved by using the heating means that combines the direct energization heating and the high frequency induction heating as described above, and the cooling means (injection nozzle 4) as described above. ), The thin plate test piece A can be accurately heated or heated-cooled with an arbitrary heat history, and for example, the processing characteristics of the steel sheet when hot-stamping a high-strength steel sheet can be accurately grasped. It will be possible. FIG. 11 shows the heat history when the thin plate test piece is heated and cooled under the same conditions as in FIG. 6 (a) corresponding to the example of the present invention, and a predetermined heat history is shown between the reference points of the thin plate test piece A. It can be seen that it can be heated or heated-cooled accurately.
このため本発明の引張試験装置は、薄板試験片Ａの引張試験ではなく、薄板試験片Ａに所定の熱履歴（例えば、図１１に示すような熱履歴）を付与するための装置として使用することもできる。すなわち、上述したような本発明の引張試験装置を用い、薄板試験片の引張試験を行うことなく、両端をチャック１x，１yで把持された薄板試験片Ａを所定の熱履歴で加熱又は加熱−冷却することにより、薄板試験片Ａに所定の熱履歴を付与するものである。この場合、薄板試験片Ａを所定の熱履歴で加熱−冷却する際の冷却工程では、薄板試験片Ａに噴射ノズル４から冷却ガスを吹き付けることができる。このような熱履歴を付与された薄板試験片は、他の装置を用いた各種試験に供される。 Therefore, the tensile test apparatus of the present invention is used not as a tensile test of the thin plate test piece A but as an apparatus for imparting a predetermined thermal history (for example, thermal history as shown in FIG. 11) to the thin plate test piece A. You can also do it. That is, using the tensile test apparatus of the present invention as described above, the thin plate test piece A whose both ends are gripped by the chucks 1x and 1y is heated or heated with a predetermined thermal history without performing the tensile test of the thin plate test piece. By cooling, a predetermined heat history is given to the thin plate test piece A. In this case, in the cooling step when the thin plate test piece A is heated and cooled with a predetermined heat history, the cooling gas can be blown to the thin plate test piece A from the injection nozzle 4. The thin plate test piece to which such a heat history is given is subjected to various tests using other devices.
なお、以上説明した本実施形態の引張試験方法及び装置は、薄板試験片Ａを上下方向に保持して引張を行うものであるが、例えば、薄板試験片Ａを水平方向に保持して引張を行うようにしてもよい。また、本実施形態では、チャック１xを可動側、チャック１yを固定側としているが、可動側と固定側を逆にしてもよい。
本発明の試験対象となる薄板金属材料に特別な制限はないが、本発明は特に高強度鋼板（一般に引張強度４９０ＭＰａ以上の鋼板）の引張試験に好適な引張試験技術である。また、試験対象となる薄板金属材料としては、例えば、アルミニウム合金や銅合金などのような非鉄材料でもよい。
The tensile test method and apparatus of the present embodiment described above hold the thin plate test piece A in the vertical direction to perform tension. For example, the thin plate test piece A is held in the horizontal direction to perform tension. You may do it. Further, in the present embodiment, the chuck 1x is the movable side and the chuck 1y is the fixed side, but the movable side and the fixed side may be reversed.
Although there are no particular restrictions on the thin metal material to be tested in the present invention, the present invention is a tensile test technique particularly suitable for a tensile test of a high-strength steel sheet (generally a steel sheet having a tensile strength of 490 MPa or more). Further, the thin metal material to be tested may be a non-ferrous material such as an aluminum alloy or a copper alloy.
１，１x，１y チャック
２，２x，２y 誘導加熱コイル
３ 伸び計
４ 噴射ノズル
５ チャック構成部材
６ ボルト
７ 熱電対
８x，８y 固定具
９ アーム
１０ 接触子
２０，２１ コイル部
Ａ 薄板試験片
ａ 部位
ｅ ボルト挿通孔
1,1x, 1y Chuck 2,2x, 2y Induction heating coil 3 Elongator 4 Injection nozzle 5 Chuck component 6 Bolt 7 Thermocouple 8x, 8y Fixture 9 Arm 10 Contact 20, 21 Coil part A Thin plate test piece a part e-bolt insertion hole
Claims (13)
両チャック（１）を電極として薄板試験片（Ａ）を直接通電加熱するとともに、薄板試験片（Ａ）の長手方向のうちの両端側の部位のみを誘導加熱コイル（２）で部分的に高周波誘導加熱することを特徴とする金属材料の引張試験方法。 This is a tensile test method for a metal material in which a thin plate test piece (A) whose both ends are gripped by a chuck (1) is heated and a tensile load is applied to the heated thin plate test piece (A).
The thin plate test piece (A) is directly energized and heated by using both chucks (1) as electrodes, and only the portions on both ends of the longitudinal direction of the thin plate test piece (A) are partially high-frequency by the induction heating coil (2). A method for tensile testing a metal material, which comprises induction heating.
両チャック（１）が、薄板試験片（Ａ）を直接通電加熱するための電極を構成するとともに、薄板試験片（Ａ）の長手方向のうちの両端側の部位のみを部分的に高周波誘導加熱する誘導加熱コイル（２）を備えることを特徴とする金属材料の引張試験装置。 A tensile test device for a metal material in which a thin plate test piece (A) whose both ends are gripped by a chuck (1) is heated and a tensile load is applied to the heated thin plate test piece (A).
Both chucks (1) form electrodes for directly energizing and heating the thin plate test piece (A), and only partially high-frequency induction heating is performed on both ends of the thin plate test piece (A) in the longitudinal direction. A tensile test device for a metal material, which comprises an induction heating coil (2).
両端をチャック（１）で把持された薄板試験片（Ａ）を所定の熱履歴で加熱又は加熱−冷却することを特徴とする、金属材料の薄板試験片に対する熱履歴付与方法。 A method of imparting a predetermined thermal history to a thin plate test piece of a metal material using the tensile test apparatus according to any one of claims 7 to 11 (excluding a method of performing a tensile test of the thin plate test piece). hand,
A method for imparting a heat history to a thin plate test piece made of a metal material, which comprises heating or heating-cooling a thin plate test piece (A) whose both ends are gripped by a chuck (1) with a predetermined heat history.
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| JP7231483B6 (en) | 2023-06-30 |
| JP7231483B2 (en) | 2023-03-01 |
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