SURFACE DEPTH MEASURING DEVICE AND SURFACE DEPTH MEASURING METHOD

PROBLEM TO BE SOLVED: To remarkably reduce a burden on preliminary creation of a calibration curve in surface depth measurement using a potentiometric method.SOLUTION: A hardening depth measuring device 10 relating to the invention comprises: a power source 11 that supplies current I to two current proves 22 and 23 to be arranged in contact with a surface 31 of a steel material 30; a potentiometer 12 that measures a potential difference Vd between two detection probes 24 and 25 to be arranged in contact with the surface 31 of the steel material 30; and a control section 13 that calculates hardening depth D of the steel material 30 on the basis of the potential difference Vd between the detection probes 24 and 25 which occurs when the current I flows between the two current probes 22 and 23. The control section 13 includes means that preliminarily creates a calibration curve, which shows a relationship between the hardening depth D of the steel material 30 and the potential difference Vd between the two detection probes 24 and 25, from the hardening depth D of a test piece of the steel material 30 whose hardening depth D is known, a resistivity of a hardened layer 32 and a resistivity of an unhardened layer 34. 【課題】電位差法を用いた表層深さ測定において、予め検量線を作成する際の負担を大幅に低減する。【解決手段】本発明に係る焼き入れ深さ測定装置１０は、鋼材３０の表面３１に接して配置される２本の電流探針２２、２３に電流Ｉを流す電源１１と、鋼材３０の表面３１に接して配置される２本の検出探針２４、２５の電位差Ｖｄを計測する電位差計測装置１２と、２本の電流探針２２、２３の間に電流Ｉを流したときに生ずる２本の検出探針２４、２５の電位差Ｖｄに基づいて、鋼材３０の焼き入れ深さＤを演算する制御部１３とを備え、制御部１３は、焼き入れ深さＤが既知である鋼材３０のテストピースの焼き入れ深さＤ、焼き入れ層３２の抵抗率 1、未焼き入れ層３４の抵抗率 2から、鋼材３０の焼き入れ深さＤと２本の検出探針２４、２５の電位差Ｖｄとの関係を表す検量線を予め作成する手段を含む。【選択図】図１