JPS6326340B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a non-destructive hardened layer measuring method and apparatus for non-destructively measuring the hardness of a specimen and its distribution, and is particularly suitable for cases where the specimen has a cylindrical shape. The present invention relates to a method and apparatus for measuring a hardened layer.

For forged steel rolls for rolling, etc., the condition of the hardened layer in the surface layer is an important requirement that affects the quality of the roll, and it is required that the entire surface of the roll has hardness and depth that exceeds specifications. be done.

The conventional method for measuring the hardened layer of a roll is
A method of checking the hardness distribution of the roll end face and the entire surface using a partially destructive hardness tester such as Vickers or Shore, and by examining the magnetic properties (especially coercive force, etc.) of the test object. A method was used to non-destructively measure the hardened layer.

However, all conventional hardened layer measurement devices can only measure the hardness of the surface of the specimen or at a relatively shallow position (approximately 10 to 20 mm from the surface) of the surface layer.
Moreover, when a hardness meter is used, traces from the measurement remain on the surface of the specimen, and when an electromagnetic measurement method is used, the specimen is magnetized and iron powder is attracted to the surface. Ta.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a method and apparatus for non-destructively measuring a hardened layer over a relatively wide range from the surface to the inside of an object using ultrasonic waves. .

Using ultrasonic waves that can penetrate into the specimen, we investigated the ultrasonic characteristics using various forged steel roll pieces with different hardness as test specimens. As a result, we found that the hardness H _s (Shor hardness) and the propagation speed of the ultrasonic waves As shown in FIG. 1, it was recognized that there was a good correspondence relationship between V and V.

A feature of the present invention is that the ultrasonic propagation velocity in an object is determined by focusing on the above-mentioned relationship, and the hardness of the object is measured from the magnitude of the velocity.

By the way, in a specimen having a cylindrical surface such as a real roll, the hardened layer (shaded area) is distributed almost symmetrically with respect to the axis O of the specimen 1, as shown in FIG. It is the hardest near the surface and becomes softer towards the inner layer.

For this reason, for example, the depth dmm from the surface of the subject 1
In order to investigate the hardness of point P at the position of This is the average value of the propagation velocities v ₁ , v ₂ , v ₃ in the layers passed through, and now the required P
It is not possible to determine the value of the propagation velocity v ₃ at a point.

On the other hand, rolls have a considerable length in the axial direction, and the depth of the hardened layer at the center of the shaft and at the end surfaces of the shaft is often different, so the propagation velocity inside the object is determined from between both end surfaces in the axial direction. That is difficult.

Therefore, in the case of such a cylindrical multi-layered object, the ultrasonic beam emitted from the transmitter is directed to the desired depth within the object by imaginably forming multiple layers symmetrical about the axis at arbitrary intervals. In order for the wave to be received by the wave receiver after passing through the center position, the distance between the wave transmitter and the wave receiver is made variable and arranged between two points on the circumferential surface of the subject. First, the propagation velocity in the first layer is determined from the propagation path length and propagation time of the ultrasonic beam that propagates only in the first layer at the shallowest position from the surface. Next, the propagation velocity of only the second layer is determined from the propagation path length and propagation time of the ultrasonic beam propagating through the first and second layers, and the already determined propagation velocity of the first layer. Hereinafter, the propagation path length and propagation time of the ultrasonic beam propagating through the first layer, second layer, third layer, . The propagation velocity of only the n-th layer is determined from the propagation velocity of each layer in .

The present invention will be described below with reference to embodiments shown in the drawings.

FIG. 3 shows a method for measuring the multilayer hardened layer of the object 1 having a cylindrical shape. The transmitter 2 and the receiver 3 are arranged so that the ultrasonic beam sent out from the transmitter 2 enters from point _T1 and is received by the receiver 3 at point _R1 .
are arranged facing each other on the circumferential surface of the subject 1. First, the path length of the ultrasonic beam from point T ₁ to point R ₂ is l ₁₁ and the propagation time of the ultrasonic beam at this time t ₁
is measured, and the propagation velocity v ₁ of the shallowest layer from the surface of the object 1 is determined using equation (1).

v ₁ = l ₁₁ / t ₁ ...(1) Here, l ₁₁ is the radius of the object to be examined, r is the maximum depth within the path through which the ultrasound beam propagates, d is
It can be determined using equation (1-1).

l ₁₁ = 2√ ² −(−) ² ...(1-1) In addition, the propagation time t ₁ is measured by the detection time difference of the transmitted wave obtained when the ultrasound beam passes through the subject using a clock pulse, etc. By doing so, it can be easily determined.

Next, in order to obtain the propagation velocity v ₂ of the layer, the transmitter 2 and the receiver 3 are installed at the T ₂ point and the R ₂ point, respectively, so that the ultrasonic beam propagates between the layers. From the propagation time t ₂ at this time, the path lengths l ₁₂ , l ₂₂ in the first and second layers, and the propagation velocity v ₁ in the second layer already determined using equation (1), the propagation velocity v ₂ in the second layer can be calculated using the equation It can be obtained by (2).

v ₂ = l ₂₂ / t ₂ − l ₁₂ / v ₁ ...(2) In equation (2), the maximum depth at the path length is
2d, l ₁₂ and l ₂₂ are expressed by formula (2-1) and formula (2
-2).

l ₁₂ =l ₁₂ /2+l ₁₂ /2 =2 [√ ² −(−2) ² −√(−) ² −(−2) ² ] (2−1) l ₂₂ =2√(−) ² −( -2) ² ... (2-2) Below, to find the propagation velocities v ₃ , v ₄ , ... v _o of the sequential layer, layer, ... Nth layer, the maximum depth of the path length is , set the positions of the wave transmitter 2 and the wave receiver 3, as shown in the layers for which the propagation velocity is calculated, and calculate the path length in each layer whose propagation time at this time can be calculated geometrically, and the already calculated layer. From the propagation velocity from to the previous layer, it can be determined by the following equation.

v ₃ = l ₃₃ / t ₃ - (l ₁₃ / v ₁ + l ₂₃ / v ₂ ) ...(3) v ₄ = l ₄₄ / t ₄ - (l ₁₄ / v ₁ + l ₂₄ / v ₂ + l ₃₄ / v ₃ ) ……(4) 〓 v _o ＝l _oo ／t _o −(l _1o ／v ₁ ＋l _2o ／v ₂ ……＋l _(o-1),o ／V _o-
1 )...(5) As mentioned above, by determining the propagation velocity of each layer sequentially starting from the
The propagation velocity up to the layer can be determined. Therefore, the hardness of each layer can finally be determined from the relationship between hardness and propagation velocity shown in the figure.

In addition, in the nondestructive hardened layer measuring method according to the present invention, the accuracy of the hardened layer depth can be improved by making the measured layer spacing (corresponding to d in this example) as small as possible. be.

By the way, in FIG. 3, when the present invention is applied using a general wave transmitter and wave receiver in which a planar vibrator is incorporated, the following problem occurs.

In other words, since the propagation path of the ultrasound beam is determined by the incident angle α of the transmitter and receiver (which corresponds to the refraction angle β in the subject), each time the propagation velocity in each layer is determined, It is necessary to change the incident angle of the transmitter and the receiver, and the positioning of the transmitter and receiver must be performed with high precision each time so that the directivity of the transmitter and receiver match, resulting in extremely inefficient work. Furthermore, since the ultrasonic beam spreads at the incident point and the receiving point, the geometrically measured path length is likely to have errors.

Next, another embodiment of the present invention that eliminates the above problems will be described. The embodiment shown in FIG. 4 is characterized by using a focusing type wave transmitter 4 and wave receiver 5 in which a concave transducer having a convergence point of an ultrasonic beam is incorporated on the surface of the subject 1.

According to this method, since the ultrasonic beam is focused on the surface of the subject 1, the path length within the subject 1 from the point of incidence to the receiving point can be measured with high accuracy.
In addition, since the ultrasonic beam is diffused and propagates through layers at different depths within the object 1, it is necessary to change the angle of incidence of the focused wave transmitter 4 and the focused wave receiver 5 each time when determining the propagation velocity. Moreover, the positioning of both can be easily performed. Note that when measuring the propagation time, in this case as well, the propagation time of the ultrasonic beam that passes through the object 1 and reaches the focusing type wave receiver 5 most quickly is measured.

FIG. 5 shows an embodiment of a non-destructive cured layer measuring device configured to be applicable to the non-destructive cured layer measuring method according to the present invention.

In FIG. 5, both settings are maintained so that the ultrasonic beam transmitted from the focusing wave transmitter 4 passes through the hardened layer at a desired depth within the subject 1 and is received by the focusing wave receiver 5. It is held on the circumferential surface of the subject 1 by a tool 6.

The ultrasonic beam sent out from the focusing wave transmitter 4 upon receiving the received pulse from the ultrasonic transmitter/receiver 7 is once focused at the point of incidence T on the subject 1 and then diffused within the subject 1 . Among these, the ultrasonic beam directed toward the receiving point R _o of the focused wave receiver 5 is received, passes through the amplification circuit of the ultrasonic transmitting/receiving section 7, and is transmitted to the propagation time measuring section 8.
is input to. The propagation time measurement unit 8 measures the propagation time of the ultrasound beam from when it is transmitted by the focused wave transmitter 4 until it is transmitted through the object 1 and received by the focused wave receiver 5 using, for example, a clock pulse.
By subtracting the propagation time in the shoe (transmission medium) of the focused wave transmitter 4 and the focused wave receiver 5 from this propagation time, the final propagation time required for the ultrasound beam to pass only through the object 1 is determined. is determined, and an electrical signal corresponding to this is output.

On the other hand, the path length calculation unit 9 inputs the radius r of the object 1 and the maximum depth d within the path length of the ultrasound beam, calculates the path length in each layer from the following formula, and calculates the electric signal l _oo = 2 √〔−(−1)〕 ² −〔−〕 ² …
…(6-1) l _o-1,o =2√[-(-2)] ² −[-] ²
−l _oo ......(6-2) l _o-2o =2√[-(-3)] ² −[-] ²
−(l _oo +l _o-1,o )……(6-3) l _o-3,o =2√[−(−4)] ² −[−] ²
−(l _oo +l _o-1,o +l _o-2,o )……(6-4) 〓 l _1o =2√[−(−)] ² −[−] ² −
( _o 〓 ⁱ⁼² lin) ...(6-5) Output as. In addition, when automatically calculating the path length in conjunction with changes in the set positions of the focused wave transmitter 4 and the focused wave receiver 5, the electrical signals corresponding to the set interval L and set angle θ are transmitted using a potentiometer, etc. and enter the formula (7-1) in the path length calculation section 9.
This becomes possible by adding the calculation function of equation (7-2).

d=r(1-cosθ/2) (7-2) The propagation velocity calculation section 10 sends data regarding the layer to be measured to the propagation time measurement section 8 and the path length calculation section 9.
The propagation velocity is calculated using the procedure shown in the flowchart of FIG. 6, for example.

In Fig. 6, when the calculation starts, first, the propagation time t 1 when the ultrasound beam propagates only through the first layer of the object 1 (the shallowest layer from the surface of the object: _n = 1) is read. , the path length at that time: l ₁₁ to 1st
The propagation velocity in the layer: v ₁ = l ₁₁ /t ₁ ) is calculated.

Next, when finding the propagation velocity in the n-th layer,
The propagation velocity will be calculated for each layer from the 2nd layer to the nth layer (the next layer where the calculation has been completed: n+1), but for example, if we have now completed the calculation up to the propagation velocity of the 3rd layer. , Next, in order to find the propagation velocity of the fourth layer, firstly, each layer up to the fourth layer [layers 1 to 3:
Path length at i=1~(n-1): l ₁₄ , l ₂₄ , l ₃₄
From the already determined propagation velocities: v ₁ , v ₂ , v ₃ , the sum of the time required for the ultrasonic beam to propagate through each of these layers: dt is calculated using equation (8), and the fourth The maximum depth of the layer is dt= _o-1 〓 ⁱ⁼¹ lin/v _i ...(8) Total path length of the ultrasonic beam: Propagation time at L: Subtract dt from t _o , and only in the 4th layer propagation time of
Find t ₄ . Then, the propagation velocity in the fourth layer: v ₄ =l ₄₄ /t ₄ is calculated from the path length: l ₄₄ and the propagation time: t ₄ only in the fourth layer. Using a similar procedure, the desired propagation velocity up to the n-th layer is calculated for each layer.

All the propagation velocities up to the n-th layer are stored in the memory section 11 (shown in FIG. 5), but ultimately these propagation velocities are combined with the hardness H _s and the propagation velocity V shown in FIG.
The hardness of each layer is calculated in the hardness calculating section 12 by multiplying it by a proportionality coefficient k obtained from the relationship diagram, and is output and displayed.

In the above embodiment, the smaller the measurement interval in the depth direction from the surface of the object to the inside, the more accurate the measurement of hardness and hardened layer depth can be.
For example, if it is predicted that a layer of uniform hardness is widely distributed in the depth direction in the surface layer, the measurement interval in that range should be relatively large, and areas near the boundary should be considered important. It is also possible to reduce the measurement interval only in the vicinity of the position, and it is not necessarily necessary to measure at constant intervals.

As explained above, the non-destructive hardened layer measuring method and device according to the present invention can measure the distribution of the hardened layer over a wide range from the surface layer to the inside of the test object without damaging the surface of the test object. Moreover, even if the hardness changes continuously in the depth direction or the shape of the object is cylindrical, the distribution of the hardened layer can be measured with high accuracy.

[Brief explanation of the drawing]

Figure 1 shows a relationship diagram when the relationship between hardness H _s (Shore hardness) and ultrasonic propagation velocity was determined experimentally, and Figure 2 shows the distribution of the hardened layer of a specimen with a cylindrical surface. FIG. FIGS. 3 and 4 are reference diagrams for carrying out the non-destructive cured layer measuring method according to the present invention. FIG. 5 is a block diagram showing an embodiment of the non-destructive photonic layer measuring device according to the present invention, and FIG. 6 is a flowchart for calculating the propagation velocity. 1... Subject, 2... Wave transmitter, 3... Wave receiver, 4... Focused wave transmitter, 5... Focused wave receiver, 6... Setting holder, 7... Ultrasonic transmitter/receiver section, 8... Propagation time measuring section,
9... Path length calculation section, 10... Propagation velocity calculation section, 11
...Memory section, 12...Hardness calculation section.

Claims (1)

[Scope of Claims] 1. Assuming that the hardened layer of a cylindrical test object in which a hardened layer is formed on the outer shell portion of a circular cross section is a multi-layered layer symmetrically arranged at arbitrary intervals about the axis, first, the hardened layer of the test object is The propagation speed of the ultrasonic beam in the first layer is determined from the propagation time and path length of the ultrasonic beam that passes only through the first layer, which is the outermost layer, and then the ultrasonic beam passes only through the first and second layers. The propagation velocity in the second layer is determined from the propagation time of the ultrasonic beam, the path length in the first and second layers, and the already determined propagation velocity in the first layer, and the total path length is determined in the same manner. From the propagation time of the ultrasonic beam at , the path length in each layer it passes through, and the propagation velocity of each layer from the first layer to the layer one before the layer to be measured, which we have already determined, we can calculate the propagation up to the nth layer. A non-destructive hardening method that is characterized by sequentially determining the velocity for each layer, and finally determining the hardness of each layer from the relationship between the propagation velocity and hardness, which has been determined in advance, based on the propagation velocity of each layer. Layer measurement method. 2. An ultrasound transmitter/receiver that transmits and receives ultrasound; a transmitter that transmits an ultrasound beam into the subject using a transmission pulse from the ultrasound transmitter/receiver; and a transmitter that receives the ultrasound beam that has passed through the subject. a wave receiver that waves; a setting holder that holds the transmitter and receiver in settings so that the ultrasonic beam is received through a layer at a desired depth within the subject; a propagation time measurement unit that measures the propagation time from when the wave is sent into the subject until it is received by the wave receiver; a path length calculation unit that calculates the path length of the incident ultrasonic beam until it reaches the wave receiver, the output of the propagation time measurement unit, the output of the path length calculation unit, and the already determined propagation velocity of each layer. a propagation velocity calculation unit that calculates the propagation velocity in the layer under measurement based on the propagation velocity; a memory unit that stores the propagation velocity of each layer for which the propagation velocity has been calculated and can read it as necessary; A non-destructive hardened layer measuring device characterized by comprising a hardness calculation section that converts hardness and displays an output. 3. Claim 2 is characterized in that the hardness of each layer of the object is measured using a focused wave transmitter and a focused wave receiver that have a focal point of an ultrasound beam on the surface of the object. A non-destructive hardened layer measuring device.