JPH07270306A - Adhesion strength evaluation method for clad steel plate - Google Patents

Abstract

PURPOSE:To enable evaluation of an adhesion strength according to the peeling state in the perimeter of a slit by performing a bending test for a laminated material and a surface side centered on the slit. CONSTITUTION:A 'bending test material' 10 with a laminated material 1 on the surface thereof and a base material 2 on the rear thereof is sampled and a slit 5 is provided on the laminated material 1 at a right angle to the longitudinal direction of a test piece with a width of 0.1-10mm and at least with the depth thereof equivalent to the thickness of the laminated material 1. Then, the 'bending test piece' 10 is supported by rollers 4 and 4 with the laminated material 1 on the surface side centered on the slit 5 and a bending test is carried out by pressing the test piece downward with a punch 3. This enables the evaluating of an adhesion strength accurately and handily during the working of a clad steel plate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a test method for evaluating the bonding strength of a clad steel sheet which is used after being subjected to bending work or mirror plate work.

[0002]

2. Description of the Related Art As a general method for evaluating the joining strength of clad steel plates, there are a shear strength test of JIS G0601 and a peel strength test described in the explanation of JIS G0601.

The characteristics of these test methods are that the JIS shear strength test evaluates the bonding strength by applying only shear stress to the bonding interface, and the peel strength test evaluates the bonding strength by applying only peeling stress to the bonding interface. Is the way to do it. In addition, there is an ultrasonic flaw detection test as a test method for evaluating the bonding state of the interface.

[0004]

One of the most severe machining processes for clad steel plates is mirror plate machining as a head portion of a pressure vessel. The end plate processing is formed by hot or cold pressing or spinning, but peeling may occur during processing depending on the bonding state.

However, even for a clad steel plate in a joined state in which peeling occurs during processing of the end plate, the JIS standard value is satisfied in the JIS shear strength test and peeling strength test as the joining strength test before working. In some cases, the joint strength may be the same as that of the clad steel sheet in which peeling did not occur in the end plate processing.

Further, in an ultrasonic flaw detection test, a clad steel plate having no defects may peel off during processing of the mirror plate.
As described above, in the conventional bonding strength test method and bonding strength evaluation method, it may not be possible to determine whether or not peeling will occur during severe processing such as end plate processing before processing.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a test method capable of accurately and simply evaluating the bonding strength of a clad steel plate during processing.

[0008]

The bonding strength evaluation method for a clad steel plate of the present invention is a bending test in which the bonding material is the front surface and the base material is the back surface in the evaluation of the bonding strength between the base material of the clad steel plate and the bonding material. Take a `` piece '', provide a slit in the laminated material at a right angle to the longitudinal direction of the test piece and have a depth of at least the thickness of the laminated material. It is characterized by evaluating the bonding strength.

[0009]

In order to solve the above-mentioned problems, the present inventors investigated in detail the relationship between the metallographic joining state of the clad steel sheet, various joining strength evaluation tests, and joining strength after working. .

As a result, the factors governing the joint strength of various clad steel sheets were clarified, and the relationship between the change in the test results by various joint strength evaluation tests due to the change and the change in the joint strength when further processed was clarified. We were able to.

First, the factors that govern the bonding strength of clad steel plates will be described. The controlling factors are mainly classified into two, one is the ratio of the unbonded portion of the bonded interface, and the other is the brittle layer generated by reaction diffusion at the bonded interface due to the combination of the joining material and the base material.

In the case of a rolled clad steel sheet, the proportion of unbonded portions varies depending on the temperature during rolling, the rolling load, the rolling reduction and the like. When the joining material is stainless steel, the melting point of the stainless steel is high, and the temperature at the time of joining can be controlled to be high, so that almost no unjoined portion remains. However, when the alloy material is a copper alloy having a low melting point, the rolling temperature cannot be increased, and thus a fine unbonded portion of 100 μm or less may remain at the bonded interface after rolling. If the ratio of the unbonded portion to the entire bonded interface increases, the bonding strength will be affected.

Another problem with the brittle layer, which is a factor controlling the bonding strength, is when the bonding material is an active metal such as titanium, and a compound which is fragile at the bonding interface with the base material or the intermediate material is formed. It is a case of forming in a shape. In this case, even if there is no unbonded portion at all, increasing the thickness of the brittle layer affects the bonding strength.

Next, the relationship between changes in these two controlling factors and various bond strength evaluation tests and the change in bond strength after working will be described. When the ratio of the unbonded portion controls the bonding strength, peeling may occur due to the end plate processing or the like when the ratio of the unbonded portion is high.

However, in the JIS shear strength test and the like, it cannot be evaluated as a change in the shear strength unless the proportion of the unbonded portion becomes considerably large. Further, in the ultrasonic flaw detection test, when the size of the unbonded part is on the order of millimeters, it can be detected, but the size of the unbonded part is 100 μm.
If it is as fine as the following, the existence of the unbonded portion can hardly be detected.

As described above, no abnormality can be found in the conventional JIS shear strength test, and no abnormality can be found in the ultrasonic flaw detection test, but a fine unbonded portion of 100 μm or less is observed in the metallographic observation of the bonding interface. In the clad steel sheet whose existence is confirmed, peeling of the laminated material may occur during severe processing such as mirror plate processing.

The inventors of the present invention have conducted a "bending test" from a clad steel plate having such a fine unbonded portion as shown in FIG. "Strip" 10 is sampled, and slits 5 having a depth of at least the thickness of the laminated material and having a width of 0.1 to 10 mm are provided on the laminated material 1 at right angles to the longitudinal direction of the test piece. As shown in FIG. 5, the "bending test piece" 10 has the laminated material 1 on the front side, is supported by the rollers 4 and 4 around the slit 5 and is pressed downward by the punch 3 to perform a bending test. It was found that peeling of No. 1 may occur.

Here, when the plate thickness of the test piece, the plate thickness ratio of the laminated material and the base material, the bending radius, etc. are appropriately determined, the presence or absence of peeling during the processing of the end plate depending on the ratio of the unbonded portion and the bending according to the present invention. It was also found that the presence or absence of peeling in the test can be matched.

On the other hand, when the brittle layer controls the bonding strength, the reaction history is promoted by the application of heat history such as hot working and heat treatment, and when the brittle layer is thickened, the tensile working, bending and both In mixed processing, the bonding material may peel off during processing, or the joint strength may decrease if a shear strength test or the like is performed after processing. This is because as the thickness of the brittle layer increases, the brittle layer is subject to plastic deformation, so that the brittle layer easily breaks during deformation.

However, in the JIS shear strength test, peel strength test, etc., even if the thickness of the brittle layer increases to such a degree that the joint strength decreases after working, the joint strength is May not be observed. Moreover, in the ultrasonic flaw detection test, not only the thickness of the brittle layer but also its presence cannot be evaluated.

As described above, according to the conventional test method, it is not possible to predict the exfoliation of the composite material at the time of processing and the decrease in the bonding strength after processing before the processing. As a test material, the inventors of the present invention have prepared a clad steel sheet in which the thickness of the brittle layer is controlled by heat treatment so that the shear strength is reduced after processing as compared with that before processing, and the composite material 1 is surface-treated in the same manner as described above. A "bending test piece" 10 having the base material 2 as a back surface is sampled, and the slit 5 is formed in the composite material 1 at a depth of at least the thickness of the composite material at right angles to the longitudinal direction of the test piece.
Then, when a bending test was performed centering on the slit 5, a width of 0.1 to 10 mm was provided, and it was found that peeling of the composite material 1 occurred.

Here, when the plate thickness of the test piece, the plate thickness ratio of the laminated material and the base material, the bending radius, etc. are properly determined, the thickness of the brittle layer, the peeling of the laminated material due to the degree of processing and the bonding strength after processing It was also found that the decrease can be matched with the presence or absence of peeling of the composite material in the bending test according to the present invention.

In the bending test, the width of the slit 5 formed in the laminated material is set to 0.1 to 10 mm because
The larger the slit width, the more difficult the peeling of the bonding material during the test becomes, and the evaluation becomes difficult. Therefore, if the slit width is too small, the processing becomes difficult. Therefore, the lower limit is 0.1 mm. Of.

[0024]

EXAMPLES First, as an example in which the ratio of unbonded portions controls the bonding strength, aluminum bronze (JIS H 3
The case of an aluminum bronze clad steel sheet using 100 C6161P) and SS400 as a base material will be described.

As a test material, manufactured by a hot rolling method,
Four types of steel plates with different manufacturing conditions were used. In these, unjoined parts of 100 μm or less are scattered at the joining interface, and the joining rate is 60% for A steel, 75% for B steel, 85% for C steel, and 9% for D steel.
It is different from 0%.

Here, the term "bonding ratio" means the ratio of the bonding interface observed from the direction perpendicular to the plate thickness direction with a scanning electron microscope or the like, and the length of the unbonded portion subtracted from the observed bonding surface length. Is.

The four plate thicknesses are 12 for the base material and 3 mm for the laminated material. About these test materials, JI
A shear strength test of S, a bending test according to the present invention, and a trial manufacture of an end plate were performed. The results are shown in Table 1.

[0028]

[Table 1]

The conditions for the bending test according to the present invention were that the plate thickness of the test piece was 10 mm for the base material, 2 mm for the laminated material, the slit widths were 0.1 mm, 5 mm, 10 mm and 15 mm, and the bending radius was 50 mm.

Further, the test piece was prepared with the plate thickness of 8 mm, the laminated material of 2 mm, the slit width of 2 mm and the bending radius of 40 mm. The prototype of the end plate is made only for A steel and B steel, and the inner diameter is
A 200 mm regular semi-elliptical end plate was processed by cold spinning.

In the JIS shear strength test, all four types are much higher than the JIS standard value of 100 MPa.
It showed a high shear strength of 00 MPa or more. However,
In the trial manufacture of the end plate, the joining material peeled off at the flange portion where the severest working of the A steel, which has the lowest bonding rate of 60%, is considered to be added. As described above, in the JIS shear strength test, it is not possible to predict the joint strength during severe processing such as mirror plate processing before processing.

On the other hand, in the bending test according to the present invention,
Except for the above-mentioned test conditions where the slit width of the laminated material was 15 mm, the steel A had peeling of the laminated material, and it was possible to predict the peeling in the end plate processing.

Next, as an example in which the brittle layer governs the bonding strength, pure titanium (JIS H4600 TP2) is used as the bonding material.
A case of a titanium clad steel sheet using 8) and SB410 as a base material will be described.

As a test material, a base material plate thickness of 19 mm and a laminated material plate thickness of 3 mm manufactured by a hot rolling method were prepared.
The heat treatment was performed at 50 to 850 ° C. for 1 to 2 hours, and the thickness of the TiC layer formed at the bonding interface was controlled to 0.5 to 1.5 μm. A JIS shear strength test, a peel strength test, a side bending test, and a bending test according to the present invention were performed on these test materials. The results are shown in Table 2.

[0035]

[Table 2]

The conditions of the bending test according to the present invention were that the plate thickness of the test piece was 10 mm as the base material, the laminated material was 2 mm, the slit width was 2 mm, and the bending radius was 48 mm. Moreover, the plate thickness of the test piece is 5 mm for the base material, 1 mm for the laminated material, and 2 m for the slit width.
The bending radius was 24 mm in m.

In addition to these tests, a trial manufacture test of an end plate was carried out. The prototype of the end plate is a regular semi-elliptical end plate with an inner diameter of 1100 mm, and is pressed by a warm press at 600 ° C and 650 ° C.
Body processed. After processing, a shear test piece was sampled from the flange portion and the shear strength was measured. The thickness of the TiC layer after processing the two end plates is 600 ° C, 0.7 μm for the processed material, 6
The 50 ° C. processed material had a thickness of 0.8 μm, and the corresponding values in Table 2 are also shown with the values of the shear strength after the end plate processing.

In the JIS shear strength test, as the thickness of the TiC layer increases from 0.5 μm to 1.5 μm, the shear strength monotonously decreases from 233 MPa to 158 MPa. All of these are JIS standard values of 140 MPa
It is stronger than.

However, in the trial manufacture of the end plate, the shear strength of the flange portion after processing is lower than that before processing, and particularly in the case of 650 ° C. processed material, it is 134 MPa and J
The value has fallen below the IS standard value, and there is a concern that peeling of the composite material may occur in the processing step after processing the mirror plate.

As described above, in the JIS shear strength test, even when the bonding strength controlling factor is the brittle layer, as in the case where the ratio of the unbonded portion is the controlling factor of the bonding strength, the JIS shear strength test is severe. It is not possible to predict the joint strength during machining before machining.

On the other hand, in the bending test according to the present invention,
When the thickness of the TiC layer is 0.8 μm or more, peeling of the laminated material occurs, and the peeling in the end plate processing can be predicted.

In addition, in the peel strength test, as with the shear strength test, as the thickness of the TiC layer increases,
Although the peel strength decreases monotonically, it is not possible to predict a sharp decrease in the joint strength after processing.

In the side bending test, the TiC layer has a thickness of up to 1.0 μm, and peeling of the laminated material does not occur, so that a decrease in the bonding strength after working is appropriately predicted as compared with the bending test of the present invention. It is not possible.

[0044]

According to the present invention, it becomes possible for the first time to accurately predict the joining strength of various clad steel plates during and after working, and as a result, it is possible to judge whether or not the work can be carried out before working, and to carry out the joining during working. It is now possible to develop a clad steel sheet having excellent strength, and it will largely contribute to the expansion of the use of a clad steel sheet having various characteristics and economical efficiency.

[Brief description of drawings]

FIG. 1 is an explanatory view of a test piece of the present invention.

FIG. 2 is an explanatory diagram of a test method according to the present invention.

[Explanation of symbols]

 1 ... Laminated material, 2 ... Base material, 5 ... Slit, 10 ... Test piece.

Claims (1)

[Claims] 1. In the evaluation of the bonding strength between a base material of a clad steel plate and a laminated material, a "bending test piece" having the laminated material as a front surface and the base material as a back surface is sampled and is perpendicular to the longitudinal direction of the test piece. Provide a slit that is at least as deep as the thickness of the mating material,
Bending test centered on the slit on the front side of the laminated material,
A bonding strength evaluation method for a clad steel plate, characterized in that the bonding strength is evaluated in a peeled state around the slit.