Manufacturing method of material simulation test piece of clad steel plate base material, material simulation test method, and manufacturing condition design method of clad steel plate

Abstract

To provide a technique for inexpensively and accurately simulating base material performance of a clad steel plate required of DWTT performance and HIC performance.SOLUTION: A method for manufacturing a material quality simulation test material of a clad steel plate base material comprises: a clad base material blank manufacturing simulation step of heating a cast piece or a steel piece having a component composition of one clad base material, and then hot-rolling it to manufacture one clad base material blank; a clad slab assembly simulation step of superposing a counter material blank on the clad base material blank to assemble a simulation clad slab; and a clad steel plate manufacturing simulation step of heating the simulation clad slab, then hot-rolling it, and executing one or more of radiational cooling, accelerated cooling, and heat treatment for an obtained clad hot-rolled material to manufacture a simulation clad steel plate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a material simulation test piece for a clad steel plate base material that requires DWTT (Drop Weight Tear Test) performance and HIC (Hydrogen Induced Cracking) resistance performance, a material simulation test method, and a method for designing manufacturing conditions for a clad steel plate using the method.

Background Art

[0002] A clad steel plate is a steel plate formed by bonding a clad material composed of stainless steel or Ni alloy and a base material composed of low alloy steel or the like. A clad steel plate is a metallurgical bond of dissimilar metals and, unlike plating, there is no risk of peeling. In addition, new properties that cannot be achieved with a single metal or alloy can be imparted to the clad steel plate.

[0003] According to the clad steel plate, by selecting a clad material having a function suitable for the purpose of each use environment, it is possible to exhibit the same function as a solid material (when the entire thickness has a metal structure of the clad material). Furthermore, by applying carbon steel or low alloy steel suitable for a severe environment such as high toughness and high strength to the base material composed of the clad steel plate, high toughness and high strength can be imparted to the clad steel plate.

[0004] In this way, the clad steel plate has the advantage that it can achieve both economy and functionality because it uses less alloying elements than a solid material, can ensure the same corrosion resistance as a solid material, and can ensure the same strength and toughness as carbon steel or low alloy steel.

[0005] From the above, clad steel using a clad material composed of stainless steel or Ni alloy is considered to be a very useful functional steel material, and in recent years, the need for it has been increasing in various industrial fields.

[0006] As bonding materials for Ni alloy clad steel plates, which are one type of clad steel plates, Alloy825 and Alloy625 are typical. Also, as a bonding material for stainless steel clad steel plates, SUS316L is typical. Ni alloy clad steel plates and stainless steel clad steel plates can be preferably used for pipeline applications due to their excellent corrosion resistance.

[0007] In addition, HIC performance may be required for the clad steel plate base material. For the development of clad steel plates with strict performance requirements for these base materials, it is essential to adjust the components, TMCP (Thermo Mechanical Control Process), or heat treatment conditions to satisfy the base material performance. (See Non-Patent Document 1)

Prior Art Documents

Non-Patent Documents

[0008]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, the prior art had the following problems. For the performance evaluation of the clad steel plate base material, the following methods have been conventionally applied. (1) Manufacture a clad steel plate and evaluate the base material performance. (2) Manufacture a solid material with the same composition as the base material and evaluate the base material performance.

[0010] Method (1) can accurately evaluate the base material performance. However, since it involves manufacturing a clad steel plate, expensive bonding materials will be used, resulting in increased costs. That is, originally, clad steel plates have the advantage of being lower in cost than solid bonding materials and being able to ensure the corrosion resistance of the bonding materials. Nevertheless, if expensive bonding materials are used for the evaluation of the base material quality, the advantage of cost reduction will be diminished.

[0011] For example, when simulating a clad steel plate manufactured by a sand clad, it is not possible to position the center segregation of the base material at the same position as the sand clad. That is, in the case of a sand clad, the center segregation generally occurs at about 1 / 4 of the slab thickness, but when using a solid material, it is at the 1 / 2 thickness position. Since the thermal history at the 1 / 4 thickness position of the clad slab is different from the thermal history at the 1 / 2 thickness position of the solid material, strictly speaking, it cannot be said that the manufacturing conditions are being simulated. Therefore, the HIC performance and DWTT performance cannot be correctly evaluated.

[0012] Also, when manufacturing a clad steel plate, as shown in Fig. 1, a base material slab 1 having the components of a base steel such as ordinary steel is heated 3 and hot rolled 4 to manufacture a base material blank 6. Also, a cladding material slab 2 having the components of a cladding material such as corrosion-resistant steel is heated 3 and hot rolled 4 to manufacture a cladding material blank 7. Then, the clad slab 9 is assembled using the base material blank 6 and the cladding material blank 7. The clad steel plate 14 is manufactured by heating 3 and hot rolling 4 the clad slab 9. Therefore, when manufacturing a clad steel plate, two hot rolling operations of base material rolling and clad rolling are carried out. However, simply heating and hot rolling a solid material only results in one hot rolling operation, so strictly speaking, it cannot be said that the manufacturing conditions are being simulated. Therefore, mainly the DWTT performance cannot be correctly evaluated.

[0013] In addition, when evaluating the material properties such as mechanical properties, the influence of the plate thickness of the test material cannot be ignored. In particular, in the evaluation regarding toughness, it is common knowledge for those skilled in the art that the influence of the plate thickness is significant. Therefore, even if a test material of a thin and small size is manufactured in the laboratory by proportionally distributing the same plate thickness configuration as that for manufacturing a clad steel plate, since the plate thickness of the obtained base material is small, it is not always possible to reproduce the material properties when manufactured at the actual machine level. From this perspective as well, a method for simulating the base material performance of a clad steel plate has been demanded.

[0014] The present invention has been made in view of the above circumstances, and an object thereof is to provide a technique for inexpensively and accurately simulating the base material performance of a clad steel plate required for DWTT performance and HIC performance.

Means for Solving the Problems

[0015] As a result of intensive studies on a method for inexpensively and accurately simulating the performance of the clad base material, the inventors have found the following method. First, it was decided to avoid using expensive composite materials as a method for inexpensive simulation. Next, in order to accurately simulate the base material performance, (1) Rolling using an assembled slab in which central segregation of the base material occurs at the same position as the base material of the clad steel plate, (2) Applying two heating and hot rolling operations and subsequent accelerated cooling or heat treatment or both, similar to the production of clad steel plates, were examined as feasible methods. As a result, it was found that simulation conditions (1) and (2) can be realized by stacking a base material material (a) having the same product thickness as the base material of the clad steel plate and a facing material material (b) having the same remaining thickness as the clad slab thickness during clad rolling to form a clad slab.

[0016] The present invention has been further developed and completed based on such findings, and the gist thereof is as follows. [1] A method for manufacturing a material simulation test piece of a clad steel plate base material, comprising: a clad base material material manufacturing simulation step of heating a slab or steel piece having a component composition of one clad base material and subsequently hot rolling to manufacture one clad base material material; a clad slab assembly simulation step of overlapping a facing material material with the one clad base material material to assemble a simulated clad slab; and a clad steel plate manufacturing simulation step of heating the simulated clad slab, subsequently hot rolling, and performing one or more treatments selected from slow cooling, accelerated cooling, and heat treatment on the obtained hot-rolled clad material to manufacture a simulated clad steel plate. [2] The method for manufacturing a material simulation test piece of a clad steel plate base material according to [1], wherein the plate thickness of the facing material is the sum of twice the plate thickness of the clad material in the case of manufacturing the clad steel plate to be the object of the material simulation test and the plate thickness of other clad base materials. [3] The method for manufacturing a material simulation test piece of a clad steel plate base material according to [1], wherein the plate thickness of the facing material is the sum of the plate thickness of the clad material in the case of manufacturing the clad steel plate to be the object of the material simulation test and the plate thickness of the sacrificial material. [4] The method for manufacturing a material simulation test piece of a clad steel plate base material according to [1], wherein the plate thickness of the facing material is the plate thickness of the clad material in the case of manufacturing the clad steel plate to be the object of the material simulation test. [5] A method for material simulation test of a clad steel plate base material, wherein a material simulation test is performed on a material simulation test piece of a clad steel plate base material manufactured from the one clad base material by the manufacturing method according to any one of [1] to [4]. [6] A method for designing manufacturing conditions of a clad steel plate, wherein the manufacturing conditions of the clad steel plate are designed based on the test results of the material simulation test according to [5]. [7] The method for designing manufacturing conditions of a clad steel plate according to [6], wherein when designing the manufacturing conditions of the clad steel plate, machine learning is performed to compare the test results with the results of investigating the material of the clad steel plate actually obtained by manufacturing the clad steel plate and correct the difference.

Advantages of the Invention

[0017] According to the method for manufacturing a material simulation test piece of a clad steel plate base material and the method for material simulation test according to the present invention, the base material performance of a clad steel plate required for DWTT performance and HIC performance can be simulated inexpensively and accurately. Furthermore, by applying it to the method for designing manufacturing conditions of a clad steel plate, a clad steel plate excellent in base material performance can be manufactured.

Brief Description of the Drawings

[0018]

Figure 1

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be specifically described. The following embodiments illustrate methods for embodying the technical idea of the present invention and do not specify the configuration to the following. That is, various modifications can be made to the technical idea of the present invention within the technical scope described in the claims.

[0020] As shown in FIG. 1, the basic of the manufacturing process of the clad steel plate 14 is, first, the clad base material 6 and the clad bonding material 7 are appropriately laminated to assemble the clad slab 9 (10). Then, the clad slab 9 is heated (3), and the heated clad slab 9 is hot-rolled (4). The obtained rolled body 13 is cut or peeled as necessary (8) to obtain the clad steel plate 14.

[0021] When assembling the clad slab 9 (10), there are roughly three types of ways to overlap the clad base material 6 and the clad bonding material 7 as follows (1) to (3). (1) Sandwich method In the sandwich method, the clad base material 6 / clad bonding material 7 / clad bonding material 7 / clad base material 6 are overlapped in this order. A release agent such as oxide powder is applied between the two clad bonding materials 7. From the clad slab 9 assembled by the sandwich method, two clad steel plates 14 are manufactured by separating the upper and lower parts of the rolled body 13 manufactured by rolling the clad slab 9. (2) Sacrificial material method (semi-sandwich method) In the sacrificial material method (semi-sandwich method), the sacrificial material / clad bonding material 7 / clad base material 6 are overlapped in this order. A release agent such as oxide powder is applied between the sacrificial material and the clad bonding material 7. From the clad slab 9 assembled by the sacrificial material method, one clad steel plate 14 is manufactured by peeling the sacrificial material in the rolled body 13 manufactured by rolling the clad slab 9. (3) Open sandwich method In the open sandwich method, a pair of clad joining material materials 7 and clad base material materials 6 are stacked in this order. From the clad slab 9 assembled by the open sandwich method, the rolled body 13 itself produced by rolling the clad slab 9 becomes one clad steel plate 14.

[0022] Here, in this specification, the value obtained by dividing the total thickness of the clad slab 9 by the total thickness of the rolled body 13 obtained by hot rolling is referred to as the clad reduction ratio.

[0023] In this embodiment, the base material of the clad steel plate 14 for which it is desired to test and evaluate by simulating the material is referred to as one clad base material 14a.

[0024] In the method for manufacturing a material simulation test material of the clad steel plate base material according to this embodiment, first, a slab 1 or a steel piece having the component composition of one clad base material 14a is heated (3), and subsequently hot rolling 4 is performed to manufacture one clad base material material 6. The conditions of this heating 3 and hot rolling 4 are made to match the conditions when manufacturing the clad steel plate 14 for which it is desired to simulate the material of the base material. The one clad base material material 6 thus obtained is used in a later process when producing a (simulated) clad slab 9.

[0025] The plate thickness of the one clad base material material 6 is set to the value obtained by multiplying the plate thickness of the clad base material 14a of the clad steel plate 14 for which it is desired to simulate the material by the clad reduction ratio.

[0026] Next, the facing material material and the one clad base material 6 are stacked to assemble a simulated clad slab 9.

[0027] In the case of the sandwich method, the facing material is one clad base material and two clad joining materials. Therefore, in the case of the sandwich method, the thickness of the facing material material is the value obtained by multiplying the sum of the plate thickness of the other clad base material and twice the plate thickness of the clad joining material by the clad reduction ratio. In the case of the sacrificial material method, the facing material consists of one clad material and one sacrificial material. Therefore, in the case of the sacrificial material method, the thickness of the facing material material is the value obtained by multiplying the sum of the plate thickness of the clad material and the plate thickness of the sacrificial material by the clad reduction ratio. In the case of the open sandwich method, the facing material is one clad material. Therefore, in the case of the open sandwich method, the thickness of the facing material material is the value obtained by multiplying the plate thickness of the clad material by the clad reduction ratio.

[0028] In any method, similar to the actual production of the clad steel plate 14, it is possible to perform surface grinding (surface cleaning) on the surface of the clad base material 6 that contacts the clad material 7 and the surface of the clad material 7 that contacts the clad base material 6, respectively (5).

[0029] In addition, in any method, when manufacturing by inserting an intermediate material between the clad material 7 and the clad base material 6, the thickness of the facing material material may be appropriately adjusted in consideration of the thickness of the intermediate material.

[0030] It is preferable that the simulated clad slab 9 is simply formed by stacking the clad base material 6 and the clad material 7 and then processing the outer periphery by electron beam welding 12 or the like in an atmosphere of high vacuum (11). The welding means may be laser welding.

[0031] In the method for manufacturing a material simulation test material of the clad steel plate base material according to the present embodiment, the obtained simulated clad slab 9 is heated (3), and then hot-rolled (4) to manufacture a clad hot-rolled material 13. Here, the heating conditions and hot-rolling conditions of the simulated clad slab are set to the conditions when manufacturing the clad steel plate 14 for which the material of the base material is to be simulated, respectively.

[0032] For the obtained clad hot-rolled material 13, one or more treatments selected from slow cooling, accelerated cooling, and heat treatment are performed to manufacture a simulated clad steel plate 14. The conditions for these slow cooling, accelerated cooling, and heat treatment are also set to the conditions when manufacturing the clad steel plate 14 for which the material of the base material is to be simulated, respectively.

[0033] The obtained simulated clad steel plate 14 is cut, and after a test piece for conducting a material simulation test is sampled from a portion corresponding to one clad base material 14a, the test piece is subjected to a material test.

[0034] As long as a test piece can be sampled from a portion corresponding to one clad base material 14a, various material tests can be carried out. For example, it is preferably applied to material tests where the influence of the thickness of the test piece on the test results is large, such as DWTT (drop weight test) and Charpy impact test. According to this embodiment, a material test using a test piece of the same size as the actual one can be carried out, and thus the effectiveness of this embodiment is significantly demonstrated.

[0035] By comparing or feeding back the test results simulating the base material quality by the method described so far with the actual quality of the base material of the clad steel plate, the manufacturing conditions of the clad steel plate can be designed.

[0036] Here, factors affecting the quality of the clad base material include (1) the steel component composition of the base material, (2) various manufacturing conditions such as the heating temperature and rolling conditions when manufacturing the base material, and in addition, (3) clad steel plate manufacturing conditions. And (3) clad steel plate manufacturing conditions include, in addition to the clad slab heating temperature, hot rolling conditions such as rolling temperature and reduction ratio, cooling conditions such as post-rolling air cooling and accelerated cooling, and further heat treatment conditions after cooling. Thus, since the factors affecting the quality of the clad base material cover a wide range, machine learning may be applied in designing the clad steel plate manufacturing conditions. For example, by considering a neural network with factors affecting the quality of the clad base material covering a wide range as described above as the input layer and the quality of the base material of the manufactured clad steel plate as the output layer and implementing machine learning, the clad steel plate manufacturing conditions can be designed.

Example

[0037] The simulated manufacturing of a clad steel plate with Alloy 825 as the clad material was carried out. One clad base metal slab was manufactured with the component composition shown in Table 1. The balance other than the components listed in Table 1 is Fe and inevitable impurities. Also, the slab for the facing material was similarly manufactured with the component composition shown in Table 1.

[0038]

Table 1

[0039] Table 2 shows the manufacturing conditions of the simulated clad steel plate. Table 3 shows the manufacturing conditions of the material simulation test specimens for the clad steel plate base metal. In Table 2, the notation "27 + 3" in the product thickness column indicates that the thickness of the clad steel plate base metal is 27 mm and the thickness of the clad steel plate clad material is 3 mm. In Table 3, the notation "27 + 33" in the product thickness column indicates that the thickness of the simulation test specimen for one clad steel plate base metal is 27 mm and the thickness of the facing material is 33 mm. In Table 2, the assembly method column describes the assembly method of the clad slab. "Sand" represents the sandwich method, "sacrificial material" represents the sacrificial material method, and "open" represents the open sandwich method.

[0040]

Table 2

[0041]

Table 3

[0042] The material tests of the manufactured simulated clad steel plate and the base metal equivalent parts of the material simulation test specimens for the clad steel plate base metal were carried out as follows. For the evaluation of mechanical properties, tensile test specimens, DWTT test specimens, and HIC test specimens conforming to the API-5L standard (API: American Petroleum Institute) were taken and tensile tests, DWTT tests, and HIC tests were carried out respectively. The evaluation of the tensile test is considered that the yield strength and tensile strength can be well simulated when the difference is within 15 MPa compared with the simulated clad steel plate. For the DWTT test evaluation, the test temperature was -40°C, and the ductile fracture area ratio (SA) was measured. If the difference in SA is within 20% compared with the simulated clad steel plate, it is considered that the simulation is successful. For the HIC test evaluation, the test was conducted with NACE TM0284 Solution A, and the crack length ratio (CLR) was measured. If the difference in CLR is within 5% compared with the simulated clad steel plate, it is considered that the simulation is successful. The material test results are shown in Table 4.

[0043]

Table 4

[0044] It can be seen that the steel plates No. A to E of the invention example can successfully simulate the base material of the corresponding simulated clad steel plate. In the comparative example, none of the material test results can successfully simulate the corresponding simulated clad steel plate. Since the steel plate No. F uses the clad slab as a clean slab casting and does not undergo the first heating and hot rolling, the evaluations of the DWTT test and HIC test are not good. Since the steel plate No. F uses the clad slab as a clean slab casting, the evaluation of the HIC test is not good. Since the first heating temperature of the steel plate No. H is different, the evaluation of the DWTT test is not good. Since the steel plate No. I is simulated by the open sandwich method of clean material instead of the sandwich method, the yield strength and tensile strength deviate upward. Since the steel plate No. J is simulated by the sandwich method instead of the open sandwich method, the yield strength and tensile strength deviate downward.

Explanation of symbols

[0045] 1 Base material casting (plain steel) 2 Cladding material casting (corrosion-resistant steel) 3 (Slab) heating 4 (Hot) rolling 5 Surface grinding (surface finishing) 6 Base material 7 Cladding material 8 Cutting and peeling 9 Clad slab 10 Assembly of clad slab 11 High vacuum 12 Electron beam welding 13 Rolled body 14 Clad steel plate 14a One clad base material

Claims

1. Heating a slab or steel sheet having the component composition of one clad base material, and then hot rolling to produce one clad base material stock, which is a simulated process for manufacturing a clad base material stock; Overlapping a facing material stock having the component composition of the one clad base material with the one clad base material stock to assemble a simulated clad slab, which is a simulated process for assembling a clad slab; Heating the simulated clad slab, then hot rolling, and performing one or more treatments selected from slow cooling, accelerated cooling, and heat treatment on the obtained hot-rolled clad material to produce a simulated clad steel sheet, which is a simulated process for manufacturing a clad steel sheet; A method for manufacturing a material simulation test piece of a clad steel sheet base material having the above.

2. The plate thickness of the facing material stock is Twice the plate thickness of the clad material stock when manufacturing a clad steel sheet to be the object of material simulation test, and The sum of the plate thicknesses of other clad base material stocks, The method for manufacturing a material simulation test piece of a clad steel sheet base material according to Claim 1.

3. The plate thickness of the facing material stock is The sum of the plate thickness of the clad material stock and the plate thickness of the sacrificial material stock when manufacturing a clad steel sheet to be the object of material simulation test, The method for manufacturing a material simulation test piece of a clad steel sheet base material according to Claim 1.

4. The plate thickness of the facing material stock is The plate thickness of the clad material stock when manufacturing a clad steel sheet to be the object of material simulation test, The method for manufacturing a material simulation test piece of a clad steel sheet base material according to Claim 1.

5. A method for material simulation test of a clad steel sheet base material, in which a material simulation test is performed on a material simulation test piece of a clad steel sheet base material manufactured from the one clad base material stock by the manufacturing method according to any one of Claims 1 to 4.

6. A method for designing the manufacturing conditions of a clad steel sheet, in which the manufacturing conditions of the clad steel sheet are designed based on the test results of the material simulation test according to Claim 5.

7. When designing the manufacturing conditions of a clad steel sheet, machine learning is performed to compare the test results with the results of investigating the material of the clad steel sheet actually obtained by manufacturing the clad steel sheet and correct the difference, which is the method for designing the manufacturing conditions of a clad steel sheet according to Claim 6. ​

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