JPS60180685A - Clad material - Google Patents

Abstract

PURPOSE:To obtain a clad material having improved corrosion resistance and exfoliation resistance in a clad material made by explosion welding a cladding material on a base metal, by interposing an intermediate material having lower melting point than at least one of the base metal and cladding material between the base metal and cladding material. CONSTITUTION:After interposing an intermediate material 16 having lower melting point than at least one of the base metal 1 and cladding material 9 between the base metal 1 and cladding material 9, explosion welding is made by exploding an explosive 10. As the cladding material 9 is joined to the base metal 1 firmly and closely, a clad material having improved corrosion resistance and adhesion can be obtained. Necessary thickness of the cladding material 9 before explosion is about 0.2mm. or more, and practical thickness of the intermediate material is about 0.5mm. or more.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cladding material with excellent corrosion resistance and bondability.

A method of completely covering a certain metal with another metal is used as a means to increase the corrosion resistance of the metal. Of these, the metallurgically bonded interface between these metals is called cladding, and is formed by overlaying, rolling, explosion bonding, or the like.

For example, corrosion damage prevention d-
Overlay welding is often performed for the purpose of . FIG. 1 shows submerged arc welding, which is a typical conventional technique for overlay welding.

Figure 1 shows stainless steel wire 2 on the base material 1 of the pressure vessel.
This figure shows the state in which overlay welding is performed using The electrode is a wire 2, which is arc melted in a flux 3 to become a weld metal 4. However, compared to the wire 2 as a material, the corrosion resistance of the grain boundaries of the weld metal 4 after overlay welding is often lower, and the original purpose of overlay welding is often not achieved. . In the figure, numeral 5 is a welding power source, 6 is a wire feeding roller, 7 is a motor,
8 is a controller.

Table 1 below shows that on the meat of low alloy @5A508013,
The composition of the overlaid stainless steel weld metal is shown together with the composition of the wire. The first layer material of overlay welding metal style is a welding material equivalent to D 309L of Z 3221 of J Engineering S standard, and the second layer material is D 308L or J of the same standard.
It is a material equivalent to YB 304L of the engineering S standard 23322.

Table 1 As you can see from the carbon content in Table 1, the first layer material wire l
The carbon content of -A is low, 0.018% by weight, but increases to 0.055% by weight after welding. Regarding the second layer material, the carbon content of wire 2-A is 0.014% by weight.
Despite this, the weld metal is 0.03'7% by weight.
It has doubled.

The cause of the increase in carbon content in the overlay weld metal is the effect of dilution of low alloy steel, which has a carbon content more than ten times higher than the content of wire metal, and contamination from flux.

Recently, through research into the causes of intergranular corrosion and stress corrosion cracking in stainless steel 5US304, it has become generally known that carbon in the material combines with chromium at grain boundaries, resulting in zero chromium carbide. 'r2. The chromium depletion phenomenon near the grain boundaries, that is, the sensitization that occurs when forming O, is harmful. It has also become clear that reducing carbon emissions is effective in preventing this sensitization.

The results of evaluating the corrosion resistance of the test materials shown in Table 1 are shown in FIG. The test method used was the sulfuric acid-sulfuric acid second test (Strauss test, J Engineering 5Go575, but the test time was 72 hours). The test results were also expressed as the intergranular corrosion rate (μm/h) determined from the intergranular corrosion attack depth. As can be seen from the test results, the corrosion resistance of the wire metal itself in both the first and second layers is excellent, whereas the corrosion resistance of the grain boundaries in the weld metal is poor. The main reason for this is thought to be the carbon content of the material.

As mentioned above, as long as the method of completely melting and welding the wire is used, an increase in the amount of harmful carbon cannot be avoided and a decrease in corrosion resistance is unavoidable even if the welding method is different.

On the other hand, the cladding welding method using explosive welding (explosion bonding) does not melt the entire cladding material but only the bonding interface with the base metal, so there is no increase in the carbon content of the cladding body.
It is considered to be a good construction method in terms of corrosion resistance.

FIG. 3 shows this explosive welding method. Base material 1
Leave an appropriate gap 10 between the material 9 and the material 9 to be joined to it. Place it at j.

A buffer material 11 is placed on top of the bomb 9, and gunpowder 12 is placed on top of it and detonated from one end. Due to the lighting power, the laminate material 9 collides with the base material 1 at high speed and is joined. Note that numeral 13 indicates the explosion direction.

The bond between the laminate material 9 and the base material 1 after lacquer welding becomes a metallurgical bond due to the high pressure during the explosion.

However, when this explosive welding method is used to join stainless steel plates onto a base material of low alloy steel, localized delamination may actually occur, which can be a problem. This is due to poor explosive welding, which is a technical difficulty that tends to occur when explosive welding is performed between materials with high melting points.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide a cladding material (hereinafter referred to as "cladding material") that improves corrosion resistance and bondability.

In short, the present invention is a clad material formed by explosion bonding between a base material and a laminate, and an intermediate material made of a material having a melting point lower than that of the base material and the laminate.

Next, prior to a detailed explanation of the present invention, FIG. 4 shows the melting temperature of each metal, and the process that led to the construction of the present invention will be explained.

FIG. 4 shows the melting points of stainless steel, nickel-based materials, and iron-based materials. The melting point of low alloy steel used in pressure vessels is about 1530°C, which is almost the same as that of pure iron, and has the highest melting point among the materials shown in the table. Stainless steel used as clad material or laminating material is approximately 140
It has a relatively high melting point of around 0.06C.

Explosive welding joins by crimping under high pressure, but on a microscopic level, the metal atoms that make up the surface of the base material and the surface of the laminate come close to each other to the point where the atoms are 11 old. This is because metal bonding occurs. This phenomenon is exactly the same as when crystal grains with different directions are connected in a metal material. Furthermore, it can be said that only the bonding interface between the base material and the laminate material was melted by the high pressure.

Therefore, an important technical issue regarding the bondability of explosive welding is how to make it easier to melt the bonding interface between the base material and the cladding material, and to bring the metal atoms on the surfaces of the base material and the cladding material closer together to the unit of atomic distance. Become.

It has become clear that in order to solve this technical problem, it is sufficient to place an intermediate material having a lower melting point than the base material and the laminate material.

The alloy of nickel-based materials Inconel 601, Hastelloy B, and Monel 400 shown in FIG. 4 has a melting point about 50 to 100 degrees Celsius lower than that of stainless steel, and has a melting point lower than that of stainless steel and the iron-based base material and gold mine of stainless steel.

It was confirmed that the bondability to the filler material was good and that it was suitable as an intermediate material.

FIGS. 5 and 6 show a method of forming a cladding material according to the present invention. Low alloy steel 5A508013
Monel 400, which becomes the intermediate material, is inserted into the base material 1 through the gap 15.
(66,5%Ni-31,'5%Cu-Fθ) plate 1
6 is placed, and a stainless steel 316L plate 9 serving as a mating material is further placed with an appropriate gap 17 provided therebetween. Furthermore, a cushioning material 11 and gunpowder 10 are arranged on the laminated material 9. In addition, at this time, the plate thickness of the intermediate material 16 was 0.5 mm+, and the plate thickness of the laminated plate 9 was 2 mm.

Here, we will discuss how to determine the thickness of intermediate materials and laminate materials. First, let's talk about the thickness of the intermediate material. The thickness of the plate is also affected by the magnitude of the explosive force due to the difference in the type and amount of gunpowder, but if the explosive force is assumed to be constant, theoretically the energy of the plate colliding with the base material is proportional to the reciprocal of the plate thickness. Therefore, the thinner the board, the better. However, when the plate thickness is thin, wavy patterns are often seen in the cross section of the joints made by explosive welding. That is, the boundary between the base material side and the bonding material becomes wavy, and the height of the wave may reach up to 0.2 mm. Therefore, from the point of view of the bonding force by explosive welding, the thinner the plate is, the better, but from the point of view of preventing the formation of wavy patterns at the joint, the plate thickness must be 0.2 mm or more.
If it is less than this, there is a risk that the base material will be exposed. In addition, the laminate material is explosively welded from above the intermediate material at the same time, and a similar wavy pattern is formed between the laminate material and the intermediate material.
In order to completely prevent the intermediate material from tearing due to this phenomenon, it is practical that the thickness of the intermediate material is about 0.5 mm or more. - On the other hand, according to the above-mentioned concept, the thickness of the laminated plate should be 0.2 mm or more, but since this laminated material will be placed in a corrosive environment, it is necessary to consider the corrosion allowance. Since the laminate is a material that is resistant to intergranular corrosion, there is no need to consider intergranular corrosion, but it is necessary to fully consider the corrosion cost due to oxide scale formation. If the combined oxidation rate is, for example, a maximum of 0.1 mm/year, then about 2 mm is sufficient to withstand 20 years of use. The thickness of the intermediate material and laminate material may be determined in consideration of the above points.

FIG. 6 shows the detonation from one end of the laminate device structure shown in FIG. 5 before explosive welding. Due to the explosion, the laminate material 9 and the intermediate material 16 violently collide with the base material at a certain angle at high speed.

Table 2 shows the intergranular corrosion characteristics of the cladding part of the test materials created by testing various combinations of materials other than those mentioned above, and summarizes the results of the sulfuric acid-copper sulfate test. It is something that

Naturally, since the laminate is not completely melted by explosive welding, no harmful increase in the amount of carbon that causes intergranular corrosion occurs. Therefore, the grain boundary erosion rate of all bonded materials after explosion bonding, that is, clad materials, is O,1μm/
A diagram showing the results of an intergranular corrosion test with excellent ear resistance of h or less,
Fig. 3 is a schematic diagram showing the conventional explosive welding method, Fig. 4 is a diagram showing the melting points of various materials such as stainless steel, nickel base, and iron base, and Fig. 5 is a diagram showing the explosion welding method as an embodiment of the present invention. The layout of each material, FIG. 6, is a diagram showing the situation during explosive welding of cladding 4O according to the present invention.

1...Base material 9... combined profit 16...Intermediate material Figure 1 Figure 3 1 Figure 4 Figure 5 n Figure 6

Claims (1)

[Claims] 1. In a device in which a laminate material is explosively bonded to a base material, an intermediate material having a melting point lower than at least one of the base material and the laminate material is provided between the base material and the laminate material. A clad material characterized by intervening arrangement of. 2. The cladding material according to claim 1, wherein the thickness of the laminated material before being applied to the field is approximately 0.2 mm or more, and the thickness of the intermediate material is approximately 0.5 mm or more.