JPH04327383A - Production of stainless steel clad product - Google Patents

Abstract

PURPOSE:To subject bag-shaped stainless steel foil and a material to be clad to solid-phase diffusion joining by inserting the latter into the former and deforming both at cold, then pressurizing both under heating. CONSTITUTION:The stainless steel foil having 20 to 30mum thickness is formed to a bag shape 2 and the material 1 to be clad is inserted therein. After the inside of the foil is hermetically sealed, >=100kg/cm<2> isotropic pressure is acted at cold on the stainless steel foil to deform the foil along the outside surface shape of the member 1 to be clad. The foil and the member are then heated under >=10kg/cm<2> isotropic pressure. The solid-phase diffusion joining of the stainless steel foil and the member to be clad is executed in this way. The stainless steel foil is thus securely joined to the member to be clad having ruggedness on the surface.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing stainless steel clad metal products using a solid phase diffusion bonding method using hydrostatic pressure and gas pressure.

0002

[Prior Art] In recent years, for metal products that we see in our daily lives, where rust is a problem in terms of aesthetics and functionality, we have changed from conventional ordinary steel to stainless steel or ordinary steel clad with stainless steel. Materials are changing. In particular, products clad with stainless steel are rapidly becoming popular, mainly for building materials and everyday products. Examples of building materials include interior materials for trains, etc., and everyday products such as drying rods and pots and pots. There are two known methods for manufacturing these products.

One method is to stack a core material and a cladding material during rolling or extrusion processing and join them together as a raw material to obtain an intermediate material such as a plate or pipe clad with stainless steel. This method involves further drawing to make pots and pots. The other method is to make use of the large coefficient of thermal expansion of stainless steel to tightly adhere stainless steel foil to the outer surface of a pipe or the like using a shrink-fitting method.

0004

The above two conventional methods have the following drawbacks. First, with both methods, it is impossible to obtain a product whose surface has irregularities of several millimeters or more. In addition, in the case of the former method of using a clad plate as an intermediate material, it is necessary to cut it to the required size and use it, but at this time, the internal material is exposed at the cut end. If the internal material is ordinary steel, there is a problem that this part will rust. Furthermore, when welding this intermediate material into a product,
The weld metal in the weld zone has a composition that is a mixture of internal ordinary steel and surface stainless steel, and is also susceptible to rust problems and, in particular, stress corrosion cracking problems.

On the other hand, in the case of the latter shrink-fitting method,
Because the shape is limited and the metallurgically clad stainless steel is not bonded to the base material, it cannot be applied to members that are particularly subject to large frictional forces in the plane direction. SUMMARY OF THE INVENTION An object of the present invention is to provide a method that eliminates the drawbacks of the prior art as described above and can be applied to products with various shapes, especially those with uneven surfaces.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the present invention forms stainless steel foil with a thickness of 30 to 300 μm into the shape of a bag or container, inserts a member to be clad inside the bag, and After airtightly sealing, 10
Applying an isotropic pressure of 0 kgf/cm2 or more to deform the stainless steel foil along the outer surface shape of the cladding member,
Next, a configuration was adopted in which the stainless steel foil and the cladding member were solid-phase diffusion bonded by heating under an isostatic pressure of 10 kgf/cm2 or more, and further processing was performed using cold isostatic pressure.
This method employs a configuration in which solid-phase diffusion bonding is performed continuously within a HIP device.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be explained in detail with reference to FIGS. 1 to 9. 1 to 4 are explanatory diagrams sequentially showing the steps of the method of the present invention. In FIG. 1, 1 is a member to be clad, and the member 1 is housed in an envelope-shaped bag 2 made by welding stainless steel foil. The thickness of stainless steel foil is
30-300 μm, preferably 50-150 μm
It is. In addition, in the present invention, the thickness of the foil is 30 to 300 μm.
The reason for limiting the thickness to m is that if the foil is less than 30 μm, the foil will often contain pinhole-like pores, and when applying isostatic pressure, the seal will fail and the bond will not be joined, or the foil will often break due to insufficient strength. by.

On the other hand, if the thickness exceeds 300 .mu.m, a large pressure is required to improve the installation property, which also causes high costs, and in normal applications, a thick cladding remains unchanged. In addition, as will be described later, from the viewpoint of reducing damage during cold compression, a material that has been annealed to provide sufficient ductility is used. High pulse TIG is used for processing into bag shapes.
, lap welding using seam welding or YAG laser welding is recommended from the viewpoint of simplicity and ensuring airtightness. The welding line in this case is as shown in numeral 3.

Next, as shown in FIG. 2A, the bag 2 is hermetically sealed by welding the opening 4 along the weld line 3. Although it is preferable to keep the inside of bag 2 in a vacuum, the inside of the bag may be made of getter material such as zirconium or titanium, which easily absorbs nitrogen and oxygen, which are the main components of air, at the temperature during heating for diffusion bonding, which will be described later. It is possible to obtain an effect similar to that of vacuum sealing even if it is placed in a vacuum chamber. Note that FIG. 2B is similar to FIG. 2A.
A cross-sectional view is shown.

The entire bag is then placed in, for example, a cold isostatic press (CIP) device as shown in FIG. 3A.
Applying hydrostatic pressure of 100 kgf/cm2 or more,
The stainless steel foil is deformed so as to follow the outer shape of the cladding material 1. The pressure is appropriately selected depending on the thickness and hardness of the stainless steel foil and the shape of the recess in the cladding material 1. However, in the present invention, the above-mentioned 100 kgf/cm2 or more is limited to 100 kgf/cm2 for many materials.
This is because if it is less than 2, the surface shape will be insufficient, and the adhesion will be poor, especially at concave corners. 100 μm thick SUS304 foil that has been annealed to have a hardness of Hv ~ 180 kgf/mm2
With a pressure of kgf/cm2, it is possible to closely deform the concave radius to less than 1 mm. Further, during this hydrostatic compression, the surface of the foil may come into contact with the water of the pressure medium and become dirty, but to prevent this, it is preferable to further enclose the entire foil in a polyethylene bag. Note that FIG. 3B shows a cross-sectional view of FIG. 3A.

[0011] The object to be processed thus prepared is subjected to HI
The sample is placed in a device that applies gas pressure under high temperature, such as P device 6, and the temperature and pressure are increased (see FIGS. 4A and 4B). The temperature/pressure increase pattern and the final temperature/pressure depend on the material of the cladding material 1 and the degree of vacuum inside the stainless foil bag, but as shown in Figure 5, at least 10 kgf/cm2 is initially applied. It is recommended to apply the above pressure to suppress expansion of the bag due to temperature rise. The reason why the pressure is limited to the above-mentioned value is that if the foil is 300 μm or less, the adhesion required for bonding can be obtained with this pressure. If the cladding material is ordinary steel such as SS41, if the temperature is 1000℃ or higher, 10kgf/cm2
Diffusion bonding is possible at the above pressure. Note that the temperature is appropriately selected depending on the material of the cladding material, but it is necessary that the temperature is higher than the recrystallization temperature. In this diffusion bonding process, an inert gas such as argon is basically used as a pressurizing medium, but if this gas is contaminated with impurities, the surface of the product after cladding may lose its luster. Because it will discolor, it is recommended to use other measures to maintain the purity of the gas, such as placing a getter material in the furnace or placing the product in a stainless steel bag (not welding it). be done.

[0012] After completing the diffusion bonding process as described above, the excess stainless steel foil portion of the product is cut and removed, and the final product (
(not shown). The noteworthy feature of the present invention is that first, the stainless steel foil to be clad is cold-deformed so as to follow the outer shape of the member to be clad. In other words, the hardness is relatively low (250 kgf/mm2 in Hv).
(below), for example, annealed stainless steel foil is
It has excellent cold deformability, and if fluid pressure is used, the height difference between the uneven parts of the cladding member can be reduced by 50 to 50% of the foil thickness.
This was possible due to the knowledge that it is possible to deform up to about 100 times as much without breaking, depending on the pressure value and the presence or absence of edges. In addition, when attempting to deform stainless steel foil in a similar manner at high temperatures, if the cladding material is made of ordinary steel such as SS41 or copper alloy, the strength of these materials decreases significantly at high temperatures, resulting in deformation of the stainless steel foil. This was achieved by discovering a phenomenon in which the cladding member also deforms at the same time.

[0013] The pressure of this cold stainless steel foil forming is:
The selection is made depending on the thickness of the foil and the shape of the cladding member, especially the curvature R of the recessed edge. As mentioned above, when the thickness of stainless steel foil is about 100μm, 100 kgf
It is possible to mold up to approximately 1 mm in radius with a pressure of 1.5 kgf/cm2, but if the foil thickness is even larger or the cladding material includes a material with a smaller radius, the pressure may be several thousand kgf/cm2.
It is preferable to apply a pressure higher than that.

[0014] In some cases, the present invention may also be implemented in which the above-mentioned cold isostatic pressure treatment and diffusion bonding treatment under gas pressure are performed continuously in the same apparatus.
It is suitable to use an IP device. The pressure/temperature pattern is as shown in FIG. 6, for example. The advantage in this case is that the stainless steel foil does not come into contact with water (usually containing anti-rust oil), so the entire process can be done cleanly;
and the pressure during the diffusion bonding process is several 100 kgf/cm.
When using a high pressure of 2 or more, the total processing time can be shortened.

Hereinafter, specific examples of the present invention will be explained with reference to Table 1 and FIGS. 7 to 9, together with comparative examples. Figure 7, Figure 8
, and the cladding members shown in FIG. 9 are difficult to manufacture using conventional techniques.

[0016]

[Table 1]

According to Examples 1 to 3 in Table 1 above,
All of the obtained products exhibited good cladding conditions. In particular, with the SUS304 clad copper material of Example 3, which is the simplest in terms of shape, a strong bond could not be obtained by conventional methods such as rolling, but a strong bond was obtained as described above. Using this material, it became possible to mold pots and other items through plastic processing.

On the other hand, in Comparative Example 1, the gas pressure, which is the diffusion bonding condition of the present invention, is as low as 5 kgf/cm2, in Comparative Example 2, the thickness of the stainless steel foil is as thin as 20 mm, and in Comparative Example 3, the thickness of the stainless steel foil is as low as 5 kgf/cm2.
As shown in the results in Table 1, good products were not obtained in either case.

[0019]

Effects of the Invention According to the present invention, stainless steel foil with a thickness of 30 to 300 μm is formed into a bag or container shape, a member to be cladded is inserted into the bag, and the inside is hermetically sealed.
A specific hydrostatic pressure is applied cold to deform the external shape of the stainless steel foil to the cladding member, and then the stainless steel foil and the cladding member are solid phase diffusion bonded by heating under a specific gas pressure. , it is possible to obtain a strong cladding condition for cladding materials with unevenness, which was difficult to manufacture with conventional techniques, and also to make it possible to attach stainless steel cladding to copper materials, for which it was not possible to obtain a strong bond with conventional techniques. It is believed that the contribution to various industrial fields is often large. In particular, from the perspective of improving the decorativeness of building materials and daily necessities in recent years, the present invention, which allows the surface of inexpensive ordinary steel to be clad with rust-free stainless steel at a relatively low cost, is a significant technology that meets the needs of the times. I think this is something to look forward to.

[0020] In addition, in the present invention, especially when cold processing of stainless steel foil using hydrostatic pressure and diffusion bonding under gas pressure are performed consecutively using the same equipment under gas pressure, the stainless steel foil does not come into contact with water. Therefore, the entire process can be performed cleanly, and the pressure during the diffusion bonding process can be reduced to several hundred
When using a high pressure of kgf/cm2 or more, there is also the effect that the total processing time can be shortened.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a set which is the first step of the method of the present invention.

FIG. 2 is an explanatory view A and a cross-sectional view B showing vacuum sealing, which is the next step of the method of the present invention.

FIG. 3 is an explanatory view A and a cross-sectional view B showing stainless steel foil forming (CIP), which is the next step in the method of the present invention.

FIG. 4: Diffusion bonding (the next step in the method of the present invention)
FIG. 2 is an explanatory view A and a cross-sectional view B showing HIP.

FIG. 5 is a graph showing a pattern of temperature increase and pressure increase in the method of the present invention.

FIG. 6 is a graph showing a pattern of temperature increase and pressure increase in the method of the present invention.

FIG. 7 is a perspective view of an example of a cladding member.

FIG. 8 is a perspective view of an example of a cladding member.

FIG. 9 is a perspective view of an example of a cladding member.

[Explanation of symbols]

1 Cladding member 2 Stainless steel foil bag 3 Welding line 4 Opening 5 Welding line 6 HIP device

Claims (2)

[Claims] Claim 1: A stainless steel foil with a thickness of 30 to 300 μm is formed into a bag or container shape, a member to be cladded is inserted into the bag, the inside is hermetically sealed, and then the bag is heated for 10 minutes in a cold state.
Applying an isotropic pressure of 0 kgf/cm2 or more to deform the stainless steel foil along the outer surface shape of the cladding member,
A method for manufacturing a stainless steel clad product, which comprises: then heating under an isotropic pressure of 10 kgf/cm2 or more to solid phase diffusion bond the stainless steel foil and the clad member. 2. The method for manufacturing a stainless steel clad product according to claim 1, wherein cold isostatic pressure processing and solid phase diffusion bonding are performed continuously in a HIP device.