JPH02172875A - Soldering method for built-up structure made of stainless steel - Google Patents

Abstract

PURPOSE:To enable soldering material to be easily utilized at a high-temp. region at low cost in a short time by applying prescribed fluidized soldering material to the joint part of a built-up structure made of stainless steel and assembling it and thereafter performing vacuum soldering. CONSTITUTION:About 130g nickel soldering powder such as BNi-1 is introduced into a spray pressurizing tank 1 and an organic binder such as ethyl polymethacrylate is introduced into a pressurizing tank 2 at about 10g not more than 1/10 of nickel soldering powder. Fluidized soldering material is obtained by mixing the nickel soldering powder with the binder by a spray gun 4 via the hoses 3, 3'. Then a film having about 0.02mm thickness is formed by applying this soldering material to the whole surface and back surface of the tube plates 5 for the constitutional member of a plate fin type heat exchanger being a built-up structure made of stainless steel by the spray gun 4. Then the heat exchanger obtained by joining the plates 5, the fins 6 and the side bars 7 is soldered and heated at about 10<-3>Torr at about 1100 deg.C in a vacuum heating oven.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for brazing stainless steel assembled structures that are mainly used in high temperature ranges.

[Conventional technology]

Generally, nickel solder is used for brazing stainless steel assembly structures that are used in high temperature ranges of about 800°C.

However, nickel solder has the disadvantage that it cannot be made into a brazing sheet like aluminum solder. That is, since nickel solder contains Si and B in its components, if it is rolled into a foil of 0.1 mm or less, it will fall apart.

For this reason, when brazing stainless steel structures with wide joints, such as plate-fin heat exchangers, conventionally, nickel solder is spread over the entire joint as an amorphous foil, or nickel solder is applied to the entire joint. A structure was assembled by laying a sheet of powder solidified with an organic binder, and then heating it in a vacuum furnace to the required brazing temperature and brazing it together.

(Issue LI to be solved by the invention) However, if the nickel solder is made into an amorphous foil as in the above conventional method, the cost is high, and moreover, the obtained foil is ribbon-shaped with a medium size of about 50 to 100 a++. However, there was a problem in that it required a great deal of labor and time to cover the entire joint and adhere it.

In addition, when nickel solder is used as a powder and solidified into a sheet shape with a large amount of organic binder, a large amount of outgas is generated due to the heat added to the wax in the vacuum furnace.
There was a problem in that this gas entered the molten solder and made the joint porous or had an adverse effect on the furnace exhaust system.

The present invention was made to solve these problems, and allows the work of applying nickel solder to wide joints to be performed easily and in a short time, while also eliminating outgassing caused by heat added to the solder in a vacuum furnace. The purpose of the present invention is to provide a method for brazing stainless steel assembly structures that generates extremely little amount.

[Means for Solving the Problems] The method of the present invention for achieving the above-mentioned object is to use a fluid solder in which a stainless steel assembly structure is joined with a nickel-based powder mixed with a binder at a weight ratio of 1/10 or less. The gist is to apply the material and assemble it, then vacuum braze it.

In the method of the present invention, nickel-based powder refers to various powdered nickel solders, and various nickel solders are
It refers to the eight types of BNi-1 to Ni-7 specified by JIS shown in the table.

Moreover, it is preferable to use a mixture of organic polyethyl methacrylate and organic polybutyl methacrylate in a solvent (alcohol) as the binder.

The amount of binder mixed into nickel-based powder is 1/1 by weight.
The value of 10 or less is the minimum amount necessary to bond the nickel-based powder to the joint of the base metal.If more than this is mixed in, the nickel-based powder will not only aggregate and form a lump, but also cause the vacuum furnace to This is because the additional heat generated during soldering generates a large amount of outgas, which may cause the joint to become porous and have an adverse effect on the vacuum furnace exhaust system.

By uniformly mixing the nickel-based powder and the binder in the above ratio using a mixer or the like, a fluid (paste-like) nickel brazing filler metal with appropriate viscosity can be obtained.

Possible methods for applying this nickel brazing material to the joints of base metals include brush painting, roller painting, and spray painting, but spray painting is preferred because it allows uniform coating over a wide joint and is more efficient. Recommended.

Vacuum brazing involves applying the nickel brazing material to the joints and placing the assembled stainless steel structure in a vacuum heating furnace equipped with a radiant screen in a vacuum of 1.0 to 1 O-hTorr or in an inert gas cloud atmosphere. This is done by uniformly heating the entire body to the brazing temperature in a brazing chamber.

In this case, the brazing temperature must be adjusted to a predetermined brazing temperature (see Table 1) depending on the type of powdered nickel solder.

Examples will be described below.

(Example) A plate-fin type heat exchanger made of stainless steel as shown in FIG. 2 was brazed according to the method of the present invention.

First, 130 g of BNi-1 nickel wax powder was charged into a pressurized tank 1 of a spray device shown in FIG.

Subsequently, binder Log was charged into the pressurized tank 2.

The amount of binder added was about 1,714 times the amount of powdered nickel solder. This binder is made by mixing organic polyethyl methacrylate and organic polybutyl methacrylate in alcohol.

Next, the spray gun 4 connected to the pressurized tank 1.2 via the hose 3.3' is operated, and the nickel solder powder fed from the pressurized tank l and the nickel solder powder fed from the pressurized tank 2 are combined. The mixture was mixed with a binder at the tip of the spray gun 4 and uniformly applied to the entire front and back surfaces of the tube plate 5, which is a component of the plate-fin type heat exchanger. At this time, the coating film of the brazing material formed on the tube plate 5 has a thickness of about 0.02 mm.
It was about mm.

After waiting for the brazing filler metal applied to the tube plate 5 to dry, the tube plate 5 is attached to the corrugated fin 6.
and the side par 7, and assembled into a plate-fin type heat exchanger as shown in FIG.

The thus assembled plate-fin type heat exchanger was fixed with a jig, placed in a vacuum heating furnace, and subjected to brazing heat at 1100° C. in a vacuum of 10-' Torr.

During this vacuum heating, the generation of outgas was tolerable, and there was no adverse effect on the vacuum furnace exhaust system.

Further, the joint forming part of the plate-fin type heat exchanger taken out from the vacuum furnace after the brazing heat was carefully investigated, but no formation of pores (porosity) due to intrusion of outgas was observed.

In the example, a method was adopted in which the nickel brazing powder and binder were mixed in the spray gun, but there is no need to be limited to this, and it is also possible to mix the nickel brazing powder and the binder in advance in a mixer, etc., and send it to the spray gun. It may also be applied by supplying the liquid.

〔Effect of the invention〕

As explained above, according to the present invention, there is no need to use nickel solder as an amorphous foil or harden it into a sheet, and it is possible to thinly and uniformly adhere nickel solder to a wide joint by simply applying it. Can be done. Therefore, this kind of soldering and fixing work is not necessary, and the cost is also reduced.

Furthermore, since less outgas is generated during brazing heating, the performance of the joint is improved and the vacuum furnace is not adversely affected.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating a spray device, and FIG. 2 is a perspective view illustrating a plate-fin type heat exchanger. 1.2: Pressurized tank, 3,3': Hose, 4 Varnish spray gun, 5: Tube plate, 6: Corrugated fin, 7: Side bar

Claims (1)

[Claims] 1. A stainless steel assembly structure characterized by applying a fluid brazing filler metal, which is a mixture of nickel-based powder and binder at a weight ratio of 1/10 or less, to the joints of the stainless steel assembly structure, assembling the structure, and then vacuum brazing the structure. Method of brazing assembled structures.