JPH01262091A - Brazing sheet for structural member of drawn cup type heat exchanger having good brazing property - Google Patents

Abstract

PURPOSE:To improve a brazing property by regulating the surface roughness of the Al alloy brazing filler metal cladded on the surface of an Al alloy core bar and making the length of the fine crack existed on its surface at less than the specified value. CONSTITUTION:The surface roughness of the one side at least of an Al alloy brazing filler metal is made in <=0.4mum: mean roughness (Ra) and <=2.5mum max. roughness (Rmax) in the orthogonal direction with the rolling direction. The length of the small crack existed on said surface is made in <=20mum as well. The brazing property of a brazing sheet is thus improved and the use as for the structural member of a drawn cup type heat exchanger, especially as a fluid tube sheet can be interfaced with. In the case of using as said fluid tube sheet, therefore, the generation of a defective part due to its brazing defect is reduced and the product yield can remarkably be improved.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides an M alloy that has excellent brazing properties and is particularly suitable for use as a fluid tube sheet material that is a structural member of a doron cup type heat exchanger. This relates to brazing sheets.

[Conventional technology]

In recent years, due to the demand for lighter weight, more compact size, and higher performance in transportation equipment such as automobiles, heat exchangers such as radiators, car cooler condensers, evaporators, oil coolers, and intercoolers have become popular. are starting to be loaded in some areas.

This doron cup type heat exchanger consists of a pair of halved fluid tube sheet materials that are structural members,
Similarly, it is manufactured by stacking one layer or two or more layers of fin material alternately, and then performing 7 lux brazing or vacuum brazing with this stacked body fixed with a jig.

In addition, the above fluid tube sheet material conforms to JIS3003
6951, or 3005, and one or both sides of which are clad with a brazing filler metal made of M alloy such as 4045 or 4004, which is formed by press processing from an M alloy brazing sheet. It is.

[Problem to be solved by the invention]

However, in the above-mentioned Dron cup heat exchanger, since a relatively large pressure is applied to the fluid flowing through it, it is required that the joints of the fluid tube sheet materials be perfectly brazed. Fluid tube sheet materials, which are conventionally composed of brazed sheets, can be used in situations where the vacuum in the vacuum brazing furnace is not high enough or the dew point of the atmospheric gas in the inert atmosphere brazing furnace is low enough. If this is not the case, or if brazing is performed under poor conditions, such as when the oil adhering to the press work before brazing is not sufficiently cleaned, the fillet formation on the inside of the mating surface (brazed joint) may be insufficient. This may result in failure of the subsequent pressure test, and in many cases, the
Many defects occur, and since these rejected products cannot be repaired, they are sometimes disposed of in units of lofts, resulting in a low manufacturing yield.

[Means to solve the problem]

Therefore, the inventors of the present invention, etc., from the above-mentioned viewpoint.

In particular, when manufacturing doron cup heat exchangers, we developed a brazing sheet that exhibits good brazing properties without being affected by brazing conditions when used as a structural member, especially as a fluid tube sheet material. This is the result of extensive research.

The surface roughness of the filler metal that makes up conventional brazing sheets is perpendicular to the rolling direction.

Average roughness (Ra): 0.4-0.6 pan.

Maximum roughness (Rmax): 3 to 4 μm s, and there are many microcracks on the surface with a length of 25 to 40 μm, about 20 or more per square meter. During production, the rolling rate in one cold rolling is made as small as possible. In other words, if the number of times of rolling is increased.

Long microcracks are now eliminated, so this 1
The rolling rate (number of rolling times) is controlled to prevent the presence of microcracks longer than 20 μm, and at least the final cold rolling in the cold rolling process of the brazing sheet is finished with a bright finish or a mirror finish on the surface. The surface roughness was measured in the direction perpendicular to the rolling direction.

Average roughness (Ra): 0.4 μm or less.

Maximum roughness (Rmax): 2.5 μm or less.

Therefore, the fluid tube sheet material formed from the brazing sheet in this state exhibits excellent brazing properties and brazing properties without being affected by the brazing conditions, that is, even under the poor brazing conditions described above. We obtained the knowledge that a good fillet was formed inside the joint (mating surface), and that it was possible to manufacture a Doron cup heat exchanger with a high yield that fully passed the pressure test. .

This invention was made based on the above findings.

In a brazing sheet formed by cladding an M alloy brazing material on one or both sides of an M alloy core material.

The surface roughness of at least one side of the M alloy brazing filler metal in a direction perpendicular to the rolling direction.

Average roughness (Ra): 014 μm or less.

Maximum roughness (RmaX): 2.5 μm or less.

At the same time, the length of the microcracks existing on the surface is
By making the brazing sheet 20 μm or less, the brazing properties of the brazing sheet are improved, and the brazing sheet is suitable for use as a structural member of a doron cup heat exchanger, especially as a fluid tube sheet material. .

Therefore, like the conventional brazing sheet mentioned above,
The surface roughness of the brazing filler metal exceeds 0.4μm in Ra and 2.5μrrL in the direction perpendicular to the rolling direction, and the micro cracks existing on the surface of the filler metal exceed 20μm.
If the length exceeds , it will not be possible to ensure good brazing.

〔Example〕

The blazing sea of the present invention will be explained in detail with reference to Examples.

3003 alloy (composition: N, -1,234Mn -0,12%Cu
), 3005 alloy (composition: Ml, -1,314Mn
-0,364M,g), and 6951 alloy (composition: M-0,62CHMg-0,38%5i-0,22
%Cu, the above vehicle weight and the following indicate weight %) were respectively melted and 4004 alloy (
Composition: M-9,36%5i-1,33%Mg) and 4
045 alloy (composition: At-10,2%Si) was melted and made into an ingot with a thickness of 414B using a vertical semi-continuous casting machine.

Temperature: 590°C for 12 hours for 3003 and 3005 alloy ingots, 12 hours at 560°C for 6951 alloy ingots, and 480°C for 12 hours for M alloy ingots for filler metal.
Homogenization heat treatment was applied to each ingot for a certain period of time, and then face side treatment was applied to both sides of these ingots to a thickness of 7B on each side, and the M alloy ingot for brazing material was subjected to Fi hot rolling. The thickness was set to 50mm, and in this state, the M alloy hot-rolled plates for brazing filler metal were superimposed on both sides of the M alloy ingot for core material in the combinations shown in Table 1 to form a total of 500mm.
This was hot-rolled at a rolling start temperature of 480°C to obtain a cladding material with a thickness of 7. Subsequently, this cladding material had a thickness of 5 rm - + 3.8 m
yth −+ 2.9 ax−+ 2.2 run−+
1. '71131-+ 1.3 m→1. Omx
By performing cold rolling in 7 stages (previously the usual 5 stages described below) in which the brazing filler metal is rolled in a manner that suppresses the formation of large microcracks on the surface of the filler metal, the thickness :At 5th grade, in inert gas atmosphere, temperature: 350℃
Intermediate annealing was performed under the condition of holding for 2 hours, and thickness: 1.
3 m and 1, Owtpr cold pressure j1. This is done using various rolling rolls with bright or mirror-finished roll surfaces and adjusted surface roughness, and finally annealed at a temperature of 350°C for 2 hours in an inert gas atmosphere. Brazing sheets 1 to 2 of the present invention having the surface roughness and the maximum length of microcracks shown in the $1 table were manufactured by applying the following methods.

In addition, for the purpose of comparison, the thickness of the above cold rolled
5B-+3.21Ll! -+2.1m-+1.4mx
-+1. The cold rolling was carried out under the same conditions as in the above rules, except that the cold rolling was carried out in 5 stages that changed to Ox, and all of these 5 stages of cold rolling were carried out using ordinary rolling rolls, that is, various types of rolling rolls with milled surfaces. Conventional brazing sheet 1 having the surface roughness and maximum length of microcracks shown in Table 1
-4 were produced, respectively. Power.

The values of the surface roughness and the maximum length of surface microcracks in Table 1 were measured at 10 appropriate locations on the brazing sheet, and the i quotient values were shown.

Next, from the various brazing sheets obtained as a result, the fluid tube sheet material of the Dron cup type heat exchanger was modified as shown in a schematic longitudinal cross-sectional view in FIG. Press-molded cup-shaped specimens with inner diameter: 40 m x φ x depth = 8 mm, and one with a center hole of 10 m φ in the center of the bottom, and one without, and 3 sets of 2 pieces were made. Stacked and in this state, flux brazing is carried out under the conditions of holding the temperature at 2600°C for 5 minutes in an inert gas atmosphere, or in a vacuum of 100 torr.
Vacuum brazing is performed at a temperature of 2,600°C for 3 minutes to produce a brazed laminate with a structure modified to a doron cup heat exchanger, and then a brazed laminate is placed in the center hole at the bottom of the brazed laminate. Attach the connecting pipe by torch brazing, connect this pipe to a pressure tester, and perform a pressure test using water pressure.

The maximum pressure at which peeling occurred on the brazed surface of the test piece was measured. These results are shown in Table 1.

〔Effect of the invention〕

From the results shown in Table 1, the brazing laminates produced using the brazing sheets 1 to 12 of the present invention are as follows.

All of them show high pressure resistance, have good brazing in the brazing direction (brazed joint), and have a good fillet formed on the inside, whereas conventional brazing sheets 1 to 4 have In the attached laminate,
It is clear that the strength of the brazed joint is low, it can only withstand relatively low internal pressure, and the brazing is not perfect.

As mentioned above, the brazing sheet of the present invention has excellent brazing properties, and when used as a fluid tube sheet material for a doron cup heat exchanger that requires particularly high brazing strength, it can be easily brazed. This brings about industrially useful effects such as a drastic reduction in the number of defective products caused by defects and a marked improvement in product yield.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical sectional view showing a brazed laminate having a modified structure of a doron cup heat exchanger. Applicant Mitsubishi Aluminum Corporation

Claims (1)

[Claims] (1) In a brazing sheet formed by cladding an Al alloy filler metal on one or both sides of an Al alloy core material, the surface roughness of at least one side of the Al alloy filler metal is determined by the average roughness in the direction perpendicular to the rolling direction. (Ra): 0.4 μm or less, maximum roughness (Rmax): 2.5 μm or less, and the length of microcracks existing on the surface is
A brazing sheet for a structural member of a Droncup type heat exchanger, characterized by having a thickness of 20 μm or less and having good brazing properties.