JPH02228443A - Zr-base nonvolatile gas absorbing alloy for aluminum brazing - Google Patents

Abstract

PURPOSE:To manufacture the Zr base nonvolatile gas absorbing alloy preferably suitable as a getter material in Al brazing by preparing a Zr base alloy contg. specified ratios of V, Fe and Ni and having specified total amt. of V, Fe and Ni. CONSTITUTION:The Zr base nonvolatile gas absorbing alloy contg., by weight, 10 to 15% V, 2 to 20% Fe and >=6% Ni and having <=55% total of Fe+V+Ni and the balance substantial Zr is prepd. When the alloy is used to Al brazing in vacuum or in the atmosphere of inert gas, the alloy is activated at relatively low temp. of about 250 to 300 deg.C and starts to absorb gas; it absorbs oxygen- series gas such as oxygen and H2O and carbon-series gas such as CO and CO2, so that the alloy is preferably suitable as a getter material for sound brazing.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is used particularly in brazing aluminum in a vacuum or inert gas atmosphere to prevent oxygen, carbon dioxide, H, O, etc. that inhibit brazing. The present invention relates to a Zr-based non-repulsion type gas-absorbing alloy suitable as a getter material that absorbs impurity gas and enables sound brazing with few joining defects.

(Conventional technology) One of the means for joining aluminum is brazing.

Brazeability is an especially convenient method for joining items with complex shapes, and brazing using plating sheets is often used to manufacture products with complex shapes such as heat exchangers. There is.

Depending on the method of brazing, there are torch brazing, furnace brazing, immersion brazing, and vacuum brazing, which are used depending on the shape of the joint.

Among these, torch brazing properties, furnace brazing properties, and immersion brazing properties, excluding vacuum brazing properties, are based on alkali metal chlorides, such as NaC/, -KCf-Licl, as the main component during brazing work. Requires expensive flux and also
If oil, oxides (scale), etc. adhere to the brazed joint surface, the flux will not work properly, so pretreatment such as alkaline cleaning or pickling must be performed. Furthermore, after brazing, it is necessary to perform post-treatments such as water washing, hot water washing, and pickling to remove residual flux. For this reason, torch brazing, furnace brazing, and immersion brazing are expensive and pose pollution problems due to processing waste liquid.

On the other hand, vacuum brazing allows brazing to be performed without using flux, and does not require pre- or post-treatment, making it cheaper and free from pollution problems. However, using flux Therefore, if an oxide film, oil, etc. remain on the surface of the bonding base material, the wettability and vortex flow between the brazing material and the base material will deteriorate, and bonding defects may occur. In addition, even if the surface of the base metal is clean during brazing, depending on the atmosphere in the vacuum furnace, an oxide film may form on the joint surface, and oil and fat adhering to the inner wall of the vacuum furnace and brazing jig may It may evaporate as the temperature rises and adhere to the bonding surface.

Therefore, when brazing in vacuum, it is necessary to place magnesium in a vacuum furnace or use a brazing filler metal containing about 1 to 3% by weight of magnesium to prevent deterioration of wettability and reduce bonding defects. Preventing occurrence. this is,
The purpose is to evaporate magnesium during the brazing temperature raising process and absorb oxygen in the furnace to prevent the formation of an oxide film. Although this method is effective in reducing the formation of an oxide film and reducing bonding defects caused by the oxide film, since magnesium does not absorb gases other than oxygen, H, and O, Magnesium is completely ineffective in removing carbon-containing gases such as oils and fats evaporated from carbonaceous solvents, and in fact, magnesium may hinder the dissociation of carbon from the bonding surface. Oil and fat adhering to the joint surface may become carbon monoxide and carbon dioxide gas during the temperature rise process and dissociate from the joint surface, but since magnesium preferentially absorbs oxygen, it prevents this dissociation phenomenon. That's what happens. As a result, the carbon on the bonding surface remains attached, resulting in poor wettability and vortex flow between the bonding surface and the brazing filler metal, which may result in bonding defects. Furthermore, scale produced by evaporation and oxidation of magnesium contaminates the inside of the vacuum furnace and lowers the degree of vacuum. Therefore, it is necessary to periodically remove the scale accumulated in the vacuum furnace, which has the disadvantage of increasing extra work.

(Problem M to be Solved by the Invention) The problem of the present invention is to solve the problem of oxygen, hydrogen, -carbon oxide, Zr-based non-evaporable gas absorption that absorbs impurity gases such as carbon, hydrocarbons, H, 0, etc. that inhibit the wettability of the joint surface and the vortex flow of the brazing material, enabling sound brazing with fewer joint defects. Our goal is to provide alloys.

(!!Means for Solving Problem I) When brazing aluminum in a vacuum or inert gas atmosphere, the cleaner the bonding atmosphere in the furnace, the more sound the bonding can be. However, as mentioned above, depending on the atmosphere inside the furnace, an oxide film may form on the joint surfaces, or oils and fats may adhere to the joint surfaces and carbon may remain on the joint surfaces, impairing the wettability between the brazing material and the base metal, and causing the joint to fail. May cause defects.

Therefore, conventionally, magnesium is used as a getter material, but since magnesium does not absorb carbon-based gases such as carbon monoxide, carbon dioxide, and hydrocarbons, it is difficult to prevent deterioration of wettability caused by these gases. However, the present inventors have discovered that an alloy with the composition described below becomes activated at a relatively low temperature and begins to absorb gases, and that this alloy absorbs not only oxygen and water vapor, but also - carbon oxide and carbon dioxide. They discovered that it also absorbs carbon-based gases such as hydrocarbons, leading to the present invention.

Here, the gist of the present invention is "in weight %, V: 10 to 50%,
Re: 2-20%, Ni: 6% or less (however, Fef
A Zr-based non-evaporable gas absorbing alloy that is used as a getter material for brazing aluminum in a vacuum or inert gas atmosphere, containing a total of 55% or less of V+N+) and the remainder substantially consisting of Zr. It is in.

The fact that the remainder is essentially composed of Zr means that in addition to Zr, Zr
r When using Zircaloy alloy as raw material and ■, F
e Impurities that are unavoidably mixed when using ferrovanadium alloy as a raw material and have no essential effect on the function of the alloy, such as Sn up to 2%, A2 up to 1.5%, and 0.5%. This means that up to Sr, etc. are allowed.

The general method for manufacturing the alloy of the present invention is to charge the raw materials into a crucible such as Calja, perform high-frequency induction melting in an inert gas atmosphere such as argon, form an agglomerate, and then mechanically crush the material. , is the method.

In addition, in the present invention, "aluminum" refers to pure Af
In addition to i, it also includes ^2 alloys.

(Function) Hereinafter, the reason for selecting the composition of the alloy of the present invention will be explained together with the function and effect.

In the Zr-based alloy of the present invention, (1) facilitates the activation treatment and serves to lower the gas equilibrium pressure during absorption. To obtain this effect, the amount of V is 10%.
The above is necessary. However, if ■ exceeds 50%, the rate at which carbon-based gases such as carbon monoxide and carbon dioxide are absorbed slows down at the tip end, and the amount of gas absorbed decreases. The absorption effect is lost. As a result, no improvement in wettability can be obtained. Therefore, it is necessary that the (1) content is 10% to 50%.

Fe functions to suppress the ignitability of the alloy and facilitate industrial handling. In order to obtain this effect, 2% or more is required. However, if the amount exceeds 20%, the rate of oxygen absorption decreases, making it easier for an oxide film to form on the joint surface during brazing. Therefore, the amount of Fe needs to be 2 to 20%.

Ni finely precipitates Zr-former intermetallic compounds such as ZrJi in the alloy and interacts with the matrix in the poisoned layer on the alloy surface.
A defect is created at the boundary with the r-old thread intermetallic compound, and diffusion of Hz, 0□ occurs starting from this defect, which not only facilitates the activation process from low temperatures, but also absorbs carbon oxide. It works to enhance the. Therefore, Xi is effective in rapidly absorbing carbon monoxide from low temperatures. However, if the amount exceeds 6%, the absorption equilibrium pressure of hydrogen gas and carbon monoxide gas becomes worse than the pressure required for vacuum brazing of aluminum, and the carbon monoxide remaining in the atmosphere without being absorbed becomes brazed. There is a situation where the material is adsorbed to the joint surface. Therefore, the carbon content adsorbed on the joint surface may deteriorate the wettability of the brazing filler metal to the joint surface, which may impede brazing bondability. Therefore, the amount of Ni needs to be 6% or less. A desirable range is 0°01 to 5%.

Regarding the above-mentioned (1), Fe and Ni, it is also important to keep the total content below a certain value. That is, V +
The total of Fe+Ni must be 55% or less0
The gas absorbing alloy of the present invention has α-Zr + Zr (vl
−, Fe, )! + It is made of three components of ZrJi, and some of the absorbed gas diffuses inside the alloy and becomes ZrJi.
It exists in types such as rC and Zr0t. Therefore, V+F
If the total content of e-Ni is more than necessary, α-ZrO
This decreases the amount of gas that can be absorbed, making it impractical.

The gas absorbing alloy of the present invention having the above composition has the following properties.

■Activates at a relatively low temperature of 250-300″C,
begins to absorb gas.

■In addition to oxygen-based gases such as oxygen, H, and O, carbon monoxide,
It can also absorb carbon-based gases such as carbon dioxide and hydrocarbons.

The gas-absorbing alloy of the present invention having such characteristics is placed near the brazed joint when brazing aluminum in a vacuum or an inert gas atmosphere.
It is used as a getter material to absorb the impurity gas remaining in the furnace and inhibiting the wettability and swirling of the solder to ensure sound brazing.

The present invention will be further explained below with reference to Examples.

(Example 1) Alloys with varying contents of the additive components shown in Table 1 were prepared, and their activation characteristics were investigated.

(1) Production of test material ■ A small ingot weighing approximately 150 g was button melted using an argon arc.

■Remelt with argon arc for homogenization.

■Create a granular alloy of 297-1680 μm by mechanical crushing.

In Table 1, alloys 1 to 7 are of the present invention, alloys 8 to 10 are comparison materials, and pure Mg (99.9% purity) is the conventional material 0 alloys 1 to 7 and alloys 8 to 10. For production, Z
Scraps of Zircaloy 2 and Zircaloy 4 are used as raw materials for r, ferro-vanadium alloy of 80% and 20% Fe is used as raw materials for and prepared using flake vanadium. Further, as for Ni, electrolytic nickel having a purity of 99.7% was used.

Incidentally, Sn mixed in from Zircaloy and A2 and S+ mixed in from ferro-vanadium are unavoidable impurities.

(Hereinafter, blank spaces) (2) Activation characteristics The activation characteristics were investigated using the apparatus shown in FIG. 1 according to the following procedure.

■In a reaction vessel (1) made of quartz glass and having a capacity of 22 mm, an alloy (1 to IO grain size 297 to 1680 μ-
2) or pure Mg (2), close the gas introduction valve (3), open the gas discharge valve (4) and vacuum gauge protection valve (5), and apply a vacuum using the vacuum pump [6]. Start pulling.

■The degree of vacuum in the reaction vessel (1) is I Xl0-'torr
When the pressure is reached, close the gas discharge valve (4) and vacuum gauge protection valve (5), open the gas introduction valve (3), and close the pressure gauge (7).
) 500ppg+ in the cylinder (8) until the pressure is indicated.
An Ar balance standard gas with a purity of 99.99% containing carbon monoxide was introduced.

■ Perform vacuuming again, and the degree of vacuum is I x 10-'
Wait until torr, then follow the same procedure as ■
Introduce r-balance standard gas until the pressure gauge (7) shows 1 atm.

■ After repeating the above replacement operation three times and filling the inside of the reaction vessel (1) with Ar balance standard gas containing 500 pp- of -carbon oxide, the gas inlet valve (3) and the gas discharge valve (4) are filled.
), and set the heating rate to 5°C/min and turn on the heater (9).
Heat at.

■Measure the temperature at that time with a thermocouple 0 [D, and -carbon oxide concentration with a densitometer O1].

Note that the reference numeral 021 shown in FIG. 1 is a gas flow rate regulator, and the reference numeral 021 is an ion vacuum gauge.

Figure 2 shows the measurement results. The horizontal axis represents the temperature increase rate of 5°C.
/min is the temperature when heated, and the vertical axis is the carbon monoxide concentration.

As shown in Figure 2, Alloys 1 to 7 of the present invention are activated and begin to absorb carbon monoxide at 200 to 3 bO<0>C during vacuum heating, and the carbon oxide concentration increases to 3
00 pp- or less. On the other hand, alloys 8 to 10, which are comparative materials, each have a temperature of 510°C, 1430°C, and 1330°C.
The activation temperature is high at 600°C, and the carbon monoxide concentration is 400 ppm or more, which is higher than the alloy of the present invention.

Note that Mg absorbs oxygen but does not absorb carbon monoxide, so its concentration is high. The activation of Mg with respect to oxygen depends on the saturated steam of ig and is 3X10-'torr.
The temperature is approximately 380°C.

(Example 2) Using an industrial vacuum furnace with a furnace capacity of 22 as shown in FIG. 3, the AWS lap joint test pieces shown in FIGS. 4(a) and (b) were brazed, and The improvement effect was investigated.

For the investigation, Alloy 1, Alloy 6, Alloy 8, Alloy 10 shown in Table 1 with a particle size of 300 to 1680 μm and block-shaped pure Mg were used, and 20 g of each of these were placed in a vacuum furnace 04).
Placed inside, vacuum pump 0! 2.0X inside the furnace with lil
After the degree of vacuum was higher than 10-' torr, four heaters (heated at lω and AWS lap joint test piece Q7) were brazed. In addition, the base material of the test piece: JrSA5052, the brazing metal: JIS Z 3263
BA4005, plate thickness (t): 2 brazing gap: 0
．． ], 5mm, overlap margin (A): 5mm.

(1) Furnace Atmosphere Vacuum Level The results of measuring the change in the vacuum level during the brazing process are shown in FIG. 5 together with the heat pattern.

In Figure 5, case 1 is brazed without gas absorbing alloy, case 2 is pure Mg, case 3 is alloy 1, case 4 is alloy 6, case 5 is alloy 8, and case 6 is alloy Cases 3 and 4 using alloys 1 and 6 of the present invention, in which alloys 1 and 6 are arranged and brazed, respectively, have the highest vacuum, followed by case 5 using alloy 8, which is a comparative material. Case 6 using Alloy 10 and Case 2 using pure Mg have a high degree of vacuum near the brazing temperature.

(2) Shear strength After completing the vacuum brazing, each test piece was subjected to a tensile test to examine the shear strength of the brazed joint. The results are shown in FIG.

From FIG. 6, it can be seen that cases 3 and 4 in which the alloy of the present invention was used had the highest shear strength and good brazing. On the other hand, in Case 1, which does not use a gas-absorbing alloy, the shear strength is low, and the strength also varies among the four test pieces. In addition, the shear strength of Case 2 using Mg is higher than that of Case I, but lower than Case 3 and Case 4 using the alloy of the present invention, and The shear strength of the alloys used was improved compared to these, but no effect was obtained with the alloy of the present invention.

(3) Oxygen and carbon adsorption on the surface of the brazing material In order to clarify the cause of the difference in shear strength, IHMA was used to measure the vicinity of the brazing position of the test piece (the position indicated by the arrow in Figure 4). , primary ion: Cs'', secondary ion:
Surface analysis was conducted under the conditions of 0-1C-1 output crab 125 V, 120 nA, analysis area: 150 to 250 μ raster, and the amount of oxygen and carbon adsorbed was investigated. The result is the 7th
As shown in FIG.

From FIG. 7 and FIG. 8, it can be seen that in cases 3 and 4, which use the alloy of the present invention, adsorption of oxygen and carbon is small. This is because the alloy of the present invention absorbs oxygen, carbon-based gas, etc.

Therefore, the wettability between the brazing material and the surface of the brazing material does not deteriorate, so that the shear strength is high and there is little variation. On the other hand, in Case I, which was brazed without using a gas alloy, the brazed joint was clearly oxidized and a large amount of carbon was adsorbed on the surface. In Case 2, which uses Mg, oxygen adsorption is small, but
Carbon adsorption cannot be suppressed, and cases 5 and 6 using comparative alloys adsorb less oxygen and carbon than these, but compared to cases 3 and 4 using the invention alloys. There are many.

(Example 3) 20g of each of the same alloy and Mg used in Example 2 were placed in a vacuum furnace, and an aluminum jet engine heat exchanger shown in FIG. 9 was assembled by vacuum brazing. The occurrence of brazing defects was investigated.

Brazing of the heat exchanger was performed as follows.

Material (7) 2mmmm aluminum pipe IS A
3052) to a length of 450 mm, and cut this pie 10
A plating sheet (JISB^) with a wall thickness of 45mm was prepared and fixed to the shell 09) as shown in Fig. 9, et al., and clad with 0.2mm thick brazing filler metal QO on both ends. V: PC) (21), that is, after being assembled into a heat exchanger by inserting it into the hole (23) drilled in the end plate (22), vacuum brazing was performed.

The vacuum furnace and heat pattern used for vacuum brazing are as follows:
This is the same as Example 2.

5 to 7 cm to the heat exchanger brazed in this way.
The presence or absence of leakage was examined by applying a water pressure of 1000 ml, and pipes with leaks were judged to have brazing defects, and the evaluation was based on the number of defective pipes out of 714 pipes. The results are shown in FIG.

As shown in FIG. 1O, no defects occurred in cases 3 and 4 in which alloys 1 and 6 of the present invention were used as getter materials during brazing of the heat exchanger. In contrast, case 2 using brazed case LMg without using a gas absorbing alloy, and cases 5 and 6 using a comparison material alloy.
There are many defects.

(Effects of the Invention) As explained above, the gas-absorbing alloy of the present invention is activated at low temperatures and absorbs oxygen, hydrogen, and carbon-based carbon monoxide, carbon dioxide, and hydrocarbons. Therefore, this alloy can be used when brazing aluminum in vacuum or in an inert gas.
When used as a getter material, these impurity gases can be absorbed, so wettability is not inhibited, and sound brazing with fewer bonding defects can be performed.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the reaction apparatus used in the investigation of the activation characteristics of gas-absorbing alloys, Figure 2 is a graph showing the measurement results of heating temperature and carbon monoxide concentration, and Figure 3 is a graph showing the measurement results of heating temperature and carbon monoxide concentration. Figure 4 is a diagram showing the shape of the AWS joint test piece used in the above investigation, and (a) is a plan view. , cD) is a side view, Figure 5 is a graph showing the measurement results of the brazing heat pattern and degree of vacuum, Figure 6 is a graph showing the results of investigating the shear strength by static S joint test, Figure 7 is a graph showing the oxygen analysis results on the surface of the brazing material by IHMA, FIG. 8 is a graph showing the carbon analysis results on the surface of the brazing material by IMA, and FIG. 9(a) is an example of a heat exchanger. FIG. 10 is a schematic perspective view showing a detailed view of part A in FIG.
2 is a graph showing the results of an investigation into the occurrence of brazing defects. (11 Reaction vessel (2) Alloy or Mg (3) Gas inlet valve (4) Gas discharge valve (5) Vacuum gauge protection valve (6) Vacuum pump (7) Pressure gauge (8) Ar balance standard gas cylinder (9) Heater Oω thermocouple (11) - Carbon oxide concentration meter 021 Gas flow rate regulator 0 Qion vacuum gauge
QIO industrial vacuum furnace (+51 vacuum pump 0
61 heater θ'l) V: Lap joint test piece 0 [DA5052 aluminum pipe 0! (L shell QL brazing metal (21) Placing sheet (22) End plate (23) Drilling hole Homare 4 figure rod 6 (2) (Kasou Nio! 7)

Claims (1)

[Claims] In weight%, V: 10-50%, Fe: 2-20%, Ni
: Zr-based non-evaporable gas absorbing alloy for aluminum brazing, containing 6% or less (however, the total of Fe+V+Ni is 55% or less), and the remainder is substantially Zr.