JPS6022061B2 - Manufacturing method of aluminum alloy thin plate for drawer fin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing aluminum alloy thin plates for drawless fins in heat exchangers.

In recent years, there has been an increasing demand for thinner aluminum alloy processed products from the standpoint of cost reduction.

In particular, when making plate fins thinner, higher strength is required to improve bundling properties and adhesion to, for example, copper pipes. In addition, there has been an increase in the use of multi-step processing methods, such as burring and ironing, which reduce the thickness of the material by performing strong processing such as burring and ironing, followed by further processing to reduce the thickness. As for the fin material of the heat exchanger described in the invention of this application, drawless fins manufactured by performing multi-stage processing have been adopted in recent years as the fins become thinner. The processing method for this Drone Fin is as follows.
The process consists of three stages: burring, ironing, and flaring, and during the first stage of burring, "elongation" is required as a characteristic of the material. Further, during ironing in the second stage, it is required as an important element to have "strength" as well as "work softening" (in this invention, the S value described later is used as a substitute characteristic value). Without this processing softening property, cracks may occur during the third stage of flaring. As described above, there are required material properties at each processing step in the production of Drensfans. This invention was developed in order to satisfy the requirements and strength in the above-mentioned multi-stage processing, and is based on Feo. 5-1.5%, Si
o. 05-0.20%, Tio. A rolled plate obtained by hot rolling and then cold rolling an aluminum alloy containing 0.05 to 0.30% and the remainder consisting of unavoidable impurities and N,
It is characterized by performing intermediate sintering at a holding temperature of 300 to 500 qo for a holding time of 2 hours or more, and then cold rolling at a processing rate of 60% or more, and improves formability and strength in multistage processing. The object of the present invention is to provide a method for manufacturing an aluminum alloy thin plate for drawer fins that satisfies contradictory requirements at the same time.

The route of this invention will be described below.

Japanese Patent Publication No. 52-6684 describes a method for producing an aluminum alloy for deep drawing, which has a composition range that is partially the same as that of the alloy of the present invention. The publication states that an alloy with a specified composition is subjected to cold rolling of 50% or more after hot rolling, or includes a step of hot rolling and forcibly cooling the aluminum alloy during the hot rolling. and hot rolling to 260
By cold rolling by 50% or more after the above-mentioned hot rolling, the occurrence of flow marks during deep drawing can be extremely reduced, the occurrence of flow marks can be prevented, and the mechanical properties in the width direction of the sheet can be improved. This makes it possible to eliminate variations. Furthermore, the properties of the alloy plate described in Japanese Patent Publication No. 52-Waki No. 4 are different from the properties of the alloy plate of this neighboring invention, and are characterized by good tearability. However, the alloy manufactured by the method described in the same publication has a small elongation required for burring, and has no work softening properties, so it cannot be used after heavy working that involves changes in plate thickness, such as burring or ironing. If further processing is attempted, cracks will occur. Therefore, it is technically extremely difficult to use it for such multi-stage processing. In addition, the present applicant also wrote, dated January 22, 1971 (Tokucho No. 7267), “Feo.10 to 0.5 weight %, Sio.0
Tio. Production of an aluminum alloy thin plate with little work hardening, which is made of an alloy containing 0.05 to 0.2% by weight, and is characterized by performing cross-rolling after hot rolling without performing intermediate dulling. ``Method'' was applied.

The aluminum alloy thin plate produced by the method of this invention has
Furthermore, when intermediate sintering is applied in the hope of improving formability, the objective of formability represented by the S value is achieved, but this results in a decrease in strength and a decrease in elongation due to coarsening of crystal grains. Put it away. Based on this fact, the present inventors conducted tests and found that Fe content of 0.10 to 0.50% was reduced to 0.5 to 1%.
．． The inventors have discovered that by increasing the strength to 5% and performing intermediate annealing, it is possible to prevent a decrease in strength and elongation even if the formability represented by the S value is improved, and this invention has been achieved. Next, the reason for limiting the content of alloying elements of this invention will be described.

Concerning Fe, containing 0.50 to 1.5% is effective in suppressing coarsening of recrystallized grains, improving strength and ductility, and suppressing work hardening.

If it is less than 0.5%, the above effect will not be sufficient, and if it exceeds 1.5%, the corrosion resistance will decrease significantly.
By containing 5 to 0.20%, it helps the effect of adding Fe and is effective in improving strength and ductility.

If it is less than 0.05%, the strength improvement effect will not be sufficient;
When it exceeds 20%, the machining hardness (G) becomes large and multi-stage workability deteriorates.

Concerning Ti, by containing 0.05 to 0.30%, the work hardening rate is reduced and ductility and multistage workability are improved.

At 0.05%, the above effect was not expressed, and at 0.30
%, the above effects cannot be further improved.

Moreover, casting becomes difficult. Next, we will discuss the reasons for limitations in the manufacturing process.

The reason for performing intermediate phosphorous annealing at a holding temperature of 300 to 50 psi and a holding time of 2 hours or more is that by precipitating solid solution elements,
During forming processing at a high processing rate that involves changes in plate thickness, the work hardening of the material is suppressed, and further active work softening is performed to prevent cracking during subsequent processing.

In other words, this is to improve multi-stage processability. 300
If the temperature is lower than 500°C, solid solution elements will not be sufficiently precipitated, and if the temperature exceeds 500°C, solid solution will occur again, impairing work softening properties.

Further, if the holding time is less than 2 hours, the solid solution elements will not be sufficiently precipitated. The reason why cold rolling is performed at a processing rate of 60% or more after the intermediate hammering is to improve strength, elongation, and work softening properties.

Examples of the present invention will be shown below to clarify the effects.

EXAMPLES Castings of aluminum alloys having the compositions shown in Table 1 were made by semi-continuous casting.

After face-cutting these fin souls, they were subjected to a heat treatment of 500 qo x 8 hours, hot-rolled to a thickness of 4 willow, and further cold-rolled to produce a plate with a thickness of 1.2. For the plates having each of the alloy compositions obtained in this way, one was subjected to intermediate dulling of 40,000 x 2 hours, and another was made without intermediate hammering.Finally, these were cold rolled to obtain a plate with a thickness of 0. 1 willow (processing rate 92%). These plates were then subjected to a tensile test, and the strength, elongation, and S value were measured and are also listed in Table 1. The S value described in this example is expressed by the following equation.

S=Kikifune≧However,.

: Stress 6: Strain In the load-elongation curve shown in the attached diagram, find the point P at 25% of the elongation after the maximum load Mo, and the point P2 at 75%.
This resulted in S.

An S value of 10 (positive)* indicates work hardening, and an S value of 1 (negative) indicates work softening. As shown in Table 1 above, JISAIlOO alloy material, JIS
The AI05 alloy material has low elongation and does not undergo processing softening.

Also, even if an intermediate dawn anchor is applied to the 110 river alloy material mentioned above,
Although the processing softening properties represented by the S value are slightly improved, the elongation is small. No. No. 4 is an example of the alloy composition described in the specification of Tokugan Sho 56-7267, which has improved elongation and work softening properties compared to the 110-fold alloy and 105-fold alloy. Earth. 5 is No. 4 was subjected to intermediate annealing, and the processing softening properties were further improved, but
Strength and elongation are reduced. The one that improves this point is the ground. The present invention shown in 8, 9, 10, 11,
A thin plate material with excellent strength, elongation, and processing softening properties can be obtained. No. 7 has the alloy composition of the present invention, but was not subjected to intermediate sintering, and was subjected to intermediate annealing (M
．． Compared to 8), the processing softening properties are slightly inferior. M. 6 is S
0.2% or more (0.35%) of i is added,
It can be seen that although the strength is improved, processing softening is suppressed by adding Si in an amount greater than the specified value. Table 2 shows the (formability) when processed with a fin forming machine corresponding to each trial number in Table 1.
This is a table showing

In the table, the number of micro-cracks in the 60-hard molded sample is shown in the numerator. As seen in the upper table of Table 2, the alloy composition of this invention is
The alloy shown in Tokubuta No. 56-7267 (No.
It has very good moldability comparable to 4).

[Brief explanation of the drawing]

The attached figure is an explanatory diagram for determining the S value from the load-elongation curve.

Claims (1)

[Claims] 1 Fe0.5-1.5%, Si0.05-0.20%
, 0.05 to 0.30% of Ti, the balance being unavoidable impurities, and Al to a rolled plate obtained by hot rolling and then cold rolling.
A method for manufacturing an aluminum alloy thin plate for a dolorous fin, which comprises performing intermediate annealing at 00° C. for a holding time of 2 hours or more, and then cold rolling at a processing rate of 60% or more.