Aluminum alloy and corresponding heat treatment process applied to manufacture aluminum/steel cladding plates resistant to high temperature brazing

Abstract

A kind of aluminum alloy and corresponding heat treatment process applied to manufacturing aluminum/steel cladding plates which are resistant to high temperature brazing belong to alloy materials technology field. In the aluminum/steel cladding plates, the aluminum part was alloyed with 0.76%0.78% Si and 0.0550.10% Er in weight percent and the rest was Al and some unavoidable impurity. The Steel part was 08Al steel. After cladding cold rolling with deformation of 55%2%, the aluminum/steel cladding plates were annealed at 510535 C. for different times. Then simulated brazing process was performed to optimize the range of annealing time and temperature. The so produced Al/St cladding plates could not only effectively solve the low interface strength in Al/St cladding plates, but also meet the mechanical properties which were necessary for further processing of Al/St cladding plates. It was provided a kind of aluminum alloy and corresponding heat treatment process which could effectively solve the low bonding strength under the condition of high temperature brazing because of the existence of brittle FeAl phases.

Claims

1. An aluminum/steel cladding plate, comprising an aluminum foil made of an aluminum alloy cladded on a steel sheet, wherein the aluminum alloy comprising 0.76%0.10% by weight of microalloying element Si and 0.055-0.10% by weight of microalloying element Er, with the balance being aluminum.

2. An aluminum alloy applied to manufacturing aluminum/steel cladding plates which are resistant to high temperature brazing, the aluminum alloy consisting of 0.76%0.10% by weight of microalloying element Si and 0.055-0.10% by weight of microalloying element Er, with the balance being aluminum.

3. A method for manufacturing an aluminum/steel cladding plate, comprising: providing an aluminum foil made of an aluminum alloy comprising 0.76%0.10% by weight of microalloying element Si and 0.055-0.10% by weight of microalloying element Er with the balance being aluminum; cladding the aluminum foil with a steel sheet via cold rolling with 552% deformation to form a raw aluminum/steel cladding plate; and annealing the raw aluminum/steel cladding plate to obtain the aluminum/steel cladding plate.

4. The method for manufacturing an aluminum/steel cladding plate according to claim 3, wherein the raw aluminum/steel cladding plate is annealed at a temperature of 510 C. for 33-100 h, or 515 C. for 16-100 h, or 520 C. for 12-72 h, or 525 C. for 8-60 h, or 535 C. for 4-60 h.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) FIG. 1 is a graph representing the optical images of the interface for Al-0.76Si-0.1Er/St upon 520 C./18 h annealing and stimulated brazing;

(2) FIG. 2 is a graph representing the optical images of the interface for Al-0.78Si-0.055Er/St upon 520 C./18 h annealing and stimulated brazing;

(3) FIG. 3 is a graph representing the optical images of the interface for Al-0.1Er/St upon 520 C./18 h annealing and stimulated brazing;

(4) FIG. 4 is a graph representing the optical images of the interface for Al-0.055Er/St upon 520 C./18 h annealing and stimulated brazing;

(5) FIG. 5 is a graph representing the optical images of the interface for pure Al/St upon 520 C./18 h annealing and stimulated brazing;

(6) FIG. 6 is a graph representing the relationship between the microhardness and annealing time of steel side in Al/St cladding plates at different annealing temperatures;

(7) FIG. 7 is a diagram representing the interface characteristics in AlSiEr/St cladding plates relative to annealing temperature and time after annealing and further simulated brazing process.

(8) The invention will be further explained below in conjunction with the accompanying drawings and the embodiments.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(9) The following is to make a further explanation on the invention combining with some practical examples, but the invention is not limited to them.

(10) Alloy ingots were prepared by smelting in graphite crucible and then casting into iron mould. The raw materials were pure Al and master alloys of Al-6Er and Al-35Si (in weight percent). At smelting temperature of 79010 C., Al ingots should be smelted firstly, then add master alloys of AlEr and AlSi into it. After the master alloy melting, use hexachloroethane to remove gas, stir vigorously and then cast into iron ingots after keeping it for a while until every element distributes uniformly. Prepare alloys of different compositions, measuring its actual composition through XRF, in which the measurement error of Si concentration is about 0.1 wt %, as shown in table 1.

(11) TABLE-US-00001 TABLE 1 Concentration of the alloys Alloy concentration Norminal Verified Experimental concentration (wt. %) concentration (wt. %) samples Er Si Al Er Si Al A1 0 0 balance 0 0 balance A2 0.05 0 balance 0.055 0 balance A3 0.10 0 balance 0.10 0 balance A4 0.05 0.8 balance 0.055 0.78 balance A5 0.10 0.8 balance 0.098 0.76 balance

(12) Roll the prepared Al alloy into foils and cold-rolled clad of 552% deformation with steel. After that, heat treatment and stimulated brazing are conducted. Through cold rolling between Al and steel, grains deform seriously and the ductility of cold rolled cladding plates decrease. In order to satisfy the further process, the cladding plates need to be annealled. Annealing at different temperature for different times on the Al/St cladding plates, get recrystallization finishing time at each temperature from the microhardness-annealing time curve. The stimulated brazing is adopted to ensure the high temperature application. The simulated brazing heat treatment in this experiment is done as follows: increase the temperature of aluminum/steel cladding plates from room temperature to 625 within 30 min, keep at 625 for 10 min, then cool in the air.

EXAMPLE 1

(13) Upon annealing and simulated brazing, there is no interfacial compound in sample A5 (Al-0.8Si-0.10Er/St), and the interfacial bonding is fine, as shown in FIG. 1.

EXAMPLE 2

(14) Upon annealing at 520 C. for 18 h and stimulated brazing, there is no interfacial compound in sample A4 (Al-0.8Si-0.05Er/St), and interfacial bonding is fine, as shown in FIG. 2.

Comparative Example 1

(15) Upon annealing at 520 C. for 18 h and stimulated brazing, there is discontinuous interfacial compound in sample A3 (Al-0.10Er/St), and its thickness is small, as shown in FIG. 3.

Comparative Example 2

(16) Upon annealing at 520 C. for 18 h and stimulated brazing, there is discontinuous interfacial compound in sample A2 (Al-0.05Er/St), as shown in FIG. 4. And the thickness of the interfacial compound is far smaller than that of pure Al/St after heat treatment with the parameters. However, its performance is not so good as AlSiEr/St.

Comparative Example 3

(17) Upon annealing at 520 C. for 18 h and stimulated brazing, there is a lot of brittle interfacial compound with layered continuous distribution in sample Al (pure Al/St), as shown in FIG. 5. It would result in separation between steel and Al. The existence of interfacial compound would decrease the bonding strength seriously.

EXAMPLE 3

(18) The recrystallization finishing time at different annealing temperatures could be obtained from microhardness measurement after annealing Al/St cladding plates at different temperature for different times. Testing temperatures are 475, 500, 505, 510, 515, 517, 520, 525, 530, 535 C., respectively. The results indicate that, the steel does not recrystallize after annealing at 475 C. for 60 h. The recrystallization of steel occurs after annealing at 500 C. for 51 h, or at 505 C. for 42 h, or at 510 C. for 33 h, or at 515 C. for 16 h, or at 520 C. for 12 h, or at 525 C. for 8 h, or at 530 C. for 6 h, or at 535 C. for 4 h. The details see FIG. 6.

EXAMPLE 4

(19) The samples A4 and A5 (AlSiEr/St) was annealed and further stimulated brazed. By observing interface, it was found that there was no intermetallic compound formed after annealing at 510 C. for 33-100 h and further stimulated brazing. With the increasing annealing temperature, the heat treatment window with no interfacial compound became narrower to 16-100 h at 515 C., 12-72 h at 520 C., 8-60 h at 525 C., and 4-60 h at 535 C. The detail is shown in FIG. 7.