JP3207512B2 - Composite metal sheet with excellent workability and bonding strength - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is to provide a composite metal sheet which is lighter than the conventional use of thin steel sheets, and is used as a material for a structure requiring machining and welding. Suitable for.

[0002]

2. Description of the Related Art Weight reduction of thin steel sheets used as structural materials has been a major issue, and various means have been proposed. One of the means for reducing the weight is to partially use aluminum. However, while weight reduction and strength by aluminum are theoretically possible, aluminum and aluminum alloys by themselves are significantly inferior in workability to steel plates. Furthermore, when both a steel material and an aluminum material are used for a structure, the joining of both may be indispensable in some cases, but the joining strength of both iron and aluminum by welding is weak and sufficient joining strength cannot be expected. From the above, at present, aluminum can be used only for limited applications.

It is considered that the above problem can be solved by using a two-layer composite plate having one side formed of an iron layer and one side formed of an aluminum layer and having a high bonding strength and excellent workability. At present, there are few practical examples of plate materials in which aluminum and iron are combined because their production is technically difficult.

[0004] On the other hand, as for a thin plate made of a composite plate of iron and aluminum, a composite plate manufactured by a lap rolling method has been proposed. For example, as disclosed in Japanese Patent Application Laid-Open No. 63-157774, 350 to 55
A method in which the steel material is heated to about 0 ° C., hot-rolled and joined to the iron material, and as disclosed in Japanese Patent Publication No. 56-52679, the surface of the iron material is previously plated with aluminum and heated to about 500 ° C. There is a method of hot rolling and joining with an aluminum material. However, the composite plate manufactured by these methods does not always have a sufficient deep drawability because distortion due to processing remains on the steel plate side. In addition, when a cold rolled material is used as the iron material, if the iron layer before joining is not heated, or if the temperature is about 500 ° C. even after the heating, the recrystallization is insufficient and the composite plate is insufficient. Almost no workability can be expected.

[0005] Furthermore, although the composite plate manufactured by these methods does not peel off in a process such as a gentle bending in which a 180 ° bending is performed once as shown in the example of JP-B-56-52679, However, in a process such as bending and unbending, or in a process such as deep drawing, it cannot be said that it has a sufficient bonding strength. As described above, a composite plate composed of two layers of iron and aluminum having sufficient workability and bonding strength, regardless of whether a cold-rolled plate or an annealed plate is used as a joining material, has been known. Not.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides iron and aluminum having good workability and bonding strength irrespective of the manufacturing history of the iron layer of the bonding material and the method of manufacturing the composite plate. It is an object of the present invention to provide a two-layer composite metal plate.

[0007]

The present invention achieves the above object and comprises two layers of iron having a thickness of 5 mm or less on one side and aluminum having a thickness of 5 mm or less on one side. By providing the composition within a specific range and the diffusion layer at the interface within a specific range, a composite plate having both good workability and bonding strength is provided.

[0008]

The present inventors have found a condition that has good press formability and, at the same time, high bonding strength between the iron layer and the aluminum layer, which are the constituent materials of the composite plate, when forming the composite plate. The present invention is based on this finding, and the gist of the present invention is to provide a composite metal plate having two layers of iron on one side and aluminum on one side, wherein the iron layer has a crystal grain size of 10 μm or more and 5 μm or more.
The composite plate is excellent in workability and bonding strength, characterized in that the grain size is 0 μm or less, and the thickness of the diffusion layer at the interface between iron and aluminum is 1 μm or more and 7 μm or less. It has the following composition. That is, in the iron layer, the chemical components are in a weight ratio of C: 0.0005 to 0.5.
01%, Si: 0.1% or less, Mn: 0.04 to 0.5
%, P: 0.1% or less, sol Al: 0.002-
0.1%, N: 0.005% or less, more than 4 times the amount of Ti: C and 0.0015 to 0.15%, the balance being iron and unavoidable impurities. The iron layer contains N
b: 0.003 to 0.015% can be contained. The aluminum layer is an aluminum alloy containing at least 99% or more of aluminum by weight or 6% or less of Mg by weight and 2% or less of Mn by weight. The aluminum layer further contains 0.5% or less of Si and 0.5% or less of C.
One or more of 0.5% or less Zn may be contained.

Hereinafter, the present invention will be described in detail. As the C content in the iron material increases, the amount of TiC generated in the steel increases, so that the r (average) value and ductility deteriorate, yield strength increases, and workability decreases. Therefore, the smaller the amount of C, the better the press workability. Therefore, the C content is preferably set to 0.010% or less. However, there is a problem that the cost of decarburization is increased in order to reduce C to 0.0005% or less. Therefore, the amount of C was limited to 0.005 to 0.01%.

Although a small amount of Si causes no problem, a large content lowers the workability. Therefore, it must be 0.1% or less. Mn is a component necessary to prevent hot embrittlement due to S present as an unavoidable content in steel. However, if it is less than 0.04%, FeS is generated and the effect is not obtained. On the other hand, if it exceeds 0.5%, the workability deteriorates. Therefore, the amount of Mn was limited to 0.04 to 0.5%. If P is contained in a large amount, it segregates at the grain boundaries and becomes brittle, causing a reduction in workability. Therefore, the P content was limited to 0.1% or less.

Al is an element necessary for controlling the amount of oxygen in steel, and is added as a deoxidizer before adding Ti. If the acid-soluble Al content in the steel is less than 0.002%, deoxidation is not sufficiently performed, and the yield of Ti is significantly reduced. However, if it exceeds 0.1%, inclusions increase and the workability of the steel sheet decreases. Therefore, the amount of Al is 0.002-0.1%
Limited to. N should be fixed as TiN by Ti because solid work in steel greatly reduces workability. Also, the amount of generated TiN is preferably as small as possible. Therefore, the N content is set to 0.005% or less.

[0012] Ti is required in an amount sufficient to fix C and N sufficiently. For that purpose, at least a Ti amount corresponding to the total number of atoms of C and N is required. However, if the number of fixed TiC or TiN is large, the workability is reduced, so that it is necessary to increase these sizes. For that purpose, the Ti amount corresponding to the total number of atoms of C and N is insufficient, and 0.015% is necessary. However, if it exceeds 0.15%, the amount of solid solution Ti increases and the workability decreases. Therefore, the amount of Ti was limited to 0.015 to 0.15%.

The components other than the above components are composed of Fe and unavoidable impurities.
003 to 0.015% may be added. Nb is 0.00
By adding 3% or more, a composite carbide with Ti precipitates, which is more likely to grow than a carbide of Ti alone, so that recrystallization at the time of annealing is performed more favorably. However, 0.
If added in excess of 15%, the workability is undesirably reduced.

Next, the composition of the aluminum material may be either pure aluminum or aluminum alloy containing 99% or more Al by weight. Although the type of the aluminum alloy is not limited, an aluminum alloy containing at least one of Mg of 6% or less and Mn of 2% or less is particularly preferable. These alloy components increase the strength of aluminum in an annealed state, and do not significantly impair workability such as drawing. 6% of Mg
, Or when the amount of Mn exceeds 2%, the curing is remarkable,
Since the processability is impaired, the above ranges of these components are appropriate. Further, when one or two types of 0.5% or less of Si, 0.5% or less of Cr, and 0.5% or less of Zn are added together with the above components, the strength is further improved while maintaining good workability. Can be raised. However, Si, Cr,
If the amount of Zn exceeds the above range, the workability is impaired, so the above range is limited.

The iron material having the above composition may be manufactured by a usual hot rolling or cold rolling process. Further, either a cold-rolled steel sheet or an annealed steel sheet may be used. However, in the iron layer in the composite plate, the crystal grains thereof must be sized and the average particle size must be 10 μm or more and 50 μm or less.
The reason for this is that if the particles are sized and the average particle size is not more than 50 μm, the surface properties are reduced during processing, and if the average particle size is not more than 10 μm, the workability is reduced.

FIG. 1 shows the average grain size obtained by changing the annealing time of the iron layer when manufacturing a composite plate of iron and aluminum having the composition and thickness shown in Table 1 using the apparatus shown in FIG. It shows the effect of the crystal grain size on the r (average) value and the surface properties when the diameter is changed. As is clear from FIG. 2, it is found that good r (average) value and surface properties can be obtained in the case where the average crystal grain size is 10 to 50 μm. In addition, even when using an iron plate and an aluminum plate having different compositions within the scope of the present invention, the average crystal grain size is similarly 10 to 10.
It has been confirmed that a good r (average) value and surface texture can be obtained in the case of sizing at 50 μm.

[0017]

[Table 1]

The thickness of the diffusion layer at the interface between the iron layer and the aluminum layer of the composite plate must be 1 μm or more and 7 μm or less. The reason is that when the thickness of the diffusion layer is 1 μm or more, the bonding strength increases. However, when the thickness of the diffusion layer exceeds 7 μm, a brittle alloy layer is formed in the diffusion layer, and the bonding strength is reduced again. Therefore, the thickness of the diffusion layer at the interface between the iron layer and the aluminum layer of the composite plate is set to 1 μm or more and 7 μm or less.

FIG. 2 shows the diffusion of the interface between the iron layer and the aluminum layer by changing the heating temperature of the iron layer and the aluminum layer when the iron layer and the aluminum layer having the compositions and plate thicknesses shown in Table 1 are joined using the apparatus shown in FIG. Bond strength and 180 ° by T-peel test between iron layer and aluminum layer when layer thickness is changed
Shows the number of times of repeated bending until peeling by the repeated bending test (bending radius: 4.0 mm). As is clear from FIG. 2, it is understood that good bonding strength can be obtained by setting the length of the diffusion layer at the interface between the iron layer and the aluminum layer to 1 μm or more and 7 μm or less. In addition, it has been confirmed that good bonding strength can be similarly obtained in the case of a diffusion layer having a thickness of 1 to 7 μm for composite plates having different compositions within the scope of the present invention.

FIG. 3 shows an electric heating and pressure welding equipment, in which energizing rolls 11 and 12 are provided on an iron layer 1 and an aluminum layer 2 of a material, respectively. The composite plate 4 is manufactured by continuously feeding the iron layer 1 and the aluminum layer 2 between the press rolls 3 and pressing them. As the power supply, either a low-frequency AC power supply or a DC power supply can be used. The electric current of the power source 21
Through the iron layer 1 and the aluminum layer 2 to reach the current-carrying roll 12. In this case, the electric resistance of the iron layer is higher than that of the aluminum layer. Therefore, when the thickness of the iron layer is equal to or smaller than that of the aluminum layer, the iron layer generates more heat and becomes higher in temperature. If the heating temperature of the iron layer does not reach the target temperature, auxiliary heating is performed by energizing the power supply roller 13 provided for auxiliary heating from the power supply 22. Hereinafter, examples of the present invention are shown together with comparative examples.

[0021]

EXAMPLE An iron plate and an aluminum plate having the compositions shown in Table 2 were used as the material for the composite plate. These materials are listed in Table 3.
Each of the sheets was wound into a coil shape, and before the joining, the coils were unwound and continuously heated and pressed by the electric heating and pressing apparatus shown in FIG. Immediately after the heating, the iron layer and the aluminum layer were continuously joined by the external force of two rolls as shown in FIG. The crystal grain size of the iron layer of the composite plate, the thickness of the diffusion layer at the interface, and the like were changed by variously changing the heating temperature and the heating time of each layer at the time of joining. Table 3 shows the crystal grain size of the iron layer and the thickness of the diffusion layer at the interface. Sample Nos. 1 to 17 are all within the scope of the present invention in terms of composition, crystal grain size of the iron layer, and thickness of the diffusion layer at the interface, and Sample Nos. 18 to 29 are one or more out of the present invention. Things.

Table 4 shows the material and bonding strength of the obtained composite plate after bonding. As can be seen from Table 4, composite plates manufactured within the scope of the present invention exhibit excellent workability and bonding strength.

[Table 2]

[0023]

[Table 3]

[0024]

[Table 4]

[0025]

[Table 5]

[0026]

As described above, the composite plate composed of iron and aluminum within the scope of the present invention has excellent workability and bonding strength.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the crystal grain size of an iron layer in a composite plate on the r (average) value and surface properties of the composite plate.

FIG. 2 is a view showing the influence of a diffusion layer at an interface on the bonding strength of a composite plate.

FIG. 3 is a diagram showing an example of an apparatus that can be used for manufacturing a composite plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Iron layer 2 Aluminum layer 3 Pressing roll 11,12 Electricity roll

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C22C 38/14 C22C 38/14 (72) Inventor Hatsuhiko Oikawa 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development (56) References JP-A-2-142685 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 B23K 20/04 B32B 15/01 C22C 21/00 C22C 38/14

Claims (4)

(57) [Claims] 1. A composite metal plate comprising two layers of iron on one side and aluminum on one side, wherein the iron layer has a chemical composition of 0.0005 to 0.01% by weight and Si: 0.1% by weight. Less than,
Mn: 0.04 to 0.5%, P: 0.1% or less, sol
Al: 0.002 to 0.1%, N: 0.005% or less, 4 times or more of Ti: C amount and 0.0015 to 0.1%
5%, the balance being iron and unavoidable impurities, the grain size is 10 μm or more and 50 μm or less, the aluminum layer contains 99% or more Al by weight, and diffusion at the interface between the iron layer and the aluminum layer. A composite metal sheet having excellent workability and bonding strength, wherein the thickness of the layer is 1 μm or more and 7 μm or less. 2. The composite metal sheet according to claim 1, wherein the iron layer further contains Nb: 0.003 to 0.015% as a chemical component. 3. The workability and bonding strength according to claim 1, wherein the aluminum layer is made of an aluminum alloy containing at least one of Mg of 6% or less by weight and Mn of 2% or less by weight. Excellent composite metal plate. 4. The method according to claim 3, wherein the aluminum layer further comprises, by weight, 0.5% or less of Si and 0.5% or less of C.
r, a composite metal sheet having excellent workability and bonding strength, characterized by containing one or more Zn of 0.5% or less.