JPS61195959A - Manufacture of vibration suppressing steel sheet having high workability - Google Patents

Abstract

PURPOSE:To obtain a vibration suppressing steel sheet having superior workability by cooling a steel sheet coated with a molten Zn-Al alloy by hot dipping optionally after holding at a specified temp. and by cold rolling the steel sheet. CONSTITUTION:A steel sheet for an automobile is coated with a molten Zn-Al alloy contg. 16-28% Al by hot dipping. The Zn-Al alloy may further contain one or more among Mn, Si, Cu, Mg, P and Fe. The Zn-Al alloy coated steel sheet is cooled and cold rolled at >=5% draft. The steel sheet may be held at 275-445 deg.C for >=2min before the cooling. The vibration damping capacity of the steel sheet is enhanced and a vibration suppressing steel sheet having superior workability such as press formability is manufactured.

Description

[Detailed Description of the Invention] (Industrial Application Field) In recent years, the quality of automobiles has focused on fuel efficiency, corrosion resistance (rust prevention), etc.
It is expected that one of the characteristics that will be emphasized in the future will be quietness. Silence is achieved through a combination of aiming to develop an engine with less vibration and using damping materials around the engine to absorb vibrations so that the vibrations generated by the engine do not propagate to passenger dust or the outside. It is something. The present invention meets the latter objective and relates to a method for manufacturing a damping steel plate having high workability and corrosion resistance.

(Prior Art) Conventionally, vibration-damping steel plates include (a) one in which a viscoelastic resin is sandwiched between two steel plates and vibration-damping properties are imparted by abrasion deformation of the resin, and (b) Mn-Cu alloy. (e) F・-
(d) Those that utilize irreversible movement of magnetic domain walls, such as Cr alloys; (d) Those that utilize viscous flow at the interface between the base metal and the second phase, such as cast iron; (e) Zn-At alloys. There are known methods that utilize viscous flow at grain boundaries, as typified by. However, none of these is suitable for use as a steel plate material for automobiles, which requires strict press formability and has areas that are subject to temperature rises. That is, the vibration damping steel plates of TIG mentioned above (,) to (・) are respectively (a) f
(b) Young's modulus is low and manufacturing cost is high; (c) damping property disappears due to cold working; (d) It has drawbacks such as extremely low cold workability, low rigidity, and high manufacturing cost.

In order to solve the drawbacks of the damping steel sheets of the types (a) to (6) above, the present inventors proposed a method of applying Zn-At based hot-dip plating to steel sheets with a focus on eutectoid plasticity (Unexamined Japanese Patent Publication No. 5
9-226161) or a method of pressure welding a superplastic Zn-AA alloy to a steel plate by rolling (Tetsu to Hagane, 70 (19
84) 16.2269), that is, a technology for manufacturing a vibration-damping steel plate is disclosed by a method of combining a Zn-At alloy with a steel plate having high rigidity into a round shape that increases the rigidity while maintaining the vibration damping ability. There is.

These have the advantage that a certain degree of damping ability can be obtained particularly in the high temperature range where Zn--At-based superplasticity appears. However, since these methods require a composite with a steel plate, the level of damping ability obtained in either method is comparable to that obtained by combining the above-mentioned steel plate and resin. It has the disadvantage that it has a low vibration damping effect compared to that of the conventional method, has a large effect on the plating layer thickness and bonding alloy thickness, and has a small vibration damping effect at a practically possible plating layer thickness. Furthermore, in the case of the latter pressure welding method, not only is the production cost high due to the use of superplastic alloy, but also a high rolling rate is required to obtain a good bond between the steel plate and the alloy, and for this reason, the base steel plate itself is in a rolled state, and its press formability is extremely inferior to that of the former, making it unsuitable as a steel plate for automobiles. Furthermore, in the former case, the obtained attenuation level is not a sufficiently high value.

(Problems to be Solved by the Invention) In view of the above circumstances, the object of the present invention is to provide a steel sheet that has press formability suitable for use as an automotive steel sheet, and also has corrosion resistance and extremely excellent vibration damping ability. The purpose of this invention is to present a coated thin steel sheet and a method for manufacturing the same, and specifically, it relates to a method of applying Zn-AA hot-dip plating to a steel sheet and obtaining extremely high vibration damping ability even with a thin plating layer thickness.

(Means for solving the problems and their effects) The gist of the present invention is as follows.

(1) At: 16 to 281, with the balance being Zn, optionally containing one or more of the following: A method for manufacturing a damping steel plate with high workability, which is characterized by cold rolling at a rolling reduction rate.

(2) A1. : Contains 16-28%, the remainder Z
n, Mn, Si, Cu, Mg, P, F as necessary
A hot-dip plated steel sheet having a composition consisting of one or more of
- A method for manufacturing a vibration-damping steel plate having high workability, which is characterized by rolling at a rolling reduction ratio of - or more.

The present inventors have conducted research on a method of applying Zn-AA hot-dip plating to a steel plate, and as a result, have discovered the following new knowledge and have completed the present invention.

The first finding is that the vibration damping ability is significantly improved by plating, cooling, and then cold rolling. This phenomenon is caused by (a) when the plating layer metal exists in a molten state, an alloy layer of both is formed at the interface between the base steel sheet and the plating layer, and micro-cracks are introduced into the alloy layer by cold rolling; This crack causes energy absorption (5llp damping) based on the upward movement of the interface, and (b) cold rolling makes the grains of the plating layer finer, facilitating viscous flow at the grain boundaries. (c) Dislocations are introduced into the alloy layer at high density by cold rolling, and absorption of vibrational energy occurs due to the movement of these dislocations. It is based on a mechanism. The synergistic effect of these three mechanisms is the basis of the present invention, and it is through this that high damping performance can be obtained.

Such a synergistic effect of the three mechanisms cannot be obtained with the prior art.

First, in the case of a single Zn-A4 alloy that does not form a composite with a steel plate, the formation of such an alloy layer naturally does not occur, and 5lip d due to microcracks in the alloy layer.
Amping cannot occur. The effect of cold rolling on a single Zn-At alloy is not known (Journal of the Japan Institute of Metals: 46 (1982) 9, 929), but in (b) above, the improvement in damping capacity due to C→ has been described. However, since 5lip damping does not occur in the alloy layer,
The effect of cold rolling is small compared to the present invention. Further, the strain caused by rolling is greatest in the surface layer, and in the case of a single alloy, a high cold rolling rate is required to make the entire grain fine, including the center in the thickness direction. On the other hand, in the present invention, since the cold rolling strain only needs to be added to the plating layer, a small amount of strain is sufficient. In addition to the problems of rigidity and manufacturing cost mentioned above, the novelty of the present invention is also evident in the effect of cold rolling.

The above-mentioned disclosed technology for press-welding a superplastic Zn-At alloy and a steel plate by rolling (Tetsu to Hagane, 7G (1984) 16°226
In 9), formation of an alloy layer effective to cause 5-lip damping does not occur. This is because rolling finishes in an extremely short time, which does not provide enough time for the elements to diffuse to form an alloy layer, and because the pressure welding method involves a solid phase-solid reaction. This is because although the strain caused by rolling slightly promotes diffusion, the alloying reaction rate is low.

In the disclosed technique, there is a description that "annealing at 350°C for 30 minutes" is performed after pressure welding in order to adjust the structure of the superplastic alloy, but even with such treatment, the 5lip dam
The result was that an alloy layer effective in causing ping could not be obtained. This is because the At concentration is high at about 22% and the alloying reaction rate is extremely slow, so in the "solid phase-solid phase reaction" an effective amount of alloy layer is not formed even if held at high temperature for a long time. That's what it means. Therefore, as a matter of course, rolling strain during pressure welding is meaningless in causing 5-lip damping.

On the other hand, in the method of the present invention, it is effective that a "solid phase-liquid phase reaction" with a high reaction rate exists during hot-dip plating. When rolling at a temperature of 275°C or higher is combined as shown later, narrow-plane diffusion at the surface of cracks that occurs in the alloy layer due to rolling, and strain-induced diffusion due to rolling.
Two mechanisms work to produce a remarkable alloying reaction, which is most desirable.

Technology disclosed by the present inventors (Japanese Unexamined Patent Publication No. 59-226161
With the hot-dip plating method, the base steel plate in a solid phase can react with the plating layer in a liquid phase for a short period of time until the plating layer metal solidifies, and compared to the pressure welding method, the alloy layer is This is advantageous for the production of. But 5lip dam
This is insufficient to obtain the above effect because the cracks in the alloy layer necessary to cause ping are not sufficiently introduced. In the above-mentioned disclosed technique, it is stated in the specification that ``If several slight deformations are applied near the eutectoid point and in the recovery temperature range of 200 to 300 degrees Celsius,
It is shown that "salad rain is formed due to recovery, the particles tend to become finer, and the cooling rate tends to be relaxed toward slow cooling," and an example of "1-inch roll reduction" is shown. . 5llp damping by an alloy layer as a technical meaning and technical concept of rolling is not described in the same way, and even if such "light deformation of several inches at 200 to 300°C" is performed, the cold rolling of the present invention is It is nowhere near as effective as rolling. This is because an effective crack density cannot be obtained.

Furthermore, "slight deformation of several degrees at 200 to 300[deg.] C." does not sufficiently provide the effects of cold rolling, which are the second and third meanings of the present invention. This is because the rolling temperature is high and the amount of strain is small, so grain refinement and introduction of dislocations into the plating layer are not sufficient.

Therefore, the damping ability of the plated layer in the unalloyed portion is also inferior to the present invention.

Improvement in damping properties by cold rolling has also been disclosed in cold rolled steel sheets and hot rolled steel sheets in which interstitial elements such as C and N are not present, but the effect of cold rolling in the present invention is different from the disclosed technology. That is, the disclosed technology relies on the resonance phenomenon of dislocations in the steel sheet itself, and therefore the steel sheet must be free of interstitial elements. On the other hand, in the present invention, the basic technical concept is to provide vibration damping properties through the three mechanisms shown above, and there is basically no need to limit the steel plate components. The improvement of the vibration damping effect due to dislocations (the third mechanism mentioned above) is also due to the fine crystal grains of the plating layer. In this case, the effect of improving vibration damping properties is greater than in the case of the steel plate of the disclosed technology. This is because the plastic deformation resistance of the plated layer is significantly better than that of steel sheets. From the above, the effects of cold rolling are essentially different from those obtained with a single steel sheet.

From the above, it is clear that the present invention not only provides an extremely superior vibration damping ability compared to the steel plate according to the conventionally disclosed technology, but also differs in its technical concept.

A rolling reduction ratio of 5% or more during cold rolling is sufficient to exhibit the above effect, but it is most preferably 10% or more. The maximum value of the rolling reduction ratio is preferably 60% or less from the viewpoint of material deterioration. As described above, the pressure welding method of the disclosed technology requires a high rolling rate (approximately 8
0%), and as a result, the base steel sheet itself becomes rolled, resulting in extremely poor press formability, making it unsuitable as a steel sheet for automobiles. In the present invention, the technical significance of rolling lies in the introduction of cracks into the alloy layer, the refinement of grains in the plating layer, and the introduction of dislocations into the plating layer. Since the strain caused by rolling is maximum near the different surfaces, the rolling reduction rate needs only to be 5 seconds or more to achieve this, and high-pressure rolling is not required. Therefore, the deterioration of workability of the steel plate due to rolling is small, making it excellent as a steel plate for press forming.

The cold rolling temperature is preferably 200°C or lower, most preferably 150°C or lower.

Furthermore, vibration damping properties are improved by holding the material at a temperature of 275° C. or more and 445° C. or less for 2 minutes or more after the metallization and before the cold rolling of the present invention is performed. This is a result of facilitating the formation of the alloy layer described above. The holding temperature is most preferably 300°C or more and 420°C or less, and the holding time is most preferably 10 minutes or more.

The upper limit of the holding time does not need to be particularly limited, but it is preferably 12 hours or less because the alloy layer becomes too thick and the plating adhesion becomes poor.

When cooling after maintaining the above temperature at 275°C or higher and 445°C or lower, control is achieved by rapid cooling from 275°C or higher to 230°C at an average cooling rate of 10°C/m@C or higher. This is the ditto effect of oscillation. This phenomenon is based on improving the viscous flow at the grain boundaries by making the grains in the unalloyed portion of the plating layer finer, thereby improving vibration damping properties. The essential effect of rapid cooling is to pass through the eutectoid transformation temperature of about 275° C. at a high rate to refine the eutectoid transformed structure.

Therefore, the temperature range for rapid cooling may be from 275°C or higher to 230°C. Effective cooling rate range is 10℃/
8@(+) or more, but most preferably 20° C./s@.

The thickness of the alloy layer is 511p. It has been found that the thickness of the alloy layer to exhibit the dumping effect most effectively is 0.2 μm or more. Maximum effectiveness is obtained with 0.4 steel or higher. As the thickness of the alloy layer increases, the workability of the entire plating layer deteriorates slightly, and the problem of plating peeling tends to appear, so the upper limit of the thickness of the alloy layer is 4.0μ.
m or less is desirable.

Next, the composition of the plating layer will be described. The plated layer that is the object of the present invention is assumed to have a nine-fine crystal structure centered on a eutectoid structure, excluding the alloyed part.This fine structure provides a vibration damping effect due to viscous flow at the grain boundaries, and 5li
It has a remarkable effect when combined with pda and mping. Therefore, the At concentration in the plated layer needs to be 16 to 28%. Outside this range, the proportion of the eutectoid structure decreases, which is not preferable.

Furthermore, in addition to this basic composition, one or more of K (Si corresponding to 2 to 10% of the AA content), Mu of 2 or less, Cu of 5% or less, and Mg of 1 or less in the plating layer Inclusion of two or more types imparts characteristic accompanying effects to the steel sheet of the present invention. The addition amount of 81 suppresses overalloying between the base steel sheet and the plating layer during long-term use at high temperatures. That is, the effect of increasing heat resistance is large. The added amount M
n has the effect of lowering the temperature range where vibration damping properties occur, and is suitable for applying the steel sheet of the present invention to applications near room temperature;
Coexistence with St increases the ductility of plating. The added amount of Cu has the effect of increasing the ductility of the plated layer and improves the adhesion of the plated layer. This added amount has the effect of increasing the corrosion resistance of the ceramic-plated layer. In addition, it is equally acceptable to contain P of 21 or less and F of 5% or less. The steel sheet of the present invention has a vibration damping effect due to the grain boundary viscous flow of the microstructure centered on the eutectoid structure, as well as the vibration damping effect due to the alloy layer. 511p
Damping is superimposed and exhibits a remarkable vibration damping effect,
Great vibration damping properties can be achieved even with extremely thin plating thickness. Therefore, the plating thickness is the basis weight: 301/F11
2 or more is sufficient, but if it is 45117 m2 or more, the vibration damping property is even greater. There is no particular upper limit to the plating thickness, but from the economic point of view it is preferably 20,017 m2 or less on one side.

The base steel sheet is not particularly limited as long as it can be used as an automotive steel sheet material for press forming, but it is even better if it is an ultra-low carbon steel sheet with additions of TI, Nb, etc. Needless to say, it is preferable because it has good resistance moldability. It is also possible, and needless to say, more desirable, to use materials such as decarburized steel sheets and ultra-low carbon steel sheets to which Ti, Nb, etc. have been added, which have increased vibration damping ability.

The steel sheet of the present invention produced as described above has good press forming as a plated steel sheet because the workability of the base steel sheet is not impaired, and the plated layer has good deformability even during press forming at room temperature. It has excellent adhesion and extremely high vibration damping properties from room temperature to high temperatures of about 270°C. Therefore, if it is used in areas that are sources of vibration and noise, the effect of reducing them is significant. 2/Non area and muffler,
It is also particularly useful for areas subject to high temperatures, such as covers for woodcutter motors. Further, the steel sheet of the present invention has excellent rust prevention properties.

(Example) Examples of the present invention are listed below along with comparative examples.

Plating was carried out using the hot-dip plating method under various conditions such as the plating layer composition, plating thickness, rolling, and heat treatment shown in Table 1 to obtain test materials for vibration damping measurement. The hot-dip plating method is based on the 7-nomer method, and the bath temperature is in the range of SOO to 570°C, which is a temperature range that is 15°C or more higher than the melting point of each alloy composition. Within this range, there were no problems with plating properties or plating adhesion, and the difference in damping properties due to bath temperature was not significant.

After plating, if the temperature was to be kept in the range of 275 to 445°C before cold rolling, the plate was passed through a furnace heated by a lazo-anto tip and kept at a constant temperature. In this example, When the plating layer temperature reached 200°C in the post-plating cooling process, it was reheated to a predetermined temperature.There is no problem in achieving these components by other methods.The cooling rate can be controlled. Although the spray pressure and spray amount of air/water jet 4 cooling were changed, there is no problem with other methods.Cold rolling is performed at room temperature to 200℃.
Although the test was carried out in the temperature range of ℃, no significant influence of temperature on each characteristic was observed. In this example, a case of room temperature is shown. The base steel plate is C: 0.03, st: o, oi, Mn: 0.2
0. P: 0.015, S: 0.01. At:0.0
50, N: o, ooso (weight cIb) aluminum killed steel thin steel plate, the plate thickness is 0.8 can. For comparison, test materials were prepared using a method in which the above-mentioned rolling was not performed and a method in which a superplastic Zn-At alloy was welded by pressure by rolling. For the latter, a commercially available superplastic Za-22% kL alloy and a steel plate (thickness 3.0 m) with an activated surface were heated at 200°C for 80°C.
It was rolled at a rolling reduction of %. The thickness of the composite plate after rolling is 0.8
am, and the thickness of the Zn-A4 alloy is 20μ on one side. After rolling, it was heated to 350°C, held for 30 minutes, water quenched, held at room temperature for one day, and then heat-treated at 200°C for 20 minutes and slowly cooled.

The vibration damping property was measured using the following equation from the free damping at the −th order resonance frequency.

Loss coefficient: y=(nπ) ・In(Ao/An) #
Ao': initial amplitude, AH: nth amplitude measurement temperature was 250°C, and some measurements were also performed at room temperature and 150°C. In addition, some of the test materials were measured after being subjected to 10% pre-tension to simulate the performance after press molding.

Mechanical properties were measured using JIS No. S test pieces.
It was carried out at room temperature based on the S tensile test method.

Table 2 shows the measurement results of damping performance and mechanical properties.

From the same table, the steel sheet of the present invention has sufficient mechanical properties as an automotive steel sheet material used for press forming, and extremely excellent control from room temperature to high temperature (250C is shown here, but the same is true below 275C). It is clear that it has vibration performance.

(Effect of the invention) By doing so, a steel plate with excellent vibration damping properties can be obtained.

Further, effects such as industrially easy and stable production can be obtained.

Table 2 Note) & 16 is the state of the base cold-rolled steel plate after annealing and cold-rolling. Mechanical properties are values at room temperature.

Claims (2)

[Claims] (1) Contains Al: 16 to 28%, the balance is Zn, and if necessary one or two of Mn, Si, Cu, Mg, P, and Fe.
1. A method for producing a vibration-damping steel sheet having high workability, the method comprising cold rolling a hot-dip galvanized steel sheet having a composition of at least 5%. (2) Contains Al: 16 to 28%, the balance is Zn, and if necessary one or two of Mn, Si, Cu, Mg, P, and Fe
Hot-dip galvanized steel sheets with a composition of 275 to 445
A method for producing a damping steel plate having high workability, the method comprising holding the plate at a temperature of 2 minutes or more, cooling it, and then rolling it at a rolling reduction of 5% or more.