JPH02227247A - Resistance welding type vibration-damping steel sheet - Google Patents

Abstract

PURPOSE:To carry out resistance welding without lowering vibration-damping performance and impairing bonding strength required for press molding by making the ratio of metallic particle average diameter before laminating and resin film/thickness after laminating, the grain diameter ratio of metallic particles in the resin thickness direction before and after laminating and the ratio between the biting amount of metallic particles into a surface skin steel sheet after laminating and resin film thickness within the specified range. CONSTITUTION:The ratio of metallic particle average diameter (d) before laminating and resin film thickness (t) after laminating is specified in the range of 1.2<=d/t<=2.5 and flattening rate of metallic particles after laminating (grain diameter ratio of metallic particles in the resin thickness direction before and after laminating) is 6% or more, and the ratio of biting amount delta into a skin steel sheet of metallic particles after laminating and resin film thickness (t) is made in the range of 1%<=delta/t. A resin film composed of metallic particles dispersed uniformly in the resin preliminarily for the purpose of providing productivity is used in manufacturing, and the resin film is laminated in the state of being bitten by two pieces of skin materials (thick steel sheet). Bonding strength is affected by anchor effect to prevent the bonding strength from weakening when the adding quantity of conductive substance is increased.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to vibration damping steel plates, which have excellent resistance welding performance as typified by spot welding and seam welding, and are particularly excellent in adhesive strength, which affects press formability. This invention relates to a resistance weldable damping steel plate.

(Prior Art) In recent years, demands for quietness and quietness have increased in various fields. This vibration is particularly important in product fields that use prime movers such as automobiles and home appliances, or in fields that require effective suppression of external vibrations and noise, such as building materials used in buildings. The application of vibration-damping steel plates, which are useful for absorbing sound energy, is being actively promoted.

Such damping steel plates include steel plates, various plated steel plates,
A so-called constrained composite material (vibration damping material) that uses stainless steel plates, aluminum plates, titanium plates, or even synthetic resin plates as the skin material, and a viscoelastic polymer resin is sandwiched between these two skin plates. is applied. However, since the resin sandwiched between the skin plates is an electrical insulator, conventional joining techniques such as spot welding, seam welding, and projection welding, which are representative joining techniques when thin materials are applied to structural members, are used. There was a drawback that the welding method could not be applied as is.

(Problems to be Solved by the Invention) Recently, in order to impart conductivity to the viscoelastic polymer resin, which is an electrical insulator, iron powder (Japanese Unexamined Patent Publication No. 57-51453), nickel powder (Unexamined Japanese Patent Publication No. 57-51453), 63-188040), carbon powder (Japanese Patent Laid-Open No. 57-1
63560) and the like are becoming widely adopted.

Although these methods impart electrical conductivity to the viscoelastic polymer resin, it is necessary to add a large amount of electrically conductive material in order to prevent welding defects during welding.

However, as the amount of conductive material added increases.

Although weldability can be stabilized and the incidence of welding defects can be reduced, a problem arises in that shear tensile adhesive strength also decreases ("Materials and Processes J Vol.

1, No. 5, Lecture number 345, [Tetsu to Hagane J Vol.

63, No. 13, p. 363), the decrease in adhesive strength causes the composite plate (two plates) to separate during press processing, which is a typical processing method for thin materials, and is fatal, making it impossible to form. This is a serious defect.

The present invention has been made in order to solve the problems of the above-mentioned conventional technology, and it is possible to achieve resistance without reducing the vibration damping performance, as well as without impairing the adhesive strength necessary for press forming. The purpose is to provide a new damping steel plate that can be welded.

(Means for Solving the Problems) In order to achieve the above object, the present inventors first investigated in detail the causes of welding defects during resistance welding and the causes of a decrease in adhesive strength. the result.

The following causes were found to be present.

In other words, the reason for the decrease in adhesive strength and the occurrence of welding defects is 1. The adhesion during vibration damping steel plate lamination is incomplete, and the conductive substance added to the resin causes the resin to be interposed between the skin steel plate and the skin steel plate after lamination. This occurs when there is a non-uniform distribution of resin-free and non-resin-filled resin. In other words, at the initial stage of energization during resistance welding, current flows through the energizing circuit without resin in between, the resin melts and softens due to resistance heat generation due to energization, and the resin is removed by the pressure applied by the electrode, creating a gap between the skin steel plate and the conductive material. This causes dielectric breakdown and sparks.

In order to prevent this, by increasing the amount of conductive substance added, the number of stable current-carrying circuits without resin intervening between one skin steel plate increases, and weldability becomes stable.

However, as the adhesive area between the steel plate surface and the resin, which provides the original adhesive strength, decreases, the adhesive strength decreases. In addition, if a conductive substance with a particle size smaller than the resin film thickness is added, an effective current-carrying circuit cannot be formed even by applying pressure to the electrode, resulting in serious problems such as non-carrying and holes that cannot be welded. It has been found that this causes defects.

Therefore, in order to stabilize resistance weldability, it is desirable to add a substance that is larger than the resin film thickness in order to improve the electrical conductivity between the skin plates, but only the conductive substance is deformed during lamination. In this case, the adhesive area between the damping resin and the skin steel plate decreases, resulting in a decrease in adhesive strength.

Based on the results of the above cause investigation, the present inventors have developed a method for forming a current-carrying circuit that is effective during resistance welding by mixing a powdered conductive substance with a viscoelastic polymer resin, which is different from the conventional technology described above. As a result of research from a completely different angle, we found that weldable vibration-damping steel plates can be easily stabilized in weldability without compromising the adhesive strength, which was difficult to do with conventional technology, and can be manufactured at low cost. It is.

In other words, 1 the resistance weldable damping steel plate according to the present invention has 2
In a damping steel plate that is laminated by sandwiching a viscoelastic polymer resin with metal particles uniformly dispersed between two thin copper plates, the average diameter of the metal particles before lamination (d) and the resin film thickness after lamination The ratio of (1) is 1.2≦d/t≦2.
5, and the oblateness of the metal particles after lamination (particle size ratio in the resin thickness direction of the metal particles before and after lamination) is 6.
% or more, and the ratio of the amount of metal particles biting into the skin steel plate after lamination (δ) and the resin film thickness (1) is 1%
It is characterized by being in the range of ≦δ/t.

The present invention will be explained in more detail below.

(Function) The resistance weldable damping steel plate according to the present invention has a structure in which a viscoelastic polymer resin in which metal particles as a conductive substance are uniformly dispersed is laminated between two thin steel plates. have.

The thin steel plate can be made of various steel types used for this type of use, such as a normal steel plate, various plated steel plates, stainless steel plates, etc., and its thickness is not particularly limited.

The thickness of the viscoelastic polymer resin layer is not particularly limited, but may be 10
-150μ is preferable, more preferably 30-80μ
This is the range of tumors. If the resin film thickness is less than 10 μ-, the vibration damping performance of the resin, that is, the effect of converting external vibration energy into thermal energy and dissipating it, will be rapidly attenuated, and the original characteristics of the vibration damping steel plate will no longer be exhibited. undesirable,
on the other hand.

Even if the resin thickness exceeds 150 μm, the damping performance itself does not deteriorate, but due to the insufficient strength of the resin itself, the amount of deviation of the end portion of the steel plate increases during processing and forming of the damping steel plate, which is disadvantageous. It goes without saying that the viscoelastic polymer resin can be made of various materials used for this type of application.

Metal particles are used as the conductivity imparting particles.

Pure iron powder is preferable.

In the present invention, the particle size of the metal particles is set larger than that of the vibration damping resin layer containing the conductivity imparting particles,
The ratio of the average particle diameter (d) to the vibration damping resin layer (1) after lamination is in the range of 1.2≦d/t≦2.5. Here, d
is the average diameter of metal particles before lamination. This ratio is 1
．． If it is 2 or more.

Although no resistance welding defects are observed, if it exceeds 2.5, the shear adhesive strength decreases somewhat, which is not preferable.

Regarding the particle size of the metal particles to be added, using the case of iron powder as an example, when using powdered particles, it is not possible to obtain only a certain particle size, but always within a certain range of particle sizes. It involves distribution. Therefore, J l
It is practical to consider the average particle diameter obtained from the nominal mesh size of the sized iron powder for the sieves with mesh sizes ranging from 2nd rank to different mesh sizes using a sieve according to the regulations of 58801.

During manufacturing, metal particles for imparting conductivity are uniformly dispersed in the resin to create a resin film, and when this resin film is sandwiched between two skin materials (thin steel plates), heating is performed. The resin is once melted and a resin pool is generated in order to prevent air from being drawn into the vibration damping resin layer. After that, when laminating with a metal roll to a predetermined resin film thickness, the metal particles, which are conductive substances, are deformed to the resin film thickness by laminating with a pressure greater than the reaction force of the molten resin. At the same time, the steel sheet is laminated with metal particles entrapped in it. By laminating the metal particles in a state where they are bitten into the skin steel plate, the contact between the metal particles and the skin steel plate becomes extremely good, and weldability becomes stable. In addition, the existence of the metal particles bitten into the skin steel plate at this time acts as an anchor effect on adhesive strength, and is effective in preventing a decrease in adhesive strength when the amount of conductive material added is increased. (See Figure 2).

To this end, it is preferable to ensure that the particle size ratio of the added metal particles in the resin film thickness direction before and after lamination, that is, the amount of deformation (oblateness), is at least 6% or more, preferably 20% or more. Note that there is no particular upper limit to the amount of deformation, but
Considering the situation where metal particles with a particle size within a commonly used range are used and laminated to a common resin thickness,
This is not done in more than 90% of cases.

In addition, in order to ensure the anchoring effect of metal particles on adhesive strength, the amount of metal particles biting into the skin steel plate after lamination (δ) should be at least 1% or more of the resin film thickness (1). effective. However, it is difficult to laminate the metal particles with more than 10% of the particles being interlocked, and in order to increase the interlocking, it is necessary to increase the hardness of the metal particles, which also affects the surface condition after pressing. give. Therefore, it is desirable to set the upper limit to 10%.

Note that the amount of metal particles added should be at least the minimum amount necessary for stable weldability. Adding just 2% by volume will not prevent welding defects and will affect vibration damping performance and adhesive strength. The maximum value is 5% by volume without any influence, and 2 to 5% by volume is preferable.

(Example) Next, examples of the present invention will be shown.

1j12 A continuously cast aluminum killed steel plate of 41111 with a thickness of 0 was used and laminated with a polyolefin resin in which iron powder had been uniformly dispersed in advance. A test piece was taken from this laminated steel plate and an accuracy test was conducted.

The conditions for trial production of the laminated steel plate are as follows.

■Conductivity imparting substance: water atomized pure iron powder ■Iron powder particle size: (1) 37-52 μea (2) 44
~61μm (3) 53~73μ layer (4) 62~87μ hazy (5) 88~104μm (6) 105~124μm ■ Iron powder addition amount: 3.5% by volume (constant) ■ Laminated resin film thickness 250μm (±3 μm) ■ Average particle diameter of iron powder (d)/resin film thickness (1) = 0.89 to 2.
30 From the prototype damping steel plate, test piece size 30++v+wX
It was cut into a shape of 100 mmQ, and 1000 samples were collected. Using this sample, spot weldability was evaluated with a single overlap of 30+++ m. Adhesive strength and loss factor were also investigated.

Welding conditions were: electrode pressure 2000kgf, welding current 8k.
A. The energization time is 12 cycles. Spot weldability is
The surface condition of the spot welded specimens after welding was observed, and the number of welding defects such as holes, burns, and non-energization on the surface of the steel plate was counted, and the incidence of welding defects was determined by the ratio of the total number of welded specimens and evaluated. .

As shown in Figure 1, in the condition range of d/t≧1゜2, no welding defects were observed, and no decrease in adhesive strength or damping performance was observed. Ta. In addition, the cross section of the steel plate manufactured within the range satisfying the conditions of the present invention was examined using an optical microscope (×400). As I guessed,
As shown in the schematic diagram of FIG. 2, it was found that all the iron powder was deformed and bitten into the skin steel plate.

A continuous cast aluminum killed steel plate with a thickness of 0.4 au was used and laminated with a polyolefin resin in which iron powder had been uniformly dispersed in advance. A test piece was taken from this laminated steel plate and an accuracy test was conducted.

The conditions for trial production of the laminated steel plate are as follows.

■Conductivity-imparting substance: water atomized pure iron powder ■Iron powder particle size: 88-104μ ■Amount of iron powder added: 1%, 2%, 3%, 4%, 5% by volume
5 levels of % ■ Laminated resin film thickness 250 μm (±3 μm) Test piece size 30 m + ww x 100 m from the prototype vibration damping steel plate
It was cut into mQ shapes and 1000 samples were collected. Using this sample, spot weldability was evaluated with an overlap of 30 tmm. Adhesive strength and loss factor were also investigated. Note that the welding conditions and evaluation of spot weldability were the same as in Example 1.

As shown in Figure 3, the results show that when the amount of iron powder added exceeds 2% by volume, no welding defects were detected.
No decrease in adhesive strength or vibration damping performance was observed.

(Effects of the Invention) As detailed above, according to the present invention, stable resistance weldability is ensured over a wide range of metal particle average diameter/resin film thickness ratios, and press formability is not affected. It is possible to provide a resistance weldable vibration damping steel plate without sacrificing its high adhesive strength or reducing the damping performance (η, loss coefficient), which is the most important feature of a damping steel plate, and the effect is significant.

In particular, inexpensive water atomized iron powder can be used as a metal filler, and its composition is close to that of pure iron, so it is equivalent to the composition of the base material that forms the welded joint, and its effect on various properties of the joint is extremely small. Very effective.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the spot weldability, adhesive strength, loss coefficient, and the ratio of iron powder average diameter/resin film thickness of a vibration damping steel plate. Figure 2 is the result of microscopic observation of a cross section of a vibration damping steel plate. FIG. 2 is a diagram schematically showing the anchoring effect of metal particles on shear adhesive strength. FIG. 3 is a diagram showing the relationship between the spot weldability, adhesive strength, and loss coefficient of a damping steel plate and the amount of iron powder added. 1... Skin steel plate, 2... Damping resin, 3... Metal filler Diagram d/t i Chair bar SO amount (Vo1%)

Claims (4)

[Claims] (1) In a vibration-damping steel plate that is laminated by sandwiching a viscoelastic polymer resin with metal particles uniformly dispersed between two thin steel plates, the average diameter of metal particles before lamination (d)
The ratio of the resin film thickness (t) after lamination is 1.2≦d/
t≦2.5, the oblateness of the metal particles after lamination (particle size ratio in the resin thickness direction of the metal particles before and after lamination) is 6% or more, and the surface of the metal particles after lamination is A resistance weldable vibration damping steel plate, characterized in that the ratio of the amount of biting (δ) into the steel plate to the resin film thickness (t) is in the range of 1%≦δ/t. (2) The damping steel plate according to claim 1, wherein the metal particles have an oblateness ratio of 20% or more after lamination. (3) The ratio of the amount of metal particles biting into the skin steel plate (δ) and the resin film thickness (t) after lamination is 1%≦δ/t≦10
%. (4) The amount of metal particles added to the viscoelastic polymer resin is 2 to 5
The vibration damping steel plate according to claim 1, which is % by volume.