JPH05162234A - Composite-type damping steel sheet with good spot weldability - Google Patents

Abstract

PURPOSE:To enhance the spot weldabillty by relatively specifying the tensile strength of resin the thickness of residual resin lying in the contact point between the steel sheet and the metallic powder in a composite-type damping steel sheet. CONSTITUTION:The composite-type damping steel sheet is of the type that resin is held between two steel sheets and then subjected to lamination, adhesion and molding, and in the resin part, a conductive compound such as metallic powder is contained which has a particle diameter or length of 1.0 time or more to the thickness after the molding. When the tensile strength of the resin less than 1kgf/mm<2>, the residual resin lying in the contact point between the steel sheet and the metallic powder and like substances is 3mum or less in its minimum value, and when the tensile strength of the resin is 1kgf/mm<2> or more, the thickness of the residual resin is restricted to 2mm<2> or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite type vibration damping steel plate having a sandwich structure in which two steel plates are laminated with a resin sandwiched therebetween, and in particular, the above composite type plate having excellent spot weldability without providing bypass wiring. Regarding damping steel plate.

[0002]

2. Description of the Related Art In a composite type damping steel sheet having a sandwich structure, the core resin layer is electrically insulating,
Originally, the spot weldability is poor due to the structure. Conventionally, as a measure for improving spot weldability in such a composite type vibration-damping steel sheet, JP-A-57-51453 and JP-A-61-29004 are known.
No. 4, JP-A-62-151332, JP-A-62-152752, the core resin layer is mixed with metal powder, metal fiber, carbon powder, etc. Granting is done. In this case, the dimension of the conductive compound such as metal powder (hereinafter referred to as metal powder) has a relationship larger than the thickness of the core resin layer, and the steel plate as the skin material and the metal powder directly contact each other. A stable spot weldability can be obtained by forming a welding current path and by uniformly distributing such contact points in the damping steel sheet. It is well known that spot welding is not stable if the size of metal powder or the like is actually smaller than the thickness of the core resin layer.

However, conversely, even if the size of the metal powder or the like is larger than the thickness of the core material resin layer, the spot weldability is not always secured stably due to other factors, and it is desired to clarify. It was rare.

[0004]

DISCLOSURE OF THE INVENTION The present invention seeks a mechanism for stabilizing such spot weldability,
It is an object of the present invention to find a condition and provide a composite type vibration damping steel plate having excellent spot weldability.

[0005]

According to the present invention, a resin is sandwiched between two steel plates, and the resin is laminated and adhered. The resin portion has a grain size 1.0 times or more the thickness after molding. In a composite type damping steel sheet containing a conductive compound such as metal powder having a diameter or length, the tensile strength of the resin is 1 kg.
If it is less than f / mm ^2, the minimum value of the residual resin thickness remaining at the contact point between the steel plate and the metal powder is 3 μm or less, and if the tensile strength of the resin is 1 kgf / mm ² or more, A composite type vibration damping steel plate excellent in spot weldability, characterized in that the thickness of the residual resin is regulated to 2 μm or less.

[0006]

[Operation] The inventors of the present invention have earnestly studied about the phenomenon that the spot weldability is not always secured stably even if the size of the metal powder or the like is larger than the thickness of the core resin layer. It became clear. Looking at the manufacturing process of composite type vibration damping steel plate, the method of mixing metal powder etc. into paste-like resin and then applying it to the steel plate that is the skin material or applying resin to the steel plate and then mixing the metal powder etc. However, in any case, when the resin layer and the skin material are pressure-bonded, the metal powder or the like sinks into the resin, and the resin covers the entire surface of the metal powder or the like by the pressure, so that the metal powder or the like forms a resin film. The thin residual resin layer is formed because the metal powder and the like are not in direct contact with the steel plate.

This residual resin layer has an electric resistance and becomes an obstacle to conductivity. In other words, the presence of this residual resin layer does not function as the original current path even if metal powder or other substances are present, and sparks, holes, and other welding defects occur during spot welding, reducing spot weldability. I am making it happen. It was also found that the spot weldability of the composite type vibration damping steel plate was correlated with the initial resistance value during spot welding. The initial resistance value here is derived from the inter-electrode voltage and welding current in the first cycle of spot welding, and FIG. 1 shows an example of the relationship between the defect occurrence rate during spot welding and the initial resistance value. The electrode in this example has a radius of 8
mm hemisphere, pressure 180kgf, current 8kA, initial pressurization time Ts
= 50 cycles (50 Hz), energization time Tw = 8 cycles (50 Hz), and holding time Th = 30 cycles (50 Hz). From FIG. 1, it can be seen that when the initial resistance value is 500 μΩ or more, the welding defect occurrence rate sharply increases.

FIG. 2 shows the results of an examination of the relationship between the thickness of the residual resin layer and the welding initial resistance value by changing the tensile strength of the resin. From this result, the initial welding resistance value is 500 μΩ
To reduce the thickness of the residual resin layer to 2
μm or less is necessary, especially tensile strength 1kgf / mm ²
It is understood that the thickness of the residual resin layer should be 3 μm or less only in the case of the following resins.

[0009]

Example A polyester resin having various tensile strengths was applied to one inner surface of a skin steel sheet, and metal powder was dispersed in the resin layer. The resin layer after molding had a thickness of 40 μm, and the metal powder used was nickel powder having an average diameter of 60 μm. After the resin was melted in the oven, it was pasted with a warm roll. At this time, the thickness of the residual resin layer can be arbitrarily controlled by the heating temperature in the oven, the linear pressure of the warm roll at the time of bonding, and the like. With respect to the composite type vibration damping steel plate after adhesion, the contact point between the skin steel plate and the metal powder was quantitatively analyzed by an X-ray microanalyzer to measure the thickness of the residual resin layer. Table 1 shows the results of a spot welding test performed on this composite type vibration-damping steel sheet, the initial resistance value was measured, and the incidence of defects such as poor nugget formation and circumferential breakage was investigated. The spot welding conditions are as follows.

Electrode tip shape: truncated cone shape, diameter 5 mm, welding current: 8.0 kA, energizing time: 8 cycles, electrode pressure:
180kgf.

[0011]

[Table 1]

As shown in Table 1, in the case of ordinary resin, the thickness of the residual resin layer is set to 2 μm or less, and particularly the tensile strength is 1 kgf / mm ²
Only in the case of the following resins, the thickness of the residual resin layer is 3 μm
If the following, the initial welding resistance value will be 500 μΩ or less,
Good results have been obtained. Although the polyester resin is used in the above embodiments, the above conditions may be applied to all resins such as polyethylene, polypropylene, polyurethane, and epoxy depending on the tensile strength. Similarly, the metal powder is not limited to nickel powder, and is applicable to all metal powders, metal fibers, carbon powders and the like.

[0013]

According to the present invention, a composite type vibration damping steel plate excellent in spot weldability can be stably produced, the applicable range of the composite type vibration damping steel plate is expanded, and noise and vibration Environmental improvement through reduction is promoted.

[Brief description of drawings]

FIG. 1 is a graph showing a relationship between an initial resistance value of spot welding and a welding defect occurrence rate.

FIG. 2 is a graph showing the relationship between average residual resin thickness and spot welding initial resistance value.

Claims (1)

[Claims] 1. A resin is sandwiched between two steel plates to be laminated and bonded.
The resin part has a thickness after molding.
Metal powder with a grain size or length 1.0 times or more than the average
Oxide of composite type vibration-damping steel plate containing conductive compound such as
The tensile strength of the resin is 1 kgf / mm²Less than before
Of residual resin remaining at the contact point between the steel plate and the metal powder, etc.
The minimum thickness is 3 μm or less, and the tensile strength of the resin is
 1kgf / mm ²In the above case, the thickness of the residual resin should be 2 μm.
Immediately spot weldability characterized by the following restrictions
Composite type vibration control steel plate.