JPH0420714B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for preventing rust of spot-welded members, and in particular to an improvement in a method of spot-welding two members together and then painting them.

[Conventional technology]

2. Description of the Related Art Fixing two members together by spot welding and then painting them is a widely used method for assembling steel plate members and preventing rust. In the case of spot welding, it is common to strive to improve the precision of the surfaces of both parts so that the areas where they abut each other during spot welding are in close contact, including that position. For example, when the range is a flat surface, the flatness of both members is made to be high.

[Problems to be Solved by the Invention] In the case of such a conventional method, the contact range is such that both members are in close contact or there is a very slight gap, so in the subsequent painting process, Even if a paint with improved properties is used, the paint does not penetrate easily, leaving the surface of the steel plate as a texture, making it susceptible to rust.

To deal with this, for example, rust-proof steel plates such as galvanized steel plates or painted steel plates are used.
There is a method of narrowing down only the spot welding position into a dish-like shape with a slight depth to create a gap in that area to the extent that the paint can penetrate.

However, the former method involves high cost of the steel plate used as the raw material, and the latter method requires strict regulation of the spot welding position, which makes it difficult to put it into practical use.

Therefore, an object of the present invention is to form a space between the two members in the area where the two members abut each other by spot welding, to facilitate the penetration of paint into the area where the two members abut, and to improve the rust prevention quality.

[Means to solve the problem]

Therefore, the present invention provides a rust prevention method for a spot welded member in which two members are fixed together by spot welding and then painted, which includes a spot welding position on one of these members, and where the spot welding is performed on one of these members. The first step is to form multiple beads adjacent to each other over an area that exceeds the range where they come into contact with the other member, and when spot welding these two members, the electrode of the welding machine approaches one member. The second step is to press the bead to the other member and spot weld it while forming a local plane by crushing the bead with the pressure of . The third step is to apply electrodeposition coating to these two spot welded members It includes.

[Effect]

By the above-described means, when spot welding one member with a bead formed thereon and the other member, the electrode of the welding machine approaching one member crushes the bead with its applied pressure to form a local plane. Welding is completed by pressing the other member together. In this case, when the two members are firmly attached, the ends of each bead are open at both ends beyond the range where they contact the other member, and therefore there is a tunnel through which liquid can freely flow in the range where the two members contact. Spaces of shapes are formed adjacent to each other. Thereafter, electrodeposition coating is applied to the two spot-welded members. In this case, the electrodeposition coating easily enters each tunnel-shaped space of the two members and forms a coating film on each inner surface thereof, that is, on the opposing surfaces of the two members that are in contact with each other.

〔Example〕

Embodiments of the present invention will be described below based on the accompanying drawings.

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a perspective view of the main part of the floor structure of a passenger car, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. FIG. 2 is a - sectional view of FIG. 1;

As shown in FIG. 1, 10 is a floor panel, 30 is a reinforcing channel with a cross-section of a hat provided on the underside of the floor panel 10, and these two members are spot-welded 40 at six positions 40a to 40f. It's fixed. Although the plate thicknesses are not shown in the figure, the floor panel 10 has a thickness of 0.7 mm, the reinforcement channel has a thickness of 1.6 mm, and both are cold-rolled steel plates.

As shown in FIGS. 2 and 3, spot welding 40
Floor panel 10 and reinforcement channel 30 by
The range of contact between the
(on both sides), and the spot welding position 40 is within this range. On the other hand, prior to this spot welding 40, the floor panel 10, which is the thinner member,
In this case, a plurality of beads 11 having a cross-sectional shape of a continuous circular arc are formed adjacent to each other in parallel. The range in which this bead 11 is formed includes the above range,
And the length slightly exceeds that in both length and width.
The range is Lp x width Wp (both sides).

In the case of this embodiment, as shown in the figure, the longitudinal direction of the bead 11 is perpendicular to the longitudinal direction of the flange 31, and the peak thereof is oriented away from the flange 31. The height H is 1 mm, and the pitch P is 6 mm.

After forming the bead 11 under such conditions, both members 10 and 30 are spot welded. In this case, the electrode of a welding machine (not shown) approaching the floor panel 10 crushes the bead 11 with its pressurizing force to form a local small plane while reinforcing the reinforcement channel 3.
0 to complete welding. As a result, when both members 10 and 30 are fixed, both ends of each bead 11 are open beyond the range where they contact the reinforcing channel 30, and openings are opened on both sides in the range where both members 10 and 30 contact. A tunnel-like space 13 having 12 is formed adjacent thereto.

Thereafter, electrodeposition coating is applied to both the spot-welded members 10 and 30. In this case, the electrocoating paint easily enters the tunnel-shaped spaces 13 of both members 10 and 30 through the openings 12 without stagnation, and the opposing surfaces of both members 10 and 30 in contact, that is, the bead 11 The surface on the flange 31 side and the bead 11 of the flange 31
Forms a coating film on the side surface.

In the case of this embodiment, as shown in the figure, the longitudinal direction of the bead 11 is perpendicular to the longitudinal direction of the flange 31, and the peak thereof is oriented away from the flange 31. The height H is 1 mm, and the pitch P is 6 mm.

In this way, since the tunnel-shaped space 13 is formed adjacent to the area where the two members 10 and 30 contact each other by spot welding, the electrodeposition paint can easily enter this space 13. Both members in contact 1
A coating film can be reliably formed on the opposing surfaces of 0 and 30.

Moreover, thereby, the rust prevention quality can be significantly improved without using an expensive rust prevention steel plate or the like.

Furthermore, since the bead 11 is formed in the floor panel 10, the bead 11 can be bent more strongly in a direction perpendicular to or close to a right angle to the longitudinal direction.

Further, the reinforcement channel 30 is connected to the floor panel 1
Since there is no need to increase the precision of the surface in the range where it contacts the zero, processing can be facilitated.

Further, since the bead 11 easily deforms in the vicinity of the position where it is crushed by the electrode of the welding machine, spot welding can be performed at any position. That is, the position can be easily changed or added as necessary, and spot welding can be performed at any position of the peaks or valleys of the bead 11, without impairing workability.

FIG. 4 and FIG. 5 show the second embodiment and the third embodiment, respectively.
In each of the embodiments, one of the members in which a bead is formed is shown in cross section, and the other member is shown in phantom lines.

In FIG. 4, the peaks of the beads 51 of one member 50 are formed toward the other member 60, contrary to FIG.

In FIG. 5, the peaks of beads 71 of one member 70 are formed on both sides of the member 70. In this case, the member 70 on which the bead 71 is formed
When used alone, the overall shape of the member does not warp, and there is an advantage that there is no need to remove distortion prior to spot welding.

In each of the embodiments described above, the longitudinal direction of the bead does not need to be perpendicular to the shape of the range in which it contacts another member. It is most preferable for the painting process to minimize the length of the tunnel-like space, but it may be selected arbitrarily depending on other processing conditions and product constraints. Further, it is easier to form the member forming the bead with a thinner member, but it may be selected for the same reason as above, including the case where the members have the same thickness.

Furthermore, the same applies to the shape and size of the cross section of the bead. However, at least the part that contacts the other member needs to be a line rather than a plane, and in this sense, it is easier to process if at least that part is an arc.

〔Effect of the invention〕

As mentioned above, this invention crushes a predetermined bead formed on one member by the pressure of an electrode to form a local plane and spot-welds it to the other member,
Since we applied electrodeposition coating to the two spot-welded parts, a tunnel-shaped space is formed adjacent to the area where the two parts contact due to spot welding, and this space allows the electrodeposition paint to easily enter. Therefore, a coating film can be reliably formed on the opposing surfaces of the two members that are in contact with each other.

Moreover, thereby, the rust prevention quality can be improved without using an expensive rust prevention steel plate.

[Brief explanation of drawings]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a perspective view of the main part of the floor structure of a passenger car, FIG. 2 is a cross-sectional view taken from FIG. 1, and FIG. 1, FIG. 4 is a sectional view of the second embodiment, and FIG. 5 is a sectional view of the third embodiment. 0...Floor panel (one member), 40...
Spot welding, 30...Reinforcement channel (other member),
Lc×Wc... Range of extension of flange 31 of reinforcement channel (range of contact), 11... Bead.

Claims (1)

[Claims] 1. In a rust prevention method for spot welded parts in which two parts are fixed by spot welding and then painted, one of these two parts includes a spot welding position, and this spot welding causes the other part to be damaged. The first step is to form multiple beads adjacent to each other over an area that exceeds the area where they contact each other, and when spot welding these two members, the pressure of the electrode of the welding machine approaching one member is applied. The second step is spot welding by pressing the bead to form a local plane while pressing it against the other member.
and a third step of applying electrodeposition coating to these two spot-welded members.