4. Recommended Connection Solutions For Different Body Parts

4. Recommended connection solutions for different body parts

Many people will ask, how to choose a good method for tinplate riveting welding and tinplate seaming process?

In 2025, in the domestic mainstream car manufacturing companies, in their car body production workshops, spot welding technology, SPR technology, FDS technology and gluing method are no longer just for you to choose one from among them, but they are mixed together to form a combined play mode.

Spot welding is still the main force but its share is shrinking

During this period of time in 2024, the domestic body-in-white spot welding process still firmly occupies almost 60% of the total number of connections, and companies like Volkswagen and BYD can complete more than 3,000 points in a single shift on the welding line. However, as more and more aluminum frames with steel core structures are used in new energy vehicles, the scope of application of the method that relies solely on steel points for welding is gradually narrowing.

The maturity of spot welding equipment is very high, and the production cycle is very fast. The completion time of each welding point can be controlled within 0.5 seconds, and its cost is the lowest among all processes.

However, the scope of application of this process is very limited. It is only suitable for the same metal sheet with a thickness between one point and three millimeters. Once it comes into contact with materials such as aluminum alloy or high-strength steel, it will be unable to do its job. In addition, the heat-affected zone will also weaken the performance of the material itself.

Thick plate and pipe disassembly of screwed and arc welded pipes

This method of connecting screws and nuts can often be seen in parts such as bumper beams and subframes that need to be disassembled after-sales service. This torque is generally controlled between 12 and 40 Nm.

But for pure welded structures, it is actually wrong to say that the weight of this method is slightly lighter than that of pure welded structures. It should be said that it will be heavier. The specific weight range is in the range of fifteen to twenty percent.

MIG welding and TIG welding are specially used to overcome thick plates with a thickness of more than three millimeters. For seam welding operations in places such as A-pillars and sill beams, we basically rely on them. Its penetration depth can reach more than eight millimeters.

During 2023, TIG seam welding technology will be widely used in the aluminum door sill parts of Great Wall Motors' tank series models. However, it has a disadvantage, that is, the deformation is relatively large. After the welding is completed, the shape correction must be carried out.

SPR self-piercing riveting opens up dissimilar materials

SPR does not require pre-opening of the white iron riveting process and the difference and selection of the bite process . The riveting gun penetrates the upper plate in 0.8 seconds and forges the blind end interlocking in the lower layer. The steel-aluminum mixed transition zone of the BMW iX body relies on it to connect the difference and selection of tin riveting and seaming processes. IV. Recommended connection schemes for different body parts, eliminating the need for drilling and tapping.

This process is particularly suitable for multi-layer lamination scenarios involving two materials: steel and aluminum, as well as steel and composite panels.

By this time in 2025, the number of points using SPR riveting technology on the body-in-white of Geely's Galaxy series models has exceeded 200. This number accounts for nearly 40% of the total number of hybrid connections. Therefore, it has become a major method for joining dissimilar materials.

FDS hot melt screw splicing with one shot and two steps

The FDS technology allows the drill wire to be rotated at high speed to complete the two operations of drilling and tapping at the same time. It takes about 1.5 seconds to complete a stud, which completely eliminates the need to drill holes in advance.

Starting in 2023, the Tesla factory in Shanghai has fully promoted and used this technology for the main body part of the Model Y model to replace part of the original use of traditional spot welding.

The connection strength of FDS is very close to that of bolts. This connection method can be disassembled to facilitate after-sales maintenance; while SPR is a permanent connection and cannot be disassembled once it is riveted. These two processes are usually used together according to parts. For those places that require subsequent replacement of parts, the FDS process is preferred.

Gluing is both a connection and a sealing line of defense

Body frame glue can be applied around those solder joints, or used to replace some of the solder joints. Thirty-five meters of structural adhesive was used in the rear floor of the BMW 5 Series in 2004, which increased the tensile and shear strength by about 12%. In addition, it also has both sealing and anti-corrosion functions.

The use of DOWIN glue for the glass and the sealing glue for the welds are both very critical. If the sealant is missing on a weld, the anti-rust life will be directly reduced by half. In 2025, the number of gluing stations of leading domestic car companies has expanded from two to four, and the pace of production has become increasingly tense.

What kind of connections should be used for different parts?

The top cover and floor are mainly made of spot welding, with the difference and selection of galvanized iron riveting and seaming processes , and gluing as an auxiliary means; for the A-pillar and B-pillar, MIG seam welding plus structural adhesive is used; in the transition area where aluminum and steel are mixed, SPR or FDS processes are preferred; detachable items, such as bumpers and bottom guards, are connected and installed with screws and nuts, each of which plays a different role.

The core principle is this. It is quite simple. It is the most economical to do spot welding of the same thin plate. If you encounter dissimilar materials, use SPR or FDS. If you encounter thick plates and thick welds, use arc welding. If you need to disassemble later, use screw joints. If you want to seal and prevent corrosion, rely on glue. There is no one method that is the strongest, only which one is more appropriate.

For your automobile manufacturer or parts supplier, what is the approximate proportion of spot welding technology and SPR semi-solid connection technology used in the body-in-white products they produce?

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