Welding Vs Riveting: A Showdown Of Body-in-white Connection Solutions

溶接 vs riveting: a showdown of body-in-white connection solutions

The key to whether a vehicle is strong or not is the body-in-white. The body-in-white is like a human skeleton, made up of various metal plates connected to each other. It must have sufficient hardness and be as light as possible. The connection process is the core technology that determines the strength of the skeleton. Today, we will directly and clearly explain how to choose from traditional welding to the current popular new process of riveting various metal materials (carbon steel, stainless steel, aluminum, copper) .

Traditional spot welding is still the main force on the production line

Among the common connection methods, resistance spot welding is the most common. Its principle is simple. It uses electric current to locally heat two layers of metal plates to a molten state, pressing out a solder joint like a button. Various metal materials (carbon steel, stainless steel, aluminum, copper) are riveted and welded . A production line can produce thousands of solder joints per minute, which is extremely fast. In 2025, spot welding will still account for more than 70% of the steel bodies of mainstream domestic car companies.

However, spot welding has limitations. It can only weld the same metal, for example, between steel plates and steel plates. If one side is aluminum and the other side is steel, the spot welding will not be able to weld firmly because aluminum has a lower melting point and a faster heat conduction speed. And there will be a heat-affected zone around the solder joint, causing the metal to soften. Spot welding is not suitable for areas where ultra-high strength is required.

Screw connections are suitable for parts that need to be disassembled and assembled

The method of fixing parts together with the help of screws and nuts is called screw connection. This connection method has the advantage of easy disassembly. Most of the door hinges, bumper brackets and repairable parts in the engine compartment are screwed. A new domestic electric vehicle will be launched in 2026. Six high-strength bolts are used to connect the front anti-collision beam and the longitudinal beam.

However, screw joints have shortcomings. Drilling holes for screws will weaken the strength of the plate itself, and the screws are prone to loosening. In order to deal with this problem, many car companies now apply thread locking glue. In addition, screw joints are heavier than welding. For models that pursue extreme lightweight, engineers will try to reduce the use of bolts.

Arc welding is used for thick plates and large structures

The categories of arc welding are MIG welding and TIG welding. With the generation of arc, high temperature will follow, and the welding wire and the base material will be melted together. This welding method has a huge penetration depth, and is quite suitable for connecting thick steel plates and aluminum alloy castings. For example, the internal reinforcements of the A-pillar and B-pillar of automobiles and the frame at the bottom of the battery pack are specific examples of MIG welding that is commonly used in this welding method.

Arc welding has the disadvantage of being slow and has high requirements on worker skills. A skilled welder must undergo more than three months of training. In addition, the spatter and smoke during welding require special ventilation equipment. Therefore, arc welding is usually used in locations that cannot be reached by robots, or on joints with extremely complex structures.

Self-piercing riveting specializes in dissimilar metal connections

The SPR process does not require drilling in advance. A rivet will be pressed into the plate at high speed, and the rivet head will expand, creating an interlocking structure in the underlying metal. This connection method is particularly suitable for the overlap connection of aluminum plates and steel plates. On Tesla’s Model Y white body, more than 3,000 SPR rivets are used.

SPR has the advantage of high connection strength, does not generate heat, and does not change the internal structure of the metal. However, it needs to be accessible from both sides, which means the rivet gun has to clamp the sheet from both sides. As a result, some closed cavity structures cannot be used. In addition, SPR equipment is more than twice as expensive as a spot welder, and the investment in a production line will increase by several million yuan.

Hot melt screw joint solves the problem of multi-layer board connection

A process that looks like a large self-tapping screw is the FDS process. It runs at high speed and generates heat to melt parts of the board. It then drills into the board and taps out threads at the same time. This process can connect three to four layers of boards of different materials at one time. The FDS process is extremely practical in places where there are multiple layers of overlap, such as inner door panels and tailgate frames.

FDS has the disadvantage that the studs will protrude on the outside of the plate. Welding VS riveting: a big showdown of body-in-white connection solutions. This not only affects the appearance, but also the connection speed is relatively slow. Driving an FDS screw takes three to five seconds, but spot welding only takes half a second. In addition, FDS has limitations on the thickness of the plate. If the material is too thin, it will be drilled through and threads cannot be formed. Therefore, it is generally used inside structures or in locations that are not exposed.

Gluing technology is both bonding and sealing

On the car body, the use of structural adhesives and sealants is increasing. The shear strength of structural adhesives can reach more than 30 MPa per square centimeter. This strength is stronger than a single spot welding point. In parts such as the body roof and rear wheel cover, the application of adhesives can increase the overall stiffness and prevent electrochemical corrosion caused by metal contact. The total length of adhesive application on the body of a medium-sized SUV will exceed one hundred meters.

In such a situation, gluing has disadvantages. This disadvantage is that the curing time is long. Generally speaking, it needs to go through the coating baking line and bake for 30 minutes at a high temperature of 180 degrees to achieve complete curing, and gluing has high requirements for surface cleanliness. , the glue is not strong where there is oil or dust. In addition, the glue cannot be used alone for riveting with various metal materials (carbon steel, stainless steel, aluminum, copper) . It must cooperate with welding or riveting, otherwise the glue layer will be torn during collision.

Returning to the original question, which connection technology is the best? The answer depends on where it is used. Spot welding is fast and cheap, and steel bodywork is indispensable for it. SPR and FDS specialize in solving the problem of hybrid joining of aluminum and steel. The responsibility of glue coating is to seal and prevent corrosion. On a vehicle, four or five types of connection processes are often used at the same time.

Regarding the body-in-white of future electric vehicles, do you think more riveting will be used to reduce welding, or will a new connection method be created? Please share your views in the comment area. If you find it useful, please give it a like and share it with more friends.