With the continuous development of automobile industry, the application of glue technology in automobile manufacturing is more and more extensive, which plays an important role in the development of automobile to lightweight, high-speed energy saving, life extension and performance improvement. The gluing process is directly related to the sealing and leakproofness, corrosion and rust prevention, heat insulation and noise reduction, and appearance aesthetics of the car body, so there are strict requirements for the gluing process. At present, in order to reduce the workload of workers, improve the production rhythm and reduce the production cost, many traditional manual gelatinization processes of workers are replaced by robot automatic construction.

At present, there are three main types of adhesive sealant used in welding process:            

1) hemming rubber            

The car door, engine cover and trunk cover are usually welded after folding the inner and outer covers. But this technology makes the body surface add many pits caused by welding, which seriously affects the appearance quality of the body.            

In order to solve this problem, foreign countries began to use the method of bonding instead of spot welding to produce the folding structure of car door, engine hood and trunk lid from the 1970s. The adhesive used is called folding adhesive.            

It has a very wide application prospect to replace welding with bonding to manufacture automobile folding parts, which is the development direction of automobile manufacturing technology. In addition to doors, engine hood, trunk lid, it can also be used in other parts such as side wall.            

2) Spot welding sealant            

The car body is welded by a number of steel plates, and the existence of welding seam is inevitable. The tightness of welding seam is directly related to the quality and corrosion resistance of the car body, and is a very important indicator of the technical performance of the car.            

In the automobile manufacturing, if the gap at the joint of each sheet metal part is not sealed by effective measures, water leakage, air leakage and dust leakage will inevitably occur during the driving of the automobile, which may seriously cause the corrosion of the steel plate at the weld joint, make the steel plate perforated prematurely, and accelerate the scrapping of the vehicle.            

Now the general sealing method of welding seam in automobile manufacturing industry is coating spot welding sealant. Its service performance can be divided into two categories: expansion type and non expansion type. The service process is as follows:            

Before welding of stamping parts, glue shall be applied to the single plate at the joint of stamping parts, then the two plates shall be closed for spot welding, and solidified together with the baking process such as electrophoretic paint, intermediate coat of finish paint, etc.      The spot welding sealant used in automobile production shall have good construction technology and thixotropy, which can ensure the sealing performance. It shall not be washed out after the pretreatment of subsequent coating process. The spot welding adhesive shall not contain silicon substances, and the micro amount of silicon resin may cause harm to the quality of electrophoretic paint and finish paint. The strength of spot welding shall not be affected. During welding, the spot welding adhesive shall not decompose toxic gas or substances that can cause metal corrosion, and shall not flow during heating. After curing, the adhesive film shall have enough elasticity and adhesion, and shall be resistant to medium and aging.            

3) Expansion type shockproof adhesive            

In the process of automobile body manufacturing, the combination between the outer plate of the body cover and the stiffening beam is usually assembled by welding. The combination of the outer plates such as the stiffening beam of the cab top cover, the stiffening beam of the engine cover and the stiffening beam of the trunk lid are all welded by welding. Because there is a certain gap between the cover plate and the stiffening beam, the noise may be produced due to the vibration during driving, and The solder joints on the cover plate also seriously damage the flatness of the appearance. In order to overcome the above shortcomings, the expansion type anti vibration adhesive can be coated in the stamping sheet and the reinforced beam structure before welding. After being heated and solidified by the paint drying equipment, the adhesive layer has a high bonding strength. After being heated and expanded, the reinforced beam and the cover plate are tightly combined to reduce or completely cancel the combined solder joints Therefore, it can improve the body color value and reduce the vibration and noise during driving.            

The expansion type anti vibration adhesive is usually liquid paste, some of which are made into adhesive tape. In the process of body welding, the adhesive (or adhesive tape) is applied on the reinforcing beam, and then the combination welding is carried out.            

Similar to spot welding sealant, the expansion type anti vibration adhesive does not need to be separately set up for heating and curing. It is usually expanded and solidified in the drying oven of electrophoretic coating, so its application process conditions and requirements are the same as spot welding sealant.