Benefits of Hot Stamping Steel for Projection Welding

Hot stamping steel has multiple advantages, including reducing the weight of the car, high strength and hardness, superior toughness, and excellent formability. It is widely used in key parts and components of the automotive body frame, such as crash guards, front and rear bumpers, A-pillars, B-pillars, roof covers, etc.

Whether the body-in-white is reliably welded is not only about the quality of the automotive parts, but also about the driver’s personal safety. As an important component in the automotive body made of hot stamping steel, its reliable and stable welding technology is crucial! Today, Heron introduces to you the best projection welding process for hot stamping steel - the medium voltage capacitor discharge welding (CDW) technology.

Projection welding involves pre-treating projections on metal sheets so that the welding can form with as little contact surface as possible between the projection and the metal sheets. This improves the current density of the contact point. Perfect projection welding requires the welding power to quickly raise the current to form the current density of the molten pool without softening the projection. Since the contact resistance decreases rapidly after the molten pool is formed at the initial contact point, according to Q=I²RT, the welding current must be continuously increased in order to generate more heat to melt more projections and form a reliable welding nugget. We have developed the CDW technology to effectively meet the above requirements.

CDW Current Curve

Our CDW technology uses a three phase AC power input to the transformer, which is controlled by the welding controller to charge the rechargeable capacitor, charging voltage can reach up to 1,000 V. Once the charging is completed, the welding controller cuts off the external power grid. Parts are welded by discharging the SCR conductive discharge welding transformer output, which produces low voltage and high current. Main advantages are:

1. Stable welding quality;

2. Short welding time, small heat affected zone, low energy consumption,electrode loss, cost saving;

3. Small power grid requirement, only 20% of the AC welder, 50% of the MFDC welder, greatly reducing the energy supporting;

4. When welding galvanized parts,the galvanized layer in the non-welded area can not be damaged, there is no need for grinding and post-treatment;

5. The welding process is not affected by grid fluctuations, especially when the nut projection welding of high-strength and hot stamping steels is very stable.

CDW Welding Effect

We have developed a full range of capacitor discharge welders that are mature and widely used. Compared to high voltage and low voltage capacitor discharge welding, Heron's medium voltage capacitor discharge resistance welding machine adopts metal film non-polarized capacitors without electrolytes, which makes the capacitors less likely to explode and decay. Additionally, due to the reduced use of capacitors, the entire system doesn’t have a high voltage of more than 3000V. The manufacturing structure of the entire machine is more compact, occupying a smaller manufacturing site, and has a larger capacity, which is increasingly favored by the market.