Hot stamped laser welded blanks (LWBs) combine the benefits of laser welding technology with the high performance of hot stamped steel. Using ArcelorMittal’s steels for hot stamping such as Usibor^® and Ductibor^®, the weight of a part can be reduced significantly while optimizing crash performance.

A key advantage of hot stamped LWBs is that several applications can be combined and stamped as a single part. As well as reducing costs and material use, these complex parts can lead to additional weight savings and even better safety performance.

Hot stamping also improves the geometric accuracy of parts – an important consideration during vehicle assembly.

The aluminum silicon (AlSi) is a unique coating which is used on ArcelorMittal’s steels for hot stamping. This allows OEMs to use a simplified hot stamping process:

• Scale and surface decarburization are eliminated without the need for protection gas.
• The final product exhibits excellent corrosion protection properties.

ArcelorMittal has developed a patented process called laser ablation which removes this coating for laser welding, without affecting the strength or corrosion resistance of the part.

Hot stamped LWBs have been adopted by most major carmakers since they were first introduced in the 1990s. Today carmakers are increasingly deploying them in production vehicles to achieve their ambitious weight reduction and safety targets.

New hot stamping grades such as Usibor^® 2000 and Ductibor^® 1000 are pushing the boundaries of what can be achieved with advanced LWBs. They are particularly useful in safety-critical structural components of the body-in-white (BIW) and provide an excellent balance between strength and formability. They can optimize BIW components in terms of:

• Anti-intrusion
• Energy absorption
• Load transfer properties

ArcelorMittal’s world-leading automotive Global R&D team have developed a single-piece door ring using LWBs. The simplified door ring replaces four separate parts. As well as optimizing weight and reducing costs, the solution enhances crash performance significantly and can lead to weight savings of up to 20 percent.

 The door ring concept has already been deployed in production vehicles on the road in various regions today and is winning awards for its innovative contribution to safety and reducing weight.

A major advantage of the single-piece door ring concept is that only one stamping tool is required. There is also only one stamping operation and post-assembly processes are eliminated. This leads to additional cost savings for the OEM.

Other advantages of the door ring are the geometric accuracy of the hot stamped part and its optimized thickness distribution. The laser welds provide continuous links and ensure there is no overlap between parts.

The aluminum-silicon coating on ArcelorMittal’s steels for hot stamping must be removed before welding. ArcelorMittal has patented a process known as laser partial ablation to efficiently weld hot stamping steels such as Usibor^® and Ductibor^®. The process partly removes the aluminum-silicon coating before the welding operation, ensures high weld quality, and maintains corrosion resistance around the welded area.

• The top layer is removed to avoid excessive Al dilution in the weld
• The intermetallic layer is intentionally kept to guarantee corrosion protection

This process allows uniform hardness distribution after hot stamping, guaranteeing the weld quality.

Thanks to the laser ablation process, ArcelorMittal Tailored Blanks can deliver high quality hot stamped welded blanks which enable OEMs to further reduce weight and improve crash resistance.

ArcelorMittal is installing a new high-technology welding line at its ArcelorMittal Tailored Blanks Lorraine facility in Uckange, France.