Metallurgy 101: A Lesson In New Vehicle Extrication

cross section of a Subaru B post
Five Star crash ratings apply to all grades of vehicles, not just higher end luxury cars. This is a cross section of a Subaru B post.
Heat treating is a process that uses the heating and cooling of an object to rearrange the molecular structure to either condense (harden) or relax (soften) the material.
Heat treating is a process that uses the heating and cooling of an object to rearrange the molecular structure to either condense (harden) or relax (soften) the material.
Heat treating is a process that uses the heating and cooling of an object to rearrange the molecular structure to either condense (harden) or relax (soften) the material.
cross section of a mercedes clk500
A cross section of a Mercedes CLK500 A post shows many layers of design deflection metals and the center boron tube. Responders will need to generate a minimum of 200,000 to 250,000 pounds of cutting force to cut or fracture this type of construction. (Champion Rescue Tool Photo)

New vehicle technology (NVT) seems to have become a mythical being that some of us, as rescue workers and firefighters, are inclined to overlook for reasons that include, “We don’t see those types of cars come into our area.”

NVT can, has and continues to create complex challenges as it spans numerous aspects of vehicle construction. One of these challenges is understanding the new and not-so-new metals that are used, how they are prepared and put together and their locations within vehicles. A better understanding of this metallurgy will prepare you for doing a more thorough, faster and – most importantly – safer job on scene.

While automobile styling and features changed, for almost two decades leading up to about 2004 or 2005, the basic framework and construction was fairly consistent. Structural components were made of heavy, but strong mild steel. This steel was easy to use and relatively inexpensive to produce.

Most hydraulic rescue tools manufactured during those two decades worked in a similar way and were able to get the job done on the vehicle technology of that era. With today’s push for smaller, more fuel-efficient cars and the introduction of the National Highway Traffic Safety Administration’s (NHTSA) Five Star Crash Ratings to promote safer cars, the old design approach to car making had to be challenged and reinvented. So too must the hydraulic rescue tool industry be reinvented to keep up with new vehicle technology.

We have all heard about exotic metals being used in today’s new cars. While the term is a bit of a misnomer – these metals aren’t exotic, they are simply new to the auto industry – we will use it since it is accepted in the industry. Basically, as opposed to plain mild steel used in the past, manufacturers are employing lighter and stronger materials, such as boron, magnesium and titanium, to meet consumer demand and industry requirements for safety and fuel economy.

Heat Treatment

Most metals can be hardened using a process called heat treating. Hardness is often measured using a scale called the Rockwell C scale. The higher the number on the Rockwell C scale, the harder the material. The higher the number and harder the material, the more brittle the material becomes. The accompanying chart (Page 34) shows some examples of common items and their hardness ratings.

Without getting too scientific, heat-treating rearranges the molecules in metal to make it hard or soft. With the application of heat, molecules can be moved to strengthen or soften an entire metal object or a portion of an object. Auto manufacturers can use heat-treating to increase the strength of structural members in cars. Ultimately, the heat-treating process keeps the construction strong, but lightweight.

Rescue Tool Blades

Let’s compare the principles of metallurgy to something we use to perform extrications – a rescue tool blade. Many rescue tool manufacturers use a process called forging to create rescue tool blades. A forged tool blade typically has a hardness of 55 to 56 Rockwell C. Materials being used in today’s NVT have hardness readings as high as 57-plus on the scale.

It doesn’t take a rocket scientist to understand the conflict created when trying to cut a component with a hardness of more than 57 with a rescue tool blade having a hardness of 55 to 56. If you haven’t experienced a broken rescue tool blade yet, I hope you never do.

Rescue tool blades store energy dur ing an attempted cut and often come apart with a velocity of over 2,700 feet per second. This velocity is equal to that of a bullet fired out of a high-powered hunting rifle. We have all heard of or seen firefighters and patients being injured by flying rescue tool blades. It seems, sadly, to be only a matter of time until a tool failure of this nature could have a fatal result. In addition to using different metals, auto manufacturers are using new construction techniques, among them:

  • Elimination of middle posts.
  • Introduction of full roll cages.
  • Using wider posts for structural strength.
  • Use of design deflection materials – many layers of metal, often laser welded or fused together to add strength and absorb impact. These materials wad up and form solid masses during a collision.
  • Addition of super strong structural tubing inside posts for rigidity and strength.
  • Stronger dash boards and integral cowl supports and reinforcements made from heat treated aluminum, magnesium and boron.
  • Heat treated and hardened parts, such as hinges, Nader bolts, and cross members on doors (becoming more prevalent as of 2010 model year).

These new materials and manufacturing techniques have forced us as firefighters and rescuers to take a different look at vehicle extrication.

While some people suggest we avoid the difficult areas on the new vehicles, we know that this suggestion is often not an option. We also know that working around these difficulties almost always increases the time for extrication, often resulting in poorer patient outcome. When working on NVT at an accident scene, we must rethink our approach. If we take a common sense approach to NVT metallurgy and new construction techniques, and apply it to our job of auto extrication, a few simple rules will help keep us safer on scene:

  • Get firsthand knowledge of the limitations of the rescue tools on your trucks.
  • While attempting a cut with a hydraulic cutter, if you see the blades of the cutter skewing – stop.
  • If your rescue tool is trying to change angles or rotate to the side – stop.
  • Make sure that the fluid pressure coming from your pump is calibrated correctly. If your pump is calibrated too high in an attempt to make your tools work harder, it increases the chances of a catastrophic tool failure.

Obviously, there is much more to dealing with NVT. Metallurgy and NVT construction are just two modules of a comprehensive NVT extrication program. Experts are saying that rescue tool technology and training must keep pace with NVT. If you are unsure about whether your department’s rescue tools can keep up, an accident scene involving NVT is not the place to test them out.

Hands-on training in a new vehicle technology training program is the only viable answer to the questions about your rescue tools and your department’s readiness to deal with the cars of today and of tomorrow.

In the meantime, please be sure to pull out and dust off your plans B, C and D to deal with the constantly changing world of NVT.

Editor’s Note: Carl Haddon is the national training director for the Five Star Training Academy, a free program started by Champion Rescue Tools that focuses on new vehicle extrication. He is a career veteran of the fire and EMS service in Southern California with more than 25 years’ experience. He has also served since the early 1980s as the fire/safety director for many racing organizations including Penske Motor-sports, NASCAR, USAC and Mickey Thompson Racing. He is a certified Level 2 fire instructor who teaches auto extrication classes across the country and is a deputy chief and fire commissioner of the North Fork Fire Department in the Rocky Mountains of Idaho.

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