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Working with Boron Steel

Ultra high-strength steel alloyed with boron is lightweight and hard – really hard! But there are some tradeoffs to its strength and weight savings that repairers need to be aware of.

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Writer Mike West, a contributing editor to BodyShop Business, retired and closed his shop in Seattle, Wash., on July 1, 2011, after more than 40 years in collision repair. The mayor of Tukwila declared that day “Mike West Day” to honor West for his 39 years as a businessman in the city. He is keeping active by restoring a 1933 Rockne Sedan Delivery and a 1934 Pierce-Arrow Rumble Seat Coupe. He plans to continue administering the I-CAR in-shop welding series in the Western Washington area.

I appreciate and like all things technical – especially metals. Much ado has been made over aluminum and its expanding use in the automobile, and it now appears that the steel manufacturers have awakened to the fact that they’re losing the market share they’ve enjoyed for so many years. Welcome to the party, boys. It’s good of you to join us.

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The idea must have occurred to them along these lines: “Hey Gunter, if we make some of our heavy steel parts out of lighter but stronger alloy steel, we won’t need to switch to aluminum to meet fuel-efficiency standards. What do you think?”

“Ya, Hans, this is a good idea. That way we can sell our cheaper steel to the automakers and retain market share over those damn aluminum guys. That’s what I call progress.”

Well, you get the idea, which seems to be emanating from Europe.

So what is this newfangled boron we’re hearing so much about and what does it mean to us collision repairers? Good question.

What Is Boron?

It’s an element of our world, meaning that it cannot be reduced down any further than this basic elemental form … boron. It has several industrial uses: the manufacture of fiberglass insulation, bleach, boric acid and borax for laundry products. It’s also used to produce the color green in pyrotechnic fireworks displays. So when you see that brilliant green in the sky on the 4th of July, think boron. It also has many other uses, including appliance enamels and as a potential medicine for arthritis.

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It’s also used extensively as an alloying element in developing ultra high-strength steel (UHSS). In its basic state, boron melts at 3,767 degrees Fahrenheit and boils at 7,232 degrees Fahrenheit. That’s hot! My little old mind is just trying to figure out what type of heating apparatus would be used to melt boron and then boil boron. Nothing my wife would want on her stove, that’s for sure.

It’s added in very small amounts to steel, about one-tenth of 1%, although the exact formula is difficult to obtain. (I find it amazing that you can add something that miniscule to anything and then name it for that miniscule ingredient. NOTE: Be warned, when you reach a certain point in your life when you no longer worry about sex or alcohol, you’ll start pondering the bigger issues – like how the addition of one-tenth of 1% of boron to steel warrants this UHSS being called boron steel. Unfettered focus is a
wonderful thing.)

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Anyway, this stuff is hard! Hard enough to cause many technicians to utter the words, “What the hell is this stuff?” after burning up a few spot weld drills and cutters in a small period of time. Not cheap!

Save your time and money. Conventional spot weld cutters and drills don’t work on boron steel. It’s just too hard.

Some Challenges of Boron

The idea here was to make something that’s a lot stronger but also a lot lighter in weight – and boron steel meets that requirement. But there are some tradeoffs to its strength and weight savings:

  1. Once bent, it can’t be straightened. It requires replacement if damaged.
  2. It’s sensitive to heat and rapidly weakens if heated.
  3. Because of its sensitivity to heat, it can’t be galvanized. Therefore, corrosion protection is crucial and essential after welding.
  4. Most manufacturers allow GMAW/MIG welding of boron but urge caution because of weakening in the HAZ (heat affect zone).
  5. It’s resistant to conventional cutting tools – spot weld drills, cutters, reciprocating saws. (Rescue efforts have been hampered at collisions where victims were trapped inside the vehicle because reciprocating saws and hydraulic cutting equipment couldn’t cut through the boron steel pillars.)


If It’s Predictable, It’s Preventable

Always, always, always remember the physician’s oath: “First do no harm.” The best way to avoid doing harm is to develop a repair plan and then work the plan. This is important. It doesn’t have to be complicated or difficult, but it does require some thought.

An easy way to proceed is to think, “If it’s predictable, it’s preventable.” So think about what could go wrong when working with boron steel. Let’s try this …

    1. We need to re-establish the correct position and dimension to properly seat our new replacement boron steel part. As always, we should pull on the damaged part to re-establish the attaching panel’s dimensional accuracy and position. Think about this: Many times, boron steel is attached to high strength steel (HSS), which is weaker in yield strength. So is it predictable that pulling our much stronger boron steel part out to its dimensional correctness would potentially distort the weaker attaching panels? Yes, it is. Therefore, proceed with caution to prevent this from happening. If it’s predictable, it’s preventable.

  1. A plasma arc cutter is a useful tool for removing spot welds on boron steel. Some units can be set low enough to remove just the top sheet, if you’re trying to preserve the undamaged bottom flange. If you cut through both parts, can you obtain access to weld the new part on through your newly created holes? Maybe. Maybe not. Think first. If it’s predictable, it’s preventable.
  2. Removal of spot welds by grinding with an abrasive wheel is a practical and viable spot weld removal method for boron steel. It’s also the most universally abused technique in existence. Is it possible to grind through the top sheet and damage and weaken the attaching flange? Yes. So proceed with care and caution. If it’s predictable, it’s preventable.
    These examples illustrate some of the common concerns a technician faces when working with boron steel. The key: Think about it … first.

Cutting Boron Steel

Several methods are possible, and all have some concerns attached to them:

  1. When drilling, tungsten carbide works. You can buy this bit from the people who offer the C-clamp-type spot weld cutter drill. Pressure (high) and speed (800-1,000 RPM) are essential elements of this technique. Lubrication is also helpful. Lifespan is about 100 holes. Cost is about $60.
  2. You can cut boron steel effectively with an abrasive wheel. Watch out for the sparks because they’ll damage glass and upholstery. This method is effective for removing spot welds, but be careful not to damage remaining flange by over-grinding.
  3. Plasma arc works but demands a sufficient level of operator skill to achieve success. Beware of sparks entering the passenger compartment. The plasma cutter works well for the attaching holes in the new part. Keep holes in the 1/4 to 5/16 diameter range and then round up with a carbide cutter on a die grinder to 5/16 diameter. Removing spot welds in the damaged part without damaging bottom sheet requires skill and a machine capable of cutting the top sheet only. Practice on another damaged part first.


Welding Boron

  1. STRSW (squeeze-type resistance spot welding) is recommended. A three-phase unit with a preheat mode is preferable. STRSW is a preferred method of welding boron steel because of corrosion issues, due to the lack of galvanizing.
  2. GMAW/MIG (wire feed) is also an effective weld method for boron steel. Just watch your heat buildup, especially when sectioning. Weld no more than a 1/2 inch before allowing to air cool. Keep the heat-affected zone (HAZ) as small as possible. Everywhere you weld, you’re weakening the strength of the boron steel.

Restoring Corrosion Protection

It’s extremely important to properly prepare all mating flanges prior to attaching welded parts.

  • Do not remove undamaged e-coat; preserve it.
  • Grind only the remaining metal from the existing spot weld sites, and keep it as small as possible.
  • Apply epoxy primer to the bare metal areas.
  • If GMAW/MIG welding through plug weld holes in a new part, remove the coating inside the plug hole in the bottom sheet with needle-point die grinder prior to welding.
  • Clean all the weld sites and epoxy prime.
  • Seam seal all seams to prevent moisture from accessing weld areas.
  • Apply a liberal coat of petroleum/ wax-based corrosion protection coating to the interior of the new part.


Accessing Information

There are some definite concerns and challenges when dealing with boron steel. However, unlike a few years ago, we now have information available to us regarding this ultra high-strength steel. The Internet is a viable resource for you. You can go to www.nastf.org (the National Automotive Service Task Force) and view the Web site addresses for every major manufacturer and then visit the appropriate one for the vehicle you’re working on. This is essential for determining if the manufacturer has recommended repair procedures – to avoid compromising the vehicle’s structural integrity.


Another invaluable resource is I-CAR. For information on boron steel, visit I-CAR’s Web site at www.i-car.com and go to “Technical Information” at the top of the page. Then choose “Advantage Online.” Look at the May 10, 2004, issue and the Aug. 22, 2005, issue. You can even take an online course in working with boron steel as applied to the Volvo XC90.
I’ve said this before (about working with aluminum) and I’m about to say it again: Working with materials such as advanced high-strength steel and UHSS alloyed with boron isn’t difficult. It’s just different.

Writer Mike West, a contributing editor to BodyShop Business, has been a shop owner for more than 30 years and a technician for more than 40 years. His shop in Seattle, Wash., has attained the I-CAR Gold Class distinction and the ASE Blue Seal of Excellence.

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How Do You Know It’s Boron?
That’s why manufacturers recommended procedures are so important nowadays. If they aren’t available, assume (a safe thing in this case) that if it’s a European vehicle, a structural part and doesn’t have galvanized coating on it, it’s boron – so if it’s damaged, it should be replaced.

PREDICTION: Aluminum probably won’t be included in the mass-produced automobile – too many production problems, not to mention costs. It’ll be used in high-dollar vehicles only. Light weight steel is the wave of the future – and this includes boron.

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