Page 16
Recyclers News Press
Over the last decade, automakers around theglobe
have been increasing the use of ultra-high-strength
steels (boron steel ormanganese-boronalloy steel) in
critical safety areas on car frames. Thesenewalloys
are anextremely difficult cutting challenge for auto
recyclers and emergency responders extracting vic-
tims from vehicle accidents. Ina series of in-house
tests, we determined that in order toeffectively cut
ultra-high-strength steelswith a reciprocating saw,
both the blade specification and the saw speed
(measured in strokes perminuteor SPM) are equally
important. Effective speed control is critical to cutting
ultra-high-strength steelsquickly and has the addi-
tional benefit of maximizing blade life.
KeyFindings:
HUBPremium1” 14TPI
blades perform best when
cutting ultra-high-strength
steel
Fastest cutting occurs at
slower blade speed; opti-
mal machine speed is
1250-1500 strokes perminute using a lower
speed control setting
Orbital motion improves blade performance (contrary
tomostmetal cutting applications)
Corded power reciprocating blademachines arenec-
essary for optimum blade performance.
NewVehicleAlloys andRescueChallenges—
Background
To improve fuel efficiencywithout sacrificing safety,
global vehiclemanufacturers are focused on improv-
ing the strength-to-weight ratio of cars and light
trucks. Ultra-high-strength steels, specificallymanga-
nese-boronalloy (referred tohereafter as “boron
steel”) arebeing used in select areas of the vehicle’s
passenger compartment, allowingmanufacturers to
achieve the lowest weight possiblewithout sacrificing
strength and safety. However, the increasing usageof
boron steel in vehicles introduces a significant cutting
challenge to first responders andauto salvage yards.
These steelsget their exceptional metallurgical prop-
erties of strengthand light weight by adding heat dur-
ing the forming processand via a rapid cooling cycle.
Boron steel is among the strongest, hardest, and
most difficult to cut of theultra-high-strength steels
due to its high tensile strength, which approaches
1500MPa (215 ksi) andhardness in the rangeof 450-
500Vickers (45-50Rc). This is 5-6 times stronger
than the steel typically used in the rest of the vehicle
frame.
There are several tools that canbe used to cut boron
steel; however, inmost cases, the reciprocating saw
is the preferred cutting tool because of its lightweight
maneuverability and the low risk it poses to the user.
Test Results
- Asmentioned above,
reciprocating saws are preferred in
vehicle rescue operations formany
reasons, butmost often they are se-
lected for their versatility. However, for
cutting boron steel, battery powered
reciprocating saws currently lack the
power and speed control necessary to
efficiently andquickly cut this steel. Therefore, corded
reciprocating sawswith electronic variable speed con-
trol are the ideal tools for cutting boron steel.
TeethPer Inch (TPI) Selection:
A critical factor in
rescue operations utilizing a reciprocating saw is the
understanding of the ideal blade specification for the
application. Using aB-Pillar andA-Pillarmadeof Bo-
ronSteel fromaMercedes-BenzR-Class, we con-
ducted hand testing using a corded reciprocatingma-
chine todetermine the optimal TPI by testing 14, 18,
10/14 1” bimetal bladesaswell as a fewothers. Test
results show cutting performance in thismaterial
measuredby length of the cut width after 60 seconds
of cutting time. This test demonstrated that our HUB
Premium1” bladewith 14TPI with its profiledesigned
for heavymetal cutting applications performed best
on theboron steel. Specifically, theblade specifica-
tion features awider, thicker bladewith a straight-
back profile. Other blade specificationswere tested
including various profiles andTPls (including 18,
10/14TPI and specialty grit blades) but, these
CuttingUltraHighStrengthSteel
EffectivelyandSafely
Solutions toSolve theProblem for BoronSteel
