WHY CAN’T I SLIT ADVANCEDHIGH-STRENGTH STEELS ON MYEXISTING SLITTING LINE?Some service centers are attemptingto slit higher strength materials usingconventional slitting equipment,thinking they can run light gaugesthrough a heavy gauge line, reducethe number of cuts or run at slowerspeeds. This typically results in signif-icantly lower production rates,unacceptable slit edges and looselywound mults. Additionally, there aresafety requirements associated withprocessing coils with higher UTS.If your equipment supplier says all

you need to do is buy the next sizeup, then you are getting some bad

advice. You want the right compo-nents, properly sized and engineeredto work together. Herr-Voss Stamco’s HS²T™ is a

slitting line specifically designed torun AHSS, so there are no compro-mises.

WHAT NEEDS TO BECONSIDERED WHEN SLITTINGAHSS?The first difficulty encountered whenprocessing AHSS is on feed up. High-strength steels are much stiffer andthreading can be very challenging.The higher the UTS, the more difficultit is to control the entry end. HS²T™takes this into consideration, safely

and efficiently allowing an operator tonot only contain the coil while un-winding, but also flatten the strip forfeeding into the slitting process. The next hurdle is the actual slit-

ting process. Putting the requiredtorque on the slitting process is im-portant and vital to success. Evenmore important is the rigidity andsize of the slitter. Slit edge quality isa problem on higher strength materi-als. Slitter tooling also breaks downat an accelerated rate, causing moretooling changeover as well as moretooling grinding time. HS²T™achieves superior edge quality due tothe precise rigid design of the slitterhead as well as the redesigned

ModernMetals

FAQsFREQUENTLY ASKED QUESTIONS

THERE ARE MANY TYPES OF SLITTING LINES and choosing theright type of line for your application is critical to success. Determining yourtrue needs is the best place to start. If you want to provide value to your cus-tomer base through shape correction, or if digging a looping pit is too costly, aStrand Extensioner is the proper choice. If you intend to process AdvancedHigh-Strength Steels (AHSS) or if an existing looping pit is in place, then a looptype line may be what you need. Choosing the right line is especially true whenlooking to slit AHSS, which is increasing its presence in the marketplace. AHSScan exceed 250,000 psi Ultimate Tensile Strength (UTS) and simply cannot beslit on conventional slitting lines. Aluminum is also on the rise as the automotivesector is increasingly turning to this material to lighten their vehicles to meetCAFE requirements. Slitting aluminum on a conventional line typically results inproduction and quality issues. Instead, slitting lines that are engineered for aspecific product are more efficient and produce a higher quality product. Insome cases, existing conventional slitting lines may be upgraded to success-fully run higher strength steels or aluminum.

Modern Metals® August 2014

slittinglines SPONSORED BY HERR VOSS STAMCO

knives, which provide for a moregradual cut. HS²T™ also allows morecuts per coil, which eliminates coilre-runs or double pass slitting onspecified material thicknesses.Another challenge with running

high UTS material is that the tensionrequired to rewind the coil is muchhigher than the rewind tensions forlower UTS material. In fact, rewindtension increases exponentially withregard to the UTS of the material. Toachieve the proper rewind tension,HS²T™ employs Herr-Voss Stamco’sStrand Extensioner® which is derivedfrom our precision leveler technology.The Strand Extensioner® provides ad-ditional tension beyond what a

Tension Stand can provide so the coilcan be wrapped safely, efficiently andaccurately. This also allows the re-wound slit mults to be safelypackaged and transported to down-stream operations. HS²T™ has truly achieved the re-

quirements to create a safe andefficient slitting process for the newAdvanced High-Strength Steels.

WHAT SPECIAL REQUIREMENTSNEED TO BE CONSIDERED FORSLITTING ALUMINUM? While processing aluminum, it is ofupmost importance that the surfacecritical nature of the material betaken into consideration. From pay-

out to recoiler, the full line must beevaluated. The line must also bemade to handle larger coils, as mostaluminum mills roll much larger coilsthan typical ferrous mills. Herr-VossStamco has extensive experiencewith aluminum slitting lines and canprovide you with the solutions best fityour needs.

YOU MENTIONED THE STRANDEXTENSIONER®. CAN YOU TELLME MORE ABOUT IT? Herr-Voss Stamco developed theStrand Extensioner® many years agoto provide a safe method of slittingwithout the requirement for an expen-sive looping pit, at the same timeoffering a competitive advantage byproviding shape correction to the strip.The reason traditional slitting

processes need looping pits is due tothe difference in thickness from thecenter of the strip to the edges, whichis termed “crown.” These thicker cen-ter strands rewind at a largerdiameter than the outside strands, re-sulting in the outside strandsdrooping and requiring a looping pit.The Strand Extensioner® is similar toa precision leveler in that it has a se-ries of small diameter work rolls withadjustable backups. By creating dif-ferential path length, the StrandExtensioner® extends the center slitstrands to the apparent length of theouter strands eliminating the need fora looping pit. Customers who operate a Strand

Extensioner® in their slitting line havediscovered additional benefits be-yond not needing a looping pit:improved strip shape, reduced slitterinduced crossbow, knockdown of slitedge burr, quicker and safer tail-outbecause all the strand ends are thesame length and the ability to steerthe strands into the recoiler resultingin tightly wound straight walled coils.It also reduces the tendency of splits

August 2014 Modern Metals®

Strand Extensioner lines slit material without the need for a looping pit.

to cross at the recoiler. They are pro-ducing slit mults that are of betterquality than the master coil!

WHAT SHOULD BE CONSIDERED WHEN PROVIDINGSHAPE CORRECTION IN ASLITTING LINE?Shape correction in slitting lines wasfirst pioneered in the early 1980s withthe advent of Herr-Voss Stamco’sStrand Extensioner®. While levelingmaterial in the slitting process hasbecome more prolific since then, notall leveling solutions are createdequal. To provide shape correction,you must first consider what materialneeds to be leveled, as well as thematerial thicknesses and yieldstrength. Once this has been estab-lished we can begin to properly sizethe Strand Extensioner®. While sizing the Strand Exten-

sioner®, important decisions need tobe made on the work roll size, framestiffness, roll spacing, backup spac-ing and backup support rigidity.Another major consideration is sizingthe recoiler for the proper amount oftorque. This is critical to ensuring thefull potential of the Strand Exten-sioner® is realized. One additional keyconsideration in shape correctionwithin a slitting line is the number of

work rolls included with the StrandExtensioner®. Having the optimumnumber of rolls in a Strand Exten-sioner® or Precision leveler is criticalto success. It would be very easy toutilize fewer rolls within the leveler orStrand Extensioner®, which wouldmean less required torque from therecoiler, but, as with many otherthings in life, nothing is free. If too fewwork rolls are included, the StrandExtensioner® may not have enoughdifferential path capability, which inturn means less leveling ability. Onthe flip side, too many rolls can havea negative impact. Herr-Voss Stamcohas designed and manufacturedthousands of Levelers and we utilizethis expertise while taking all of thesefactors into consideration so that theoptimum leveling solution is provided.

ARE THERE ANY SPECIALCONSIDERATIONS NEEDEDWHEN SHAPE CORRECTINGALUMINUM WITHIN THESLITTING PROCESS?In a word, Yes! As with many other ma-terials, when sizing a leveler or StrandExtensioner® for aluminum special at-tention needs to be paid to the rollsize, roll spacing and recoiler torque.Functionally, the roll configurationmust also be different. Considering the

surface critical nature of aluminum,most Strand Extensioner® work rollarrangements have a 5 or 6 high con-figuration. That is to say that there is aset of intermediate rolls between thework rolls and the backups on eitherthe top, bottom or both. Aluminum canalso leave an oxide on the rolls thatmost other materials do not. This re-quires a special work roll finish andcoating. Operationally, aluminum alsorequires different entry and exit set-tings than steel. For ease of operation,Herr-Voss Stamco provides an auto-mated set up feature called Punch’NGo which allows operators to set theStrand Extensioner® with the push of abutton.

DO ALL THE HERR-VOSS STAMCOSLITTING LINES OPERATEWITHOUT A LOOPING PIT? No. Herr-Voss Stamco provides a fullsuite of slitting lines, including fullloop slitting. Our loop slitting linescome with our industry-leading Syn-chrowind tension device, providingthe very best roll tension the markethas to offer. As innovators of theloop slitting line, we continue to offerthat technology as well as the StrandExtensioner®. Our slitting lines include high-

strength slitting (HS²T™), StrandExtensioner® slitting, loop slitting,heavy gauge tube slitting and alu-minum/stainless steel slitting.

CAN I UPGRADE MY EXISTINGCONVENTIONAL SLITTING LINEFOR HIGH-STRENGTH STEELS?That depends on the specific gradeof AHSS required to be run on theslitting line, as well as the specifics ofthe equipment. In some cases, a con-ventional line can be modified to runsome degree of high-strength steels.As the innovator of slitting AHSS,Herr-Voss Stamco knows what ittakes for equipment to be opera-tionally successful and can assist youin determining the best solution. �

Thomas Smrekar, Manager, CustomerSolutions with Herr-Voss Stamco.

Modern Metals® August 2014

slittinglines

Herr-Voss Stamco also offers loop slitting lines.