How tra­di­tional HSS tools meet the needs of to­day

RICKY PAYLING PROD­UCT STRAT­EGY MAN­AGER FOR ROUND TOOLS AT DORMER PRAMET, LOOKS AT WHY HSS RE­MAINS A POP­U­LAR OP­TION, THE DIF­FER­ENT COM­PO­SI­TIONS AVAIL­ABLE AND HOW THE MA­TE­RIAL HAS ADAPTED TO A FAST-CHANG­ING IN­DUS­TRY.

DEMM Engineering & Manufacturing - - PRODUCT WATCH -

Cut­ting tools made from High Speed Steel (HSS) are wit­ness­ing a level of growth around the world which shows no signs of slow­ing down with the global mar­ket for HSS cut­ting tools ex­pected to grow to more than USD 10 bil­lion by 20201

This is a sig­nif­i­cant amount, es­pe­cially when the cur­rent global mar­ket for the en­tire cut­ting tools in­dus­try is val­ued at around USD 18.5 bil­lion. The in­crease is sup­ported by a steady de­mand from key seg­ments, such as au­to­mo­tive and con­struc­tion, as well as heavy elec­tri­cal and in­dus­trial equip­ment.

A POP­U­LAR OP­TION

De­spite the grow­ing com­pe­ti­tion from solid car­bide, HSS con­tin­ues to be pop­u­lar with man­u­fac­tur­ers due to its high wear re­sis­tance and ex­cel­lent hard­ness and tough­ness prop­er­ties.

HSS cut­ting tools are best suited to mass pro­duc­tion en­vi­ron­ments where tool life, ver­sa­til­ity, pro­duc­tiv­ity and tool cost are of the high­est im­por­tance to an end user. It there­fore still has a ma­jor part to play in ef­fi­cient and re­li­able ma­chin­ing of many com­po­nents. Also, the cur­rent fo­cus for a good prod­uct qual­ity, which meets the cus­tomer ap­pli­ca­tion re­quire­ments at a cost- ef­fec­tive price, is prov­ing at­trac­tive in the present global eco­nomic cli­mate.

To sup­port the grow­ing world­wide de­mand for HSS, cut­ting tool man­u­fac­tur­ers have com­mit­ted ex­ten­sive re­sources to this seg­ment. This in­cludes in­creased in­vest­ment in not just new prod­uct devel­op­ment but also re­search and devel­op­ment ac­tiv­i­ties. This has led to HSS tools be­com­ing more re­li­able with a re­duc­tion in the num­ber of de­fects, lower pro­duc­tion costs and shorter lead times. The ad­di­tion of im­proved sub­strates, in­clud­ing pow­der met­al­lurgy and coat­ings have been in­stru­men­tal in fur­ther en­hanc­ing per­for­mance.

Across Dormer’s range of round tools there are cur­rently four dif­fer­ent ma­te­rial types avail­able; High Speed Steel (HSS), High Speed Cobalt (HSS-E), High Speed Steel / Car­bide (HSS HM) and HSS-E Pow­der Met­al­lurgy Steel (HSS-E PM). These ma­te­ri­als are used across our as­sort­ment of drills, coun­ter­sinks, ream­ers, taps and milling cut­ters.

HSS COM­PO­SI­TION

A typ­i­cal HSS com­po­si­tion fea­tures chromium (four per­cent), tung­sten (ap­prox. six per­cent), molyb­de­num (up to 10 per­cent), vana­dium (around two per­cent), cobalt (up to nine per­cent) and car­bon (one per­cent). The dif­fer­ent grade types de­pend on the vary­ing lev­els of el­e­ments added.

Chromium im­proves hard­en­abil­ity and pre­vents scal­ing. Tung­sten of­fers greater cut­ting ef­fi­ciency and re­sis­tance to tem­per­ing, as well as im­proved hard­ness and high tem­per­a­ture strength.

Molyb­de­num – a by-prod­uct of cop­per and tung­sten pro­duc­tion – also im­proves cut­ting ef­fi­ciency and hard­ness, as well as re­sis­tance to tem­per­ing. Vana­dium, which is present in many min­er­als, forms very hard car­bides for good abra­sive wear re­sis­tance, in­creases high tem­per­a­ture wear re­sis­tance and strength, as well as re­ten­tion of hard­ness.

Cobalt im­proves heat re­sis­tance, re­ten­tion of hard­ness and slightly im­proves heat con­duc­tiv­ity, while Car­bon, in­creases wear re­sis­tance and is re­spon­si­ble for the ba­sic hard­ness (ap­prox­i­mately 62- 65 Rc). The ad­di­tion of five to eight per cent more cobalt to HSS im­proves strength and wear re­sis­tance.

Typ­i­cally, drills made with the ad­di­tion of more cobalt are used in ap­pli­ca­tion spe­cific op­er­a­tions.

AD­VAN­TAGES

HSS tools can re­sist vi­bra­tions, what­ever the type of ma­chine tool, even if rigid­ity has been lost over time and re­gard­less of work­piece clamp­ing con­di­tions. It can prevent me­chan­i­cal shocks at tooth level in milling op­er­a­tions and cope with vary­ing lu­bri­ca­tion con­di­tions which may re­sult in ther­mal changes.

Also, thanks to the unique strength of High Speed Steels, tool man­u­fac­tur­ers can pro­duce ex­tremely sharp cut­ting edges. This make it eas­ier to ma­chine dif­fi­cult ma­te­ri­als, of­fers less work hard­en­ing of austenitic stain­less steels and nickel al­loys, gives a bet­ter sur­face qual­ity and tol­er­ances of ma­chined parts.

As the metal is cut and not torn, it pro­vides longer tool life with lower cut­ting edge tem­per­a­tures. It also re­quires lower cut­ting forces, which ul­ti­mately means less power con­sump­tion from the ma­chine tools.

From a tool life point of view, HSS per­forms very well with in­ter­mit­tent cut­ting ap­pli­ca­tions. How­ever, it has lim­ited cut­ting speed range which is far lower when com­pared to car­bide tools.

COAT­INGS AND SUB­STRATES

HSS may be an es­tab­lished cut­ting tool ma­te­rial, but it does not mean it has not been sub­ject to con­stant devel­op­ment and im­prove­ments since it was first used back in the late 19th Cen­tury.

Dormer Pramet’s range of HSS sub­strates, for ex­am­ple, is any­thing but out­dated. We have in­vested in pow­der tech­nol­ogy to de­velop a ma­te­rial that pro­vides bet­ter re­sults.

HSS-E with pow­der met­al­lurgy of­fers a higher con­tent of al­loy el­e­ments and a com­bi­na­tion of unique prop­er­ties to im­prove tough­ness, wear re­sis­tance and hard­ness. Us­ing HSS-E-PM pro­longs tool life, makes it more pre­dictable, im­proves feed and speed per­for­mance, as well as helps re­duce chip­ping prob­lems.

The most re­cent ap­pli­ca­tion of this pow­dered met­al­lurgy tech­nol­ogy is in Dormer’s Shark Line taps. They are man­u­fac­tured from a HSS-E-PM sub­strate, specif­i­cally de­vel­oped for taps to give the ad­di­tional tough­ness re­quired, con­sis­tently sta­ble prop­er­ties and su­pe­rior grind-abil­ity com­pared to con­ven­tional high-speed steels. These im­proved char­ac­ter­is­tics mean the taps

have a more pre­dictable and as­sured life.

Also, HSS-E and HSS-E-PM are ex­cel­lent sub­strates for a va­ri­ety of coat­ings, such as Ti­ta­nium Nitride ( TiN), Ti­ta­nium Alu­minum Nitride ( TiAlN), Ti­ta­nium Car­bon-Nitride ( TiCN), as well as mul­ti­layer coat­ings.

Coat­ings con­sid­er­ably im­prove tool life and fur­ther boost the per­for­mance of HSS tools in en­vi­ron­ments where pro­duc­tiv­ity and speed and feed rates are high, as well as in dry op­er­a­tions and for ma­chin­ing of dif­fi­cult ma­te­ri­als.

They of­fer in­creased sur­face hard­ness for higher wear re­sis­tance, re­duced fric­tion for bet­ter chip cre­ation, re­duce cut­ting forces and less heat gen­er­a­tion, crater wear re­sis­tance and im­proved sur­face qual­ity of fin­ished parts. TiAlN- coated HSS-E cut­ting tools, for ex­am­ple, are highly suited to dry ma­chin­ing of cast iron as this helps re­sist high tem­per­a­tures, while TiAlN coated HSS-E-PM tools are suit­able for the ma­chin­ing of ti­ta­nium and nickel al­loys.

SUM­MARY

In an age where users re­quire re­li­able, con­sis­tent, ver­sa­tile tools at a cost- ef­fec­tive price, High Speed Steel is still the ideal choice for many ap­pli­ca­tions. As such, it can still hold its own in the mar­ket place against younger and more tech­ni­cally ad­vanced ma­te­ri­als.

If any­thing, HSS has over the many years be­come stronger, by adapt­ing it­self with new coat­ings, ad­just­ing its com­po­si­tion and adding new tech­nol­ogy, all help­ing to re­tain its po­si­tion as a vi­tal ma­te­rial in the metal cut­ting in­dus­try. The cut­ting tool in­dus­try has al­ways been a com­pet­i­tive land­scape and HSS re­mains a key com­po­nent to of­fer­ing cus­tomers what has al­ways been an es­sen­tial re­quire­ment: choice.

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