Die and punch materials

6.7.3 Die and punch materials

Mat erials u sed fo r co ld an d warm fo rm in g are req u ired t o h ave h igh st ren gt h , h igh t o u gh n ess an d h igh h ard n ess. Fo r an eco n o m ical d ie life, ext rem ely go o d wear an d t em p erin g resist an ce are n ecessary. Die m at e- rials sh o u ld be ch o sen , wh ere p o ssible, t o en su re go o d m ach in abilit y, an d as a resu lt , lo w m an u fact u rin g co st s cf. Sect . 4.1.3 . All t h ese req u irem en t s can n o t be fu lfilled sim u lt an eo u sly by each t yp e o f t o o l st eel. Th e ch aract erist ics wear resist an ce an d t o u gh n ess, fo r exam p le, sh o w o p p o sin g t en d en cies. Th e m at erials 55NiCrMo V6 1.2713, 57NiCrMo V7 1.2714 an d X3NiCo Mo Ti1895 1.2709 are ext rem ely t o u gh an d are u sed fo r sh rin k rin gs an d in sert s wh ich are su bject ed t o h igh levels o f elo n gat io n . Th eir wear ch aract erist ics, in 496 Solid forming Forging Table 6.7.3: Survey of the most frequently used cold, w arm and hot forging tool steels Die materials I Cold forging tool steels Active components M aterial No. DIN ANSI JIS Composition in to DIN Germany USA Japan C Si M n P S Co Cr M o Ni V W Ti 1.2363 X100CrM oV51 A2 SKD11 1.00 0.30 0.55 0.03 0.03 – 5.00 1.10 – 0.20 – – 1.2369 81M 0CrV4216 0.81 0.25 0.35 – – – 4.00 4.20 – 1.00 – – 1.2379 X155CrVM o12 1 D2 SKD11 1.55 0.30 0.35 0.03 0.03 – 12 0.70 – 1.00 – – 1.2709 X3NiCoM oTi1895 0.03 0.10 0.15 0.01 0.01 9.25 0.25 5.00 18 – – – 1.2713 1. NiCrM o 55NiCrM oV6 6F2 0.55 0.30 0.60 0.03 0.03 – 0.70 0.30 1.70 0,10 – – 1.2714 57NiCrM oV7 SKT4 0.58 0.30 0.70 0.03 0.03 – 1.00 0.50 1.70 0.10 – - 1.2767 X45NiCrM o4 6F7 0.45 0.25 0.30 0.03 0.03 – 1.35 0.25 4.00 – – – 1.3207 HSS S10-4-3-10 T42 SKH57 1.3343 S-6-5-2 M 2 SKH51 0.90 0.45 0.40 0.03 0.03 – 4.15 5.00 – 1.85 6.35 – 1.3344 S-6-10-2 M 32 1.20 0.45 0.40 0.03 0.03 – 4.15 5.00 – 3.00 6.35 – Die materials I Hot-w arm forging tool steels Active components M aterial No. DIN ANSI JIS Composition in to DIN Germany USA Japan C Si M n P S Co Cr M o Ni V W Ti 1.2713 1. NiCrM o 55NiCrM oV6 6F2 SKT4 0.55 0.30 0.60 0.03 0.03 – 0.70 0.30 1.70 0.10 – – 1.2714 57NiCrM oV7 SKT4 0.58 0.30 0.70 0.03 0.03 – 1.00 0.50 1.70 0.10 – – 1.2343 2. CrNiM oV X32CrM oV51 0.38 1.00 0.40 0.03 0.03 – 5.30 1.10 – 0.40 – – 1.2344 X40CrM oV51 H13 H11 SKD6 SKD61 0.40 1.00 0.40 0.03 0.03 – 5.30 1.40 – 1.00 – – 1.2365 X32CrM oV33 H10 0.32 0.30 0.30 0.03 0.03 – 0.30 2.80 – – – – 1.2367 X40CrM oV53 SKD7 0.30 0.20 0.30 0.03 0.03 – 2.40 – – – 4.30 – 1.2606 3. WCrV X40CrM oW51 1.2622 X60WCrCoV93 SKH51 SKD62 SKT4 Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 co n t rast , are n o t q u it e as favo rable. Th e h igh -sp eed st eel S10-4-3-10 1.3207 o ffers o u t st an d in g wear ch aract erist ics, bu t t en d s t o be m o re brit t le. Th e m at erials X155CrVMo 121 1.2379 an d S-6-5-2 S-6-10-2 1.3343 44 rep resen t a co m p ro m ise co n cern in g wear an d t o u gh n ess ch aract erist ics: Th eir t em p erin g resist an ce can also be co n sid ered t o be very go o d at 550 °C. Th e m o st im p o rt an t crit erio n t o be co n sid ered wh en select in g a t o o l m at erial is t h e t yp e an d ext en t o f lo ad , fo llo wed by t h e layo u t an d geo m et ry o f t h e d ie. Table 6.7.3 p ro vid es a su m m ary o f t h e m o st co m m o n ly u sed t o o l m at erials fo r co ld an d warm fo rm in g. Th e t able also sp ecifies t h e d esig- n at io n s o f co m p arable st eels fro m t h e USA o r Jap an an d t h eir co m p o si- t io n s. Table 6.7.4 d escribes t h e h eat t reat m en t , i. e. t h e an n ealin g t em - 497 Die design Table 6.7.4: Heat treatment of cold, w arm and hot forging tool steels Die material II Cold forging tool steels Active components No. Heat treatment ° C Hardness Cooling Applicationhardness HRCNmm 2 Annealing Hardening Quenching medium Quenching medium Tempering customary W ater 1.2363 800-840 930-970 Ö,WB 400 180-400 60 +–1 blankingpunching dies 1.2369 800-840 1,070-1,100 Ö,WB 450-550 550 61 +–1 punches, blankingpunching dies 1.2379 840-860 1,040-1,080 Ö,L,WB 400 180-250 60 +–1 punches, dies 1.2709 840 480 L – 55 shrink ring 1.2713 650-700 830-870 Ö 300-650 45 +–1 P,Ö,W shrinkintermediate ring and 1.2714 650-700 860-900 L 300-650 45 +–1 P,Ö,W pressure pin 53+-1 HRC, 1,150 Nmm 2 1.2767 610-630 840-870 W,Ö,L 160-250 54 +–1 punch, mandrel, one piece press container 1.3343 1,100-900 790-820 Ö,L,WB 550 540-560 62 +–1 punch, die insert, press container and 1.3344 1,100-900 770-820 Ö,L,WB 550 550-570 62 +–1 counterpunch, mandrel Die material II Hot, w arm forging tool steels Active components No. Heat treatment ° C Hardness Cooling Applicationhardness Annealing Hardening Tempering customary HRC 1.2713 650-700 830-870 Ö 300-650 42 +2 P,Ö,W shrinkintermediate ring and 1.2714 650-700 860-900 L 300-650 42 +2 P,Ö,W pressure pin 52+2 HRC, 1,150 Nmm 2 1.2343 750-800 1,000-1,040 L,Ö,WB 500-550 550-650 50 +2 W,P,Ö die insert, shrink ring 45+–1 HRC 1.2344 750-800 1,020-1,060 L,Ö,WB 500-550 550-650 50 +2 P,Ö mandrel and counterpunch 1.2365 750-800 1,020-1,060 Ö,WB 500-550 500-670 50 +2 W,L,P,Ö die insert, punch and 1.2367 750-800 1,060-1,100 L,Ö,WB 500-550 600-700 54 +2 W,L,P,Ö counterpunch 1.2606 750-790 1,020-1,050 Ö,L,WB 500-550 550-650 W,L,P,Ö 1.2622 760-800 1,150-1,200 Ö,WB 500-550 500-650 56 +2 L,Ö blanking die W = w ater WB = w ater bath L = air P = compressed air Ö = oil Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 p erat u re, t h e h ard en in g t em p erat u re, t h e q u en ch in g m ed iu m an d t h e t em p erin g t em p erat u res. Th e levels o f h ard n ess gen erally req u ired fo r d ies u sed in co ld fo rm in g ap p licat io n s are also given . Table 6.7.5 d escribes t h e ch aract erist ics o f wear, t o u gh n ess, m ach in abilit y an d grin d in g u sin g a 10-p o in t scale, wh ereby a h igh n u m ber in d icat es esp e- cially go o d cap abilit y. Th e t ables m ake n o claim t o co m p let en ess, bu t p resen t a su bst an t ially red u ced n u m ber o f act u ally req u ired t o o l st eels in fo llo win g t h e p rin cip les o f o p t im ised an d red u ced in ven t o ry. Th e m o st freq u en t t o o l m at erial u sed fo r co ld fo rgin g is h igh -sp eed st eel, wh ile fo r warm fo rgin g t em p erat u re-resist an t t o o l st eel is u sed . 498 Solid forming Forging Table 6.7.5: Properties of cold, w arm and hot forging tool steels Die materials III Cold forging tool steel Active components Characteristics Remark V Z B S 7 6 8 7 78 5 8 4 4 4 12 Cr-steel 5 9 5 7 special steel 2 10 6 8 4 10 6 8 9 2 4 5 9 4 4 5 10 3 3 4 2 10 6 8 44 HRC 1,400 -1,480 Nmm 2 52 HRC 1,800 - 1,900 Nmm 2 5 8 50 HRC 1,700 - 1,800 Nmm 2 5 8 8 8 surface w elding Capilla 521 for erosive machining surface w elding Capilla 5200 for machining 4 8 8 8 50 HRC 1,700 - 1,800 Nmm 2 5 7 8 8 54 HRC 1,925 - 2,050 Nmm 2 56 HRC 2,050 - 2,200 Nmm 2 V = w ear resistance Z = toughness B = machinability S = grindability No. 1.2363 1.2369 1.2379 1.2709 1.2713 1.2714 1.2767 1.3343 1.3344 No. 1.2713 1.2714 1.2343 1.2344 1.2365 1.2367 1.2606 1.2622 Die materials III Hot, w arm forging tool steel Active components V Z B S Characteristics Remark Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Powd er m etal-m an u factu red h igh -sp eed steels d em on strate very u n i- form carbid e d istribu tion an d are segregation -free. Th is resu lts in im p roved tou gh n ess p rop erties an d extrem ely h igh com p ressive stren gth . If a larger wear resistan ce is req u ired , for exam p le for forward rod extru sion or iron in g d ies, for large-p rod u ction series carbid es are also u sed . Th e carbid e typ es u sed com p rise tu n gsten carbid e as a p h ase in a cobalt m atrix. Th e cobalt con ten t wh ich d eterm in es th e ch aracter- istics of th e carbid e, lies between 15 an d 30 . With a risin g tu n gsten carbid e con ten t, h ard n ess, com p ressive stren gth an d wear resistan ce all in crease. However, at th e sam e tim e tou gh n ess, n otch im p act stren gth , ben d in g an d bu cklin g resistan ce are red u ced . Th e grain size exerts an in flu en ce h ere: fin e-grain ed carbid es are u n su itable as a resu lt of p oor tou gh n ess ch aracteristics. Table 6.7.6 p rovid es a su m m ary of th e m ech an ical ch aracteristics of carbid es. Th e stren gth valu es ap p ly to sta- tic load s an d m u st be red u ced by 50 for stress cycles greater th an 10 6 . Tool steels for warm form ing Th e m at erials X40CrMo V53 1.2367, X38CrMo V51 1.2343, X40- CrMo V51 1.2344 an d X60W CrCo V93 1.2622 are cu rren t ly u sed fo r warm fo rm in g an d in co n ju n ct io n wit h t h e wat er co o lin g m et h o d gen - erally ap p lied t o d ay; In t h e case o f sh rin k rin gs, 55NiCrMo V6 1.2713 57NiCrMo V7 1.2714 o r X38CrMo V51 1.2343 X40CrMo V- 51 1.2344 can be u sed . Du e t o t h eir lo w t h erm al sh o ck resist an ce, car- bid es, h igh -sp eed st eels an d co ld fo rm in g t o o l st eel 81Mo CrV4216 1.2369 are o n ly su it able wh en u sin g wat er-free co o lin g m et h o d s wh ich were co m m o n in t h e p ast . O n clo ser exam in at io n , it beco m es clear t h at m at erials fo r warm fo rgin g are gen erally t h o se u sed in t h e classical field o f h o t fo rgin g. Sp ecial m at erials fo r warm fo rgin g, wh ich are cap able o f wit h st an d in g relat ively h igh p ressu re levels an d relat ive- ly h igh t em p erat u res sim u lt an eo u sly, h ave n o t yet been d evelo p ed fo r im p lem en t at io n in series p ro d u ct io n . Develo p m en t s o f d ie m at erials fo r warm fo rm in g are m o vin g in t h e fo llo win g d irect io n s: Co m p ared t o h o t fo rgin g t o o l st eels, h igh -sp eed st eels alread y exh ib- it go o d wear an d h eat resist an ce p ro p ert ies as well as im p ro ved t em p er- in g resist an ce. By a grad u al red u ct io n o f t h e carbo n co n t en t , at t em p t s h ave been m ad e t o ach ieve a fu rt h er im p ro vem en t in t h erm al sh o ck resist an ce o f h igh -sp eed st eels. Wit h sim u lt an eo u s d et erio rat io n o f t h e wear an d h eat resist an ce, h o wever, t h e t h erm al sh o ck resist an ce level 499 Die design Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 was far belo w t h at o f h o t fo rm in g t o o l st eels. In view o f t h e su ccessfu l im p lem en t at io n o f en viro n m en t ally frien d ly wat er-so lu ble lu brican t s, t h e fact o r t h erm al sh o ck resist an ce is exp ect ed t o co n t in u e t o be a su b- ject o f p art icu lar in t erest . Th u s, in vest igat io n s are co n cen t rat ed o n t o o l st eels wh ich are d erived fro m h o t fo rm in g t o o l st eels, i. e. t h o se wh ich h ave a relat ively lo w carbo n co n t en t . Th ese t o o l st eels d em o n st rat e su p erio r wear an d h eat resist an ce p ro p ert ies as well as very go o d t h erm al sh o ck resist an ce. A n u m ber of d ifferen t d ie m aterials are bein g d evelop ed con cu rren tly, for exam p le u sin g n ickel-based alloys In con ell 718, wh ich h ave alread y p rod u ced good resu lts in bar extru sion tem p eratu res 1,150 °C, p ressu res of 900 to 1,100 N m m 2 an d isoth erm forgin g ap p lication s. Die coatings V DI 3198 Th e co st -effect iven ess o f co ld fo rgin g p ro cesses d ep en d s largely o n t h e t o o l co st s an d acco rd in gly o n t h e ach ievable service life o f d ies. Die wear in flu en ces t h e d im en sio n al st abilit y an d su rface q u alit y o f t h e p ro - d u ced wo rkp ieces. Th ere are t wo m ain t yp es o f wear resist an t co at in gs co n sid ered fo r u se in fo rgin g t ech n o lo gy. Co at in gs, fo r exam p le u sin g ad d in g-o n p ro cesses su ch as CVD o r PVD p ro cesses, an d co at in gs o bt ain ed t h ro u gh react io n layers su ch as n it rid in g an d io n im p lan t a- t io n . Pro cesses wh ich h ave p ro ven su ccessfu l fo r co ld fo rm in g d ies in clu d e t h e CVD an d PVD t ech n iq u es, wh ich p erm it service life t o be m o re t h an d o u bled cf. Sect . 4.1.3 . An essen tial p rereq u isite for a su ccessfu l coatin g is good ad h esion between th e coatin g m aterial an d th e su bstrate, wh ose h ard n ess an d com p ressive stren gth m u st p rovid e ad eq u ate su p p ort. High -sp eed steels, 500 Solid forming Forging Table 6.7.6: M echanical properties of carbides Carbide types E-modulus Ultimate strength Co content Density Hardness Compressive strength Bending strength by w eight gcm 3 HV Nmm 2 Nmm 2 Nmm 2 15 14.0 1,150 530,000 4,000 2,400 20 13.5 1,050 480,000 3,800 2,600 25 13.1 900 450,000 3,300 2,600 30 12.7 800 420,000 3,100 2,700 Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 led ebu ritic 12 ch rom iu m steels 1.2379 an d carbid es fu lly com p ly with th ese req u irem en ts. Co at in gs are ap p lied m ain ly by sp ecialized co m p an ies. Th is m ean s t h at p art icu lar at t en t io n m u st be p aid t o t h e p rep arat io n o f d ies by t h e d ie m an u fact u rer. Prio r t o co at in g, t h e wo rk su rfaces m u st be free o f gro o ves an d p o lish ed t o a su rface ro u gh n ess o f R z 1 m m . Th e lim it fo r o p t im u m co at in g o f in t ern al h o les is aro u n d l len gt h = d d iam et er wh en u sin g t h e PVD t ech n iq u e. Wit h t h e CVD t ech n iq u e, t h ere are n o kn o wn lim it at io n s. Th e lim it s fo r t h e rat io bet ween t h e d iam et er D an d t h ickn ess H o f co at ed p an els in cases wh ere a “d eflect io n ” o f 0,02 m m is req u ired aft er t reat m en t , are as fo llo ws wh en u sin g t h e CVD t ech - n iq u e: D 7 · H fo r st eels an d D 15 · H fo r carbid es an d wh en u sin g t h e PVD t ech n iq u e D 20 · H It is o n ly p o ssible t o co at p re-st ressed d ies in cases wh ere t h e in sert is p ressed o u t , co at ed an d p ressed in again aft er co at in g. In o rd er t o p re- ven t t h e fo rm at io n o f bead s, sh arp ed ges m u st be bro ken befo reh an d . In cases wh ere a m ean d eviat io n o f t h e m an d rel len gt h L an d d iam et er D aft er co at in g o f 0.01 m m is req u ired , t h e CVD p ro cess sh o u ld be u sed in p referen ce fo r t h e fo llo win g d im en sio n s L 10 . D in t h e case o f st eel L 15 . D in t h e case o f carbid e an d t h e PVD p ro cess fo r t h e len gt h L 20 . D Reliable im p ro vem en t in d ie life, as a resu lt o f co at in g warm fo rm in g d ies wit h t h e CVD o r PVD t ech n iq u es, h as n o t been d em o n st rat ed yet , classical n it rid in g an d weld in g-o n t ech n iq u es are gen erally u sed t o en h an ce p erfo rm an ce. Th e p ro blem faced h ere is t h at t h e base m at eri- als h ave lo wer d egrees o f h ard n ess co m p ared t o t h e req u irem en t s o f 501 Die design Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 co ld fo rgin g, an d t h e n ecessary su p p o rt in g effect o f t h e su bst rat e m at e- rial is n o t ach ieved . O n ce a co n t in u o u s in crease in t h e h ard n ess o f t h e su bst rat e m at erial t h ro u gh t o t h e act u al co at in g h as been su ccessfu lly ach ieved , m o re su ccess can be exp ect ed . It m ay be p o ssible t o ach ieve t h is resu lt u sin g p lasm a n it rid in g an d su bseq u en t co at in g wit h CrN o r TiAlN, o r t h ro u gh t h e d evelo p m en t o f sp ecial san d wich co at in gs.

6.7.4 Die closing systems multiple-action dies