Die materials Casting of dies

4.1.3 Die materials

Th e p ro cessin g o f h igh st ren gt h sh eet m et al, wh ich is beco m in g m o re wid ely u sed in st am p in g t ech n o lo gy, calls fo r h igh er p ressin g fo rces. Th is m ean s h igh er lo ad s o n t h e d ies an d great er o verall wear o n t h e t o o ls. In o rd er t o m eet t h e req u irem en t s fo r lo n g d ie life, wh ile m ain - t ain in g accep t able co m p o n en t q u alit y, sp ecial m at erials – m o st o f wh ich h ave been h ard en ed o r co at ed – m u st be u sed in t h e co n st ru c- t io n o f t h e d ies. Th e basic st ru ct u re o f d ifferen t t yp es o f d ies an d t h eir m o st im p o rt an t co m p o n en t s are sh o wn in Figs. 4.1.16 an d 4.1.17 . Table 4.1.2 list s t h e vario u s co m p o n en t s o f d ies u sed fo r d rawin g, blan kin g, fo ld in g an d flan gin g as well as t h e m at erials u sed t o m an u - fact u re t h em . Table 4.1.3 list s vario u s su rface h ard en in g p ro cesses an d co at in g m et h o d s fo r d ies. Co at in gs, fo r exam p le t h ro u gh h ard ch ro m i- u m p lat in g, can im p ro ve t h e slid in g ch aract erist ics in d eep d rawin g, so t h at t h e n eed fo r lu bricat io n is great ly red u ced .

4.1.4 Casting of dies

Th e cast in g p ro cess is o n e o f t h e st ep s in t h e o verall p ro cess o f m an u - fact u rin g p ro d u ct io n d ies fo r sh eet m et al fo rm in g wh ere t h e h igh est st an d ard s are req u ired by d ie m akers. In co n t rast t o cast in gs u sed in gen eral m ach in ery m an u fact u re, in d ie m an u fact u re, m u lt ip le u sage o f a m o d el is n o t p o ssible, as n o t wo t o o ls are exact ly t h e sam e. A d isp o s- able p at t ern m ad e fro m p o lyst yren e p o lyest er, h ard fo am is t h erefo re u sed fo r t h e d ie cast in g p ro cess Fig. 4.1.18 . Th e cast in g is carried o u t as a fu ll fo rm cast in g p ro cess: t h e p o ly- st yren e p at t ern st ays in it s resin -h ard en ed q u art z san d fo rm . Th e liq u id m et al, wh ich is p o u red in , evap o rat es o r rat h er m elt s t h e p at t ern . Wit h t h e fu ll fo rm cast in g p ro cess, t h e fo u n d ry in d u st ry h as d evelo p ed a p ro - d u ct io n m et h o d wh ich o ffers a large m easu re o f d esign -relat ed , t ech n i- cal, eco n o m ic an d lo gist ical im p ro vem en t s in d ie m akin g. Fo r t h e d esign er, t h ere is t h e p o ssibilit y o f p recise m easu rem en t an d fu n ct io n al co n t ro l, as t h e fu ll fo rm p at t ern is id en t ical in sh ap e t o t h e p iece bein g cast . Pro d u ct d evelo p m en t is m ad e easier, as t h e p at t ern can be alt ered wit h o u t an y p ro blem s by m ean s o f m ach in in g o r glu in g p ro cesses. Fu rt h erm o re, t h e co st s o f co re bo x, co re p ro d u ct io n , co re t ran sp o rt an d co re in st allat io n are red u ced . 142 Sheet metal forming and blanking Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 143 Principles of die manufacture Fig. 4.1.16 Basic design of different draw dies blank holder slide plates draw punch female die female die blank holder pressure pins double-action drawing die single-action drawing die die substructure draw punch slide plates Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 144 Sheet metal forming and blanking Fig. 4.1.17 Basic design of different blanking, edge bending and flanging dies driver driver filling slide partial support bracket substructure filling slide blocks slide upper structure female blanking die punch retaining plate blanking segments sub- structure pressure plate pressure plate female die retaining plate waste chute panel retaining blocks support upper structure bracket stripper upper structure restrike block stripper on final pressure support substructure bracket embossing block blanking die restrike edge bending die flanging die Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 14 5 Pr in cip le s o f d ie m an ufa ctu re Die material No. 1.0046 1.0555 1.7140 1.2067 1.2769 1.2601 1.2363 Designation GS-45 GS-62 GS-47 Cr M n 6 G-100 Cr 6 G-45 Cr Ni M o 42 G-X 165 Cr M o V 12 G-X 100 Cr M o V 51 DIN 16006 R m [Nmm 2 ] 450 620 tempered, stress relieved 850 tempered to 800-900 800-900 820-930 1000-1030 Heat w eldable, hardening w eldable hardenable surface hardenable, hardenable hardenable treatment not hardenable conditionally possible surface hardenable glow nitrided Hardness – max. HRC 56 + 2 HRC 56 + 2 HCR 60 + 2 w orking hardness HRC 60+–2 HRC 60+–2 after heat 3 mm deep HRC 50+–2 treatment Application thin-w alled blank holders, forming punch, forming punch, forming punches, blanking strips, blanking strips, blank holders, upper structures blanking segments, female die inserts, female die inserts, blanking punches, blanking punches, upper structures subject to female blanking dies forming blocks, forming blocks, coining punches, coining punches, and substructures high loads counterpressure blank holders and draw punches, draw punches, for small dies pads retainers w ith female draw ing dies, female draw ing dies, end pressure forming punches forming punches Die material No. 1.2379 0.6025 0.6025 Cr M o 0.7050 0.7060 0.7070 0.7070 L Designation G-X 155 Cr V M o 12 1 GG-25 GG-25 Cr M o GGG-50 GGG-60 GGG-70 GGG-70 L DIN 16006 Basic hardness HB max. 250 160-230 200-230 170-220 190-240 220-270 220-270 R m [Nmm 2 ] 860 250-350 250 500 600 700 700 Heat hardenable, conditionally w eldable, surface hardening, surface hardening, conditionally w eldable, conditionally w eldable, surface hardening, treatment TIC-TIN coating glow nitriding glow nitriding temperable surface hardening, surface hardening, glow nitriding glow nitriding glow nitriding Hardness HRC 60 + 2 approx. 1200-1400 HV2 approx. 53 HRC approx. 54 HRC approx. 56 HRC approx. 56 HRC approx. 56 HRC after heat treatment Application hemming blocks, standard material for blank holders, instead of GG 25 blank holders, blank holders, blank holders for parts edge bending blocks, cast die components, draw punches, and GS 45 draw punches female draw ing dies w ith draw ing depths coining punches for blank holders adapters, female draw ing dies w ith thin-w alled materials female draw ing dies, 120 mm of outer sheet metals up to upper structures and in particular in case of brackets bodyw ork parts on 2,9mm, blanking cutters, substructures, compressive stress, transfer presses bottom blanking dies, mounted parts, e.g. counterpressure pads blanking punches drives, slides and strippers Table 4.1.2: Die materials and applications Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Sh ee t m eta l fo rm in g a nd b la nk in g S U RFA CE H A RD EN I N G P ROCES S ES COAT I N G P ROCES S ES electrical physical CVD process hard chromium PVD process induction hardening flame hardening glow nitriding Ti C Ti C - Ti N plating Ti N Cr N Ti C N M ethod hardening temperature hardening temperature inclusion of nitrogen combination of hardening and coating application of heating to coating temperature below 500 °C, through high- through acetylene through electrical process: hardening of the base chrome coat in vacuum coating, vacuum cooling, frequency induced oxygen flame discharge in a material to approx. 60-62 HRC, vacuum, diffusion distortion-free process eddy currents vacuum coating 1 000 °C, or electrical pre- austenitizing, tempering cipitation at around 100 °C Usable unalloyed and alloyed unalloyed and alloyed all ferrous materials ledeburitic chromium steels, carbides cast iron, steel, cold and hot w ork steels, HSS, carbides, w orkpiece steels 0.2 - 0.6 C steels 0.2 - 0.6 C non-ferrous metals rust-proof steels material e.g. Ck 45, e.g. Ck 45, e.g. 1. 2379, 1.2842, preferably 1.2379 e.g. 1. 2379, 1. 2601, 1. 2369, 1. 2378 50 Cr M o 4 50 Cr M o 4 1.2601, 1.0062, 0.6025, 1.7131 Workpiece metalically metalically finish machined, metalically bright and polished metalically bright electrically conductive, non-magnetic condition, requirement bright surface bright surface metalically surface, roughness R z 3 µm, non- surface, no material, no shrinkage in case of soldered parts, bright surface functional surfaces fitting surfaces processing or sur- metalically bright surface, roughness w ith allow ance, specification of face faults, as a rule R z = 2 - 4 µm, no burr, no assembled parts tolerance field in the draw ing prior to surface hardening Layer 53 - 59 HRC, hardening w ear-resistant approx. 1200-1400 HV2, approx. 4 000 HV, approx. 3 000 HV, 600 - 1 100 HV0,1, approx. 2 400 HV, approx. 2 000 HV, approx. 3 000 HV, character- depth 1,5 - 3 mm, surface, w orkpiece improvement of max. charging max. charging rustproof surface, max. charging max. charging max. charging istics w ear-resistant surface, core w ith high sliding properties, temperature 300 °C, temperature increased w ear temperature temperature temperature w orkpiece core w ith toughness, danger of increase of strength, brittle, layer thick- approx. 450 °C, resistance, good approx. 500 °C, approx 600 °C, approx. 400 °C, high toughness, scaling, follow ing increase of ness up to layer thickness coefficients of chemical resis- good chemical resis- layer thickness follow ing finish finish surface roughness approx. 9 µm, up to approx. friction, max. layer tance, layer thick- tance, layer thick- up to 3 µm, D R a = 0.1– 0.3 µm grey metal colored 9 µm, grey thickness ness up to 3 µm, ness up to 50-70 µm, brow n-violet metal colored 100 µm gold colored silver colored active parts of forming and active parts of blanking and separating dies draw ing dies and machining tools Range of cast blanking cutters, lifting bolts, all w ear active primarily for primarily for draw punches, primarily non-ferrous metals primarily for parts gib rails, gib elements, die parts and thicker uncoated aluminium plated female dies, unalloyed and Cr Ni steels low and high partial draw cast blanking cutters, gib elements sheet steels and galvanized blank holders deep-draw n alloyed steels, punches and partial draw sheet metals sheets e.g. VA sheet female dies punches and metals female dies Table 4.1.3: Specifications and applications for surface hardening and coating of dies Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 Co m p ared t o t h e u se o f o t h er p at t ern m at erials su ch as wo o d , m et al, o r p last ic, t h e d esign er is n o t rest rict ed by t h e lim it at io n s o f t h e co n - ven t io n al cast in g t ech n o lo gy. As t h e p at t ern rem ain s in sid e t h e fo rm , t h ere is n o n eed t o co n sid er t h e p art in g lin e, u n d ercu t s, co n icit y an d t h e t ap ers fo r p at t ern rem o val. All ferro u s m at erials are su it able as cast in g m at erial fo r p ro d u ct io n d ies. Th e resid u al m at t er left o ver fro m t h e vap o risat io n o f t h e p at t ern im p airs t h e fin ish o f t h e su rface q u alit y o f t h e d ie o n ly t o a m in im al d egree. Ho wever, in o rd er t o en su re t h at t h e o p erat in g su rface o f t h e d ie can h ave t h e best su rface q u alit y, t h is su rface is p laced face d o wn in t h e cast in g bo x. Th e m ain t en an ce o f t h e p at t ern d u rin g fabricat io n p re- sen t s n o p ro blem s – wit h a sp ecific weigh t o f 20 kg m 3 , even large p o ly- st yren e p at t ern s can be t ran sp o rt ed wit h o u t h avin g t o u se large cran es. Co m p ared t o co n ven t io n al p rep arat io n m et h o d s su ch as weld in g, cast - in g t ech n iq u es h ave t h e fo llo win g ad van t ages: 147 Principles of die manufacture Fig. 4.1.18 Polystyrene pattern of a die Metal Forming Handbook Schuler c Springer-Verlag Berlin Heidelberg 1998 – abilit y t o wo rk wit h co m p licat ed co m p o n en t s wit h sm all m an u fac- t u rin g t o leran ces, – bet t er d ist ribu t io n o f fo rces in t h e cast p iece via cu rvat u res an d sm o o t h blen d in g o f su rfaces, – better d am p in g ch aracteristics of cast iron com p ared to steel p late con - stru ction ; as a resu lt, q u iet an d low vibration p roven com p on en ts th at can be h igh ly stressed an d p rovid e low n oise level in p rod u ction , – less t en d en cy t o d ist o rt io n wit h cast iro n , wh ich en su res t h at a h igh level o f p recisio n is d elivered fro m t h e p ro d u ct io n syst em , – go o d wear an d slid in g ch aract erist ics, – d ie m at erials t h at can be h ard en ed ; t h u s, t h e cast co m p o n en t can fu llfill vario u s fu n ct io n al req u irem en t s wit h o u t an y ad d it io n al at - t ach m en t s, – o il-t igh t co n t ain ers, et c., – n o co rn ers an d cracks in t h e seam s, wh ich can lead t o abso rp t io n o f m o ist u re an d co rro sio n , – go o d m ach in abilit y, t h ro u gh wh ich savin gs in t h e o rd er o f 20 t o 50 o n m ach in in g co st s can be ach ieved , – as a ru le, n o st ress-relievin g p ro cess is n ecessary.

4.1.5 Try-out equipment