VIDAR SUPREME Hot work tool steel

Transcription

1 VIDAR SUPREME Hot work tool steel This information is based on our present state of knowledge and is intended to provide general notes on our products and their uses. It should not therefore be construed as a warranty of specific properties of the products described or a warranty for fitness for a particular purpose.

2 VIDARSUPREME General Vidar Supreme is a chromium-molybdenumvanadium alloyed hot work tool steel which is characterized by: High level of resistance to thermal shock and thermal fatigue Good high-temperature strength Excellent toughness and ductility in all directions Uniform and high level of machinability Excellent through-hardening properties Good dimensional stability during hardening. Typical C Si Mn Cr Mo V analysis % 0,38 1,0 0,4 5,0 1,3 0,4 Standard AISI H11, B H11, W.-Nr , specification AFNOR Z38 CDV 5, UNI X37 CrMoV 51 KU, UNE X37 CrMoV 5 Delivery condition Soft annealed to approx.180 HB Colour code Orange/red TOOLS FOR HOT PRESSING Austenitizing Material temperature (approx.) HRC Aluminium, magnesium 1000 C (1832 F) Copper alloys 1000 C (1832 F) Steel 1000 C (1832 F) 50 OTHER APPLICATIONS Austenitizing Application temperature (approx.) HRC Severe cold 1000 C (1832 F) punching, Tempering: scarp shears 250 C (482 F) Shrink rings 1000 C (1832 F) (e.g. for cemented Tempering: carbide dies) C ( F) Wear-resisting 1000 C (1832 F) Core parts Tempering: C (1067 F) Surface + Nitriding ~ 1000 HV0,2 IMPROVED TOOLING PERFORMANCE The name Supreme implies that by special processing techniques and close process control, the steel attains high purity and a very fine structure. Further, Vidar Supreme shows significant improvements in isotropic properties compared to conventionally produced material of the X38 CrMo V 51 (W.-Nr ) type. These improved isotropic properties are particularly valuable for tooling subjected to high mech-anical and thermal stresses, e.g. die casting dies and forging tools. In practical terms, tools may be used at somewhat higher working hardnesses (2 HRC) without loss of toughness. Since increased service hardness limits the formation of heat checking cracks, improved tool performance can be expected. Applications TOOLS FOR DIE CASTING Aluminium-, Tin, lead, Magnesium zinc alloys alloys Part HRC HRC Dies Fixed inserts, cores Sprue parts (ORVAR) (ORVAR) Nozzles (ORVAR) (ORVAR) Ejector pins (nitrided) (ORVAR) (ORVAR) Plunger, shot-sleeve (normally nitrided) (ORVAR) (ORVAR) Austenitizing 990 C 1000 C temperature (1814 F) (1832 F) 2

3 VIDAR SUPREME Properties PHYSICAL DATA All specimens are taken from the centre of a 500 x 110 mm (19,7" x 4,3") bar. Unless otherwise is indicated all specimens were hardened from 1000 C (1832 F), quenched in air and tempered 2 + 2h at 610 C (11 F). The hardness were 45 ±1 HRC. Temperature 20 C 0 C 600 C (68 F) (750 F) (1010 F) Density, kg/m lbs/in 3 0,281 0,277 0,274 Modulus of elasticity MPa psi,5 x ,1 x ,3 x 10 6 Coefficient of thermal expansion per C from 20 C 12,6 x ,2 x 10 6 per F from 68 F 7,0 x ,3 x 10 6 Thermal conductivity W/m C Btu in/(ft 2 h F) Effect of time at high temperatures on hardness Hardness, HRC Effect of testing temperatures on impact energy Charpy V specimens, short transverse direction. ft. lbs Impact energy, J 650 C (1202 F) 500 C (932 F) 550 C (1022 F) 600 C (1112 F) Time, h MECHANICAL PROPERTIES Approximate tensile strength at room temperature. Hardness 44 HRC Tensile strength, Rm 1410 MPa 144 kp/mm HRC Yield strength, Rp0, MPa 119 kp/mm 2 Elongation, A5 12% Reduction in area, Z 50% Approximate strength at elevated temperatures Longitudinal direction C F Testing temperature psi Rm, Rp x MPa Z Rm Rp0, A C A5, Z % F Testing temperature 3

4 VIDARSUPREME Heat treatment SOFT ANNEALING Protect the steel and heat through to 850 C (1562 F). Then cool in furnace at 10 C (20 F) per hour to 650 C (1202 F), then freely in air. STRESS RELIEVING After rough machining the tool should be heated through to 650 C (1202 F), holding time 2 hours. Cool slowly to 500 C (932 F), then freely in air. HARDENING Preheating temperature: C ( F) (normally two preheating steps). Austenitizing temperature: C ( F), normally C ( F). Soaking time: 45 minutes. Soaking time = time at austenitizing temperature after the tool is fully heated through. Protect the tool against decarburization and oxidation during austenitizing. QUENCHING MEDIA High speed gas/circulating atmosphere. Vacuum (high speed gas with sufficient positive pressure). Martempering bath (salt or fluidized bed) at C ( F). Martempering bath (salt or fluidized bed) at C ( F). Warm oil. Note 1: Temper the tool as soon as its temperature reaches C ( F). Note 2: In order to obtain the optimum properties for the tool, the cooling rate should be fast, but not at a level that gives excessive distortion or cracks. CCT graph Austenitizing temperature1000 C (1832 F). Holding time minutes. F C Austenitizing temperature 1000 C (1832 F) Holding time min Carbides Pearlite A c 3 = 915 C (1680 F) A c1 = 850 C (1562 F) Cooling Hardcurve ness T No. HV 10 (sec) M s M f Martensite Bainite Seconds Minutes Hours 0,2 1, ,0079 0,059 0,394 3,54 23,6 Air cooling of bars, Ø mm inch 4

5 VIDAR SUPREME Hardness, grain size and retained austenite as a function of austenitizing temperature Grain size ASTM Hardness, HRC Hardness Grain size Retained austenite C F Austenitizing temperature Tempering graph Air cooling of specimen 15 x 15 x mm (0,6" x 0,6" x 1,6") Hardness, HRC Retained austenite % Austenitizing temperature 1000 C (1832 F) Retained austenite Retained austenite % TEMPERING Choose the tempering temperature according to the hardness required by reference to the tempering graph below. Temper twice with intermediate cooling to room temperature. Lowest tempering temperature 180 C (356 F). Holding time at temperature minimum 2 hours. To avoid brittleness do not temper in the range C ( F) C F Tempering temperature (2 + 2h) Approximate impact strength at different tempering temperatures. Charpy V specimens, short transverse direction. ft.lb Impact strength - KV Joule C F Tempering temperature (2h + 2h) Tempering within the range C ( F) is normally not recommended due to impaired toughness. DIMENSIONAL CHANGES DURING HARDENING AND TEMPERING During hardening and tempering the die is exposed to thermal as well as transformation stresses. This will inevitably result in dimensional changes and in the work case distortion. It is therefore recommended to always leave a machining allowance after machining before the die is hardened and tempered. Normally the size in the largest direction will shrink and the size in the smallest direction might increase but this is also a matter of the die size, the die design as well as the cooling rate after hardening. For Vidar Supreme it is recommended to leave a machining allowance of 0,2 per cent of the dimension in length, width and thickness. NITRIDING AND NITROCARBURIZING Nitriding and nitrocarburizing result in a hard surface layer which is very resistant to wear and erosion. The nitrided layer is, however, brittle and my crack or spall when exposed to mechanical or thermal shock, the risk increasing with layer thickness. Before nitriding, the tool should be hardened and tempered at a temperature at least 50 C (120 F) above the nitriding temperature. Nitriding in ammonia gas at 510 C (950 F) or plasma nitriding in a 75% hydrogen/25% nitrogen at 480 C (896 F) both result in a surface hardness of 1100 HV 0,2. In general, plasma nitriding is the preferred method because of better control over nitrogen potential; in particular, formation of the 5

6 VIDARSUPREME so-called white layer, which is not recommended of hot-work service, can readily be avoided. However, careful gas nitriding can give perfectly acceptable results. Vidar Supreme can also be nitrocarburized in either gas or salt bath. The surface hardness after nitrocarburizing is HV0,2. DEPTH OF NITRIDING Depth Process Time mm inch Gas nitriding 10 h 0,12 0,0047 at 510 C (950 F) h 0,20 0,0079 Plasma nitriding 10 h 0,14 0,0055 at 480 C (895 F) h 0,19 0,0075 Nitrocarburizing in gas at 580 C (1075 F) 2,5 h 0,12 0,0047 in salt bath at 580 C (1075 F) 1 h 0,07 0,0028 * Depth of case = distance from surface where hardness is 50 HV 0,2 over base hardness. Nitriding to case depths >0,3 mm (0,012") is not recommended for hot-work applications. Vidar Supreme can also be nitrided in the soft annealed condition. The hardness and depth of case will, however, be reduced somewhat in this case. Cutting data recommendations The cutting data below are to be considered as guide values which must be adapted to existing local conditions. More information can be found in the Uddeholm publication Cutting data recommendation. TURNING Turning with Turning carbide with high Cutting data speed steel parameters Rough turning Fine turning Fine turning Cutting speed (v c ) m/min f.p.m Feed (f) mm/rev. 0,2 0,4 0,05 0,2 0,05 0,3 i.p.r. 0,008 0,016 0,002 0,008 0,002 0,01 Depth of cut (a p ) mm 2 4 0,5 2 0,5 3 inch 0,08 0,16 0,02 0,08 0,02 0,1 Carbide designation ISO P20 P P10 Coated carbide Coated carbide or cermet MILLING Face- and square shoulder milling Milling with carbide Cutting data parameters Rough milling Fine milling Cutting speed (v c ) m/min f.p.m Feed (f z ) mm/tooth 0,2 0,4 0,1 0,2 inch/tooth 0,008 0,016 0,004 0,008 Depth of cut (a p ) mm 2 4 0,5 2 inch 0,08 0,16 0,02 0,08 Carbide designation ISO P20 P P10 P20 Coated Coated carbide carbide or cermet End milling Type of milling Carbide Cutting data Solid indexable High parameters carbide insert speed steel Cutting speed (v c ) m/min ) f.p.m ) Feed (f z ) mm/tooth 0,01 0,2 2) 0,06 0,2 2) 0,01 0,3 2) inch/tooth 0,0004 0,008 2) 0,0024 0,008 2) 0,0004 0,01 2) Carbide designation ISO P20 P 1) For coated HSS end mill v c = m/min. ( f.p.m.). 2) Depending on radial depth of cut and cutter diameter. DRILLING High speed steel twist drill Drill diameter Cutting Feed (f) speed (v c ) mm inch m/min f.p.m. mm/rev. i.p.r. 5 3/ * 52 59* 0,05 0,15 0,002 0, /16 3/ * 52 59* 0,15 0,20 0,006 0, /8 5/ * 52 59* 0,20 0,25 0,008 0, /8 3/ * 52 59* 0,25 0,35 0,010 0,014 1) For coated HSS drill v c = 28 m/min. ( f.p.m.). Carbide drill Type of drill Cutting data Indexable Solid Brazed parameters insert carbide carbide 1) Cutting speed (v c ) m/min f.p.m Feed (f) mm/rev. 0,03 0,10 2) 0,10 0,25 2) 0,15 0,25 2) i.p.r. 0,001 0,004 2) 0,004 0,01 2) 0,006 0,01 2) 1) Drill with internal cooling channels and brazed carbide tip. 2) Depending on drill diameter. 6

7 VIDAR SUPREME GRINDING A general grinding wheel recommendation is given below. More information can be found in the Uddeholm publication Grinding of Tool Steel. Wheel recommendation Soft annealed Hardened Type of grinding condition condition Face grinding straight wheel A 46 HV A 46 GV Face grinding segments A 24 GV A 36 GV Cylindrical grinding A 46 LV A 60 JV Internal grinding A 46 JV A 60 KV Profile grinding A 100 LV A 120 JV Electrical-discharge machining If spark-erosion is performed in the hardened and tempered condition, the white re-cast layer should be removed mechanically e.g. by grinding or stoning. The tool should then be given an additional temper at approx. 25 C (50 F) below the previous tempering temperature. Welding Welding of tool steel can be performed with good results if proper precautions are taken regarding elevated temperature, joint preparation, choice of consumables and welding procedure. Welding method TIG MMA Working C C temperature ( F) ( F) QRO 90 Filler metals TIG-WELD QRO 90 WELD Hardness after welding HRC HRC Heat treatment after welding Hardened Temper at 25 C (50 F) below the condition original tempering temperature. Soft annealed Soft-anneal the material at 850 C condition (1560 F) in protected atmosphere. Then cool in the furnace at 10 C (20 F) per hour to 650 C (1200 F) then freely in air. More detailed information can be found in the Uddeholm brochure Welding of tool steel. A die casting die in Vidar Supreme. 7

8 VIDARSUPREME Hard-chromium plating After plating, parts should be tempered at 180 C (360 F) for 4 hours to avoid the risk of hydrogen embrittlement. Photo-etching Vidar Supreme is particularly suitable for texturing by the photo-etching method. Its high level of homogeneity and low sulphur content ensures accurate and consistent pattern reproduction. Polishing Vidar Supreme exhibits good polishability in the hardened and tempered condition. Polishing after grinding can be effected using aluminium oxide or diamond paste. Typical procedure: 1. Rough grinding to grain size using a wheel or stone. 2. Fine grinding with abrasive paper or powder down to grain size. 3. Polish with diamond paste grade 15 (15µm grain size) using a polishing tool of soft wood or fibre. 4. Polish with diamond paste (8 6 3µm grain size) using a polishing tool of soft wood or fibre. 5. When demands on surface finish are high, grade 1 (1µm grain size) diamond paste can be used for final polishing with a fibre polishing pad. Further information Please contact your local Uddeholm office for further information on the selection, heat treatment, application and availability of Uddeholm tool steels. 8

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