presentazione orale al TMS 2008 Annual Meeting & Exhibition (TMS2008), New Orleans, LA, USA, 9/3/2008 - 13/3/200

CHIARBONELLO M.

FABBRESCHI M.

FIRRAO D.

GEROSA R.

GHIDINI A.

IENCO M.G.

MATTEIS P.

MISSORI S.

MONTANARI R.

MORTARINO G.M.M.

PINASCO M.R.

RIVOLTA B.

RUSSO SPENA P.

SILVA G.

TATA M.

English

FIRRAO, Donato

MATTEIS, PAOLO

RUSSO SPENA, PASQUALE

MORTARINO, GIOVANNI MARCO MARIA

CHIARBONELLO, MAURIZIO

PINASCO M. R.

IENCO M. G.

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

05 August 2020POLITECNICO DI TORINORepository ISTITUZIONALEEffects of microalloying on an innovative quenched and tempered plastic mold steel / FIRRAO D.; MATTEIS P.; RUSSOSPENA P.; MORTARINO G.M.M.; CHIARBONELLO M.; PINASCO M.R.; IENCO M.G.; FABBRESCHI M.; SILVA G.;RIVOLTA B.; GEROSA R.; TATA M.; MISSORI S.; MONTANARI R.; GHIDINI A.. - (2008).OriginalEffects of microalloying on an innovative quenched and tempered plastic mold steelPublisher:PublishedDOI:Terms of use:openAccessPublisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/1854510 since:2008 TMS Annual Meeting & Exhibition Characterization of Minerals, Metals and Materials Effects of Microalloying on an Innovative Quenched and Tempered Plastic Mold SteelDonato Firrao & al. – Politecnico di TorinoMaria Rosa Pinasco & al. – Università di GenovaGiuseppe Silva & al. – Politecnico di Milano, Polo Regionale di LeccoRoberto Montanari & al. – Università degli studi di Roma Tor VergataAndrea Ghidini – Lucchini Sidermeccanica S.p.A.Speaker: Gerosa Riccardo - Politecnico di Milano, Polo Regionale di LeccoMAIN AIMS Two innovative steels for plastic molds wereconsidered and many different investigationssuch as hardenability, tensile, impact, fracturetoughness and rotating bending fatigue tests wereperformed; the prior austenitic grain growth wasinvestigated too. Mereover some weldability tests were performedon one of the new steels and on the most commonplastic molds steel, i.e. the ISO 1.2738.MATERIALS (1) One of the most common and studied steels for plastic moldsis the ISO 1.2738 and so in this work it will be considered asthe reference steel. All the ISO 1.2738 data refer to aprevious experimental investigation performed by the sameauthors. New generation steels were proposed aiming to preserve thegood mechanical properties of ISO 1.2738 increasing thefracture toughness and the weldability.C% Cr% Mn% Ni% Mo% Si% S% P%0.35 1.80 1.30 0.90 0.15 0.20 <0.03 <0.030.45 2.10 1.60 1.20 0.25 0.40C Mn Cr Ni Mo Si V Nb Zr B0.2 1.3 1.2 0.9 0.4 0.1 0.10 0.01 0.02 0.0010.3 1.6 1.5 1.2 0.7 0.4 0.14 0.03 0.04 0.0020.2 1.3 1.2 0.9 0.4 0.1 0.10 / / /0.3 1.6 1.5 1.2 0.7 0.4 0.14 / / /Steel ASteel BMATERIALS (2) ISO 1.2738 and Steel A were heavy sized blooms(about 1.3m x 1.2m x 2.7m for the ISO 1.2738and 1.2m x 1.0m x 2.9m for the Steel A ), whilethe Steel B had smaller dimensions (about350mm x 300mm x 1000mm). The materials were delivered after the commonindustrial thermo-mechanical process: forging,dehydrogenation treatment, quench andtempering. All the materials were investigated at differentdepths from the surface to the core.444648505254560 10 20 30 40 50 60 70Distance from the quenched surface [mm]HRCSteel ASteel ASteel BSteel BHardenability - Jominy test Hardenability tests were carried out on Steels A and B inorder to investigate the effect of microalloying elements.01234560 10 20 30 40 50 60 70Distance from the quenched surface [mm]DHRCSteel ASteel BMicrostructure The microstrucure was investigated for both Steels Aand B and it was compared with the ISO 1.2738 one. In the superficial layers we found tempered martensite,while in the core bainitic structures were observed. In a previous investigation mixed microstructures ofbainite and pearlite were found in ISO 1.2738.Steel A - Core ISO 1.2738 - Core05101520250 0.5 1 3 6time [h]d [mm]Steel B - CoreSteel B - SurfaceAustenitic grain size05101520250 0.5 1 3 6time [h]d [mm]Steel A - CoreSteel A - Surface The austenitic grain size and growth rate were investigated on SteelsA and B. The austenitization temperature was T=890°C.The soaking times were 0.5,1, 3, 6 hours.0102030405060510 255 0Distance from the Surface [mm][%]A% Z%Tensile tests – Steel APrevious investigations onISO 1.2738 showed averagevalues of 1000 MPa for theUTS and 800 MPa for theyield stress.02004006008001000120014001600510 255 0Distance from the Surface [mm][MPa]UTS [MPa]Rp0.2 [MPa]Tensile tests – Steel B0102030405060152 0Distance from the Surface [mm][%]A% Z%02004006008001000120014001600152 0Distance from the Surface [mm][MPa]UTS [MPa]Rp0.2 [MPa]01020304050607080901000 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375T[C°]KV [J]Steel A - SurfaceSteel A - CoreSteel B - SurfaceSteel B - Core02550751000 25 50 75 100 125 150 175 200 225 250 275 300 325 350 375T[°C]Shear [%]Steel A - SurfaceSteel A - CoreSteel B - SurfaceSteel B - CoreMaterial Position FATT [°C]Steel A Surface 150Steel A Core 260Steel B Surface 130Steel B Core 190Impact TestsPrevious investigations onISO 1.2738 showed FATTincluded between 150°C and270°C depending onsampling position.Rotating Bending Fatigue• The tests were carried out according to the StaircaseMethod.• Steels A and B (both in surface position) wereinvestigated finding a fatigue limit equal to 627 MPafor Steel A and 652 MPa for Steel B (both with 50%probability of failure)• Previous investigations on ISO 1.2738 steel (insurface position) resulted in a much lower fatigue limitequal to 550 MPa.0102030405060708090100150 0Distance from the Surface [mm]Kq [MPam0.5]Steel BFracture Toughness01020304050510 255 0Distance from the Surface [mm]Kq [MPam0.5]Steel APrevious investigations onISO 1.2738 showed Kqincluded between 35MPam0.5and 45MPam0.5 depending onsampling position.SENB3 samples were usedB=35mm W=70mm L=160mmThe tests were carried outaccording to ASTM E399-06.Fracture ToughnessSteel A – Core sampleSteel B – Core sampleWeldability Tests• Weldability test were carried out on ISO 1.2738 and Steel A (both incore position) in order to compare the old material with the new one.• The welding tests were performed on one half of the broken fracturetoughness samples (35mm x 70mm x 150mm) by GTAW techniquewithout welding metal.• Four weldings wereperformed (one for eachsurface of the sample) varyingthe applied current.• HV 0.1 microhardness testswere carried out starting fromthe melted zone, through theHAZ (that is the mostinteresting region) till theparent metal.Material I (A) U (V)Steel ASide 1 150 12.0Side 2 200 12.7Side 3 250 15.0Side 4 300 15.5ISO 1.2738Side 1 150 14.5Side 2 200 14.0Side 3 250 15.0Side 4 300 17.0Steel A – I = 200 AISO1.2738 – I = 200 AWeldability Tests – Some picturesSteel A – I = 300 AISO1.2738 – I = 300 AWHThe HAZ thickness (t)were measured alongthe H direction.Weldability Tests – ISO 1.27380246810121416100 150 200 250 300 350I [A][mm]HWt01002003004005006007008009000 1 2 3 4 5 6 7 8Distance from the centre of the melted zone [mm]HV0.1Side 1Side 2Side 3Side 40246810121416100 150 200 250 300 350I [A][mm]HWtWHThe HAZ thickness (t)were measured alongthe H direction.Weldability Tests – Steel A2002503003504004505005506006507000 1 2 3 4 5 6 7 8 9Distance from the centre of the melted zone [mm]HV0.1Side 1Side 2Side 3Side 4Concluding Remarks (1) Steels A and B hardenability is very close, even if theSteel A is slightly better. In both Steels A and B the microalloying elements(such as V, Nb, Zr) are very effective in controlling theprior austenitic grain growth. Steels A and B show very close tensile properties,generally higher than ISO 1.2738 ones. Steel B showed a better behaviour during the impacttests. The transition temperatures of both Steels A andB are comparable with the ISO 1.2738 ones.Concluding Remarks (2) Steel B showed a slighly better rotating bending fatiguelimit. Nevertheless both Steels A and B resulted inhigher values respect to ISO 1.2738. Steel B showed a fracture toughness remarkably higherthan Steel A, whose values are close to ISO 1.2738ones. The thickness probably influence the heattreatment effectiveness and so the fracture toughness. The weldability tests confirm the better behaviour ofthe new steel (Steel A) respect to ISO 1.2738.

Effects of microalloying on an innovative quenched and tempered plastic mold steel

https://iris.polito.it/retrieve/handle/11583/1854510/50416/TMS-2008-Mold-Steel.pdf

Effects of microalloying on an innovative quenched and tempered plastic mold steel

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