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Steels

1. STEELS 2. Classification of steels (EN 10020) Inclusions, % Non-alloy steels (carbon steels) Alloy steels Mn ≤ 1,65 > 1,8 Si ≤ 0,5 > 0,5 Cr ≤ 0,3 > 0,5…
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  • 1. STEELS
  • 2. Classification of steels (EN 10020) Inclusions, % Non-alloy steels (carbon steels) Alloy steels Mn ≤ 1,65 > 1,8 Si ≤ 0,5 > 0,5 Cr ≤ 0,3 > 0,5 Ni ≤ 0,3 > 0,5 Ti ≤ 0,05 > 0,12 V ≤ 0,1 > 0,12 Steels • Non-alloy steels (carbon steels) • Alloy steels
  • 3. Non-alloy and alloy steels classification (1) C content based Alloying degree based - low C-steels (<0,25%) - low alloy steels (<2,5%) - medium C-steels (0,3…0,6%) - medium alloy steels (<5%) - high C-steels (>0,6%) - high alloy steels (>5%) Alloying degree based - Cr steels - Mn steels - Cr-Ni steels etc. Non-alloy steels (carbon steels) Alloy steels Steels
  • 4. Non-alloy and alloy steels (2) Quality based (degree of purity): -ordinary quality - quality steels (≤ 0,035 S,P) - high quality steels (≤ 0,025 S,P) Deoxidation degree based - killed steels (Mn, ↑ Si) - semikilled steels (Mn, ↓ Si) - rimmed steels (Mn) Quality based: - quality steels - high quality steels Structure based: - in annealed condition - in normalized condition (ferrite, pearlite, martensite and austenitic steels) Non-alloy steels (carbon steels) Alloy steels Steels
  • 5. Non-alloy and alloy steels classification (3) Application based: C<0,7%C – structural steels – 0,2...0,7% C C>0,7%C – tool steels – 0,4...1,6% C Non-alloy steels (carbon steels) Alloy steels Steels • corrosion resistant • heat resistant • high temperature strength • magnetic • cryogenic
  • 6. Classification of structural steels Heat treatment based: - case hardening steels (≤ 0,25% C) - quenching and tempering steels (0,3…0,6% C) - nitriding and carbonitriding steels (0,1…0,2 or 0,3…0,4% C) Non-alloy steels (carbon steels) Alloy steels Steels
  • 7. Steels (EN10027) Designations (1) • Mechanical properties based on: Re – steels for steel constructions S355J0 – steels for pressure vessel P265B – steels for machine constructions E295 – steels for pipes L360QB – concrete reinforcing steel B500N • Based on: Rm – rail steels RO880Mn – prestressing steels Y1770C °C KU, J 27 40 60 +20 0 -20 -30 -40 -50 -60 JR J0 J2 J3 J4 J5 J6 KR K0 K2 K3 K4 K5 K6 LR L0 L2 L3 L4 L5 L6 Steels Designation of steels (1) Notch impact energy
  • 8. • Chemical composition based – C (non-alloy steels (carbon steels), ex free cutting steels C35E G-C35E (cast steel) 35 – C%x100 (E – max S-content) – C, alloying elements (low- ja medium alloy steels, all. elem., ≤5%, non-alloy steels (carbon steels) Mn ≥1%, non-alloy free cutting steels) 28Mn6 G-28Mn6 – C, all. elem. (high alloy steels, all. elem. >5%) X5CrNi18-10 – All. elem. (high speed steels) HS 12-9-1-8 W-Mo-V-Co Alloying element Factor Cr, Co, Mn, Si, Ni, W 4 Al, Cu, Mo, Nb, Ti, V, Zr 10 Ce, P, S 100 B 1000 Steels Designations (2)
  • 9. Materials numbers (EN 10027) Pos. 2 and 3 Ordinary grade steels 00...90 Tool steels 20...29 High quality grade Special steels 40...49 10 – spec. phyc. prop. steels (stainless and heat resistant. etc.) 11 – construction and machine construction steell 12 – machine contruct. steels 13 – spec. constr. and ja machine constr. steels High quality 01...91 – structural steels 02...92 – non heat treatable structural steels 07...97 – high P- ja S-cont. steels Pos. 4 ja 5 Order no. in class Steels Designations (3) Material group Steel class Order in class Additional numbers 1. XX (XX)XX
  • 10. Structural steels (1) Non-alloy structural steels (C = 0,2...0,65%) • ordinary (quality) steels • quality steels C15E (max S), C15R (S range) • high quality steels (S, P ≤ 0,025%) • Free cutting steels (C = 0,12...0,4%;  0,2% S) – 10S20, 35S20 • Cast steels (C = 0,15...0,55%) – GE250, G28Mn6 Steels
  • 11. Structural steels (2) Alloy structural steels (C = 0,2...0,7%, wear resistant steels 0,9...1,3%) • low alloy steels (all. elem.  2,5%) – structural steels – cold forming steels – spring steels (C = 0,5...0,7%, Si = 1...2%) – ball bearing steels (C ≈ 1%, Cr = 0,5...0,6%) • medium alloy steels (all. elem. 2,5...5%) – cementizing steels – quenching and tempering steels – nitriding steels • high alloy steels (leg. el. > 5%) – steels with specific properties – corrosion resistant steels – high temperature strength steels – wear resistant steels Steels
  • 12. Structural steels (3) Low alloy steels (1) Steels for structural construction Low alloy carbon steels C≤0,22%; 1...2% Si, Mn Requirements: • Cold brittleness: low TBCT, T50 high toughness ( impact energy KU, KV) • Weldability CE%=C%+Mn%/6+(Cr%+Mo%+V%)/5+(Ni%+Cu%)/15 CE≤0,40% - satisfactory weldability CE≥0,40% - special means: preheating, low annealing. Alloying principles: P,S TBCT Simultaneous alloying with V,NTBCT -80°C Steels
  • 13. Structural steels (4) Low alloy steels (2) Cold forming steels Requirements • low yield strength ratio (Rp0,2/Rm = 0,5...0,65) • high plasticity (A ≥ 40%) Principles of alloying: C and Si% Rp0,2  formability; Mn%  Rm, Rp0,2≈  good formability Preferred: – rimmed steels (Si ≈ 0%) – dual phase steels (F + 20...30% M or B) (C = 0,06...0,12%, partial-hardening  Rp0,2/Rm = 0,5)  good deep drawability at 10% degree of deformation Rp0,2/Rm = 0,8...0,9 • Ballon steels • Pressure vessel steels • Seamless pipes • Welded pipes Steels
  • 14. Structural steels (5) Low alloy steels (3) Spring steels high Re, σR, modulus of elasticity E C = 0,5...0,7% Mn-steels (1...2% Mn) Si-steels (2...3% Si) Cr-V-steels TT: Hardening + mid. temp. (300...400°C)  Trostite structure Ball bearing steels High hardness (≥ 62 HRC) C ≈ 1%; Cr = 0,6...1,5% – 105 Cr6 Ball races (63...64 HRC), balls (61...62 HRC) Steels
  • 15. Structural steels (6) Medium alloy steels (1) Cementizing (case hardening) steels (0,1...0,25% C) • Cr-steels • Cr-Mn-steels • Cr-Ni-steels • B-steels HT: Tcem + hard. + low. temp. Surface (C0,8) – 58...62 HRC Core (C = 0,1...0,25) – 30...42 HRC Steels
  • 16. Structural steels (7) Medium alloy steels (2) Quenching and tempering steels Requirements: • Reliability (↑ Rm, Rp0,2; acceptable KU and TBCT) • High hardenability (D50, D95, T50) Principles pf alloying: • Alloying →↑hardenability (↓Ma, Ml) (all exc. Al and Co) • At solution in F, ↑ Rm and TBCT, alloying degree as low as possible (for ↑D50) Steels
  • 17. Structural steels (8) Medium alloy steels (3) Quenching and tempering steels (0,3...0,5% C; 3...5% all.elem.) Rm 1200 N/mm2 ; Rp0,2  1100 N/mm2 ; A = 10...12%; KU40J D95, mm T50, °C I gr – non-alloy steels (carbon steels) 10...15 20 II gr – Si-Mn/Cr-steels (~1%) 20 -30...-50 III gr – Mn-Cr-steels 25 -60 IV gr – Ni-Mo-steels 40 -80 V gr – Ni-refractory. (W, Mo, V jt.) 100 -100 Steels
  • 18. Structural steels (9) Medium alloy steels (4) Nitriding steels (C-, all. elem. – same as in hard. and temp. steels) Tnitr 500...600°C (differently from cem.) All. elem. Cr, Mo, Al + N  CrN, MoN, AlN Properties: Hardness: surface – alloy steels 950...1150 HV, non-alloy steels (carbon steels) 400...500 HV Core 250...300 HB High fatigue strength ( by comp. stresses induced nitrides) Steels
  • 19. Structural steels (10) High alloy steels (1) Corrosion resistant steels (1) • Cr-steels, C – min (0,08...0,2%) 0,1...0,4% – for hardenability Cr = 13, 17 or 27% C↑→corrosion resistance ↓, C < 0,1 %C – ferritic steels For hardness/ wear resiatance → 0,1...0,4 %C – martensitic steels Steels
  • 20. Structural steels (11) High alloy steels (2) • Cr-Ni steels C ≤ 0,12% 18% Cr, 10...12% Ni, Ti/Nb ≤ 1% Rm = 500...600 N/mm2 Rp0,2 = 200...250 N/mm2 Intergranular corrosion (at to . 500...600 o C): C↑→corr. resist, , especially in welds  Cr3C2  Cr % reduction in A. To avoid:  Ti, Nb (0,1...0,2%)  C (<0,03%) Steels
  • 21. Structural steels (12) High alloy steels (3) High temperature strength steels High temperature strength = heat resiatance + high temp. strength Heat resistance = oxidation resistance High temp. strength: endurance limit σt T creep strength σε/t T 350...500°C – boiler steels 0,1...0,15% C, 0,5...1% Mo, W või V 0,5...1% Cr (pearlite steels) 2...6% Cr (martensite steels) - silchrome 0,5...0,6% C, 1,5...3% Si, 5...15% Cr 600...700°C – austenitic steels 13...25% Cr; 14...20% Ni 13...25% Cr; 37% Ni + Al, W, Nb, Ti, Mo > 700°C - Ni- ja Co-alloys (superalloys) 5 0 0 7 0 0 9 0 0 5 1 0 1 5 2 0 2 5 C r , % T , C k u u m u s p ü s i v m i t t e k u u m u s p ü s i v 1 1 0 0 Steels
  • 22. Structural steels (13) High alloy steels (4) Wear resistant steels Requirements: High surface hardness Principles of alloying: – through alloying (uneffective – 2...3% /Ø100mm) – surface alloying • Non-alloy- and alloy steels (Cr, Mn, W jt.) • Cementizing steels • Mn-steels (Hadfield steel) (1,1...1,3% C, 12...13% Mn) HT: H (1050...1100°C)  A-structure Rm=800...1000, Rp0,2=250...350 N/mm2 , A = 40...50%, 180...220 HB In cold worked conditions  50...55 HRC – self hardening Steels
  • 23. Tool steels (1) Requirements: • hardness and wear resistance • strength and toughness • heat resistance • Non-alloy tool steels (C = 0,7...1,3%) • Alloy steels (C = 0,4...1,6%) – non-heat resistant (200°C) – semi heat resistant (300...500°C) • coldwork tool steels • hot work tool steels – Heat resistant steels (500...750°C) • Carbide induced tempering hardness, • Intermetallics induced tempering hardness Steels
  • 24. Tool steels (2) Non heat resistant steels (200...250°C) • non-alloy tool steels (0,7...1,2% C) • low alloy steels (Cr, W, Mn) Semi heat resistant steels (300...500°C) • Cold work tool steels (150...200°C) Cr-steels (1,2...2,3% C; 12% Cr + Mo, V) Structure: M + 13...20% carbides C = 0,6...0,7 – cutting- ja impact tools • Hot work tool steels Requirements: • high temperature strength, • heat resistance ja thermal resistance • high hardenability and not prone to tempering brittleness • low adhesion Steels 0,5...0,6% C  good toughness 1,5...2% Ni, Mo  high hardenability Steels
  • 25. Tool steels (3) Heat resistant steels (500...750°C) • Steels with carbide induced tempering hardness (500...650°C) Alloying elements: W (18 or 9%) + Mo, V, Co • HS-18-0-1 • HS-6-5-2-5 (P6M5K5) HT: H (1200...1300°C); 3x T (570...650°C)  Arest ;  64...65 HRC • Steels with intermetallics induced tempering hardness (650...750°C) Alloying elements: Co, W, Mo  Co7W6; (Co,Fe)7W6 etc. (0,1...0,3% C, 20...25% Co, 11...20% W, ca 7% Mo) HT: Hard. (1200...1300°C)  68 HRC; T (700...720°C)  60 HRC Steels
  • 26. Special steels ja -alloys (1) Magnetic steels • Soft magnetic materials – pure Fe (C < 0,05%) – electrotechnical (1...4% Si) • Hard magnetic materials – High C-content Non-alloy tool steels (1,1...1,3% C) – Cr-steels (ca 1% C; 1,5...3% Cr) – Co-steels (ca 1% C; 1,5...3% Cr; 5...15% Co) – Fe-Ni-Al-alloys (alniko) (11...14% Al; 22...34% Ni) Steels
  • 27. Special steels ja -alloys (2) Cryogenic steels Requirements: • low transition temperature TBCT Steels for low temperature applications • ≤ –60°C (non-alloy- ja low alloy steel) • ≤ –100°C – low C-content Ni-steels – 2...5% Ni + Cr, V, Ti • ≤ –190°C (liquid N2) – austenitic stainless steels) • below –190°C (liquid H2, O2) – high alloy corrosion resistant steels – Cr > 10%; Ni > 20% Steels
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