Abstract: JFE JFE SA440. TiN B FL. 100 mm

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1 JFE No p 44 High Tensile Strength Steel Plates and Welding onsumables for Architectural onstruction with Excellent Toughness in Welded Joints JFE EWEL Technology for Excellent Quality in Large Heat Input Welded Joints KIM SU KI JFE JFE JFE JFE EWEL 590 N/mm 2 SA440 EWELG TiN BN a B FL mm SA440 Abstract: The JFE EWEL technology for improving the toughness of heat affected zone () effected by large heat input welding has been applied to make SA440 high strength steel plates for architectural constructions. The developed JFE EWEL technology consists of minimizing the coarse grain region through controlling TiN particles, refi ning the microstructure of by using BN and a inclusions as nucleation sites of intra-granular ferrites and decreasing carbon equivalent (eq ) of steel. Furthermore, welding consumables have been newly developed to control the microstructure of through diffusive B atoms from weld metal to base material. The developed mm thick SA440 grade steel plate exhibits excellent toughness in welded joints produced by and ESW with large heat inputs. onsequently, JFE Steel has various kinds of high strength steel plate and welding consumable for architectural construction with excellent toughness in welded joint. 1. 1) 2) 3) - 3,4) 40 mm ESW HA JFE 5,6) 440 N/mm 2 38

2 590 N/mm N/mm N/mm 2 JFE EWEL 590 N/mm 2 SA440-E ESW Table 1 Aimed properties of steel ptates and welded joints Grade HBL325-E HBL355-E HBL385-E SA440-E YP (MPa) * Test piece : JIS No.4 TS (MPa) Base material YR (%) El* (%) VEV Welded joint VEV ESW 60 kj/mmesw kj/mm ESW Fig. 1 H γ γ/α γ γ M-A eqe 2.2 Table 1 Weld metal () Base material (BM) Heat affected zone () oarse grain (Low toughness) Fine grain (High toughness) Upper bainite Ferrite side plate Fig. 1 Schematic illustration of microstructure in large heat input welded joint BM HBL325HBL355HBL385 SA440 ESW FL 0 VE V 0 7) 70 J -E JFE EWEL JFE EWEL JFE EWEL Fig. 2 γ 2 3 B γ Gγ 5,6,8 12) TiN γ ontrol of grain size in Pinning by optimized TiN Low eq alloying design ontrol of microstructure in grain Fusion line microstructure controlling by welded metal High cooling rate by Super-OLA Optimize of heat treatment (SA440-E) AR control Microalloying technology B atom diffusion from to FL Fig. 2 oncepts of JFE EWEL technology for improving toughness of welded joints with large heat input welding 39

Thermo-alc TiN Ti/N TiN 1 400 1 450TiN γ 1 4001 200 80 s γ Photo 1 γ γ 200 µm G 3.3 eqe 0.34 0.44 60 mm kj/mm ESW 1 40080 500 t8008 5001 000 s eqe Fig.

45 eq (mass%) 500 µm Advanced TiN steel Photo 1 Microstructures of synthetic of conventional and advanced TiN steels made by heating to 1 400 followed by quenching Fig.

40 BN a γ/α 8) BN N a a OS a ARatom concentration ratio 13 3.

3 Thermo-alc TiN Ti/N TiN TiN γ s γ Photo 1 γ γ 200 µm G 3.3 eqe mm kj/mm ESW t s eqe Fig. 3 eqe UB eqe U B Hardness, HV Synthetic toughness V T rs ( ) onventional steel Ferrite pearlite (F P) Ferrite upper bainite (F UB) Upper bainite (UB) eq (mass%) 500 µm Advanced TiN steel Photo 1 Microstructures of synthetic of conventional and advanced TiN steels made by heating to followed by quenching Fig. 3 Effect of microstructure on synthetic toughness and hardness (Reheating cycle: 1 400, t : s) 0.5 P M-A 5 eqe HBL325 F P eqe 0.35 HBL385 SA440 F B eqe 0.40 BN a γ/α 8) BN N a a OS a ARatom concentration ratio γ eqe AR HBL325-E SA440-E t s Photo 2 VE V 0 HBL325 F PSA440 F B VEV J 173 J eqe H HBL385 Super-OLAon-line - accelerated cooling TMPthermo-mechanical proces 14) γ α 2 Reheating temperature : 1 400, t : s (a) V E J HV135 (b) V E J HV µm Photo 2 Synthetic toughness (V( VE E0) and microstructures of the developed steels, (a) HBL325 grade and (b) SA440 grade JFE No

Fusion line oarse grain BN γ interior /Fine acicular ferrite High B bearing TiN dissolution Free N increse 3.5 B TiN G 1 450 FL TiN B G 15) Fig.

4 Schematic illustration for behavior of TiN dissolution and B diffusion from high B bearing during large heat input welding Developed welding consumables (B free)

ferrite Fig. 5 γ ESW 20 50 Acicular ferrite or bainitic ferrite onventional Developed Fig.

4 Fusion line oarse grain BN γ interior /Fine acicular ferrite High B bearing TiN dissolution Free N increse 3.5 B TiN G FL TiN B G 15) Fig. 4 FL G TiN B 8) TiN FL N B N BN N BN eqe B diffusion BN formation Temperature ( ) 0.34 mass 60 mm HBL325-E kj/mm ESW Photo 3 B FL G Fig. 4 Schematic illustration for behavior of TiN dissolution and B diffusion from high B bearing during large heat input welding Developed welding consumables (B free) Developed welding consumables (High B) FL FL µm Photo 3 Microstructure of in welded joints made by using conventional and developed welding consumables ESW Grain boundary ferrite Fig. 5 γ ESW Acicular ferrite or bainitic ferrite onventional Developed Fig. 5 Schematic illustration of microstructure for improving toughness of large heat input welded joint JFE EWEL ESW 5. SA440-E JFE EWEL ESW HBL325-E355-E 385-E 5,6 SA440-E 5.1 Table mass Ni eqe 0.40 mass TiN AR 60 mm mm γ α 2 γ grain boundary /Restraining ferrite grain growth 41 JFE No

Table 2 hemical compositions of developed steel plates, SA440-E Thickness (mm) Si Mn P S t 60 60 t 0.08 0.22 1.58 0.002 0.001 0.08 0.21 1.53 0.008 0.

22 Table 3 Mechanical properties of developed steel plates, SA440-E Thickness (mm) Position Direction Tensile properties harpy impact test Reduction of area obtained YP TS YR El by Z-direction test

5 Table 2 hemical compositions of developed steel plates, SA440-E Thickness (mm) Si Mn P S t t Others * eq (WES) Si/24 Mn/6 Ni/40 r/5 Mo/4 V/14 ** P M Si/30 Mn/20 u/20 Ni/60 r/20 Mo/15 V/10 5B eq (WES)* u, Ni, Ti, etc u, Ni, Ti, etc (mass%) P M ** Table 3 Mechanical properties of developed steel plates, SA440-E Thickness (mm) Position Direction Tensile properties harpy impact test Reduction of area obtained YP TS YR El by Z-direction test (N/mm 2 ) (N/mm 2 Position Direction VEV 0 ) (%) (%) (%) Target (Each 15) Developed thick plates (73, 72, 70) 62 (64, 61, 60) mmt- 5.2 Table 3 60 mm mm mm Photo 4 γ α 2 mm µm 60 mm ESW 25 µm Photo 4 Typical microstructures of developed thick plates Table 4 63 kj/mm 2 1 ESW kj/mm ESW FL Photo 5 G γ ESW Photo 6 F B FL G AR B ESW FL 3 mm Table 5 ESW 0 FL 70 J Table 4 Welding conditions for evaluation of welded joint toughness Welding method Electrode (Diameter) Flux urrent (A) Voltage (V) Speed (mm/min) Heat input (kj/mm) Pass Groove shape Plate Thickness (mm) (Tandem electrode) L T KW-55 (φ6.4 mm) KB-55I AD Y shape 60 ESW KW-60 AD (φ1.6 mm) KF- AD : 60 : 60 JFE No

Table 6 Results of tensile test for welded joints Welded joint type TS (N/mm 2 ) Fracture position Illustration of tensile

JASS 6) 658 of diaphragm side 50 R 50 Skin plate ESW O 2 60 150 6 6 Beam flange 25 6 6 50 unit : mm (a) Flange Web (c) Table 5

surface harpy absorbed energy, V E V 0 247* 123* FL 165 132 95 (b) (d) ESW side 2 mm from surface 185* 210* 92 98 78 * 3 mm

6 Table 6 Results of tensile test for welded joints Welded joint type TS (N/mm 2 ) Fracture position Illustration of tensile test specimen welded joint (according to JASS 6) R columnbeam flange crossshaped welded joint (according to JASS 6) 658 of diaphragm side 50 R 50 Skin plate ESW O Beam flange unit : mm (a) Flange Web (c) Table 5 Results of V-notch harpy impact test of welded joints Joint type Position Web side Flange side Notchaa position 2 mm from surface harpy absorbed energy, V E V 0 247* 123* FL (b) (d) ESW side 2 mm from surface 185* 210* * 3 mm from fusion line FL : Fusion line µm Photo 5 Macrostructures of (a), (b) ESW welded joints and microstructures of (c), and (d) ESW welded joints FL 50 mm ESW kj/mm O2 ESW Table 4 Table N/mm N/mm N/mm 2 6. Observed position Photo 6 Microstructure of ESW welded joint µm 60 mm ESW JFE EWEL SA440-E ESW JFE 490 N/mm N/mm 2 ESW Table 78 JFE 43 JFE No

Table 9 List of JFE Steel s steel plates for architectural construction TMP HBL352B, 325 HBL355B, 355 JIS (JIS G 3136) SN400A, 400B, 400 SN490B, 490 550 N/mm 2 TMP 590 N/mm 2 HBL385B, 385 SA440B,

strength steel plates with excellent toughness for large heat input weld joints 490 N/mm 2 520 N/mm 2 550 N/mm 2 590 N/mm 2 SN490TM-E HBL325-E HBL355-E HBL385-E SA440-E JIS G 3136, 19 40 mm, 40.

1 mm 19 mm 19 mm Table 8 List of welding consumables with excellent toughness for large heat input weld joints JIS 490 520 N/mm 2 KW-55 Z 3351 YS-M1 550 590 N/mm 2 KW-101B KW-55 Z 3351 YS-NM1 Z

7 Table 9 List of JFE Steel s steel plates for architectural construction TMP HBL352B, 325 HBL355B, 355 JIS (JIS G 3136) SN400A, 400B, 400 SN490B, N/mm 2 TMP 590 N/mm 2 HBL385B, 385 SA440B, 440 SA440B-U, 440-U JFE-LY JFE-LY160 JFE-LY225 SN400B-FR, 400-FR SM400B-FR, 400-FR SN490B-FR, 490-FR SM490B-FR, 490-FR HBL325B-FR, 325-FR SM520B-FR HBL355B-FR, 355-FR Table 7 List of high strength steel plates with excellent toughness for large heat input weld joints 490 N/mm N/mm N/mm N/mm 2 SN490TM-E HBL325-E HBL355-E HBL385-E SA440-E JIS G 3136, mm, 40.1 mm,,, 40.1 mm 19 mm 19 mm Table 8 List of welding consumables with excellent toughness for large heat input weld joints JIS N/mm 2 KW-55 Z 3351 YS-M N/mm 2 KW-101B KW-55 Z 3351 YS-NM1 Z 3351 YS-M1 KB-55I AD KB-60I AD JIS Z 3352 FS-BT1 Z 3352 FS-BT1 3 AMP-ISIJ STRUTE 5 vol. 34no no vol. 43no vol. 63no p AMP-ISIJvol p vol. 65no vol p N no vol p 109. ESW N/mm 2 KW-60AD Z 3353 YES 62 KF- KF-AD Z 3353 FS-FG3 Table no

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