Metallography

The BethStar 50 combination of microalloying and thermomechanical processing typically produces ferrite/pearlite microstructures with a fine ferritic grain size ranging from ASTM 10 to 12. A fine-grained duplex grain size, elongated ferrite grains, warm-worked ferrite, and occasional bainite/martensite patches may also be observed. The grain refinement results from the interaction between alloying and low-finish temperature control rolled processing. The columbium microalloying inhibits austenite recrystallization, and below a critical temperature, the rolling deformation becomes cumulative. As a result, a pancaked austenite grain morphology is obtained during rolling, which produces a very fine ferrite grain size after transformation. The microstructures shown in Figures 6 are representative of 3/8 in. (6A), 1 in. (6B) and 2 in. (6C) BethStar 50 plates. A fine, uniform ferrite grain size is the key to improved strength, toughness and formability for BethStar plate.


Representative microstructures of BethStar 50 plates at an original magnification of 200 X.

Welding Suggestions

BethStar 50 is readily weldable, and normally will require no preheat for temperatures above 0�F, provided low-hydrogen conditions can be maintained. When base metal temperature is below 32�F, the plate should be preheated to remove any moisture.

Consumables:
Manual-Shielded Metal-Arc Welding. Any low-hydrogen (EXXX15, 16 or 18) electrode of the E70 strength level or above. Submerged Arc Welding. Many electrodes falling under the general classification F10X-EXXX will provide welds with adequate strength. More detailed specifications are necessary if impact properties are required. Gas Metal-Arc Welding. An electrode meeting AWS specifications ER70S-1 will provide strength and toughness sufficient for this grade. Flux-Cored Arc Welding. An electrode meeting AWS A5.29 specification E7XT-X, except -2, -3, -10 or -GS, will provide adequate strength and toughness for this grade.

Procedural Testing:
For production applications where strength and toughness are critical, weld procedural tests should be made to simulate actual joints. Figures 7, 8 and 9 indicate the excellent balance of strength and CVN toughness maintained across the welded joint.


Transverse Charpy impact data for base metal and HAZ of a submerged arc welded 1 1/4 in. (32 mm) BethSatr 50 plate.


Hardness traverse across a submerged arc welded 1 1/4 in.
(32 mm) BethStar 50 plate.


Hardness traverse across a submerged arc welded 2 in. (50 mm) BethStar 50 plate.

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BethStar Steel Plate BethStar Characteristics BethStar 50 (page1) BethStar 50 (page 2)
BethStar 60 BethStar 70 BethStar 80 (page1) BethStar 80 (page 2)

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