|
 |
BethStar 70
BethStar 70 plate has 70 ksi minimum yield strength and is available through 1 in. thickness. High strength, outstanding strength/cost ratio, and ease of fabrication make it a logical replacement for many alloy and heat-treated grades.
BethStar 70 is an ideal grade where strength/weight ratios are important
in complex fabrications for critical applications. Potential applications include
cantilevered components such as excavator booms, front-end loader hoist arms, or dump body
frame components. It may be ordered to ASTM A656, Type 7 specification.
Metallography
The microstructure of BethStar 70 plate is essentially a combination of
ferrite and pearlite. Figures 12A and 12B illustrate representative microstructures for
1�2 in. and 1 in. plates at an original magnification of 200X. The material is extremely
fine grained, with a typical ferrite grain size of ASTM 10 or finer.
Welding Suggestions
BethStar 70 is readily weldable and requires 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
E90 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 specification ER90S-1 will provide strength and toughness sufficient for this grade.
Flux-Cored Arc Welding. An electrode meeting AWS A5.29 specification
E8XT-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.
Representative Mechanical Properties*
Thick |
Avg. Yield |
Avg. Tensile |
Avg. |
Longitudinal Charpy |
1/4 |
78.3 |
85.5 |
18.3 (8") |
62 (1/3 size) |
1/2 |
78.2 |
85.9 |
17.7 (8") |
66 |
1 |
75.2 |
87.2 |
19.1 (8") |
56 |
*Based on production tests of over 30plates.
Representative microstructures of BethStar 70 plates at an original magnification of
200X - 1/2 in. (Fig. 12A) and 1 in. (Fig. 12B).
