ASTM SA516 Gr. 60N

ASTM SA-20/A20M

MT:

Plates that are required to be heat treated,

and have been so heat treated, shall be marked by the

party that performed the heat treatment with the letters

"MT" (denoting material treated) following the required

ASTM designation mark.

NOTE 1 - Any stress relief of test specimens intended to simulate

post-weld heat treatment is not included in the above heat treatment.

N: Normalizated.

Code SA516 /516M do not covers general requirement. For general requirement of plate you have to consult SA20/20M in which under clause no 13, plate identification is covered: For ready ref. part is as below:

13. Identification of Plates

13.1 Except as specified in 13.2, the name or brand

of the manufacturer, heat and slab number, and specification

number and grade, class and type, where indicated

in the material specification, shall be legibly steel die

stamped unless stenciling is specified by the purchaser

on each finished plate in two places not less than 12

in. [300 mm] from the edges. The year-date of the

specification to which the material is furnished need

not be included in the marking. For plates produced

from coils, the processor's identity shall be used rather

than the identity of the manufacturer. Plates, the maximum

lengthwise and crosswise dimensions of which

do not exceed 72 in. [1800 mm], shall have the marking

stamped in one place approximately midway between

the center and an edge. The manufacturer's or processor's

test identification number shall be legibly stamped

on each test specimen.

13.1.1 Bar coding is acceptable as a supplementary

identification method. Bar coding should be consistent

with the Automotive Industry Action Group (AIAG)

standard prepared by the Primary Metals Subcommittee

of the AIAG Bar Code Project Team.

13.2 For plates under 1⁄4 in. [6 mm] in thickness,

the marking specified in 13.1 shall be legibly stenciled

instead of stamped.

13.3 Plates that are required to be heat treated, but

have not been so heat treated, shall be marked by

the manufacturer with the letter "G" (denoting green)

following the specification designation mark required

by 13.1. Such plates shall have been qualified for

shipment on the basis of test specimens that have been

so heat treated. "G" marking is not required for such

plates that are for shipment, for the purpose of obtaining

the required heat treatment, to a processor under the

manufacturer's control.

NOTE 1 - Any stress relief of test specimens intended to simulate

post-weld heat treatment is not included in the above required heat

treatment.

13.4 Plates that are required to be heat treated, and

have been so heat treated, shall be marked by the party

that performed the heat treatment with the letters "MT"

(denoting material treated) following the specification

designation mark required by 13.1.

This shall clear the difference.