Hardness Values - API

[WendelTrento]

Dear all,

Good afternoon,

The API 6A standard specifies the minimum hardness values for carbon steels with a yield strength of 36K to 75K.



I have a hardness standard from a client that informs the minimum value for steels with a yield strength above the API.

Hardness standard text:

The minimum Brinell hardness values from ISO 10423 or API 6A [1], ISO 13628-4 [3] and API 17D [4] are given in Table 2.



Could you, if possible, inform me from which literature my client obtained these minimum hardness values for steels with a yield strength of 80ksi to 120ksi?

Att,

Wendel Trento

 

[EdStainless]

Do you own and have you read the referenced standards?

 

[A M Contractor]

It looks like specific requirement. Extended though

 

[mrfailure]

ASTM A370 only reports equivalent tensile strength for steel hardness, not yield strength. There may well be some proprietary equivalency but I do not think it is reported in any standards. This is the standard of your customer so you have to make sure you meet it.

 

[jmec87]

The API 6A material designations are based on the yield strengths but there is also a tensile strength requirement for each material designation. The hardness requirements are based on the ASTM A370 hardness equivalent for the tensile strength requirement for each material class.

 

[dtimberlake]

From Alro steel. Alro.com

"Cold Drawing
Cold drawing is the most common of the cold finishing methods. It starts with a hot rolled bar that has been
descaled and coated with a lubricant. The bar is then pulled through a precision die that is dimensionally smaller than
the hot rolled bar. Cold drawn bars are available in rounds, squares, flats or hexagons.
Cold drawing gives the hot rolled bar a clean, uniform surface. It increases tensile and yield strength but
decreases ductility. The increase in yield strength is about 2-1/2 times greater than the increase in tensile.

 

[EdStainless]

Some steels respond a lot more to cold finishing (drawing) than other grades.
In cold finish you can get the yield very close to the UTS.
You have to be careful.
Often cold finishing is fairly small amount of reduction.
Not trying to get higher strength as much as to get tighter dimensions and better surfaces.
There are some very clever processes that use cold finish followed by stress relief to recover some ductility.

 

[WKTaylor]

ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products
TABLE 2 Approximate Hardness Conversion Numbers for Nonaustenitic Steels (Rockwell C to Other Hardness Numbers)
TABLE 3 Approximate Hardness Conversion Numbers for Nonaustenitic Steels (Rockwell B to Other Hardness Numbers

/NOTE/ For the FTu as determined by Hardness on these charts, the approx shear strength can be determined from the FTu values, thus... FTu x 0.55 = FSu

Also, secret handshake for all...
NAS531 CHARTS, ROCKWELL HARDNESS...
General Notes:
(1) These charts contain approximate hardness values for use in determining the condition or temper of commonly used aircraft materials. Materials and parts meeting the hardness requirements of these charts may be accepted providing other material property and processing requirements established by individual companies have been satisfactorily met. Material shall not be rejected solely on the basis of failing to meet the hardness requirements of these charts.
(2) Procurement specifications are listed for information only and may be superseded at any time.
(3) In case of conflict between these values and those given in the applicable procurement specification or individual company specification, the latter specifications, as applicable, shall govern.
(4) Additional aluminum alloy hardness values may be obtained from AMS2658.
* Hardness values followed by an asterisk (*) indicate the data were taken from procurement specifications. All other values were established on the basis of data compiled and analyzed by the subcommittee members. ** Specification numbers followed by two asterisks (**) indicates the documents have been cancelled, superseded, inactivated, or are noncurrent.

and... the typical hardness VS Tensile strength for alloy steels is repeated on the last sheet.