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ASTM A276 F55 strain hardened FLT with extended charpy impact requirements

Broder Metals Group announce that we can offer our ASTM A276 F55 (UNS S32760) FLT material to the extended charpy impact requirements now required by many end users.

Base material for strain hardening is ASTM A276. UNS S32760 F55 solution annealed material that complies with Condition A. After strain hardening our material complies with ASTM A276, UNS 32760 F55 Condition S, and is fully charpy impact tested to show compliance with the requirements of grade ‘FG’, or ‘FLT’.

However we can now also guarantee the extended requirements many modern customer specifications call for (minimum single value of 35 Joules, with a minimum average across 3 tests of 45 Joules at a test temperature of -101oC) – what we are calling our BMG-FLT+ material.

Our material is melted using Electric Arc / Electric + AOD (or equivalent) furnaces.

The F55 chemistry range is as follows:

Element

Cr

Ni

Mo

Cu

N

Si

C

Mn

P

S

Fe

PREN

Min %

24.0

6.0

3.0

0.5

0.5

0.2

40.0

Max %

26.0

8.0

4.0

1.0

1.0

0.3

1.0

0.03

1.0

0.03

0.01

Bal

Note:

The PREN formula usually reported by mills is %Cr+(3.3%Mo)+(16%N) (the PREN 40.0 minimum shown above) For Standards that refer to ISO 15056 / NACE MR0175 and BS 4515-2 a different PREN formula including tungsten should be used: PREN = %Cr+(3.3%Mo)+(0.5%W)+(16%N). The result needs to be greater than 41.0.

Heat Treatment solution anneal times and temperatures are sufficient to produce the required properties and the material is cooled to prevent 475 degree C embrittlement and sigma-phase embrittlement. Times and temperatures are recorded and reported.

Tensile Properties: material is tested at room temperature and tested in accordance with ASTM A370 (latest edition) midway between surface and centre of cross-section. Requirements:

ASTM A276. UNS S32760 F55

YS – 0.2% offset (MPa)

Tensile Strength (MPa)

Elongation in 50 mm or 4D (%)

Reduction of area(%)

Hardness (maximum)

Condition A

550 minimum

750 minimum

25 minimum

Reported only

290 HBW / 31 HRC

Condition S

720 minimum

860 minimum

16 minimum

Reported only

335 HBW / 36 HRC

The hardness result conforms to NACE MR0175

Metallographic examination tests are conducted on samples taken from near surface and mid-thickness. Samples are etched according to ASTM 407 (etchant 98, KOH or NOH). Etching is performed in such a manner as to provide optimum resolution of potential precipitates. The etched sample is examined and reported at a magnification of 500x minimum and acceptance is that the material is free of grain boundary carbides, sigma, chi and laves phases. Intermetallic phases or precipitates are allowed up to a maximum of 0.005%

The ferrite content is determined by the manual point count in accordance with ASTM E562 at locations near the surface and at mid-thickness. Samples are electrolytically etched in either NaOH or KOH and in such a manner as to provide optimum contrast for austenite and ferrite phase discrimination. Point count is conducted at a minimum 500x magnification. A minimum of 30 fields and 16 points are used. The ferrite count value will lie between 35% to 55% and reported.

The material is also corrosion resistance tested in accordance with ASTM G48 (Method A) (latest version). The test piece is taken from the same location as those for mechanical testing. Acceptance is that no pitting is to be observed at 20x magnification after exposure for 24 hours at 50 degrees C. Weight loss will not exceed 4.0 g/mm2. Method and results are reported.

Once the base material is confirmed as meeting the above requirements, it is strain hardened by cold drawing and charpy impact tested in accordance with ASTM A320 at the times and temperatures shown below. Sample test pieces are full size at 10 x 10 mm dia unless the bar diameter necessitates a sub-size specimen to be used:

Variant

Test Temperature

Value required

‘FLT+’

-101 degrees C

Minimum single value: 35 Joules

Minimum average of 3 tests: 45 Joules

‘FLT’

-101 degrees C

Minimum single value: 20 Joules

Minimum average of 3 tests: 27 Joules

‘FG’

-46 degrees C

Minimum single value: 35 Joules

Minimum average of 3 tests: 40 Joules

Material handling discipline is very important for this type of material and our warehouse is equipped such as to avoid free iron contamination of the F55 material. Material is not handled with base iron or steel hooks, chains or lifting forks. Material stored does not come into contact with bare iron or steel rack arms.

If any suspected free iron contamination, such as unusual stains or discolouration, is discovered it is verified by ferroxyl testing in accordance with ASTM A380 and any free iron contaminated areas are cleaned and passivated in accordance with ASTM A380.

We do not use steel strapping on bundles.

Material is of course supported by our 3.1 certification and copy independent impact test certificates.

For sizes and quantities available in stock, please contact our sales department on ++44 (0)114 232 9241 or email: sales@broder-metals-group.com

The Broder Blogger

Tea and Chocolate and Broder Metals Sheffield Office

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