Variations between ASTM A29 Standard for steel bars and Mill test certificates specs

[Moumen H]

Hi Everyone,

When comparing ASTM A29 Standard for steel bars grade 4145 specifications for chemical composition and Mill test certificates specs of 4145H Mod. from most suppliers, a number of variations in minimum and maximum values is observed;
In ASTM A29 the acceptance criteria for grade 4145 is:
Manganese: (min.0.75 max 1.00.)
Molybdenum (min 0.15- max 0.25).
Chromium (min.0.80- max.1.10).

In most MTC for grade 4145H modified is:

Manganese: (min.0.75 max 1.20.)
Molybdenum (min 0.15- max 0.35).
Chromium (min.0.75- max.1.20).

the suppliers answer is that ASTM A29 is a Standard Specification for General Requirements for Steel Bars, Carbon and Alloy, Hot-Wrought
The chemical composition specified in ASTM A29 has been modified (mainly the quenching elements ) to get the required mechanical properties based on the specs practiced and implemented by major oil and gas servicing companies like Weatherford, SLB, halliburton, baker..etc. The content of these elements was determined by experience and gives excellent result.

We understand that it is a common practice to modify grade 4145H to get the desired mechanical properties. The question is: Is there any standard that allows these limits to be modified? And to what extent or tolerances theses limits can be modified?

Thanks,

 

[jmech]

Modifying the limits beyond the standard makes the material non-standard. In many cases, there is no need to use standard material and no limit on how non-standard the material can be.

The limits can be modified to whatever the customer wants, but the documentation still needs to be accurate. For example, the documentation shouldn't state "4145 per ASTM A29" if the actual manganese is higher than allowed by A29, but could state "4145H per Customer Spec XYZ".