Fw: [MW:507] Hardness of ASTM A217 C12A

[des...@toyoindia.com]

Sorry all; typing mistake; it's C12A

Thanks & Regards,
Dhwani Desai.
TOYO - PLANNING & PIPING DEPT.
91-22-2573 7213.
----- Forwarded by Desai Dhwani 01752/TEIL on 01/21/2008 06:09 PM -----

des...@toyoindia.com Sent by: material...@googlegroups.com 01/21/2008 06:11 PM Please respond to material...@googlegroups.com

To <material...@googlegroups.com> cc Subject [MW:507] Hardness of ASTM A217 CA12

Dears,

Can any one inform about the hardness of ASTM A217 CA12? ASTM & SA standard doesn't mention clearly this.

Thanks & Regards,
Dhwani.

[Shyam Herur]

Could you pl check in astmA703.

Scope of astm A703 says"This specification covers a group of common requirements that, unless otherwise specified in an individual specification, shall apply to steel castings for pressure-containing parts under each of the following ASTM specifications"

Title of Specification	ASTM Designation
Steel Castings, Carbon, Suitable for Fusion Welding	A 216/A 216M
for High-Temperature Service
Steel Castings, Martensitic Stainless and Alloy, for	A 217/A 217M
Pressure-Containing Parts Suitable for High-
Temperature Service
Castings, Austenitic, Austenitic-Ferritic (Duplex)	A 351/A 351M
Pressure-Containing Parts
Steel Castings, Ferritic and Martensitic, for Pressure-	A 352/A 352M
Containing Parts Suitable for Low-Temperature
Service
Steel Castings, Alloy, Specially Heat-Treated, for	A 389/A 389M
Pressure-Containing Parts, Suitable for High-
Temperature Service
Steel Castings Suitable for Pressure Service	A 487/A 487M

 

also, point3 in A217 says "material furnished to this specification shall conform to the requirements of specification A703/A703M including any supplementary requirements that are indicated in the purchse order."........

 

Since im at home I dont have A703. correct me if Im wrong.

 

Regards

shyam

[Bathula Raghuram (Mumbai - PIPING)]

well it is a supplimentary requirement and to be agreed between manufacturer and purchaser

The development of a cast material often lags a number of years behind the development of its wrought counterpart.
C12A, the 9Cr-1Mo-V cast grade, is no exception. Although the 9Cr-1Mo-V materials were developed in the mid-1970s,
cast 9Cr-1Mo-V did not appear in a North American industry standard until 1995, when ASME Code Case 2192 was issued.

C12A was added to ASTM A217 later in 1995. ASME still has not adopted C12A into the SA217 specification. ASME
has re-approved Code Case 2192 twice, the most recent being version 2192-2 in October of 1999.

Specific requirements for the cast version are still being actively developed in the ASTM and ASME standards
committees. Put simply, it is quite possible to produce cast material that meets all of the industry-standard chemical and mechanical property requirements for C12A, but which does not provide the excellent high-temperature strength and
creep resistance that is necessary for the intended use. None of the ASTM or ASME specifications contain adequate
chemistry requirements to ensure proper deoxidation practices will be followed. Even the ASME Code Case 2192-2 composition, with its tighter aluminum restriction and additional titanium restriction, does not ensure that other elements with high nitrogen affinity (zirconium, for example) will not be utilized. Unless this issue has been specifically communicated, it’s likely that many foundries will be unaware of the effect that deoxidation practices can have on the high-temperature properties. In fact, there is a good chance that extra killing agents might be added to counteract the potential for the nitrogen to outgas and cause porosity in the casting.

THE IMPORTANCE OF MICROSTRUCTURE

The chemistry of the 9Cr-1Mo-V material is specially designed to support the formation of a microstructure which provides excellent long-term high-temperature strength, creep and stress rupture properties. When the material is normalized by air-cooling from a target temperature of 1900°F (1040°C), a completely martensitic structure with a hardness of approximately
35-40 HRC is formed.

Tempering at the target temperature of 1400°F (760°C) softens the martensite and ultimately produces a hardness on the order of 95 HRB. However, in addition to the conventional tempering effects, a secondary precipitation process also occurs. The first stage of this process involves the precipitation of very fine Nb(C,N) (niobium carbonitride) particles. The
Nb(C,N) particles subsequently act as nucleation sites for the formation of very fine particles of M23C6.1 M23C6 is metallurgical shorthand for a carbide structure containing a mixture of 23 Metal atoms and 6 Carbon atoms. The 23 metal atoms are generally rich in the alloy’s stronger carbide-forming elements such as chromium, vanadium, niobium, etc.

Research on the 9Cr-1Mo-V material indicates that the M23C6 phase contains an appreciable amount of vanadium, which makes it very stable at the intended service temperature. This stability mitigates growth and consolidation of the M23C6 particles in service.
Since high-temperature strength and creep resistance are enhanced by the presence of large quantities of very small particles, both the initial precipitation of Nb(C,N) and the subsequent formation of stable submicroscopic vanadium-rich M23C6 particles are key
elements contributing to the long-term performance of this alloy.

Source: Valve mnagazine, Winter 2001, Vol 13 no1.

[Jignesh Patel]

I have seen A703. In A703, Hardness is supplementary reqt and there too it says the hardness reqt shall be as agreed upon by purchaser and manufacturer. From this I think, in that case it all should be dependent only on the purchase spec.

 

Thanks and regards,

 

Jignesh

Kuwait

 

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