ASTM A-747 CB-7Cu-1: COMPOSITION APPLICATION, WELDABILITY AND PROPERTIES

 DESCRIPTION

CB-7Cu-1 is a precipitation hardening, martensitic stainless steel, known in the wrought form as 17-4PH. Resistance to atmospheric corrosion, organic compounds, sea water and paper mill liquors is intermediate between that of the hardenable CA alloys and the non-hardenable CF alloy grades. The alloy is particularly suited to service combining corrosion resistance and high strength at temperatures up to 700oF. Machining is frequently conducted on castings in the solution annealed condition, followed by hardening at a low temperature thus alleviating distortion and scaling. Service at temperatures below -40oF should be avoided due to poor impact properties at this temperature.

COMPOSITION

	C	Mn	Si	Cr	Ni	P	S	Cu(i)	Nb(ii)	N2
Min %				15.5	3.6			2.5	0.20
Max %	0.07	0.7	1.0	17.7	4.6	0.035	0.03	3.2	0.35	0.05

Notes: (i) Copper should be less than 3% if the castings require welding.

           (ii) Niobium should be omitted if the castings are hardened at 900oF

APPLICATIONS

Centrifuge components, food mixers and processing machinery, pump and compressor impellers, pump shafts and sleeves, screw conveyors,valve bodies and trim, propeller shafts,and hydraulic cylinders 

PRODUCT FORMS

Horizontal and vertical centrifugal castings; static castings.

PHYSICAL PROPERTIES

Density (lbs/in3)	0.280
Liquidus(oF)	2750
Thermal Conductivity (Btu/h/ft2/ft/oF)	9.9 @ 212oF 11.3 @ 500oF 13.0 @ 860oF 13.1 @ 900oF

		Aged at 900oF	Aged at 1100oF
Thermal Expansion (10-6in/in oF)	70-200oF 70-400oF 70-600oF 70-800oF	6.0 6.1 6.3 6.5	6.6 6.9 7.1 7.2

Magnetic Permeability            Ferromagnetic

MECHANICAL PROPERTIES

WELDABILITY

CB-Cu7-1 may be welded by the SMAW, GTAW or GMAW processes.

Electrodes	Same composition or 308
Preheat	Not required for section less than 0.75" thick. Heavier sections with substantial
welding may be preheated to 500oF.
Post weld heat treatment	900 to 1100oF, Air Cool.

RELATED SPECIFICATIONS

ASTM: A747(CB7Cu-1 and CB7Cu-2).

Nearest wrought grade: 17-4PH, 15-5PH.

Source: Kobuta steel datasheet