316 or 304

Guys,

I am having some struts built for my new shafts. I need some help researching the best materials to use. My shafts are 2"OD and the drop from the hull to the center of the shafts is about 14". The yard wants to use 1" flat-bar stock and a .5" wall thickness tube for the bearing housing. This seems over-kill to me. They also don't have a preference between 316 or 304. This scares me a little as I am under the understanding that 304 was a no-no under the waterline.

do I need to spend the extra money on 316?

Should I be looking to have bronze struts cast and avoid any SS? Does anyone have experience ordering custom struts from Buck Algonquin or Marine Hardware?

Thanks in advance,

Mike

 

304/316

Hello Terminated Stainless Man,

Differences between 304 to 316

Oktay Çemberci

Code:

304  	UNS:S 30400
 
MECHANICAL PROPERTIES
Tensile Strength 	87 000 psi
Yield Strength 	39 000 psi
Elongation 	% 56
Reduction of Area 	% 70
Brinell Hardness 	135
Impact Strength 	85 ft Lb
Endurance Limits 	35 000 psi
 
Chemical Composition
Ni 	9.25
C 	0.08 Max
Mn 	2.00 Max
P 	0.045 Max
Cr 	19.00
Si 	1.00 Max
S 	0.030 Max
 
Physical Properties
Density 	0:290 Lb/in3
Electrical Res 	433 ohm-CMF
Service Temp 	870 C
Coef of Exp 0-200 F 	9.6 * 10 -6
 

Code:

 
316 	UNS : S 31600
 
MECHANICAL PROPERTIES
Tensile Strength 	84 000 psi
Yield Strength 	40 000 psi
Elongation 	% 52
Reduction of Area 	------
Brinell Hardness 	128
Impact Strength 	--------
Endurance Limits 	39 000 psi
 
Chemical Composition
Ni 	12.00
C 	0.08 Max
Mn 	2.00 Max
P 	0.045 Max
Cr 	17.00
Si 	1.00 Max
S 	0.030 Max
Mo 	2.50
 
Physical Properties
Density 	0.288 Lb/in3
Electrical Res 	444 ohm-CMF
Service Temp 	870 C
Coef of Exp 0-200 F 	8.9 * 10 –6
 
Source from Nikel Developmant Institute-NiDI

 

so which is best under water??????

 

316

Underwater material is both 316 or 316 L
oktay Çemberci

 

316 L prefered, if not then 316.

 

no 304???

 

SS is not the first choice below the waterline, if you must, use 316 and put up with the 15% loss in strength compared to 302/304.

I'd price the bronze before I decided.

 

316 L...