CF8M Stainless Steel Casting

  Like other stainless steel alloys, CF8M stainless steel is one of the common grades used in investment casting. Our Foundry can make CF8M stainless steel castings in various shapes.

What is CF8M stainless steel ?

  CF8M stainless steel is the most widely used in US standard austenitic stainless steel casting grades. In its symbol,letter “C” means this alloy is mainly for the purpose of corrosion resistance. Letter “F” is the approximate location on the iron-chromium-nickel (FeCrNi) ternary diagram and indicates the iron, chromium and nickel content. The number “8” means the maximum carbon content in increments of 0.01%. In this instance, 8 means 0.08%. Letter “M” means that Molybdenum. The exist of molybdenum increases the general corrosion resistance and the resistance to pitting by chlorides. CF8M austenitic stainless steel is the wrought of Stainless steel 316.

CF8M Stainless Steel Properties

General Information

Cast Alloy Designation: CF8M
Alloy family: Austenitic Stainless Steel
UNS #: J92900
ASTM Standard(s): A351 A743 A744
Wrought: 316

Chemical Composition

C: 0.00-0.08
Mn: 0.00-1.50
Cr: 18.00-21.00
Mo: 2.00-3.00
Ni: 9.00-12.00
Fe: 62.42-71.00
Cu: 0.00-0.00

Mechanical Properties

Tensile strength (ksi): 0.00-70.00
Yield strength (ksi): 30
Elongation (%): 30
Hardness (Brinell): 146.00-212.00

Applications:

  CF8M austenitic stainless steel is a commonly used alloy for products that require excellent overall corrosion resistance.Applications include valves casting, flanges, fittings and other pressure-containing parts.

  This alloy is commonly used whenever the part will not be welded or can be solution annealed after welding. CF8M may be used at temperatures Casting of CF8M Stainless Steel. CF8M may be used at temperatures up to 1500F.

  It provides a good balance of corrosion resistance, availability, strength and cost. It also has excellent corrosion resistance in normal atmospheric conditions, including coastal exposure. It resists most water and brines at ambient temperature as well.

FAQ:

Q:These valve is cast based on “CF8M” process. Can anyone help me why these 316 SS(CF8M) valves are corroding? Other valves are attracting the magnet why?

  A. CF8M is the casting alloy that corresponds to the wrought 316 material. It has slightly different chemical composition, which has several consequences.

  1. Foundries usually balance the relative amounts of the various elements (while maintaining each within its own specified range) so that the microstructure is predominantly austenitic. But with typically 5-8 percent ferrite. The ferrite phase is attracted to a magnet (if it is present to say 5% of the structure, the strength of the attraction will be in the vicinity of 5% of that of mild steel).

  2. A consequence of the ferrite is an increase in strength during and immediately after solidification. It greatly reduces the possibility of hot-tear defects occurring which would require subsequent repair by the foundry

  3. An incidental benefit is that the room temperature yield strength is increased, although this benefit is rarely exploited by design engineers.

  4. An incidental benefit is enhanced corrosion resistance, because the chromium specification range for CF8M is higher than that for 316. Furthermore it is usual to manufacture CF8M towards the top end of its chromium range as part of the ferrite-inducing element balance. But to manufacture 316 towards the bottom end of its chromium range as part of the ferrite-avoiding element balance.

  5. All of the above relies on the manufacturer heat treating the product appropriately. So as to avoid the presence of any of carbides, or sigma phase, or chi phase, in the microstructure because any of these will detract from corrosion resistance.