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304V

Melt Practice

This austenitic stainless steel is initially electric-arc melted. Then as a refinement to the purity and homogeneity of the metal, 304V is Vacuum Arc Remelted (VAR). This process yields a more uniform chemistry with minimal voids and contaminants.


Chemistry
  ASTM A313
Carbon 0.08
Manganese 2.00
Silicon 1.00
Phosphorus 0.045
Sulfur 0.030
Chromium 18.0-20.00
Nickel 8.00-10.50
Molybdenum -
Copper -
Nitrogen 0.10
Iron Balance
Cobalt -

Physical Properties
Density 0.286 lbs/in3
Modulus Of Elasticity 28.5 psi x 106
Electrical Resistivity 720 µohms-mm
Thermal Conductivity 16.36 W/mK (100°C)

Thermal Treatment

In wire form, 304V will gain tensile strength when stress relieved at 350-427°C. A reducing atmosphere is preferred but inert gas can be used. 304V will fully anneal at 1010-1121°C in just a few minutes. There is a carbide precipitation phenomenon that occurs between 427 and 899°C that reduces the corrosion resistance of the alloy. American Society for Testing Materials has described a test method to ensure the alloy has not been damaged.


Applications

This alloy is the most popular for medical appliances. The ease of joining with solder or welding, combined with excellent strength makes it desirable. This alloy is also one of the least expensive medical materials.

Some examples of end products are stylets, catheters, guide wires, springs and needles. Fort Wayne Metals routinely makes cables, strands, flat wire and shapes from this alloy.


Mechanical Properties
%CW Y.S.(psi) U.T.S.(psi) % Elongation
(10" gauge length)
0% 50,000 107,000 41%
20% 70,000 140,000 14%
37% 90,000 184,000 4%
50% 140,000 208,000 3%
60% 160,000 229,000 2.6%
68% 180,000 247,000 2.7%
75% 200,000 265,000 2.6%
80% 215,000 272,000 2.9%
84% 230,000 289,000 2.5%
90% 245,000 306,000 2.6%
93% 250,000 316,000 2.7%
95% 280,000 334,000 2.6%

Values are typical and may not represent all diameters. Test method will affect results.


Surface Condition

Stainless steels develop a highly polished appearance as they are drawn to fine diameters. Surface roughness can be less than 5 RMS when processed using SCND* dies and measured with a profilometer. Diameters over 0.040" are finished with polycrystalline dies and exhibit a rougher surface than natural diamond dies. Diameters over 0.100" will have an even rougher surface because they are drawn with carbide dies.

*SCND means single crystal natural diamond.