Chrome Core® 12-FM Alloy
Type Analysis
Single figures are nominal except where noted.
Carbon (Maximum) 0.03 % Manganese 0.20 to 0.70 %
Phosphorus 0.030 % Sulfur 0.200 to 0.400 %
Silicon 0.30 to 0.70 % Chromium 11.50 to 12.50 %
Molybdenum 0.20 to 0.50 % Iron Balance
General Information
Description
Chrome Core® 12-FM alloy is in a family of controlled chemistry, chromium-iron alloys which are candidates for use in magnetic components where corrosion resistance superior to that of pure iron, low carbon steel and silicon-iron alloys is desired without the substantial decrease in saturation induction associated with 18% Cr ferritic stainless steels.
Applications
Applications could include electro-mechanical devices requiring some degree of corrosion resistance, either in service or for extended shelf life without the need for protective coatings.
Chrome Core 12-FM alloy has been considered for use in automotive components such as fuel injectors, fuel pump motor laminations and ABS solenoids.
Corrosion Resistance
Chrome Core 12-FM alloy exhibited no noticeable rusting in 95°F (35°C) - 95% relative humidity tests and have demonstrated corrosion resistance generally similar to 18% chromium ferric stainless steel in certain simulated alcohol-base fuel environments.
Chrome Core alloys were evaluated along with comparison materials in environments designed to simulate or exceed the corrosive effects of some methanol fuels. These included boiling corrosive water (proprietary low-pH solution containing chlorides) and a mixture of 50 percent ethanol and 50 percent of this corrosive water at room temperature. As seen in the Corrosion Test Results - Simulated Fuel Environment chart, there was very light or no significant attack of the Chrome Core alloys. Silicon Core Iron "B-FM", a material widely used in less corrosive environments, experienced considerably greater attack than the other alloys listed in the table.
Chrome Core alloys and comparison materials were also evaluated in CM85A corrosive fuel mixture ("Gasoline/Methanol Mixtures of Materials Testing", SAE Cooperative Research Report, September 1990). This was composed of 15% gasoline and 85% aggressive methanol, which contained 0.1% distilled water, 3 ppm chloride ion (NaCl) and 60 ppm formic acid. All specimens were exposed without deaeration in an autoclave at 176°F (80°C) for 250 hours. The following table illustrates that Chrome Core 12 alloy and Chrome Core 12-FM alloy approached the resistance of Type 430F Solenoid Quality. All Chrome Core alloys were superior to Silicon Core Iron "B-FM". Apparently, this test provided an oxidizing chloride environment and was, therefore, more severe than many anticipated service applications.
A second autoclave test using the same solution was performed with the air evacuated and without the Silicon Core Iron "B-FM" specimens to reduce both oxygen and iron contamination. The Chrome Core alloys and Type 430F Solenoid Quality displayed good resistance (corrosion rates of 0.2 mdd or less) in spite of the increased test duration of 763 hours.
Like most ferritic stainless steels, Chrome Core 12-FM alloy will rust in neutral salt spray (fog) testing, although the degree and severity of rusting is substantially less than for either iron, low carbon steel or silicon-iron alloys.