Steels and superalloys · Banned
Mild steel and cast iron, bare
Fevalues describe: mild steel
Why it's out
Porosity, rust, water retention, magnetic.
Where it hides
Acceptable painted or plated in rough vacuum housings, nowhere beyond.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: O'Hanlon, A User's Guide to Vacuum Technology.
Wet cleaning
| Recipe | not applicable in UHV |
|---|---|
| Forbidden | aqueous anything: it rusts while you rinse it |
| Limit | THE CONDEMNING MECHANISM: rust is hydrated and porous, an inexhaustible water reservoir, and cast iron is porous throughout |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-7 rusted mbar·L/s/cm² |
|---|---|
| Vapour pressure | THE CONDEMNING MECHANISM: porous hydrated rust is a bottomless water reservoir; every bakeout drives it off and it re-forms on air exposure, so base pressure never settles |
Thermal
| CTE | 12 ppm/K |
|---|---|
| Thermal conductivity | 50 W/m·K |
| Specific heat | 450 J/kg·K |
| Emissivity | 0.7 oxidised |
| Melting / softening | 1500 °C |
Mechanical
| Strength | 250 MPa |
|---|---|
| Tensile | 400 MPa |
| Elongation | 25 % |
| Young's modulus | 200 GPa |
| Density | 7.87 g/cm3 |
Electrical and magnetic
| Relative permeability | ferromagnetic |
|---|---|
| Resistivity | 10 µΩ·cm |
Engineering
| Corrosion | poor |
|---|---|
| Joining | weldable |
| Availability and cost | cheap and everywhere |
Outgassing
2 sourced measurements for this card. A rate means nothing without the pumping time it was read at, so each one states it or declares it missing. The whole base, filters included, is at /tools/outgassing/.
Signature: 1e-6 unbaked to no baked reading baked.
| Material as published | Species | State | Pumping time | Rate |
|---|---|---|---|---|
| Mild steel | total | unbaked | the abscissa of the curve below | 7.20e-7 at 1 h to 6.67e-8 at 10 h |
| Mild steel (slightly rusty) | total | unbaked | the abscissa of the curve below | 8.00e-7 at 1 h to 1.73e-8 at 10 h |
Sources: S-ELSEY-1975-II. Full citations and conditions at the base and in /data/outgassing.json.
Sources · 1
- O Hanlon, A Users Guide to Vacuum Technology