303values describe: 303
Why it's out
Sulfur and lead stringers create leak paths through welds and porosity.
Where it hides
The machine shops default bar stock: specify 304L or 316L explicitly on every drawing.
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; ASM Handbook: properties, corrosion, heat treatment.
Wet cleaning
| Recipe | not applicable |
|---|
| Forbidden | the sulphur inclusions, which also nucleate corrosion pits |
|---|
| Limit | composition |
|---|
Vacuum and outgassing
| Vapour pressure | THE CONDEMNING MECHANISM: sulphur (303) or lead (12L14) added for chip breaking, both volatile, both destroying weldability |
|---|
Thermal
| CTE | 17.3 ppm/K |
|---|
| Thermal conductivity | 16 W/m·K |
|---|
| Specific heat | 500 J/kg·K |
|---|
| Melting / softening | 1400 °C |
|---|
Mechanical
| Strength | 240 MPa |
|---|
| Tensile | 620 MPa |
|---|
| Elongation | 40 % |
|---|
| Young's modulus | 193 GPa |
|---|
| Density | 8 g/cm3 |
|---|
Electrical and magnetic
| Relative permeability | magnetic |
|---|
| Resistivity | 72 µΩ·cm |
|---|
Engineering
| Corrosion | worse than 304 despite being stainless |
|---|
| Joining | not weldable to vacuum quality |
|---|
| Availability and cost | the default bar stock in every machine shop, which is exactly the hazard |
|---|
Sources · 1
- O Hanlon, A Users Guide to Vacuum Technology
← The Matter