Alloy 800H/AT is an austenitic heat resistant alloy designed for high temperature structural applications. The strength of 800H/AT is achieved by controlled levels of carbon, aluminum and titanium along with a 1148°C minimum anneal to achieve a grain size of ASTM 5 or coarser.
| % | Cr | Ni | Si | C | Mn | P | S | Cu | Fe | Al | Al+Ti |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | 19 | 30 | 0.06 | 39.5 | 0.15 | 0.85 | |||||
| Max | 23 | 35 | 1 | 0.1 | 1.5 | 0.045 | 0.015 | 0.75 | 0.6 | 1.2 |
With close control of the carbon, aluminium and titanium contents combined with the high temperature anneal, 800H/AT has significantly higher creep-stress rupture strength than Alloy 800.
This alloy is commonly welded using RA82 (ERNiCr-3) bare wire for applications under 788°C. RA330-04 (UNS N08334) bare filler wire offers a closer match than RA82 based on the thermal expansion coefficient and higher strength. For maximum strength alloy 617 (ERNiCrCoMo-1) bare wire or 117 (ENiCrCoMo-1) covered electrodes are suggested.
To avoid possible stress relaxation grain boundary cracking in applications above 538°C the welded fabrication may be heat treated at 899°C for approximately one hour per inch of thickness or 30 minutes minimum followed by air cooling.
| Mechanical & Physical Properties | 21.1°C | 537.8°C | 649°C | 760°C | 871°C | 982°C |
|---|---|---|---|---|---|---|
| Ultimate Tensile Strength /MPa | 530.9 | 437.8 | 384 | 222.7 | 128.2 | 70.3 |
| 199.9 | 113.8 | 102 | 99.3 | 80 | 61.4 | |
| - | - | - | - | - | - | |
| 52 | 51 | 50 | 78 | 120 | 120 | |
| - | - | - | 41.4 | 24.8 | 7.2 | |
| - | - | - | 50.3 | 24.1 | 8.3 | |
| - | - | - | 17.8 | 18.4 | - | |
| 10 | - | - | 20.5 | 22.5 | 26.5 | |
| 1.97 | - | - | 1.45 | 1.32 | - |
Proud members of the British Valve & Actuator Association