Overview
ASTM A335 P91 is a superalloy steel, which is a low-alloy chromium
molybdenum steel. It is widely used in pipelines and equipment
under high temperature and pressure environment, such as
petrochemical, electric power, nuclear power plant and other
fields. The main components of the material are chromium,
molybdenum, copper, manganese, silicon, phosphorus, sulfur and
other elements, among which the content of chromium and molybdenum
is relatively high, which can improve the high temperature
resistance and oxidation resistance of the material.
Chrome Moly Pipe – ASTM A335 Pipe
ASTM A335 / ASME SA335 Pipe named chrome moly pipe as they have a
high level of Chromium and Molybdenum.
Chromium will increase oxidation resistance and provides
high-temperature strength, along with the better tensile & yield
strength and proper hardness at room temperature. When the chromium
content increased more than 12%, it can be classified as stainless
steel.
Molybdenum increases the overall strength, resistance, elasticity,
hardenability and overall quality, moly ensures that the material
is more resistant to softening, restrains the growth of grains and
lessens the chances of embrittlement. It is the single additive
that is responsible for the increase in high temperature resistance
(to 540-750°C) and it also improves the corrosion resistance to
steel.
Elongation
Elongation in 2 in or 50mm or 4D minimum%
For wall thickness 5/16 in [8mm] and over
Longitudinal 30% and Transverse 20%
Elongation smaller 2 in or 50mm or 4D minimum%
For wall thickness 5/16 in [8mm] and over
Longitudinal 22% and Transverse 14%
For strip tests a deduction of each 0.8mm below 8mm shall be
calculated with the Table 5 in ASTM A335
Chemical Composition
| C, % | Mn, % | P, % | S, % | Si, % | Cr, % | Mo, % | V, % | N, % | Ni, % | Al, % | Nb, % |
| 0.08-0.12 | 0.3-0.6 | 0.02 max | 0.01 max | 0.2-0.5 | 8.0-9.5 | 0.85-1.05 | 0.18-0.25 | 0.03-0.07 | 0.4 max | 0.04 max | 0.06-0.10 |
Mechanical Properties
| Tensile Strength , MPa | Yield Strength, MPa | Elongation, % | Hardness, HB |
| 585 min | 415 min | 20 min | 250 max |
Heat Treatment
ASTM A335 P91 shall be heat treated with normalize and temper, or
quench and temper, normalize temperature 1900-1975℉ [1040-1080℃],
subcritical annealing or tempering temperature minimum or range
1350-1470 ℉ [730-800℃].
Application
Power generation
Gas processing equipment
Oil services
Petrochemical plants
Heaters/reheat lines
Boilers
Test
Tensile tests: Transverse and Longitudinal
Flattening test
Hardness test not exceeding 250 HBW/265 HV30 [25HRC]
Bend Test shall be carried as per ASTM A370
Hydrostatic Test shall be carried , depending on the buyer a
nondestructive examination shall be performed plus with hydrostatic
test.
Package Process
1.with plastic cap to protect both ends
2.weaving bag wrapped outside the pipe
3.then pack into wooden case.
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