PH13-8 Mo UNS S13800/Werkstoff 1.4548 stainless steel

overview

PH 13-8 Mo stainless is a martensitic precipitation/age-hardening stainless steel capable of high strength and hardness along with good levels of resistance to both general corrosion and stress-corrosion cracking. the alloy exhibits good ductility and toughness in large sections in both the longitudinal and transverse directions.  Compared to other ferrous-based materials, this alloy offers a high level of useful mechanical properties under severe environmental conditions.

13-8 Mo stainless has good fabrication characteristics and can be age-hardened by a single low temperature treatment. 

13-8 Mo stainless has been used for valve parts, fittings, cold-headed and machined fasteners, shafts, landing gear parts, pins, lockwashers, aircraft components, nuclear reactor components and petrochemical applications requiring resistance to stress-corrosion cracking. 

Limiting Chemical Composition, %

iron..............................................................................................................................................................................................balance

Chromium...........................................................................................................................................................................12.25--13.25

Nickel.......................................................................................................................................................................................7.50--8.50

Molybdenum............................................................................................................................................................................2.00--2.50

Aluminium...............................................................................................................................................................................0.90--1.35

Manganese...............................................................................................................................................................................1.00 max.

Nitrogen....................................................................................................................................................................................0.01 max.

Silicon........................................................................................................................................................................................1.00 max.

Carbon........................................................................................................................................................................................0.05 max.

Phosphorus................................................................................................................................................................................0.01 max.

Sulphur......................................................................................................................................................................................0.008 max.

Physical Constants

Below are some physical constants and thermal properties of

Mechanical properties

Corrosion Resistance

Stainless steel PH13-8 Mo   level of general-corrosion reistance is greatest in the fully hardened condition and decreased slightly as the aging temperature is increased. Numerous tests representing a marine environment have shown the alloy, in both the wrought and welded conditions, to have a high level of resistance to stress-corrosion cracking. For best resistance to stress-corrosion cracking, a minimum aging temperature of 1000°F (538°C) is suggested.

For optimum corrosion resistance, surfaces must be free of scale and foreign particles and finished parts should be passivated.

Heat Treatment

PH 13-8 Mo Precipitation Hardening Alloy is produced in the annealed condition. This is also called the solution heat treated condition, or Condition A. Solution treat from 1675 to 1725°F (910 to 940°C) for 15 to 30 minutes at temperature. Air cool or oil quench to below 60°F (15°C) to effect complete transformation to martensite. Aging is normally carried out from 950 to 1150°F (510 to 620°C), depending upon the desired final properties. Heat treatment is usually performed in air. Heat treatment of brazed components may be done in inert atmospheres. Reducing atmospheres should not be used because of the potential for hydrogen contamination.

WELDING

Weldability Carpenter 13-8 stainless can be welded using the inert-gas shielded or resistance welding processes. When a filler metal is required, 13-8 welding consumables should provide welds with properties similar to those of the base metal. When designing the weld joint, care should be exercised to avoid stress concentrators, such as sharp corners, threads, and partial- penetration welds. When high weld strength is not needed, a standard austenitic stainless filler, such as E/ER308L, should be considered. Normally, welding in the solution-annealed condition has been satisfactory; however, where high welding stresses are anticipated, it may be advantageous to weld in the overaged (H 1150) condition. Usually, preheating is not required to prevent cracking. If welded in the solution-treated condition, the alloy can be directly aged to the desired strength level after welding. However, the optimum combination of strength, ductility and corrosion resistance is obtained by solution treating the welded part before aging. If welded in the overaged condition, the part must be solution treated before aging.