Category Archives: Specialty Alloy Steel

Nitralloy 135 Alloy Steel

General Characteristics of Nitralloy Steel

This is a low alloy nitriding steel with moderate hardenability. It shows high case hardness and maintains its core strength during nitriding. Vacuum arc remelting provides superior micro-cleanliness.

Chemical analysis-typical

C% Mn% Si% Cr% Mo% Al%
0.40 0.60 0.30 1.60 0.35 1.20

Applications

Aircraft gears, forged shafts, pinions, crankshafts, cams, camshafts and bolts

Forging

Heat uniformly to 2000-2025ºF (1090-1105ºC) and do not forge below 1700ºF (925ºC.) Air cool after forging.

Heat Treatment

Annealing:

Heat to 1700ºF (925ºC) and slow cool or sub-critical anneal at 1250-1300ºF (675-705.)

Normalizing:

at 1800ºF (980ºC) for 1-4 hours and air cool.

Hardening:

Austenitize at 1700-1750ºF (925-955ºC) for ½ hr per inch of cross section and water or oil quench. Water quench is preferred when cross section exceeds 1 inch in thickness.

Tempering:

The tempering temperature is between 1000-1300ºF (540-705ºC) depending upon required properties, and basically 1 hour at temperature per inch of thickness.

Nitriding:

the nitriding time, temperature and method will depend upon the final product application. The nitriding temperature is normally 900-1100ºF (480-595ºC.)

Machinability

Machinability is satisfactory in the annealed or normalized conditions.

Weldability

This alloy may be welded by normal fusion methods, with preferable preheat and postheat. Welding will only be carried out prior to surface hardening.

HP9 4 30 alloy steel

General Characteristics

This is a low-alloy, high-strength steel with high nickel and cobalt additions to promote toughness. The alloy has good hardenability and weldability and excellent fracture toughness. It is typically used in the 220/240 ksi (1520/1655Mpa) tensile strength range. For optimum cleanliness, the alloy is produced by the consumable electrode vacuum arc remelting process.

Chemical Analysis

C% Mn% Si% Cr% V% Mo% Ni% Co%
0.29/0.34 0.10/0.35 0.20 max 0.90/1.10 0.06/0.12 0.90/1.10 7.0/8.0 4.25/4.75

Applications

Aircraft structural components, rocket motor cases, armor plate, pressure vessels, gears

Forging

For ingot breakdown heat to 2200ºF (1205ºC) and to 1900ºF (1040ºC) for finish forging. Do not forge below 1700ºF (925ºC). Parts may be transferred to an annealing furnace after forging – see heat treatment.

Heat Treatment

Annealing:

1250ºF (675ºC) for 4 hours, air cool to room temp, plus 1150ºF (620ºC) for 4-8 hours and air cool. Alternative is a sub-critical anneal at 1150ºF (620ºC) for 12-24 hours and air cool.

Normalizing:

would normally be carried out prior to hardening and tempering, at 1600-1700ºF (870-925ºC) for 1 hour followed by air cooling.

Hardening:

Austenitize at 1525-1575ºF (830-850ºC) for 1 hour and oil quench

Tempering:

At 400-1100ºF (205-595ºC) depending upon desired properties. Double tempering is recommended.
Refrigeration : this treatment would be carried out to remove any retained austenite, and might be performed at –100ºF (-73ºC) for 2 hours followed by air warm back to room temperature.

Machinability

Those practices used for machining 4340 steel at similar hardness levels are recommended for HP 9-4-30 grade.

Weldability:

Helium-shielded TIG welding is the preferred method, using HP 9-4-30 filler wire.

HP9 – 4 – 20 Alloy Steel

General Characteristics

This is a low-alloy, high-strength steel with high nickel and cobalt additions to promote toughness. The alloy has good hardenability and weldability and excellent fracture toughness. For optimum cleanliness, the alloy is produced by the consumable electrode vacuum arc remelting process.

Chemical Analysis

C% Mn% Si% Cr% V% Mo% Ni% Co%
0.16/0.23 0.25/0.40 0.20max 0.65/0.85 0.06/0.12 0.90/1.10 8.50/9.05 4.25/4.75

Applications

Aircraft structural components, rocket motor cases, armor plate, pressure vessels, gears

Forging

For ingot breakdown heat to 2250ºF (1230ºC) and to 1950ºF (1065ºC) for finish forging. Do not forge below 1700ºF (925ºC). Parts may be transferred to an annealing furnace after forging – see heat treatment.

Heat Treatment

Annealing: 1300ºF (705ºC) for 4 hours, air cool to room temp, plus 1150ºF (620ºC) for 4-8 hours and air cool. Alternative is a sub-critical anneal at 1150ºF (620ºC) for 12-24 hours and air cool.

Normalizing:

would normally be carried out prior to hardening and tempering, at 1650-1750ºF (900-955ºC) for 1 hour followed by air cooling.

Hardening:

Austenitize at 1550-1600ºF (845-870ºC) for 1 hour and oil quench

Tempering:

At 400-1100ºF (205-595ºC) depending upon desired properties. Double tempering is recommended.
Refrigeration : this treatment would be carried out to remove any retained austenite, and might be performed at –100ºF (-73ºC) for 2 hours followed by air warm back to room temperature.

Machinability

Those practices used for machining 4320 steel at similar hardness levels are recommended for HP 9-4-20 grade.

Weldability:

Helium-shielded TIG welding is the preferred method, using HP 9-4-20 filler wire.

Greek Ascoloy Grade

General Characteristics

Greek Ascoloy is a chromium-nickel-tungsten martensitic alloy for service up to 1200ºF (650ºC) in highly-stressed parts. It has very good hardenability.

Chemical Analysis

C% Mn% P% S% Si% Cr% Ni% Mo% W%
.15/.20 .50 max .030 max .030 max .50 max 12.0/14.0 1.8/2.2 .50 max 2.5/3.5

 

Applications

This alloy is used in the manufacture of steam turbine buckets and blades, forged compressor parts in gas turbines and forged high temperature bolts.

Forging

The alloy may be readily worked between 1750-2150ºF (955-1175ºC.) Large sections should be preheated to 1200-1400ºF (650-760ºC) prior to heating to forging or rolling temperature. Parts should be cooled slowly following forging.

Heat Treatment

Annealing: The alloy may be process annealed at 1300ºF (705ºC) for 4 hours followed by air cooling, but to obtain maximum softness and complete stress relief a much longer cycle is required. This cycle involves heating to 1450ºF (790ºC) for 2-4 hours, furnace cooling to 800ºF (425ºC) and then air cooling to at least 200ºF (90ºC). Next is a reheat to 1250-1300ºF (675-705ºC) for 12 hours, followed by air cooling.

Hardening:

Austenitize at 1700-1800ºF (925-980ºC) followed by air or oil quench depending upon section size or complexity of part. Heavy or complex parts should be preheated to 1200/1400ºF (650-760ºC) prior to hardening.
Tempering: Should be carried out as soon as possible following the hardening treatment. Check with the heat treat operation for temperature and time requirements.

Machinability

Greek Ascoloy machines like types 403 and 410 when in the annealed condition

Weldability

Preheating to 400-600ºF (205-315ºC) is recommended due to the air hardening qualities of this alloy. Anneal as soon as possible after welding and use a type 310 stainless filler rod for maximum ductility.

CBS 600 Alloy Steel

General Characteristics

CBS 600 is a carburising bearing and gear steel suitable for service up to 600ºF (315ºC.)  Double vacuum melting is used to give maximum cleanliness and optimum strength and toughness properties.

Chemical Analysis

C% Mn% Si% Cr% Mo% Al%
0.19 0.60 1.10 1.45 1.00 0.06

Applications

CBS 600 is used for bearings, forged gears, shafts and bushings and similar applications where standard 9310 and 8620 grades are insufficiently temperature-resistant.

Forging

CBS 600 may be forged from a start temperature between 1800 to 2000ºF (980 to 1090ºC) with finishing temperature being not critical. Air cooling may be satisfactory, but a retarded rate of cooling might be used to prevent strain cracking.

Heat Treatment

A sub-critical anneal at 1300ºF (705ºC) is suitable to render this grade suitable for further heat treatment.
Further heat treatment, including carburising and hardening and tempering, should be put in the hands of a reliable heat treat organization. A wide range of properties can be obtained with this grade of steel.

Machinability

The grade may be easily machined in the annealed condition.

Weldability

Welding of this grade will not be a problem, but welding should be carried out only in the as-forged or annealed conditions.

ASTM A350 LF1, LF2 AND LF3 CARBON/ALLOY STEELS

ASTM A350 LF1, LF2 AND LF3 CARBON/ALLOY STEELS

General Characteristics

These grades of steel are used as pipeline steels and also in the production of forged flanges. They are suitable for use down to –20ºF (LF1,) –50ºF (LF2) and –150ºF (LF3.)

Chemical Analysis

LF1:

C% Mn% Si% S% P% Cr% Ni%
0.30 max 0.6/1.35 .15/.30 .040 max .035 max 0.30 max 0.40 max

LF2:

C% Mn% Si% S% P% Cr% Ni%
0.30 max 0.6/1.35 .15/.30 .040 max .035 max 0.30 max 0.40 max

 LF3:

C% Mn% Si% S% P% Cr% Ni%
0.20 max 0.90 .20/.35 .040 max .035 max 0.30 max 3.3/3.7

 

Applications

These steels are primarily used for pipelines and for forged flanges.

Forging

LF1 and LF2 grades would ideally be forged at around 2250-2300ºF(1230-1260ºC) and not forged below 1650-1700ºF(900-925ºC.) LF3 grade would be forged at around 2150-2200ºF (1175-1205ºC) and not forged below 1700ºF (925ºC.)

Welding/Heat Treatment

Heat treatment of pipeline steels will no doubt be done on a continuous basis, and after welding. The structure of these steels will be initially determined by the rolling/forging process. The pipeline itself will be supplied from hot-rolled steels, the flanges etc. from forgings. The actual welding process will be primordial in ensuring the suitability and security of the pipeline and its subsequent performance. Preheat and postheat treatments are essential.
The three grades listed here are easily weldable by all tried and tested methods.

Machinability

In the case of forged fittings and flanges, these grades may be machined as required, and ongoing experience will determine if machining is best done on an as-forged structure, a normalized structure or an annealed structure. In either case, in view of the critical nature of the end use, advice should be taken from a recognized heat treatment company.