Category Archives: Alloy Steel

ALLOY STEEL 4615

Chemical Analysis
C% Carbon
0.13 – 0.18
Mn% Manganese
0.45 – 0.65
Si% Silicon
0.20 – 0.35
P% Phosphorus
0.035 max
S% Sulfur
0.040 max
Ni% Nickel
1.65 – 2.00
Mo% Molybdenum
0.20 – 0.30

General characteristics of Alloy Steel 4615

This is a nickel-molybdenum alloy steel that is normally used in a carburized condition

Applications

This alloy is used for parts where strength and toughness are required, such as forged gears and shafts.

Forging

The alloy is forged at a maximum temperature of 2275ºF (1245ºC) and should not be forged below 1650ºF (925ºC).

Heat treatment

Annealing

This grade does not normally require annealing, and machining may be carried out after either normalizing or following an isothermal anneal – 1290ºF (700ºC) for 8 hours – after forging.

Normalizing

This grade is normalized at a nominal temperature of 1700ºF (925ºC) followed by air cooling.

Hardening

A maximum hardness of Rc 35-40 may be obtained from this grade by direct hardening. Surface hardening is normally by carburizing or carbonitriding, when surface hardnesses of Rc 60-65 are easily obtainable.

Tempering

Tempering will be carried out after surface hardening at temperatures based on acquired experience.

Process routing

This grade might typically be processed as follows:

Forge – Normalize – Anneal (optional) – Rough and Semi-finish machine – Case harden – Temper – Finish machine (case-hardened parts only.)

Machinability

As noted above, this alloy is readily machinable providing appropriate heat treatments are carried out.

Weldability

This grade may be welded in the normalized or annealed condition, but should not be welded in the surface-hardened state.

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Alloy Steel 4337

Chemical Analysis
C% Carbon
0.35 – 0.40
Mn% Manganese
0.60 – 0.80
Si% Silicon
0.20 – 0.35
P% Phosphorus
0.035 max
S% Sulfur
0.04 max
Cr% Chromium
0.70 – 0.90
Mo% Molybdenum
0.20 – 0.30
Ni% Nickel
1.65 – 2.00

General characteristics of Alloy Steel 4337

Alloy steel 4337 is a nickel-chromium-molybdenum engineering alloy steel that may be heat treated to a full range of strength, ductility and toughness levels.

Applications

Commercial and military aircraft, automotive systems, forged hydraulic and other machine tool applications, forged crankshafts.

Forging

This alloy steel should be forged between 2250ºF (1230 ºC) and 1700ºF (980ºC) and slow cooled after forging.

Heat treatment

Heat treatment after forging is carried out to render the part suitable for machining and to meet certain mechanical property requirements. Treatments, temperatures and conditions will be learned through practice, and any parameters given here should be taken as a guide only.

Annealing

To obtain a predominantly pearlitic structure, the parts should be slowly heated to around 1525ºF (830ºC), cooled to 1350ºF (730ºC) and furnace cooled to 1130ºF (610ºC) at 20ºF (11ºC) per hour, then air cooled.
This is a very time consuming operation, and as such it may be better to opt for a spheroidize anneal, heating to 1380ºF (750ºC), furnace cooling to 1300ºF (705ºC) then to 1050ºF (565ºC) at 5ºF (3ºC) per hour and air cooling. It may well be that the spheroidized structure gives better machinability than the lamellar pearlite structure.
It is always best, if in doubt, to consult with a heat treat provider.

Normalizing

The nominal normalizing temperature for 4337 grade is 1550ºF (840 ºC) but production experience may suggest a temperature either 50ºF (10ºC) above or below this temperature. When forgings are normalized before, say, hardening and tempering, the upper temperature range is used, whereas the lower range is used when normalizing is the final heat treatment.

Hardening

The austenitizing temperature for hardening grade 4337 is 1500 – 1550ºF (815 – 845ºC). Parts should be oil quenched as hardenability is conducive to this.

Tempering

If very high strength is required in the finished part then a stress relief should be used: otherwise tempering should be carried out to meet mechanical property requirements. Tempering in the range 400 – 790ºF (200 – 420ºC) may cause embrittlement and is not to be recommended.

This grade may also be hardened by nitriding or by flame or induction hardening.

Machinability

A lamellar pearlite or spheroidized structure may be used for machinability reasons, depending upon the part’s section size and complexity and the amount of machining to be done. If there is any doubt it may be best to opt for the spheroidized structure.

Weldability

Welding should be carried out in the annealed condition. Welding in the hardened and tempered, nitrided, flame or induction hardened conditions is not recommended. Parts should be preheated at 400 – 570ºF (200 – 300ºC), to be maintained during welding, slow cooled after welding in sand or ashes, and stress relieved if possible.

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AISI / Alloy Steel 4330

Chemical Analysis
C% Carbon
0.30 – 0.34
Mn% Manganese
0.75 – 1.00
P% Phosphorus
0.025 max
S% Sulfur
0.010 max
Si% Silicon
0.15 – 0.35
Cr% Chromium
0.75 – 1.00
Ni% Nickel
1.65 – 2.00
Mo% Molybdenum
0.40 – 0.50
V% Vanadium
0.05 – 0.10

General characteristics of Alloy Steel 4330

This is a fine-grained, medium carbon, chromium-nickel-molybdenum alloy steel with good hardenability, and excellent transverse strength and toughness. It also shows excellent low-temperature impact properties.

Applications

This alloy finds forging applications as aircraft landing gear, and in other high-performance applications where toughness and wear resistance are required. The alloy is used in the oil and gas industry as raise bore drill rods and as drive subs for downhole motors.

Forging

Bars are forged to approximate dimensions, rough machined and bored (as required) prior to heat treatment. Preheat steel carefully then raise to 1950-2250ºF (1070-1230ºC) start forge temperature. Not to be forged below 1560ºF (850ºC) and slow cooling in ash or lime is recommended.

Heat treatment

Annealing: Heat slowly to 1510-1580ºF (820-860ºC), soak and slow furnace cool to 1075ºF (580ºC) and air cool.

Normalizing: this steel should be normalized at 1600-1700ºF (870-925ºC) and air cooled

Hardening: at 1550-1600ºF (845-870ºC) and water or oil quench according to size and intricacy of part.

Tempering: to desired strength levels, based on available data and experience.

Machinability: It is reported that best machinability is obtained in the normalized and tempered – at 1250ºF (675ºC) – condition.

Weldability: Preheat and post-weld stress relief recommended if this alloy is to be welded . It should be welded in the annealed condition only.

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ALLOY STEEL 4145

Chemical Analysis
C% Carbon
0.43 – 0.49
Mn% Manganese
0.85 – 1.10 max
Si% Silicon
0.10 – 0.35
P% Phosphorus
0.035 max
S% Sulfur
0.040 max
Cr% Chromium
0.80 – 1.10
Mo% Molybdenum
0.15 – 0.25

General characteristics of Alloy Steel 4145

This is a direct hardening chromium-molybdenum low alloy steel that may be readily forged, machined and welded. It may be heat treated to a wide range of strength and ductility levels.

Applications

This alloy is used in the oil and gas industry as forged down-hole drilling tools such as drill collars. Other applications are forged gears, shafts for hydraulic presses, rolls for paper mills, pump shafts and tool holders.

Forging

Stock should be carefully preheated then the temperature raised to 2100-2200ºF (1150-1200ºC) for forging. Forging should not be carried out below 1600ºF (850ºC) and parts should be slow cooled after forging to prevent possible cracking.

Heat treatment

Annealing

Parts should be heated slowly to 1470-1560ºF ( 800 – 850ºC), soaked and furnace cooled to 900ºF (480ºC) then air cooled.

Normalizing

A typical normalizing temperature for 4145 forgings is 1600ºF (870ºC), but based on production experience this temperature may vary from 100ºF (38ºC) above to 50ºF (10ºC) below this figure. If normalizing is carried out before a hardening and tempering treatment, then the upper temperature range is used; if normalizing is the final treatment then the lower range is used.

Hardening

The austenitizing temperature for this grade is in the range 1500-1550ºF (815-845ºC). Parts should be slowly heated to this temperature, soaked and oil quenched. Parts should be tempered as soon as they reach room temperature.

Tempering

Parts will be tempered between 1020-1300ºF (550-700ºC) for 2 hours per inch (25 mm), then air cooled. Reduced impact values will be obtained on tempering at 500ºF (260ºC) or at 750 to 1025ºF (340 to 550ºC).
The optimum combination of strength and toughness is obtained from a microstructure that is tempered martensite. If very high strength is required then tempering is carried out at a low temperature – in fact this is a stress relief – when lightly-tempered martensite will result.

Machinability

Best machinability in this alloy is obtained from a structure that runs from coarse lamellar pearlite to coarse spheroidite. Heat treatment providers should be consulted for the best treatment required to obtain these structures, always bearing in mind the complexity and section size of the parts to be machined.

Weldability

The grade may be welded by fusion or resistance methods, but preheating and post-weld stress relief are recommended. The grade should not be welded in the hardened and tempered condition.

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Forging Alloy Steel 4125

Alloy Steel 4125

General Characteristics

This is a chromium-molybdenum alloy steel used in the case-hardened condition and displaying good strength and toughness properties.

C%     

 Mn% 

Si%   

P%   

S% 

 Mo%

Cr% 

 0.23/0.28

0.7/0.9

0.20/0.35

0.04 max

0.04 max

 0.20/0.30

0.40/0.60

This is a chromium-molybdenum alloy steel used in the case-hardened condition and displaying good strength and toughness properties.

Chemical Analysis

Applications

The alloy is used for components of medium and large cross section, requiring high strength and toughness properties for automotive engineering and gear and engine construction, such as forged crankshafts, steering knuckles, connecting rods, spindles, intermediate gears, pump and gear shafts.

Forging

The alloy may be forged at a temperature in the region of 2200ºF (1205ºC) down to a temperature of around 1700ºF (925ºC) and subsequently air cooled.

Heat Treatment

Annealing: The alloy may not normally be annealed since optimum machining performance at this carbon level may be found in either an as-forged or normalized structure, the normalized structure being best suited to smaller sections.
Normalizing: At around 1650ºF (900ºC) and air cooling. Normalizing is advantageous prior to carburizing.
Hardening: Austenitize at 1545 – 1615ºF (840 – 880ºC) and water or oil quench depending on size and complexity of part.
Tempering: Temper at a temperature that will be based on past experience and will give the required mechanical properties.
Machinability
This alloy is readily machinable providing the appropriate heat treatments are employed.
Weldability
This alloy is readily weldable by normal fusion methods, but should always be welded prior to carburizing and other heat treatments.

ALLOY STEEL 4037

Chemical Analysis
C% Carbon
0.35 – 0.40
Mn% Manganese
0.70 – 0.90 max
Si% Silicon
0.20 – 0.35
P% Phosphorus
0.035 max
S% Sulfur
0.040 max
Mo% Molybdenum
0.20 – 0.30

General characteristics of Alloy Steel 4037

Alloy steel 4037 is a direct hardening, molybdenum-bearing engineering steel that may be readily forged, machined and welded.

Applications

This grade may be forged into parts for the aerospace industry, for example landing gear parts, and for shafts and collets for the oil and gas industry.

Forging

The alloy should be forged at 2250ºF (1230ºC) and forging should preferably be finished at a temperature above 1700ºF (925ºC).

Heat treatment

Annealing

For optimum machinability, this alloy should have a microstructure that is primarily coarse pearlite, with a minimum of ferrite. This would involve annealing at 1525ºF (830ºC) and slow furnace cooling.

Normalizing

A typical normalizing temperature for 4037 forgings is 1600ºF (870ºC), but based on production experience this temperature may vary from 100ºF (38ºC) above to 50ºF (10 ºC) below this figure. If normalizing is carried out before a hardening and tempering treatment, then the upper temperature range is used; if normalizing is the final treatment then the lower range is used.

Hardening

The austenitizing temperature used for this grade is in the range 1525- 1575ºF (830-860ºC). Quenching will be in oil or water, depending upon the section size and the complexity of the part being treated. A qualified heat treat operation should be consulted to obtain a detailed heating, soaking and quenching procedure.

Tempering

The tempering temperature – and time – will of course determine final hardness figures, but a typical 4037 alloy will give a hardness of Rc52 after 1 hour at 400ºF (205ºC) and a hardness of Rc25 after 1 hour at 1200ºF (650ºC).

Machinability

Machining of this alloy is best done with a microstructure of coarse pearlite, which will be obtained by following the annealing procedures described above. Any finish machining to be done on say a hardened and tempered part should be undertaken following professional advice or according to experience.

Weldability

This grade may be welded by fusion or resistance methods. Preheating and post-weld stress relief are advised. Welding in the hardened and tempered condition may result in loss of required mechanical properties in the weld and heat-affected zones.

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ALLOY STEEL 4023 

Chemical Analysis
C% Carbon
0.20 – 0.25
Mn% Manganese
0.7 – 0.9
Si% Silicon
0.15 – 0.30
P% Phosphorus
0.035 max
S% Sulfur
0.04 max
Mo% Molybdenum
0.20 – 0.30

General characteristics of Alloy Steel 4023

Alloy steel 4023 is a low-carbon, molybdenum-bearing steel that may be case hardened while showing good core toughness and ductility.

Applications

Alloy 4023 finds applications as forged shafts and bushings in such industries as oil and gas, aerospace, and machinery.

Forging

The maximum forging temperature for this alloy is approximately 2250ºF (1230ºC). The alloy should preferably not be forged below 1700ºF (925 ºC.)

Heat treatment

Annealing

Depending upon the complexity of the piece after forging, this alloy may or may not require annealing. It may, in any event, be transferred after forging to a furnace held at around 1550 -1600ºF (845-870 ºC), soaked and slow cooled.

Normalizing

This grade, with its relatively low carbon content, is not normally normalized. If experience proves that in certain cases normalizing prior to, say, carburizing, is beneficial, then a temperature of 1650ºF (900ºC) would be used.

Hardening and tempering

This grade would not be hardened and tempered unless previously surface hardened by, for example, carburizing. In this case hardening and tempering would be carried out on the carburized part, and consultation with a heat treat operator is recommended to ensure optimum properties in both case and core.

Machinability

Alloy 4023 may be readily machined providing the optimum microstructures are obtained. Again, consultation with a heat treat operation is the best way to ensure that this case obtains.

Weldability

This grade may be welded by all normal fusion and resistance methods. Pre and post heat as necessary, and weld prior to any surface hardening carried out on material.

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AISI / Alloy Steel 3310

Chemical Analysis
C% Carbon
0.08– 0.13
Mn% Manganese
0.45 – .60
P% Phosphorus
0.025 max
S% Sulfur
0.025 max
Si% Silicon
0.20 – 0.35
Ni% Nickel
3.25 – 3.75
Cr% Chromium
1.4 – 1.75

General characteristics of Alloy Steel 3310

Alloy steel 3310 is a case-hardening nickel-chromium steel with excellent toughness and strength properties.

Applications

This alloy is used in the production of forged components with large cross sections that require high toughness and core strength such as forged gears, crankshafts and heavy-duty gear shafts in aircraft and truck manufacture.

Forging

This alloy would be forged at a temperature in the region of 2200 to 1700ºF (1200 and 925ºC.)

Heat treatment

Annealing: This alloy would seldom be annealed

Normalizing: A nominal normalizing temperature for this steel is 1700ºF (925ºC) followed by air cooling.

Carburizing: The steel would be carburized at 1650-1740ºF (900-950ºC) followed by water quench for large components of simple shape only, otherwise oil quench.

Hardening: Core: 1525-1580ºF (830-860ºC.). Case: 1440-1470ºF (780-800ºC.)

For both core and case hardening, water quench for large components of simple shape only, otherwise oil quench

Tempering: At 340-410ºF (170-210ºC.)

Machinability: This alloy is readily machined from either an as-forged or normalized structure.

Weldability: The alloy may be readily welded, but only prior to case hardening and subsequent heat treatment.

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4340 ALLOY STEEL

General Characteristics of Alloy Steel 4340

4340 is a nickel-chromium-molybdenum alloy steel known for its toughness and its ability to attain high strengths in the heat-treated condition. It has very good fatigue resistance.

 

Chemical Analysis

Carbon 0.38 – 0.43
Chromium 0.7 – 0.9
Iron Balance
Manganese 0.6 – 0.8
Molybdenum 0.2 – 0.3
Nickel 1.65 – 2
Phosphorus 0.035 max
Silicon 0.15 – 0.3
Sulphur 0.04 max

 

 

Applications

Commercial and military aircraft, automotive systems, forged hydraulic and other machine tool applications, forged steel crankshafts.

 

Forging

Forging should be carried out between 2250 and 1800ºF (1230 and 980 degrees C). Parts should be slow cooled after forging in ashes or sand etc.

 

Heat Treatment

Heat treatment after forging is carried out to render the steel suitable for machining, and to meet the mechanical property limits specified for the steel’s particular applications. There are several ways to heat treat a given steel part and it is only through practice that the optimum treatments, temperatures and conditions may be defined. The following information should be taken as a guide only.

Annealing

To obtain a pearlitic structure on certain parts for machining, 4340 should be annealed at a nominal temperature of 1525º F (830ºC,) cooling to 1350ºF (730ºC) and furnace cooling to 1130º F (610ºC) at a rate of 20ºF (11ºC) per hour, then air cooling. This process, known as full annealing, is very time consuming as it involves slow cooling over the entire temperature range from the austenitizing temperature to a temperature well below that at which transformation is complete. To obtain a spheroidized structure in 4340 grade involves austenitizing at 1380 o F (750ºC,) furnace cooling to 1300 o F (705ºC) then to 1050ºF (565º C) at a rate of 5ºF (3ºC) per hour. This structure will probably result in better machinability than will the coarse lamellar pearlite structure obtained by the full anneal process.

Normalizing

This process is defined as heating a steel to a temperature above the ferrite to austenite transformation temperature, then cooling in air to a temperature well below this transformation temperature. The treatment may be carried out on forged products as a conditioning treatment prior to final heat treatment. Normalizing also serves to refine the structure of forgings that might have cooled non-uniformly from their forging operation. The nominal normalizing temperature for 4340 grade is 1500ºF (815ºC,) but production experience may necessitate a temperature either 50º F (10º C) above or below this temperature. . As a rule of thumb, when forgings are normalized before, say, carburizing or hardening and tempering, the upper range of normalizing temperatures is used. When normalizing is the final heat treatment, the lower temperature range is used.

Hardening

This heat treatment results in the formation of martensite after quenching, resulting in increased hardness and tensile strength. A temperature range of 1500 – 1550º  F (815 – 845ºC) is the normal austenitizing temperature for direct hardening of 4340 grade. Oil quenching is normally used for 4340 as the alloy’s hardenability is suited to this quenching method.

Tempering

Tempering is carried out to relieve stresses from the hardening process, but primarily to obtain mechanical properties required for the final application. The actual tempering temperature will be chosen to meet the required properties, and in many cases will be a matter of trial and error. This alloy steel should not be tempered between 400-790 o F (200-420 o C) to prevent embrittlement

This grade may also be hardened by nitriding or flame or induction hardening.

Machinability

This grade is readily machinable, with either a coarse lamellar pearlitic structure or a spheroidized structure being best advised, depending upon section size and complexity and amount of machining to be carried out. If there is doubt about the suitability of any other structure, then a spheroidizrd structure should be aimed for in heat treatment.

Welding

This grade is readily welded in the annealed condition, but welding in the hardened and tempered condition should be avoided where possible because of the effect on mechanical properties. Welding in the nitrided or flame or induction hardened conditions is not recommended.

Guidance details for welding include the use of low-hydrogen electrodes and a preheat from 400 –

570ºF (200 – 300º C,) if possible to be maintained during welding. Parts should be slow cooled after

Welding in ashes or sand and stress relieved if possible.

Comments

This alloy, 4340, may be heat treated to high strength levels while maintaining

good toughness, wear resistance and fatigue strength levels, combined with good atmospheric corrosion resistance, and strength up to around 600º F (315º C.)