Heat Treating 4140 steel FAQ : anvilfire.com How-to. (2022)

I'm looking for some advice on an anvil I'm constructing. I have used an forklift fork for the construction. I am at a point when I am trying to do some type of hardening to the face. The section that I am attempting to harden is approximately 2" x 5" x 18". It was cut from the upright portion of the fork and after heat treating will be welded onto the the tapered flat portion which will protrude from the front with a small section of a horn. My question concerns the hardening heat and quench. I am not certain as to the type of steel, but after doing some research, I am proceeding under the assumption I am working with 4140. For the sake of ease, will any attempt to air harden this steel work? If I were to get a good soak time and then pull the peice and cool the face with an air compressor, will the sheer mass of the piece prevent me from getting a good hard face? I know that this steel is best oil quenched, but I believe it would be dangerous for me to try and submerge that much steel in a drum full of oil. I really prefer not to use hardfacing electrodes, but will if I must. Is it possible that carburizing this peice would be a better option for me?
Don - Wednesday, 03/23/11 20:27:15 EDT

Don, Normally 4140 is an oil quench steel. In a section this large you cannot blow enough air to make difference.

You might get away with a water mist spray.

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Carburizing also requires a quench to be hard and is VERY shallow, insufficient for an anvil.

4140 is pretty tough and those forks were already heat treated. I would use it as-is.

- guru - Wednesday, 03/23/11 21:21:32 EDT

4140 and oil quench It depends on the size. I spent about 3 years running the quench and temper line as the HT Metallurgist at Crucible Steel in Midland, PA. One of our bread and butter items was quenched and tempered 4140 to ASTM bolting specification sizes from 1/2 " round to 8" round, minimum tempering temperature was 1100 F. 2" round and under we almost always oil quenched (Sometimes with 2", if the Cr and Mo content were low we'd water quench.) Any diameter over 2", we water quenched in an extremely well agitated water quench that was coupled with a heat exchanger to maintain water temp. In the summer, we struggled to keep it below 100 F, which was where we needed it to be. The oil quench was also well agitated, and was heated to maintain a relatively constant temperature.
- Gavainh - Thursday, 03/24/11 22:10:58 EDT

Harden 4140 at 1550-1600°F Oil quench

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4140 Power Hammer Dies:
I asked this question over on iforgeiron and was surprised with the answer, so I wanted to double check. I'm ready to heat treat the main flat dies for my homebrewed power hammer. The ram weight is 88 lbs, and the dies are 3" square 4140. After hardening (thanks for the timely tip on quench medium on large 4140, Gavainh!), where do I need to draw the temper to? I was thinking in the 500-600 degree range, but the answer I got was 350-400. I don't want the dies deforming during use, but I also don't want them cracking or chipping and sending out high-speed shrapnel.
- Stormcrow - Friday, 03/25/11 02:57:58 EDT

Hammer Die Hardness:
Stormcrow, the steel used and the heat treat are somewhat shape dependent on power hammer dies.

1) 4140 is an OK die steel but is not recommended for radical shaped dies such as narrow fullering, crown and so on.

2) Fully hardened 4140 ranges from 54 to 59 HRC. But it should be tempered for any heavy use.

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3) Tempering recommendations from the ASM heat treaters guide for 4140-4142 is a minimum of 400°F. This leaves near full hardness. The following table is extrapolated from a hardness graph given in Brinell Hardness with nearest points taken from a conversion table for Rockwell hardness. Tensile values are generic, not specifically for 4140. Note that conversion tables rarely agree on Brinell to Rockwell.

SAE 4140 Steel Tempering
Tempering
Temperature
Hardness
Brinell
Hardness
Rockwell
Tensile
400°F 200°C 514 HB 55 HRc 297 KSI
500°F 260°C 477 HB 50 HRc 243 KSI
550°F 290°C 461 HB 48 HRc 235 KSI
600°F 320°C 444 HB 47 HRc 225 KSI
650°F 340°C 429 HB 46 HRc 217 KSI
700°F 370°C 415 HB 44 HRc 210 KSI
800°F 430°C 363 HB 39 HRc 182 KSI
900°F 480°C 331 HB 36 HRc 166 KSI
1000°F540°C 293 HB 31 HRc 145 KSI
Data extrapolated from a hardness graph given in Brinell with nearest points taken from a conversion table for Rockwell hardness. Temperature conversion to Celcius rounded to nearest 10°. Tensile not specifically for 4140. All data +/- 10%

Die Steels:

The ASM Handbook on forging recommends 6G and 6F2 (??) steels for large dies and 4150 for small dies (4370 for higher carbon dies). In this case "small" is probably 300 pounds or less. . . Small die hardness in 4150 steel is recommended at only 277 to 321 BHn (HB = Bhn).

In our small blacksmith shops with hammer sizes of 50 to 150 pounds and dies of only about 5 pounds they are generally harder. All those fancy relatively aggressive dies and dies used for cold work that Big BLU sells are made of carefully heat treated S7. Early Big BLU dies were 4140, Bull and Phoenix dies are H13, Chinese hammers C45 (1045?). S7's carbon content is 0.55% and is a Chrome Vanadium steel. Very tough and wear resistant.

Conclusion:

So, your initial thought was right (a 500 to 600°F temper resulting in a 45 to 50 HRc).

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Note that Rockwell 44-45 is just barely in the machinable range and that a grade of H13 is sold in this condition to avoid heat treatment after machining. This saves a lot of trouble in small shops. I have seen corner impact chips in this steel but would not recommend softer for small hammer dies. Corners should be rounded to avoid chipping.

The 350-400°F value commonly given is a MINIMUM starting point for almost all steels so is a safe answer but non specific. I often use this value but qualify it as a minimum AND because it can be achieved in a kitchen oven. It is recommended that you temper immediately after hardening and before the steel reaches room temperature to avoid cracking or warping. But you can always re-temper to a higher temperature - so a minimum temper is a good start if you do not know what your final temper should be.

The one thing I do not like about the ASM Heat Treaters Guide is that the data, collected from many sources is not given in a uniform form. Charts on the same page will give Rockwell and Brinell hardnesses and then differently on the next alloy.
- guru - Friday, 03/25/11 09:45:37 EDT

Stormcrow: one of the reasons for using a higher alloy (4340, S-7, etc) than 4140 is quench reliability. While large 4140 rounds can be water-quenched, squares are a different story. Each corner of a die is a three-sided pyramid and in quenching the corners will cool very quickly, often causing "finger-nail" cracking of the corners. That is the main reason for switching to an alloy that will give good results by oil quenching. If your dies survived the water-quench then you're good to go.
- grant - nakedanvil - Friday, 03/25/11 18:52:37 EDT

(Video) Blacksmithing: The best tools for beginners!

Good reason to round corners as much as possible before heat treating - guru

References and Links

  • Heat Treating FAQ anvilfire Q&A compilation.
  • Temper Color Chart anvilfire online chart
  • Junkyard Steels FAQ Using recycled steel or steels of unknown pedigree.
  • Alphabet Soup What's that acronym?
  • Glossary Blacksmithing and Metalworking Terms
  • Knives01 anvilfire 21st Century Page FAQ
  • Anvils V - Testing rebound Hardness testing anvils, Shores Scleroscope
  • Hardness Conversion Table Metal hardness value conversion table Brinell to Rockwell A, B, C scales.
  • Quenchants FAQ With Super Quench Recipe
  • ASM Metals Reference Book, American Society for Metals International
  • ASM Heat Treater's Guide to Ferrous Metals, American Society for Metals International
  • Tempil - Basic Guide to Ferrous Metallurgy Chart, Tempil Division, Big Three Industries, Inc.
  • MACHINERY'S HANDBOOK, Industrial Press
  • NEW Edge of the Anvil, Jack Andrews, Skipjack Press.
  • MatWeb.com On-line materials database
  • Timken Latrobe Steels web page

FAQs

How do you heat treat 4140 steel? ›

For 4140 steel, the recommended heat treatment [1] consists of heating to austenitizing temperature, typically 1570°F (855°C), followed by oil quenching. Tempering (reheating after quenching) will achieve the desired hardness range.

How high can you heat treat 4140 steel? ›

HEAT TREATING

4140 has a hardening range of 1525° -1625° F. Quench in oil. A wide range of mechanical properties can be obtained by tempering between 400° and 1300° F.

Is 4140 quenched and tempered? ›

It is common for 4140 alloy steel to be supplied in either the annealed (soft) condition, or Quench & Tempered (Q & T), the hardened condition. The hardened condition is used where added strength or resistance to wear is desired.

What is the max hardness for 4140? ›

Surface hardness achievable is 600 to 650HV. Atlas 4140 can be surface hardened to 58HRC (typical value). Welding is not recommended because of the likelihood of quench cracking occurring.

How can I harden 4140 at home? ›

Heat the steel to 1,675 degrees Fahrenheit in a heat treat furnace or forge and hold it at that temperature for approximately 30 minutes per inch of length to normalize the steel. Normalizing removes any stresses within the steel that could create cracks when hardened.

Can you flame harden 4140? ›

Flame hardening is a surface hardening process used on medium carbon mild or alloy steels (such as 1045, 4140, 4340), or cast irons, to produce a hard wear resistant surface (case) on the part.

What is the Rockwell of 4140 annealed? ›

4140 (modified) Cold Finished, Annealed Alloy Bar Stock

Typical hardness is Rockwell “C” 19/24. Typical tensile strength 114,000 PSI. Its wear resistant properties far exceed that of “cold roll” steels. It is easy to machine and will accept additional heat treatment.

What grade of steel is 4140? ›

4140 Grade Designation

Designates that 4140 steel is molybdenum steel, indicating that it possesses higher amounts of molybdenum than other steels, such as the 1xxx series. Designates that 4140 steel has additions of chromium as well; more so than 46xx steel for example.

Is 4140 hard to machine? ›

4140 responds readily to heat treatment and is comparatively easy to machine in the heat-treated condition. 4140 resists creep in temperatures up to 1000 degrees Fahrenheit and maintains its properties even after long exposure at these high working temperatures. The chromium content provides good hardness penetration.

What do the numbers in 4140 steel mean? ›

ANSWER: The first “4” is 4140 indicates that the steel contains molybdenum at higher levels than other steels like the 1xxx series. The “1” in 4140 indicates the addition of chromium at higher levels than 46xx steels. The “40” differentiates this steel from other 41xx series steels.

How hard is pre hardened 4140? ›

4140 PREHARD is heat treated to a medium hardness (HRC 28/32) and is designated as 4140 HT.

What is normalized 4140? ›

The nominal normalizing temperature for 4140 grade is 1600 º F (870 º C), but production experience may necessitate a temperature either 50 º F (10 º C) above or below this figure.

Can you case harden 4140 steel? ›

4140 can be safely color cased hardened by lowering the temperature at quench to 1375 degrees. The critical temperature for 4140 is 1575 so by quenching at below this will not harden the piece except for the high carbon surface.

What is the yield strength of 4140 steel? ›

Project Description
PropertiesMetricImperial
Tensile strength655 MPa95000 psi
Yield strength415 MPa60200 psi
Bulk modulus (typical for steel)140 GPa20300 ksi
Shear modulus (typical for steel)80 GPa11600 ksi
9 more rows
17 Mar 2021

Can you weld mild steel 4140? ›

A:4140 steel will weld very similar to your low carbon steels. The difference is that its high carbon content can screw things up. To avoid cracking you need to preheat 4140 steel prior to welding.

Can you heat treat 4140 annealed? ›

Annealed Alloy Steel

For this reason, it is often used as stock for forging, as 4140 has self scaling properties. 4140 responds readily to heat treatment and is comparatively easy to machine in the heat condition.

How do you anneal 4140? ›

ANNEALING: Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1500°F (816°C), and hold at temperature for 1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 20°F per hour (11°C per hour) to 1230°F (666°C).

Can you Carburize 4140? ›

There is an increased risk of cracking when carburizing 4140 compared to carburizing grade steels but by being expeditious with getting it out of the quench and into a tempering furnace will substantially mitigate the risk of cracking.

What is the disadvantage of flame hardening in the heat treatment process? ›

Disadvantages of flame hardening include:

While the surface might display higher hardness, it might also become more susceptible to cracking and flaking. Flame hardening can not be applied as precisely as other case hardening processes, such as induction hardening or boronizing.

Is 4140 a tool steel? ›

Yes. This is definitely a type of tool steel. One of the reasons why 4140 qualifies to be tool steel is the high content of chromium and carbon. The higher the chromium content the better.

What is flame hardening? ›

Flame hardening is a heat treatment process where oxyfuel gas flames are directly impinged onto the gear-tooth surface area to be hardened which is then subjected to quenching. It results in a hard surface layer of martensite over a softer interior core. Its cost is considerably less than induction hardening.

What is the carbon content of 4140 steel? ›

Chemical Composition

AISI 4140 is versatile because of its simple chemistry and has the following composition: 0.40 % carbon and 0.85 % manganese which offers toughness and can be heat treated and hardened 0.1 % chromium adds to overall toughness but is not enough to be made into stainless steel.

Is 4140 a carbon steel? ›

In addition, any steel that requires alloying elements (like 4140 and 4340, for example) are not carbon steels. Within the carbon steel definition, materials can be defined as either low-carbon steel or high-carbon steel.

Is 4140 stainless steel magnetic? ›

It is magnetic and heat treatable. 4140 alloy steel is generally harder and stronger than carbon steel. Additionally, it provides high impact resistance, fatigue strength, and torsional strength, which makes 4140 a great choice for drive shafts, axles, and torsion bars.

Is 4140 steel hot or cold rolled? ›

Hot rolled 4140 steel bar is a medium-carbon alloy steel that has a high hardenability. This grade is also widely used for forging. Hot rolled 4140 steel also has good fatigue and impact resistance after heat treating.

Is 4140 harder than stainless steel? ›

4140 is a chromium and molybdenum alloy steel that has an excellent weight to strength ratio. It is considerably stronger than standard steel. Although it is chromium steel and often referred to as “chromoly steel” it does not contain as much chromium as stainless steel.

Can you bend 4140? ›

4140 may be supplied in several hardness ranges to deliver several levels of strength. In most cases it is considered to be fairly machinable and weldable. You can forge it and bend it with caution. It is considered to be a “through hardening steel”, but it will also accept surface hardening to maintain a ductile core.

What is the SFM for 4140? ›

Recommended Cutting speed range for turning at stable conditions is 850 - 1160 [SFM] / 260 - 355 [m/min].

Is 4140 good for gears? ›

Their strength makes 4130 and 4140 steels well-suited for components such as gears that require high strength and durability. However, the higher carbon, chromium and molybdenum levels that make these materials strong and highly hardenable also make them more susceptible to cracking.

What is machinability rating? ›

The machinability rating is determined by measuring the weighed averages of the normal cutting speed, surface finish, and tool life for each material. Machinability rating less than 100% is more difficult to machine than B1112 and material with a value more than 100% is easier.

What is the strongest grade of steel? ›

1,000-N grade steel is the world's strongest ultra high strength steel for building structures that was developed to improve the earthquake resistance of buildings and has approximately 2.7 times the yield strength (*2) of conventional 490-N grade steel.

How do you read steel numbers? ›

Carbon steel

Carbon steels and alloy steels are designated a four digit number, whereby the first digit indicates the main alloying element(s), the second digit indicates tg (top grade) element(s), and the last two digits indicate the amount of carbon, in hundredths of a percent (basis points) by weight.

Can you heat treat 4140 PH? ›

Gateway 4140 PH may be heat treated to higher levels of hardness for higher strength. Pre- heat to 1300/1350 F and hold for one hour. Heat to 1550/1575 F and soak one half hour when material is up to temperature. Oil quench below 200 F and temper immediately.

What is the difference between 4340 and 4140 steel? ›

However, 4340 has more carbon, while 4140 has more chromium. One of the most significant differences between the two metals is the inclusion of nickel in 4340 steel, which accounts for the metal's greater strength and fracture toughness.

What does pre hardened mean? ›

High-speed steel that is hardened and ready for your process upon receipt. Pre-Harden.

Is EN19 the same as 4140? ›

EN19 steel also known as AMERICAN SAE 4140 material. EN19 material is a high quality alloy steel with tensile strength. It is a high quality medium carbon. EN19 Steel is one steel grade in BS 970-1955 standard, which is specification for wrought steels for mechanical and allied engineering purpose.

What grade is a 4140 bolt? ›

AISI 4140 Fasteners is high strength chromium-molybdenum alloy steel grade used for low temperature bolting fasteners applications.
...
AISI 4140 Alloy Fasteners Mechanical Properties.
Grade AISI 4140MetricImperial
Tensile strength655 MPa95000 psi
Yield strength415 MPa60200 psi
11 more rows

What is the yield strength of AISI 4140 steel quenched and tempered at 400 F? ›

1515 MPa 219700 psi

Can you induce hardened 4140? ›

2.1.

Since the aim of the induction hardening is to improve the surface hardness, the carbon content in steel to be induction hardened should be between 0.3 and 0.5%. Thus, the AISI 4140 (42CrMo4) steel used in the tests was normalised prior to the induction hardening.

How hard is pre hardened 4140? ›

4140 PREHARD is heat treated to a medium hardness (HRC 28/32) and is designated as 4140 HT.

Can you case harden 4140 steel? ›

4140 can be safely color cased hardened by lowering the temperature at quench to 1375 degrees. The critical temperature for 4140 is 1575 so by quenching at below this will not harden the piece except for the high carbon surface.

How do you anneal 4140? ›

ANNEALING: Heat at a rate not exceeding 400°F per hour (222°C per hour) to 1500°F (816°C), and hold at temperature for 1 hour per inch (25.4mm) of maximum thickness; 2 hours minimum. Then cool slowly with the furnace at a rate not exceeding 20°F per hour (11°C per hour) to 1230°F (666°C).

What is the carbon percentage in 4140 steel? ›

Chemical Composition

AISI 4140 is versatile because of its simple chemistry and has the following composition: 0.40 % carbon and 0.85 % manganese which offers toughness and can be heat treated and hardened 0.1 % chromium adds to overall toughness but is not enough to be made into stainless steel.

Can 4140 be Carburized? ›

There is an increased risk of cracking when carburizing 4140 compared to carburizing grade steels but by being expeditious with getting it out of the quench and into a tempering furnace will substantially mitigate the risk of cracking.

What is difference between induction hardening and quenching? ›

The quenched metal undergoes a martensitic transformation, increasing the hardness and brittleness of the part. Induction hardening is used to selectively harden areas of a part or assembly without affecting the properties of the part as a whole.

What is the tensile strength of 4140 steel? ›

Tensile Strength: AISI 4140 steel typically has a target ultimate tensile strength of around 95,000 psi.

Can you heat treat 4140 PH? ›

Gateway 4140 PH may be heat treated to higher levels of hardness for higher strength. Pre- heat to 1300/1350 F and hold for one hour. Heat to 1550/1575 F and soak one half hour when material is up to temperature. Oil quench below 200 F and temper immediately.

What is 4140 annealed? ›

4140 cold finished annealed is a popular type of alloy steel containing chromium and molybdenum. This type of steel can be oil hardened for high hardness and offers extreme strength for varying industrial applications.

Is 4140 harder than stainless steel? ›

4140 is a chromium and molybdenum alloy steel that has an excellent weight to strength ratio. It is considerably stronger than standard steel. Although it is chromium steel and often referred to as “chromoly steel” it does not contain as much chromium as stainless steel.

Is 4140 a high carbon steel? ›

Is 4140 a carbon steel? ANSWER: It is considered a low alloy or carbon steel. With the addition of chromium and molybdenum, it is one of the most common alloy steels.

Does 4140 steel rust? ›

Excellent resistance to corrosion is the reason why 4140 steel does not rust so fast as compared to other types of steel. This can be attributed to a significant percentage of chromium and molybdenum. However, once corroded, the 4140 steel will just rust like most steel that undergoes the same damage.

What is the difference between annealing and tempering? ›

Both heat treatments are used for treating steel, although annealing creates a softer steel that is easier to work while tempering produces a less brittle version that is widely used in building and industrial applications.

What is the annealing temperature? ›

The temperature range for process annealing ranges from 260 °C (500 °F) to 760 °C (1400 °F), depending on the alloy in question. This process is mainly suited for low-carbon steel. The material is heated up to a temperature just below the lower critical temperature of steel.

How hard is annealed 4140? ›

4140 (modified) Cold Finished, Annealed Alloy Bar Stock

It is offered in the cold finished annealed condition. Typical hardness is Rockwell “C” 19/24. Typical tensile strength 114,000 PSI. Its wear resistant properties far exceed that of “cold roll” steels.

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