Steel 4037
AISI/SAE 4037 · UNS G40370
4037 is a widely used medium-carbon molybdenum alloy steel (UNS G40370) in the SAE-AISI 40xx family, with roughly 0.37 % C giving a good balance of strength, toughness and machinability after quench and temper.
Reference datasheet — 4037 is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the QT-28-32HRC condition
4037 tempers and conditions
4037 is supplied in 8 conditions, soft to hard. QT-28-32HRC is the default FabDigit quotes; the values on this page are for it.
Compare all 8 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Hot rolled | Cheapest mill condition for parts that will be heat treated after rough machining or forging. | 380 | 620 | 22 | 179 HB | — |
Solution annealed | Softest, most machinable and most formable condition; use before quench and temper or for cold heading stock. | 400 | 585 | 27 | 170 HB | — |
Normalized | Uniform fine-grain structure and mid-range strength for forgings and weld fabrications not requiring full Q&T. | 450 | 690 | 22 | 200 HB | — |
Cold drawn | Close-tolerance bright bar with raised yield strength for shafts and screw-machine work with no further heat treatment. | 585 | 690 | 15 | 200 HB | — |
quenched and tempered, ~250 HB | Toughest Q&T level; choose for shock-loaded shafts and couplings where impact matters more than strength. | 700 | 830 | 20 | 24 HRC | — |
QT-28-32HRCDefault quenched and tempered, ~285 HB | Standard general-purpose condition for machined shafts, studs and high-strength fasteners. | 860 | 965 | 18 | 30 HRC | — |
quenched and tempered, ~320 HB | Higher-strength Q&T level typical of SAE J429 Grade 8 / ASTM A354 BC fastener requirements. | 965 | 1,080 | 15 | 34 HRC | — |
quenched and low-temperature tempered | Maximum-strength condition for small wear parts and pins; reduced ductility and notch sensitivity must be accepted. | 1,240 | 1,380 | 12 | 42 HRC | — |
What is 4037?
4037 is a widely used medium-carbon molybdenum alloy steel (UNS G40370) in the SAE-AISI 40xx family, with roughly 0.37 % C giving a good balance of strength, toughness and machinability after quench and temper. In the default quenched-and-tempered condition it reaches about 860 MPa yield, 965 MPa tensile, 18 % elongation and 285 HB (30 HRC), and it is supplied hot-rolled, annealed, normalized, cold-drawn and in Q&T bands from 22–26 HRC up to 40–45 HRC. Machinability drops to a score of 52 and welding requires 200–300 °C preheat plus post-weld tempering; the steel has no inherent corrosion resistance. Where welding is frequent, the lower-carbon 4027 is the nearest alternative. 4037 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F). 4037 has a yield strength of 860 MPa (125 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 89% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
What is 4037 used for?
- bolts
- studs
- shafts
- gears
Advantages
- High strength — 860 MPa (125 ksi), better than 89% of steel grades
4037 properties
Typical room-temperature values for 4037-QT-28-32HRC; bars are the position among steel grades.
Physical3
4037 has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,416°C (2,581 °F).
Mechanical16
4037 has a yield strength of 860 MPa (125 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 89% of steel grades. Elongation at break is 18% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4037 is rated for continuous service to 400°C (752 °F). It conducts heat at 42 W/m·K (24.3 BTU/hr·ft·°F), worse than 56% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
4037 conducts electricity at 8 % IACS, better than 55% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (12/100), worse than 53% of steel grades.
Sustainability4
Producing a kilogram of 4037 takes about 31 MJ of energy and emits 2.2 kg of CO₂ — more than 64% of steel grades. Typical recycled content is 25%.
Manufacturability7
4037's machinability is fair (52/100, better than 52% of steel grades); weldability fair (50/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the steel family
Yield strength against density for every steel grade FabDigit runs. 4037 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 4037
Is 4037 easy to machine?
Machine in the annealed or ≤32 HRC Q&T condition with coated carbide, ~120–180 m/min; above 36 HRC expect tool wear and prefer grinding or hard turning with CBN.
Can 4037 be welded?
Weldable with low-hydrogen consumables but the ~0.37 %C requires 200–300 °C preheat, interpass control and post-weld temper/stress relief to avoid HAZ cracking.
Can 4037 be formed, bent or molded?
Cold heading and bending are practical only in the annealed/spheroidized state; hot forge 1200 °C down to ~950 °C then normalize before quench and temper.
4037 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| C | 0.35 – 0.4 | 0.37 |
| Mn | 0.7 – 0.9 | 0.8 |
| Si | 0.15 – 0.35 | 0.25 |
| Mo | 0.2 – 0.3 | 0.25 |
| P | ≤ 0.04 | |
| S | ≤ 0.04 | |
| Fe | balance |
What surface finishes work on 4037?
No inherent corrosion resistance — specify zinc, zinc-nickel or chrome plating, black oxide, phosphate-and-oil or paint; bake after plating at ≥190 °C to relieve hydrogen embrittlement above 32 HRC.
Surface treatments FabDigit runs on steel parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Organic Coating
Black / Phosphate
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Steel 4037 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- G40370
How much does 4037 cost?
4037 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
4037 — frequently asked
What is 4037 used for?
4037 is typically used for bolts, studs, shafts and gears. In short: strongest 40xx moly grade; wide Q&T hardness range; good strength-to-cost ratio.
What is the yield strength of 4037?
4037 has a typical yield strength of 860 MPa (125 ksi) and a tensile strength of 965 MPa (140 ksi) — stronger than 89% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 4037 easy to machine?
Reasonably — machinability is rated fair (52/100, better than 52% of steel grades). Machine in the annealed or ≤32 HRC Q&T condition with coated carbide, ~120–180 m/min; above 36 HRC expect tool wear and prefer grinding or hard turning with CBN.
Can 4037 be welded?
With care — weldability is rated fair (50/100). Weldable with low-hydrogen consumables but the ~0.37 %C requires 200–300 °C preheat, interpass control and post-weld temper/stress relief to avoid HAZ cracking.
What surface finishes work on 4037?
No inherent corrosion resistance — specify zinc, zinc-nickel or chrome plating, black oxide, phosphate-and-oil or paint; bake after plating at ≥190 °C to relieve hydrogen embrittlement above 32 HRC.
Can 4037 be formed, bent or molded?
Cold heading and bending are practical only in the annealed/spheroidized state; hot forge 1200 °C down to ~950 °C then normalize before quench and temper.
What is the maximum service temperature of 4037?
4037 is rated for continuous use to about 400°C (752 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4037 QT-28-32HRC and 4037-HR?
QT-28-32HRC is the default condition — standard general-purpose condition for machined shafts, studs and high-strength fasteners. HR: cheapest mill condition for parts that will be heat treated after rough machining or forging. Yield strength is 860 MPa in QT-28-32HRC versus 380 MPa in HR.
How much does 4037 cost?
4037 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J429 — Mechanical and Material Requirements for Externally Threaded Fasteners — SAE International (2014)
- ASTM A322 — Standard Specification for Steel Bars, Alloy, Hot-Wrought — ASTM (2020)
- ASM Handbook Vol. 1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol. 4A — Steel Heat Treating Fundamentals and Processes — ASM International (2013)
- Machinery's Handbook, 31st ed. — Industrial Press (2020)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.