Steel 4145-CR (Cold rolled)
Supply condition
AISI/SAE 4145 · UNS G41450 · JIS SCM445 · GB 45CrMo
Rarely stocked; use for thin flat product needing tight thickness and a smooth surface before hardening.
Values for the CR condition
Other 4145 tempers and conditions
4145 is listed in 12 conditions; see the grade overview at 4145.
Compare all 12 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
full anneal, soft machining condition | Pick when the part will be rough-machined or cold-worked before final heat treatment. | 435 | 725 | 22 | 207 HB | — |
HRDefault Hot rolled | Cheapest stock form for parts that will be heat treated after rough machining. | 520 | 830 | 18 | 22 HRC | 7.8 % IACS |
Normalized and tempered | Pick for large forgings/heavy sections where oil quenching risks cracking but moderate strength is needed. | 620 | 900 | 18 | 26 HRC | 7.8 % IACS |
austenitized ~870 °C, air cooled | Pick for uniform fine-grain structure in forgings before machining or final Q&T. | 675 | 1,030 | 16 | 32 HRC | — |
CRThis page Cold rolled | Rarely stocked; use for thin flat product needing tight thickness and a smooth surface before hardening. | 700 | 850 | 10 | 24 HRC | 7.8 % IACS |
Cold drawn | Pick for small-diameter bar needing good straightness, size tolerance and a bright turned/drawn surface. | 700 | 830 | 12 | 23 HRC | 7.8 % IACS |
high-temper sour-service condition (NACE MR0175) | Pick for H2S / sour well components where sulphide stress cracking must be avoided. | 700 | 830 | 20 | 21 HRC | — |
general machinery / shaft condition | Pick for shafts, mandrels and tool bodies needing a balance of strength, toughness and machinability. | 860 | 1,000 | 17 | 30 HRC | 7.8 % IACS |
Quenched and tempered | Default oilfield/heavy-shaft condition: ~110 ksi minimum yield with usable toughness through thick sections. | 900 | 1,080 | 16 | 33 HRC | — |
Induction hardened | Pick for journals, pins and wear surfaces needing a hard skin over a tough Q&T core. | 900 | 1,080 | 14 | 55 HRC | 7.5 % IACS |
high-strength Q&T condition | Pick when higher yield and wear resistance are needed and impact loading is moderate. | 1,000 | 1,140 | 15 | 34 HRC | 7.8 % IACS |
maximum practical bulk hardness | Pick for wear-critical, non-sour parts; toughness and machinability drop sharply and hydrogen-cracking risk rises. | 1,120 | 1,250 | 13 | 38 HRC | — |
What is 4145-CR?
4145-CR is 4145 supplied in the CR condition — rarely stocked; use for thin flat product needing tight thickness and a smooth surface before hardening. 4145-CR has a yield strength of 700 MPa (102 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 81% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi). 4145-CR 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). HR is the default condition FabDigit quotes; CR is available on request or by drawing note.
Advantages
- High strength — 700 MPa (102 ksi), better than 81% of steel grades
Limitations
- Limited ductility — 10%, worse than 91% of steel grades
- Limited formability — 18/100, worse than 84% of steel grades
4145-CR properties
Typical room-temperature values for 4145-CR; 23 are specific to this condition. Other listed values are 4145 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
4145-CR 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).
Mechanical17
4145-CR has a yield strength of 700 MPa (102 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 81% of steel grades. Elongation at break is 10% and the elastic modulus is 205 GPa (29.7 Msi).
Thermal6
4145-CR is rated for continuous service to 350°C (662 °F). It conducts heat at 43 W/m·K (24.8 BTU/hr·ft·°F), better than 51% of steel grades. Thermal expansion is 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
4145-CR conducts electricity at 7.8 % IACS, worse than 57% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (13/100), better than 66% of steel grades.
Sustainability4
Producing a kilogram of 4145-CR takes about 29 MJ of energy and emits 2.3 kg of CO₂ — less than 53% of steel grades. Typical recycled content is 30%.
Manufacturability7
4145-CR's machinability is fair (48/100, worse than 57% of steel grades); weldability poor (30/100); formability poor (18/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with 4145-CR
Is 4145 easy to machine?
Machine best at 200–280 HB (annealed/N+T); at 30–37 HRC use rigid setups, carbide/coated inserts, ~80–120 m/min and heavy positive feeds to avoid work hardening.
Can 4145 be welded?
Poor weldability — preheat 300–350 °C, low-hydrogen consumables or matching 4145 filler, interpass control, and immediate 600–650 °C PWHT; avoid welding parts above 32 HRC in sour service.
Can 4145 be formed, bent or molded?
A hot-work grade: forge 1100–1200 °C, finish above 900 °C, then normalize or Q&T; cold forming is limited to mild straightening.
What surface finishes work on 4145?
No inherent corrosion resistance — use black oxide, phosphate + oil, zinc/nickel plating (bake at 190–220 °C to de-embrittle) or hard chrome; grinds and polishes well for seal surfaces.
4145 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 |
|---|---|---|
| C4145H band: 0.42–0.49 | 0.43 – 0.48 | 0.45 |
| Mn4145H band: 0.70–1.05 | 0.75 – 1 | 0.88 |
| Si | 0.15 – 0.35 | 0.25 |
| Cr4145H band: 0.75–1.20 | 0.8 – 1.1 | 0.95 |
| Mo4145H band: 0.13–0.28 | 0.15 – 0.25 | 0.2 |
| P | ≤ 0.04 | — |
| Smax; ≤0.015 typical for oilfield/HIC service | ≤ 0.04 | — |
| Fe | balance | — |
4145-CR — frequently asked
What is 4145-CR used for?
4145-CR is typically used for oilfield drill collars, downhole tool bodies and subs, heavy shafting, mandrels and stabilizers, forged couplings and flanges and wear-resistant machine spindles. In short: premium Cr-Mo forging bar.
What is the yield strength of 4145-CR?
4145-CR has a typical yield strength of 700 MPa (102 ksi) and a tensile strength of 850 MPa (123 ksi) — stronger than 81% of steel grades. Strength varies by condition: see the 12 listed tempers.
Is 4145-CR easy to machine?
Reasonably — machinability is rated fair (48/100, worse than 57% of steel grades). Machine best at 200–280 HB (annealed/N+T); at 30–37 HRC use rigid setups, carbide/coated inserts, ~80–120 m/min and heavy positive feeds to avoid work hardening.
Can 4145-CR be welded?
Not readily — weldability is rated poor (30/100). Poor weldability — preheat 300–350 °C, low-hydrogen consumables or matching 4145 filler, interpass control, and immediate 600–650 °C PWHT; avoid welding parts above 32 HRC in sour service.
What surface finishes work on 4145-CR?
No inherent corrosion resistance — use black oxide, phosphate + oil, zinc/nickel plating (bake at 190–220 °C to de-embrittle) or hard chrome; grinds and polishes well for seal surfaces.
Can 4145-CR be formed, bent or molded?
A hot-work grade: forge 1100–1200 °C, finish above 900 °C, then normalize or Q&T; cold forming is limited to mild straightening.
What is the maximum service temperature of 4145-CR?
4145-CR is rated for continuous use to about 350°C (662 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between 4145-HR and 4145-IH?
HR is the default condition — cheapest stock form for parts that will be heat treated after rough machining. IH: pick for journals, pins and wear surfaces needing a hard skin over a tough Q&T core. Yield strength is 520 MPa in HR versus 900 MPa in IH.
Can FabDigit make parts in 4145-CR?
Yes — 4145-CR is available for CNC machining and sheet metal; every part is priced by an engineer rather than instantly. Upload a STEP file to get a price and a DFM check.
Sources
- SAE J404 — Chemical Compositions of SAE Alloy Steels — SAE International (2021)
- SAE J1268 — Hardenability Bands for Alloy H-Steels (4145H) — SAE International (2019)
- ASTM A29/A29M — Steel Bars, Carbon and Alloy, Hot-Wrought — ASTM (2020)
- API Spec 7-1 — Rotary Drill Stem Elements (drill collar 285–341 HB) — American Petroleum Institute (2016)
- GB/T 3077 — (45CrMo) — SAC / (2015)
- NACE MR0175 / ISO 15156-2 — Materials for H2S-containing environments — NACE/ISO (2020)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels — ASM International (1990)
- ASM Handbook Vol.4 — Heat Treating — ASM International (1991)
- Machinery's Handbook (machinability ratings) — Industrial Press (2020)
- 45CrMo — Mysteel / 1688 (2026)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.