Steel 38Si7
EN 38Si7
38Si7 (1.5023) is a medium-carbon, silicon-alloyed spring steel from the EN low-alloy engineering steel range, strengthened by quenching and tempering rather than by heavy alloying.
Reference datasheet — 38Si7 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 condition
38Si7 tempers and conditions
38Si7 is supplied in 8 conditions, soft to hard. +QT 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 |
|---|---|---|---|---|---|---|
Spheroidize annealed | Softest, most ductile delivery state — choose for heavy cold upsetting, cold extrusion or deep machining before hardening. | 350 | 590 | 22 | 195 HB | — |
Annealed | Standard soft delivery condition for bar and flat that will be machined, cold formed or coiled before hardening. | 390 | 640 | 18 | 215 HB | — |
Restricted (narrow) hardenability band | Tighter Jominy scatter than +H for heat-treaters needing repeatable core hardness and distortion in mass-produced springs. | 395 | 650 | 17 | 17 HRC | 7.5 % IACS |
Supplied to a specified hardenability (Jominy) band | Order option when the quench response must be guaranteed; bar ships soft (annealed/hot rolled) and quench-hardens to about 52–57 HRC before tempering. | 400 | 660 | 17 | 18 HRC | 7.8 % IACS |
Treated for high shearability | Hardness deliberately held in a narrow mid band so bar can be cold-sheared to blanks without cracking or excessive burr. | 430 | 700 | 16 | 225 HB | — |
Hot rolled | Cheapest mill condition for stock that will be fully re-heat-treated after forming; surface decarburization must be machined or ground off. | 470 | 780 | 14 | 22 HRC | 7.5 % IACS |
Cold drawn | Bright, close-tolerance bar for machined spring pins and clips where only moderate strength is needed without heat treatment. | 660 | 820 | 9 | 23 HRC | 7.2 % IACS |
+QTDefault Quenched and tempered | Standard in-service condition for leaf/coil springs and torsion bars: oil-quench from ~870 °C, temper 400–500 °C. | 1,150 | 1,300 | 9 | 42 HRC | — |
What is 38Si7?
38Si7 (1.5023) is a medium-carbon, silicon-alloyed spring steel from the EN low-alloy engineering steel range, strengthened by quenching and tempering rather than by heavy alloying. In the +QT condition it reaches about 1150 MPa yield and 1300 MPa tensile strength at 390 HB (42 HRC), which is why it is specified for leaf and coil springs needing moderate elastic strength; it is stocked as flat bar, round bar and wire, with +A/+AC soft stock for machining. Limits are low ductility (9 % elongation), a 250 °C service ceiling, no corrosion resistance and effectively no weldability. Where higher elastic strength is required, 46Si7 or 56Si7 are the next grades up. 38Si7 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F). 38Si7 has a yield strength of 1,150 MPa (167 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 94% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
What is 38Si7 used for?
- leaf springs
- coil springs
- stabilizer bars
Advantages
- High strength — 1,150 MPa (167 ksi), better than 94% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Limited ductility — 9%, worse than 93% of steel grades
- Difficult to weld — 15/100, worse than 91% of steel grades
- Difficult to machine — 30/100, worse than 89% of steel grades
- Limited formability — 15/100, worse than 87% of steel grades
- Low fracture toughness — 50 MPa·√m (45.5 ksi·√in), worse than 86% of steel grades
38Si7 properties
Typical room-temperature values for 38Si7-+QT; bars are the position among steel grades.
Physical3
38Si7 has a density of 7.8 g/cm³ (0.282 lb/in³), lighter than 87% of steel grades. It melts at 1,420°C (2,588 °F).
Mechanical16
38Si7 has a yield strength of 1,150 MPa (167 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 94% of steel grades. Elongation at break is 9% and the elastic modulus is 206 GPa (29.9 Msi).
Thermal6
38Si7 is rated for continuous service to 250°C (482 °F). It conducts heat at 40 W/m·K (23.1 BTU/hr·ft·°F), worse than 64% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical3
38Si7 conducts electricity at 7 % IACS, worse than 74% of steel grades.
Chemical & Environmental3
Corrosion resistance is not recommended (11/100), worse than 73% of steel grades.
Sustainability4
Producing a kilogram of 38Si7 takes about 24 MJ of energy and emits 1.9 kg of CO₂ — less than 97% of steel grades. Typical recycled content is 30%.
Manufacturability6
38Si7's machinability is poor (30/100, worse than 89% of steel grades); weldability poor (15/100); formability poor (15/100).
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. 38Si7 is highlighted; hover a dot for its name, or open the interactive family chart.
Working with 38Si7
Is 38Si7 easy to machine?
Machine in +A/+AC condition with sharp carbide tooling; the high Si makes chips gummy and abrasive, and above ~40 HRC only grinding or ceramic/CBN turning is practical.
Can 38Si7 be welded?
Essentially not recommended for loaded springs — high carbon equivalent and Si cause hard, crack-prone HAZ; if unavoidable, preheat 250–350 °C, use low-hydrogen consumables and temper immediately after.
Can 38Si7 be formed, bent or molded?
Cold coil or bend only in the spheroidized/annealed state; hot form at 900–1050 °C, then austenitize ~860–880 °C, oil quench and temper 400–500 °C to the target 40–45 HRC.
38Si7 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 – 0.42 | 0.38 |
| Simain alloying element; raises elastic limit and relaxation resistance | 1.5 – 1.8 | 1.65 |
| Mn | 0.5 – 0.8 | 0.65 |
| Crresidual limit | ≤ 0.4 | 0.15 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.03 | 0.01 |
| Fe | balance |
What surface finishes work on 38Si7?
Shot-peen springs after tempering for fatigue life; protect with phosphate + oil, zinc-rich or epoxy paint — avoid acid pickling and electroplating on hardened parts unless baked to relieve hydrogen.
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 38Si7 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- EN / DIN / Werkstoff-Nr.
- 1.5023
How much does 38Si7 cost?
38Si7 is a budget-cost steel ($), cheaper than about 90% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
38Si7 — frequently asked
What is 38Si7 used for?
38Si7 is typically used for leaf springs, coil springs and stabilizer bars. In short: entry-level silicon spring steel; 1300 MPa at 42 HRC; not weldable when hardened.
What is the yield strength of 38Si7?
38Si7 has a typical yield strength of 1,150 MPa (167 ksi) and a tensile strength of 1,300 MPa (189 ksi) — stronger than 94% of steel grades. Strength varies by condition: see the 8 listed tempers.
Is 38Si7 easy to machine?
Not especially — machinability is rated poor (30/100, worse than 89% of steel grades). Machine in +A/+AC condition with sharp carbide tooling; the high Si makes chips gummy and abrasive, and above ~40 HRC only grinding or ceramic/CBN turning is practical.
Can 38Si7 be welded?
Not readily — weldability is rated poor (15/100). Essentially not recommended for loaded springs — high carbon equivalent and Si cause hard, crack-prone HAZ; if unavoidable, preheat 250–350 °C, use low-hydrogen consumables and temper immediately after.
What surface finishes work on 38Si7?
Shot-peen springs after tempering for fatigue life; protect with phosphate + oil, zinc-rich or epoxy paint — avoid acid pickling and electroplating on hardened parts unless baked to relieve hydrogen.
Can 38Si7 be formed, bent or molded?
Cold coil or bend only in the spheroidized/annealed state; hot form at 900–1050 °C, then austenitize ~860–880 °C, oil quench and temper 400–500 °C to the target 40–45 HRC.
What is the maximum service temperature of 38Si7?
38Si7 is rated for continuous use to about 250°C (482 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
How much does 38Si7 cost?
38Si7 is a budget-cost steel ($), 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
- EN 10089 — Hot rolled steels for quenched and tempered springs — CEN (2002)
- EN 10083-1/-2 — Steels for quenching and tempering, general and technical delivery conditions — CEN (2006)
- EN 10084 — Case hardening steels (delivery-condition symbols +A, +AC, +S, +H, +HH, +HL) — CEN (2008)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Stahlschlüssel (Key to Steel) — Verlag Stahlschlüssel Wegst (2019)
- EN 13906-1 — Cylindrical helical springs, design and calculation — CEN (2013)
- Mysteel / 1688 (2026)
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.