Steel G18Mo5-QT (Quenched and tempered)
Heat-treated state
EN 1.5422
Chosen for heavier sections or where higher yield strength and better low-temperature toughness are required.
Values for the QT condition
Other G18Mo5 tempers and conditions
G18Mo5 is listed in 6 conditions; see the grade overview at G18Mo5.
Compare all 6 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Softest condition — used when heavy machining or extensive weld repair precedes the final normalize/temper. | 250 | 450 | 28 | 130 HB | 8.3 % IACS |
As fabricated | Raw casting before heat treatment — non-uniform dendritic structure, not for pressure service. | 260 | 480 | 16 | 150 HB | 8.1 % IACS |
Stress relieved | Post-weld heat treatment at ~600–680 °C for pressure parts; slightly lowers yield but restores HAZ toughness. | 275 | 490 | 26 | 140 HB | 8.2 % IACS |
N+TDefault Normalized and tempered | Standard delivery condition for pressure castings: balanced strength, ductility and creep behaviour up to ~500 °C. | 285 | 500 | 25 | 145 HB | — |
Normalized | Intermediate condition after casting/weld repair; usually followed by tempering before delivery. | 300 | 520 | 23 | 155 HB | 8.2 % IACS |
QTThis page Quenched and tempered | Chosen for heavier sections or where higher yield strength and better low-temperature toughness are required. | 360 | 560 | 22 | 170 HB | 8 % IACS |
What is G18Mo5-QT?
G18Mo5-QT is G18Mo5 heat treated to QT — chosen for heavier sections or where higher yield strength and better low-temperature toughness are required. G18Mo5-QT has a yield strength of 360 MPa (52.2 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 72% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi). G18Mo5-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F). N+T is the default condition FabDigit quotes; QT is available on request or by drawing note.
Advantages
- High service temperature — 450°C (842 °F), better than 86% of steel grades
Limitations
- Limited formability — 12/100, worse than 92% of steel grades
- Hard to polish — 45/100, worse than 84% of steel grades
G18Mo5-QT properties
Typical room-temperature values for G18Mo5-QT; 22 are specific to this condition. Other listed values are G18Mo5 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
G18Mo5-QT has a density of 7.85 g/cm³ (0.284 lb/in³), heavier than 56% of steel grades. It melts at 1,425°C (2,597 °F).
Mechanical16
G18Mo5-QT has a yield strength of 360 MPa (52.2 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 72% of steel grades. Elongation at break is 22% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
G18Mo5-QT is rated for continuous service to 450°C (842 °F). It conducts heat at 41 W/m·K (23.7 BTU/hr·ft·°F), worse than 62% of steel grades. Thermal expansion is 12.2 µm/m·K (6.78 µin/in·°F).
Electrical3
G18Mo5-QT 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 G18Mo5-QT takes about 28 MJ of energy and emits 2.2 kg of CO₂ — less than 56% of steel grades. Typical recycled content is 70%.
Manufacturability7
G18Mo5-QT's machinability is fair (54/100, better than 54% of steel grades); weldability good (68/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with G18Mo5-QT
Is G18Mo5 easy to machine?
Machines like a normalized 0.5Mo low-alloy steel at ~60 % of AISI 1212 — use rigid setups and carbide inserts, and remove the hard cast skin/sand inclusions with a first heavy cut.
Can G18Mo5 be welded?
Good weldability for a creep-resisting cast steel: use low-hydrogen 1Mo consumables (e.g. E7018-A1 / SFA-5.5), preheat 150–250 °C and PWHT at 620–680 °C for pressure parts.
Can G18Mo5 be formed, bent or molded?
Sand or investment cast; feed heavy sections generously (solidification shrinkage ~2 %) and normalize + temper after casting to break up the dendritic structure.
What surface finishes work on G18Mo5?
No natural corrosion resistance — shot blast then prime/paint, aluminize or insulate; not anodizable, and pressure faces are typically machined and lapped rather than polished.
G18Mo5 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 |
|---|---|---|
| Clow-carbon variant of G20Mo5 for weldability | 0.15 – 0.2 | 0.18 |
| Si | ≤ 0.6 | 0.35 |
| Mn | 0.5 – 1 | 0.75 |
| P | ≤ 0.03 | 0.02 |
| S | ≤ 0.02 | 0.01 |
| Mocreep strengthening element | 0.4 – 0.6 | 0.5 |
| Crresidual | ≤ 0.3 | 0.15 |
| Niresidual | ≤ 0.4 | 0.2 |
| Curesidual | ≤ 0.3 | 0.15 |
| Vresidual | ≤ 0.05 | 0.02 |
| Fe | balance | — |
G18Mo5-QT — frequently asked
What is G18Mo5-QT used for?
G18Mo5-QT is typically used for valve bodies, flanges and pressure vessel castings. In short: weldable 0.5Mo cast steel; lower carbon than G20Mo5; ductile at 25% elongation.
What is the yield strength of G18Mo5-QT?
G18Mo5-QT has a typical yield strength of 360 MPa (52.2 ksi) and a tensile strength of 560 MPa (81.2 ksi) — weaker than 72% of steel grades. Strength varies by condition: see the 6 listed tempers.
Is G18Mo5-QT easy to machine?
Reasonably — machinability is rated fair (54/100, better than 54% of steel grades). Machines like a normalized 0.5Mo low-alloy steel at ~60 % of AISI 1212 — use rigid setups and carbide inserts, and remove the hard cast skin/sand inclusions with a first heavy cut.
Can G18Mo5-QT be welded?
Yes — weldability is rated good (68/100). Good weldability for a creep-resisting cast steel: use low-hydrogen 1Mo consumables (e.g. E7018-A1 / SFA-5.5), preheat 150–250 °C and PWHT at 620–680 °C for pressure parts.
What surface finishes work on G18Mo5-QT?
No natural corrosion resistance — shot blast then prime/paint, aluminize or insulate; not anodizable, and pressure faces are typically machined and lapped rather than polished.
Can G18Mo5-QT be formed, bent or molded?
Sand or investment cast; feed heavy sections generously (solidification shrinkage ~2 %) and normalize + temper after casting to break up the dendritic structure.
What is the maximum service temperature of G18Mo5-QT?
G18Mo5-QT is rated for continuous use to about 450°C (842 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between G18Mo5 N+T and G18Mo5-QT?
N+T is the default condition — standard delivery condition for pressure castings: balanced strength, ductility and creep behaviour up to ~500 °C. QT: chosen for heavier sections or where higher yield strength and better low-temperature toughness are required. Yield strength is 285 MPa in N+T versus 360 MPa in QT.
Sources
- EN 10213 — Steel castings for pressure purposes — CEN (2016)
- DIN 17245 / SEW 685 — Ferritic creep-resisting steel castings — DIN / VDEh (1987)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels and High-Performance Alloys — ASM International (1990)
- Steel Castings Handbook, 6th ed. — Steel Founders' Society of America / ASM (1995)
- SEW 310 — Physical properties of steels — Verein Deutscher Eisenhüttenleute (1992)
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.