Steel G3500-G1800
Grade
ASTM A48 Class 35B · EN EN-GJL-250 · JIS FC250 · GB HT250
Softest J431 grade — pick for maximum machinability and damping where strength is unimportant (covers, housings, low-stress brackets).
Values for the G1800 condition
Other G3500 tempers and conditions
G3500 is listed in 9 conditions; see the grade overview at G3500.
Compare all 9 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
G1800This page as-cast ferritic-pearlitic gray iron, 187 HB max | Softest J431 grade — pick for maximum machinability and damping where strength is unimportant (covers, housings, low-stress brackets). | 100 | 140 | 0.6 | 175 HB | 53 W/m·K |
as-cast gray iron, 170–229 HB | General-purpose light-duty grade for small engine blocks, clutch plates, transmission cases and pressure-tight housings. | 130 | 190 | 0.5 | 200 HB | 50 W/m·K |
high-carbon (≥3.4 % C) gray iron, 170–229 HB, ≥70 % pearlite | Same hardness band as G2500 but high carbon and pearlitic matrix for brake drums and clutch parts that must resist heat checking. | 130 | 190 | 0.5 | 200 HB | 53 W/m·K |
as-cast gray iron, 187–241 HB | Workhorse grade for engine blocks, cylinder heads, flywheels and pump bodies needing moderate strength with easy machining. | 155 | 220 | 0.5 | 210 HB | 48 W/m·K |
very high carbon pearlitic gray iron, 207–255 HB, severe brake service | Highest-carbon J431 brake grade — maximum thermal conductivity and crack resistance for severe-duty brake drums and discs. | 172 | 245 | 0.5 | 225 HB | 53 W/m·K |
high-carbon pearlitic gray iron, 207–255 HB, heavy-duty brake service | Choose for truck/bus brake drums and heavy clutch plates: same hardness as G3500 but higher carbon for heat-check resistance and conductivity. | 175 | 250 | 0.5 | 225 HB | 50 W/m·K |
G3500Default as-cast pearlitic gray iron, 207–255 HB | Default stocked condition: higher-strength pearlitic gray iron for engine blocks, heads, brake components and machine-tool structures. | 180 | 250 | 0.5 | 225 HB | 46 W/m·K |
as-cast pearlitic gray iron, 217–269 HB | Highest plain (unalloyed) strength grade — for heavily loaded engine blocks, heads, camshafts and hydraulic bodies where stiffness matters. | 205 | 290 | 0.4 | 22 HRC | 43 W/m·K |
alloyed pearlitic gray iron for diesel castings, 241–321 HB | Cr/Mo-alloyed, fully pearlitic and often heat treated — used for diesel cylinder heads and blocks needing hot strength and wear resistance. | 215 | 300 | 0.4 | 29 HRC | 40 W/m·K |
What is G3500-G1800?
G3500-G1800 is G3500 in the G1800 grade — softest J431 grade — pick for maximum machinability and damping where strength is unimportant (covers, housings, low-stress brackets). G3500-G1800 has a yield strength of 100 MPa (14.5 ksi) and a tensile strength of 140 MPa (20.3 ksi) — weaker than 100% of steel grades. Elongation at break is 0.6% and the elastic modulus is 80 GPa (11.6 Msi). G3500-G1800 has a density of 7.2 g/cm³ (0.26 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F). G3500 is the default condition FabDigit quotes; G1800 is available on request or by drawing note.
Advantages
- Conducts heat well — 53 W/m·K (30.6 BTU/hr·ft·°F), better than 99% of steel grades
- Easy to machine — 90/100, better than 99% of steel grades
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
Limitations
- Low strength — 100 MPa (14.5 ksi), worse than 100% of steel grades
- Low stiffness — 80 GPa (11.6 Msi), worse than 100% of steel grades
- Low fracture toughness — 15 MPa·√m (13.7 ksi·√in), worse than 100% of steel grades
- Limited ductility — 0.6%, worse than 99% of steel grades
- Limited formability — 3/100, worse than 99% of steel grades
G3500-G1800 properties
Typical room-temperature values for G3500-G1800; 15 are specific to this condition. Other listed values are G3500 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
G3500-G1800 has a density of 7.2 g/cm³ (0.26 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F).
Mechanical14
G3500-G1800 has a yield strength of 100 MPa (14.5 ksi) and a tensile strength of 140 MPa (20.3 ksi) — weaker than 100% of steel grades. Elongation at break is 0.6% and the elastic modulus is 80 GPa (11.6 Msi).
Thermal6
G3500-G1800 is rated for continuous service to 400°C (752 °F). It conducts heat at 53 W/m·K (30.6 BTU/hr·ft·°F), better than 99% of steel grades. Thermal expansion is 11.7 µm/m·K (6.5 µin/in·°F).
Electrical3
G3500-G1800 conducts electricity at 2.2 % IACS, worse than 98% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of G3500-G1800 takes about 21 MJ of energy and emits 1.9 kg of CO₂ — less than 99% of steel grades. Typical recycled content is 85%.
Manufacturability8
G3500-G1800's machinability is excellent (90/100, better than 99% of steel grades); weldability fair (35/100); formability not recommended (3/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with G3500-G1800
Is G3500 easy to machine?
Excellent dry machinability with carbide or CBN; flake graphite breaks chips, but hard cast skin and any chill/carbide areas demand rigid setups and depth of cut below the skin.
Can G3500 be welded?
Poor fusion weldability — repair only with NiFe/Ni electrodes, 300–400 °C preheat, short stringer beads and peening, or braze-weld to avoid martensite and cracking in the HAZ.
Can G3500 be formed, bent or molded?
Not cold formable; the grade is produced by green-sand or shell casting with excellent fluidity, low shrinkage and inoculation control to get A-type graphite and 207–255 HB as-cast.
What surface finishes work on G3500?
Shot blast then phosphate + paint or e-coat for corrosion protection; can be flame/induction hardened or nitrocarburized on wear faces; graphite flakes limit mirror polishing and plating adhesion.
G3500 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 |
|---|---|---|
| Ctotal carbon; SAE J431 leaves chemistry to the foundry except for the high-carbon brake grades (G2500a/G3500b/G3500c) and alloyed G4000d | 3.1 – 3.5 | 3.25 |
| Si | 1.8 – 2.4 | 2.1 |
| Mn | 0.5 – 0.9 | 0.7 |
| Plower P for pressure-tight castings | ≤ 0.15 | 0.08 |
| S | ≤ 0.15 | 0.1 |
| Cr0.25–0.45 % typical in alloyed G4000d for pearlite stabilisation | ≤ 0.45 | 0.15 |
| Cuoptional pearlite promoter | ≤ 0.6 | 0.2 |
| Mooptional, mainly G4000d | ≤ 0.35 | — |
| Nioptional | ≤ 0.5 | — |
| Fe | balance | — |
G3500-G1800 — frequently asked
What is G3500-G1800 used for?
G3500-G1800 is typically used for engine blocks, brake drums/rotors, cylinder liners and flywheels. In short: automotive-grade gray iron; stronger than Class 30; good conductivity and wear resistance.
What is the yield strength of G3500-G1800?
G3500-G1800 has a typical yield strength of 100 MPa (14.5 ksi) and a tensile strength of 140 MPa (20.3 ksi) — weaker than 100% of steel grades. Strength varies by condition: see the 9 listed tempers.
Is G3500-G1800 easy to machine?
Yes — machinability is rated excellent (90/100, better than 99% of steel grades). Excellent dry machinability with carbide or CBN; flake graphite breaks chips, but hard cast skin and any chill/carbide areas demand rigid setups and depth of cut below the skin.
Can G3500-G1800 be welded?
With care — weldability is rated fair (35/100). Poor fusion weldability — repair only with NiFe/Ni electrodes, 300–400 °C preheat, short stringer beads and peening, or braze-weld to avoid martensite and cracking in the HAZ.
What surface finishes work on G3500-G1800?
Shot blast then phosphate + paint or e-coat for corrosion protection; can be flame/induction hardened or nitrocarburized on wear faces; graphite flakes limit mirror polishing and plating adhesion.
Can G3500-G1800 be formed, bent or molded?
Not cold formable; the grade is produced by green-sand or shell casting with excellent fluidity, low shrinkage and inoculation control to get A-type graphite and 207–255 HB as-cast.
What is the maximum service temperature of G3500-G1800?
G3500-G1800 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 G3500 and G3500-G1800?
G3500 is the default condition — default stocked condition: higher-strength pearlitic gray iron for engine blocks, heads, brake components and machine-tool structures. G1800: softest J431 grade — pick for maximum machinability and damping where strength is unimportant (covers, housings, low-stress brackets). Yield strength is 180 MPa in G3500 versus 100 MPa in G1800.
Sources
- SAE J431 — Automotive Gray Iron Castings — SAE International (2021)
- ASTM A48/A48M — Standard Specification for Gray Iron Castings — ASTM International (2022)
- GB/T 9439 (2010)
- EN 1561 — Founding: Grey cast irons — CEN (2011)
- ASM Handbook Vol.1 — Properties and Selection: Irons, Steels, and High-Performance Alloys — ASM International (1990)
- ASM Handbook Vol.15 — Casting — ASM International (2008)
- Continuous-cast gray iron bar property data (Class 35 / G2) — Dura-Bar (2023)
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.