Steel A842 Grade 300-SR (Stress relieved)
Heat-treated state
ASTM A842 Grade 300 · EN EN-GJV-300 · GB RuT300
Standard treatment for dimensionally critical machined castings (blocks, heads, moulds) — removes casting residual stress with minimal property change.
Values for the SR condition
Other A842 Grade 300 tempers and conditions
A842 Grade 300 is listed in 4 conditions; see the grade overview at A842 Grade 300.
Compare all 4 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Pick when maximum thermal conductivity, ductility and easy machining matter more than strength (exhaust manifolds, thermally cycled parts). | 215 | 310 | 4 | 150 HB | 3.1 % IACS |
SRThis page Stress relieved | Standard treatment for dimensionally critical machined castings (blocks, heads, moulds) — removes casting residual stress with minimal property change. | 225 | 320 | 2.5 | 165 HB | 2.9 % IACS |
AS-CASTDefault ferritic/pearlitic compacted graphite iron | Standard supply condition: meets A842 Grade 300 straight from the mould with a mixed matrix, best balance of strength and thermal conductivity. | 230 | 330 | 2.5 | 170 HB | 36 W/m·K |
Normalized | Use when a Grade 300 casting must be lifted toward Grade 350/400 strength and wear resistance, accepting lower conductivity and worse machinability. | 295 | 400 | 1.5 | 20 HRC | 2.7 % IACS |
What is A842 Grade 300-SR?
A842 Grade 300-SR is A842 Grade 300 heat treated to SR — standard treatment for dimensionally critical machined castings (blocks, heads, moulds) — removes casting residual stress with minimal property change. A842 Grade 300-SR has a yield strength of 225 MPa (32.6 ksi) and a tensile strength of 320 MPa (46.4 ksi) — weaker than 97% of steel grades. Elongation at break is 2.5% and the elastic modulus is 145 GPa (21 Msi). A842 Grade 300-SR has a density of 7.1 g/cm³ (0.257 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F). AS-CAST is the default condition FabDigit quotes; SR is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.7 kg CO₂/kg, better than 99% of steel grades
Limitations
- Limited ductility — 2.5%, worse than 99% of steel grades
- Limited formability — 5/100, worse than 99% of steel grades
- Hard to polish — 35/100, worse than 99% of steel grades
- Low stiffness — 145 GPa (21 Msi), worse than 98% of steel grades
- Low strength — 225 MPa (32.6 ksi), worse than 97% of steel grades
A842 Grade 300-SR properties
Typical room-temperature values for A842 Grade 300-SR; 21 are specific to this condition. Other listed values are A842 Grade 300 reference data and may not represent this condition. Bars are the position among steel grades.
Physical3
A842 Grade 300-SR has a density of 7.1 g/cm³ (0.257 lb/in³), lighter than 99% of steel grades. It melts at 1,150°C (2,102 °F).
Mechanical14
A842 Grade 300-SR has a yield strength of 225 MPa (32.6 ksi) and a tensile strength of 320 MPa (46.4 ksi) — weaker than 97% of steel grades. Elongation at break is 2.5% and the elastic modulus is 145 GPa (21 Msi).
Thermal6
A842 Grade 300-SR is rated for continuous service to 400°C (752 °F). It conducts heat at 37 W/m·K (21.4 BTU/hr·ft·°F), worse than 71% of steel grades. Thermal expansion is 11.5 µm/m·K (6.39 µin/in·°F).
Electrical2
A842 Grade 300-SR has an electrical resistivity of 6×10⁻⁷ Ω·m.
Chemical & Environmental3
Corrosion resistance is poor (16/100), better than 79% of steel grades.
Sustainability4
Producing a kilogram of A842 Grade 300-SR takes about 19 MJ of energy and emits 1.7 kg of CO₂ — less than 100% of steel grades. Typical recycled content is 90%.
Manufacturability8
A842 Grade 300-SR's machinability is fair (42/100, worse than 73% of steel grades); weldability poor (25/100); formability not recommended (5/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with A842 Grade 300-SR
Is A842 Grade 300 easy to machine?
Cuts harder than grey iron — no MnS lubricating layer, so use CBN/ceramic at moderate speed or coated carbide with rigid setups; keep residual Ti low and control nodularity to protect tool life.
Can A842 Grade 300 be welded?
Poor; repair only with Ni or NiFe electrodes, 300–400 °C preheat and slow cooling to avoid carbides and cracking in the HAZ.
Can A842 Grade 300 be formed, bent or molded?
Sand or shell moulded with in-mould/ladle Mg treatment plus process control (thermal analysis) — the compacted window is narrow, so over-treatment gives nodules and under-treatment flake graphite.
What surface finishes work on A842 Grade 300?
Shot blast then paint, phosphate or oil; not anodizable. Graphite pull-out limits mirror polishing; sealed machined faces are needed for gasket sealing.
A842 Grade 300 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; A842 leaves chemistry to producer/purchaser agreement — values are typical CGI practice | 3.4 – 3.9 | 3.6 |
| Si | 1.9 – 2.6 | 2.3 |
| Mnhigher end promotes pearlite | 0.2 – 0.6 | 0.35 |
| Mgresidual; controls compacted vs nodular graphite | 0.01 – 0.02 | 0.01 |
| Tioptional anti-nodularizer; degrades machinability if high | 0 – 0.15 | 0.03 |
| Cupearlite stabilizer | 0 – 0.8 | 0.3 |
| S | ≤ 0.03 | 0.01 |
| P | ≤ 0.05 | 0.03 |
| Fe | balance | — |
A842 Grade 300-SR — frequently asked
What is A842 Grade 300-SR used for?
A842 Grade 300-SR is typically used for exhaust manifolds, brake components and housings. In short: grey-iron conductivity, higher strength; thermal-cycling casting grade; between grey and ductile iron.
What is the yield strength of A842 Grade 300-SR?
A842 Grade 300-SR has a typical yield strength of 225 MPa (32.6 ksi) and a tensile strength of 320 MPa (46.4 ksi) — weaker than 97% of steel grades. Strength varies by condition: see the 4 listed tempers.
Is A842 Grade 300-SR easy to machine?
Not especially — machinability is rated fair (42/100, worse than 73% of steel grades). Cuts harder than grey iron — no MnS lubricating layer, so use CBN/ceramic at moderate speed or coated carbide with rigid setups; keep residual Ti low and control nodularity to protect tool life.
Can A842 Grade 300-SR be welded?
Not readily — weldability is rated poor (25/100). Poor; repair only with Ni or NiFe electrodes, 300–400 °C preheat and slow cooling to avoid carbides and cracking in the HAZ.
What surface finishes work on A842 Grade 300-SR?
Shot blast then paint, phosphate or oil; not anodizable. Graphite pull-out limits mirror polishing; sealed machined faces are needed for gasket sealing.
Can A842 Grade 300-SR be formed, bent or molded?
Sand or shell moulded with in-mould/ladle Mg treatment plus process control (thermal analysis) — the compacted window is narrow, so over-treatment gives nodules and under-treatment flake graphite.
What is the maximum service temperature of A842 Grade 300-SR?
A842 Grade 300-SR 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 A842 Grade 300 AS-CAST and A842 Grade 300 NORM?
AS-CAST is the default condition — standard supply condition: meets A842 Grade 300 straight from the mould with a mixed matrix, best balance of strength and thermal conductivity. NORM: use when a Grade 300 casting must be lifted toward Grade 350/400 strength and wear resistance, accepting lower conductivity and worse machinability. Yield strength is 230 MPa in AS-CAST versus 295 MPa in NORM.
Sources
- ASTM A842 Standard Specification for Compacted Graphite Iron Castings — ASTM International (2020)
- EN 16079 Founding — Compacted (vermicular) graphite cast irons — CEN (2011)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels and High-Performance Alloys (Cast Irons) — ASM International (1990)
- SinterCast Compacted Graphite Iron material properties — SinterCast AB (2020)
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.