Steel A572 · grade
Steel A572-Gr55
Properties of the Gr55 condition, compared with the other A572 tempers.
Intermediate level used where a modest weight saving over Grade 50 is worthwhile; availability is limited.
What is A572-Gr55?
A572-Gr55 is A572 in the Gr55 grade — intermediate level used where a modest weight saving over Grade 50 is worthwhile; availability is limited. A572-Gr55 has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 525 MPa (76.1 ksi) — weaker than 57% of steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi). A572-Gr55 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). HR is the default condition FabDigit quotes; Gr55 is available on request or by drawing note.
Advantages
- Low embodied carbon — 1.9 kg CO₂/kg, better than 92% of steel grades
- Tough — resists crack growth — 120 MPa·√m (109.2 ksi·√in), better than 80% of steel grades
- Readily welded — 78/100, better than 78% of steel grades
Limitations
- Hard to polish — 45/100, worse than 84% of steel grades
A572-Gr55 properties
Typical room-temperature values for A572-Gr55 — 31 properties are specific to this condition; the rest are grade-level values shared by every A572 temper. Each bar shows where the value sits among the steel grades in FabDigit's library — further right is higher.
Physical3
A572-Gr55 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).
Mechanical15
A572-Gr55 has a yield strength of 405 MPa (58.7 ksi) and a tensile strength of 525 MPa (76.1 ksi) — weaker than 57% of steel grades. Elongation at break is 20% and the elastic modulus is 200 GPa (29 Msi).
Thermal6
A572-Gr55 is rated for continuous service to 400°C (752 °F). It conducts heat at 46 W/m·K (26.6 BTU/hr·ft·°F), better than 71% of steel grades. Thermal expansion is 11.9 µm/m·K (6.61 µin/in·°F).
Electrical3
A572-Gr55 conducts electricity at 9 % IACS, better than 70% of steel grades.
Chemical & Environmental3
Corrosion resistance is poor (15/100), better than 75% of steel grades.
Sustainability4
Producing a kilogram of A572-Gr55 takes about 25 MJ of energy and emits 1.9 kg of CO₂ — less than 82% of steel grades. Typical recycled content is 40%.
Manufacturability7
A572-Gr55's machinability is good (57/100, better than 71% of steel grades); weldability very good (78/100); formability good (60/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other A572 tempers and conditions
A572 is also supplied in 9 other conditions. The full side-by-side table is on the A572 overview.
- HRDefaultDefault stock condition: as-rolled A572 Gr.50 plate, beam or channel for welded structures.360 MPa yield · 145 HB
- Gr65Highest A572 level (≤32 mm) for maximum weight saving; needs the tightest preheat and forming-radius control.475 MPa yield · 180 HB
- CDCold-drawn round/flat bar: highest strength and best surface finish/straightness, at the cost of ductility and residual stress.470 MPa yield · 180 HB
- Gr60Higher-strength level limited to ~32 mm thickness; used for lighter beams, poles and equipment frames.440 MPa yield · 165 HB
- Gr55Intermediate level used where a modest weight saving over Grade 50 is worthwhile; availability is limited.405 MPa yield · 155 HB
- Gr50The industry standard HSLA structural grade — best balance of strength, weldability and availability.370 MPa yield · 145 HB
- NormalizedSpecified for heavy plate or low-temperature service to refine grain and restore uniform toughness through thickness.365 MPa yield · 150 HB
- Gr42Lowest strength level, available to 150 mm thickness; pick when thick sections and easy forming matter more than strength.310 MPa yield · 130 HB
Working with A572-Gr55
Is A572 easy to machine?
Machines like a tough medium-carbon steel — roughly 55% of 1212; use rigid setups, positive-rake carbide and generous coolant, expect stringy chips and some distortion from rolling residual stress.
Can A572 be welded?
Prequalified in AWS D1.1 with E70/ER70S consumables; low carbon equivalent means little preheat below ~20 mm, but limit heat input on Gr.60/65 and use low-hydrogen practice on thick plate.
Can A572 be formed, bent or molded?
Cold bends and press-brakes well with radii ~2–3t (larger than A36 and larger still for Gr.60/65); bend transverse to the rolling direction and avoid re-bending sheared edges.
What surface finishes work on A572?
No natural corrosion protection — shot blast to SA 2.5 then zinc-rich primer, paint, hot-dip galvanize (watch Si for coating thickness) or metallize; not anodizable.
A572 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 |
|---|---|---|
| C0.26 max for Gr.42 shapes/bars per product form | ≤ 0.23 | 0.18 |
| Mn1.65 max for Gr.55–65 plate in some product forms | ≤ 1.35 | 1.15 |
| Si | ≤ 0.4 | 0.25 |
| P | ≤ 0.04 | 0.02 |
| S | ≤ 0.05 | 0.02 |
| Nbcolumbium — Type 1 and Type 3 | 0.01 – 0.05 | 0.03 |
| VType 2 and Type 3 | 0.01 – 0.15 | 0.05 |
| TiType 4/5 options | ≤ 0.05 | — |
| NType 5 (V+N) only | ≤ 0.03 | — |
| Fe | balance | — |
A572-Gr55 — frequently asked
What is A572-Gr55 used for?
A572-Gr55 is typically used for bridge girders and gusset plates, building beams and columns, construction equipment frames, crane booms and runway girders, transmission poles and lattice towers and truck and trailer chassis members. In short: standard structural grade.
What is the yield strength of A572-Gr55?
A572-Gr55 has a typical yield strength of 405 MPa (58.7 ksi) and a tensile strength of 525 MPa (76.1 ksi) — weaker than 57% of steel grades. Strength varies by condition: see the 10 listed tempers.
Is A572-Gr55 easy to machine?
Reasonably — machinability is rated good (57/100, better than 71% of steel grades). Machines like a tough medium-carbon steel — roughly 55% of 1212; use rigid setups, positive-rake carbide and generous coolant, expect stringy chips and some distortion from rolling residual stress.
Can A572-Gr55 be welded?
Yes — weldability is rated very good (78/100). Prequalified in AWS D1.1 with E70/ER70S consumables; low carbon equivalent means little preheat below ~20 mm, but limit heat input on Gr.60/65 and use low-hydrogen practice on thick plate.
What surface finishes work on A572-Gr55?
No natural corrosion protection — shot blast to SA 2.5 then zinc-rich primer, paint, hot-dip galvanize (watch Si for coating thickness) or metallize; not anodizable.
Can A572-Gr55 be formed, bent or molded?
Cold bends and press-brakes well with radii ~2–3t (larger than A36 and larger still for Gr.60/65); bend transverse to the rolling direction and avoid re-bending sheared edges.
What is the maximum service temperature of A572-Gr55?
A572-Gr55 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 A572-HR and A572-Gr65?
HR is the default condition — default stock condition: as-rolled A572 Gr.50 plate, beam or channel for welded structures. Gr65: highest A572 level (≤32 mm) for maximum weight saving; needs the tightest preheat and forming-radius control. Yield strength is 360 MPa in HR versus 475 MPa in Gr65.
Can FabDigit make parts in A572-Gr55?
Yes — A572-Gr55 is available for CNC machining and sheet metal with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM A572/A572M — High-Strength Low-Alloy Columbium-Vanadium Structural Steel — ASTM International (2021)
- AWS D1.1/D1.1M Structural Welding Code — Steel — American Welding Society (2020)
- ASM Handbook Vol.1: Properties and Selection — Irons, Steels, and High-Performance Alloys — ASM International (1990)
- Steel Construction Manual, 15th ed. — AISC (2017)
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.