Grade 50 for riveted, bolted or welded structures
ASTM A572 Grade 50 is a columbium-vanadium high-strength low-alloy structural steel grade. The A572/A572M-25 public Scope places Grades 42, 50 and 55 in riveted, bolted or welded structures; Grade 50 is not restricted to riveted or bolted bridges. The specification also requires notch toughness to be negotiated where the application, such as welded bridge construction, needs it. Intended structural use is not a guarantee of an impact-test result.
Send Gangsteel the full ASTM designation, Grade 50, edition and plate dimensions rather than a shorthand “50 steel” request. Identify the A6/A6M requirements basis and the purchasing unit system. Inch-pound and SI are independent systems, so a material line should not mix selectively converted limits. Agree the required delivered condition, test scope and certificate arrangement before comparing offers.
| Decision | What to identify | Why it matters |
|---|---|---|
| Material line | A572/A572M Grade 50, edition and units | A grade name without an edition leaves the acceptance basis incomplete |
| Plate schedule | Thickness, width, length and quantity | Product form and dimensions affect applicable provisions |
| Chemistry options | Required type, copper-bearing option and analysis scope | Options should not be assumed or silently omitted |
| Inspection package | Required tension basis, toughness criteria and certificate form | A product description does not establish every test or approval |
Mechanical references: minimum strengths, not typical delivered results
| Property | Grade 50 reference | Report detail |
|---|---|---|
| Yield strength, minimum | 50 ksi [345 MPa] | Minimum requirement, not a typical heat result |
| Tensile strength, minimum | 65 ksi [450 MPa] | Minimum rather than one exact stress value |
| Elongation, minimum | 18% in 8 in. [200 mm] | Retain the gauge and applicable specimen basis |
| Elongation, minimum | 21% in 2 in. [50 mm] | Retain the gauge and applicable specimen basis |
SSAB’s Grade 50 datasheet dated 20 May 2019, MetalMate’s guide citing A572/A572M-25 and American Alloy Steel’s compilation restate this set. It is a mill/public-reference summary, not an official tensile-table extract. MetalMate describes no general base-grade tensile maximum. SSAB identifies transverse testing within its mill reference; the report for an order should retain its actual specimen and orientation basis.
For plates wider than 24 in. [600 mm], MetalMate and SSAB both restate a two-percentage-point elongation reduction, with further A6 adjustments where applicable. That agreement remains a public reference, not an inspected official clause. The 18% and 21% entries concern gauge lengths, not thickness bands. Product-form exceptions, including floor plate or heavy shapes, must not be transferred to ordinary plate without the applicable provisions.
Keep the 4 in. plate reference distinct from other product sizes
The official public Scope refers maximum thicknesses to Table 1, whose numerical contents are not reproduced here. Grade 50 public references are consistent: MetalMate citing the 25 edition, Ferrobend and American Alloy Steel show 4 in. [100 mm] for plate. SSAB’s mill offering to 4.00 in. is consistent with that reference but remains a producer range, not an official specification cap or a Gangsteel availability statement.
MetalMate separately gives rectangular or square bar a 4 in. reference and round bar an exception to 11 in. [275 mm] diameter. A bar exception does not enlarge the plate limit. Review the actual product and ordered edition before accepting dimensions; do not extend properties beyond the referenced plate scope or create an extra thick-plate band simply to complete a schedule.
Grade 50 chemistry: preserve each source and analysis condition
The table uses Grade 50-specific public compilations. MetalMate cites A572/A572M-25; Ferrobend and American Alloy Steel agree on the basic carbon/manganese maxima. None is presented as an official chemistry-table reproduction. Silicon’s precise plate-thickness break below is Ferrobend’s compilation restatement: the MetalMate Grade 50 page describes heavy sections without printing that boundary.
| Element / condition | Heat reference, % | Source / qualification |
|---|---|---|
| Carbon (C) | 0.23 max | Grade 50 reference within its product-size limits |
| Manganese (Mn) | 1.35 max | Basic maximum before any applicable carbon–manganese allowance |
| Silicon (Si), through 1 1/2 in. [40 mm] plate | 0.40 max | Ferrobend thickness split; not a printed break on MetalMate Grade 50 |
| Silicon (Si), over 1 1/2 in. [40 mm] plate | 0.15–0.40 | Ferrobend thickness split within the applicable size range |
| Phosphorus (P) | 0.030 max | MetalMate principal reference; conditional exception below |
| Sulfur (S) | 0.030 max | MetalMate principal reference; conditional exception below |
| Copper (Cu), only when specified | 0.20 min | MetalMate conditional heat-analysis reference |
MetalMate qualifies the P/S limits: 0.04% P and 0.05% S are permitted for shapes, sheet piling, bars and plates no more than 15 in. [380 mm] wide. Those are not universal plate maxima. Undated distributor grids printing the higher figures without that condition should not override a width- and product-specific review. Copper is an ordered option, not a universal Grade 50 requirement or a weathering-steel designation.
The cited carbon–manganese allowance permits 0.06 percentage point above the Mn maximum for each 0.01 percentage point below the carbon maximum, up to 1.60%. Heat Mn minima are 0.80% for plate over 3/8 in. [10 mm] and 0.50% for thinner plate and other products, with Mn/C at least 2:1. Product minima of 0.75% and 0.45% come specifically from Ferrobend note B; MetalMate Grade 50 does not print them. These entries do not establish a complete product-analysis column.
Specify a microalloying route only where the order requires one
Official Scope 1.4 requires niobium/columbium, vanadium, titanium, nitrogen or combinations as Type 1, 2, 3 or 5, normally at producer option unless specified by the purchaser under S90. Numeric ranges below are MetalMate Grade 50 public references only, not independently cross-checked official type limits.
- Type 1: Nb 0.005–0.05%.
- Type 2: V 0.01–0.15%.
- Type 3: Nb 0.005–0.05% and V 0.01–0.15%, with Nb+V 0.02–0.15%.
- Type 5: Ti 0.006–0.04%, N 0.003–0.015%, V 0.06% maximum.
Keep the selected type and analysis basis connected to the material records. Required impact tests, supplementary examinations and certificate coverage must be agreed for the order. No stock, delivery-time, welding-performance or default dual-certification promise follows from this description. The official Scope also disallows substituting A588 without agreement.
Related family choices are A572 Grade 42 and A572 Grade 60; neither supplies Grade 50 acceptance numbers. A573 Grade 70 structural carbon plate is a purpose contrast, not an HSLA equivalent. Alternatives require engineering and purchasing approval; no automatic national-grade equivalence is asserted.
Grade 50 purchasing questions
Does Grade 50 cover welded structures as well as bolted work?
Yes. The 25 edition public Scope includes riveted, bolted or welded structures for this grade. That does not remove project-specific fabrication or toughness requirements. Define the intended application and any required tests rather than interpret the grade name as approval of a welding procedure.
Does a round-bar size exception permit thicker Grade 50 plate?
No. The 11 in. [275 mm] diameter reference concerns round bar. The public-reference plate pattern is 4 in. [100 mm], subject to the ordered edition. Product-form exceptions must remain with their own product, not be used to expand a plate schedule.
Where do the product manganese minima come from?
Ferrobend note B provides 0.75% for the thicker-plate case and 0.45% for thinner plate and other products. MetalMate Grade 50 says product minima are lower without printing those numbers. The distinction is retained here; it does not justify inventing product limits for other elements.
Should an elongation result be compared with 18% or 21%?
First identify its gauge and specimen basis: the public references pair 18% with 8 in. [200 mm] and 21% with 2 in. [50 mm]. Then assess applicable width and A6 adjustments. Thickness alone does not select between those two gauge values.
Does a familiar international grade name authorize substitution?
No. A proposed JIS, GB, EN or other alternative needs a comparison of the complete ordered requirements and the necessary approval. Shared strength terminology is insufficient, and an optional mill certification arrangement is not a general equivalence or a supply commitment.
Request an A572 Grade 50 quotation
Provide one consistent purchasing basis for the requested plate.
- Edition, units, dimensions and quantities
- Delivered condition, any specified type or copper option
- Analysis scope, tension basis, any toughness criteria and certificate requirements
Supply and documentation are reviewed for the particular enquiry. Contact Gangsteel with your plate schedule.