ASTM A1011 vs A36: Steel Grade Comparison

The primary distinction between ASTM A1011 and ASTM A36 lies in their form and application scope rather than just chemistry. ASTM A36 is the standard specification for carbon structural steel, primarily utilized in plate, shape, and bar forms where structural rigidity and load-bearing capacity are paramount (bridges, building frames). In contrast, ASTM A1011 is the standard for steel sheet and strip (hot-rolled), designed for high formability, bending, and drawing applications (automotive parts, brackets, drums). If you need a thick structural plate, specify A36; if you require a thinner sheet that will undergo bending or stamping, A1011 is the superior choice.

At MWalloys, we frequently see confusion arise when material thickness overlaps (specifically between 1/8" and 1/4"), leading to improper specification. This guide provides the technical clarity required to make the correct material selection.

1. Defining the Standards: What are A36 and A1011?

To select the correct material, one must understand the governing bodies and the intent behind each specification. Both fall under the jurisdiction of ASTM International, yet they serve different sectors of the manufacturing industry.

What is ASTM A36?

ASTM A36 is perhaps the most recognized steel specification in North America. It covers carbon steel shapes, plates, and bars of structural quality for use in riveted, bolted, or welded construction of bridges and buildings, and for general structural purposes.

• Key Characteristic: Minimum Yield Strength of 36,000 psi (36 ksi).

• Primary Form: Heavy plates, I-beams, H-beams, channels, and angles.

• Focus: Structural integrity and weldability.

What is ASTM A1011?

ASTM A1011 acts as the standard specification for steel, sheet and strip, hot-rolled, carbon, structural, high-strength low-alloy, high-strength low-alloy with improved formability, and ultra-high strength. It officially replaced the older ASTM A569 and A1018 standards for specific thickness ranges.

• Key Characteristic: High ductility and surface quality suitable for processing.

• Primary Form: Coils, cut lengths, and sheets.

• Focus: Formability, surface finish, and stamping capabilities.

MWalloys Note: A1011 is often supplied as "CS Type B" (Commercial Steel), which is the standard generic grade for general fabrication.

2. Chemical Composition Analysis

The chemistry determines the weldability and hardening capabilities of the steel. A36 allows for higher carbon and manganese content compared to standard A1011 grades, which contributes to its structural hardness but reduces its ability to be bent tightly without cracking.

Table 1: Chemical Composition Comparison (Max %)

Element	ASTM A36 (Plate/Bar)	ASTM A1011 (CS Type B)	Impact on Material
Carbon (C)	0.25% - 0.29%	0.02% - 0.15%	Higher carbon increases hardness but reduces ductility.
Manganese (Mn)	0.80% - 1.20%	0.60% max	Manganese improves tensile strength and weldability.
Phosphorus (P)	0.04%	0.03%	Lower phosphorus prevents brittleness.
Sulfur (S)	0.05%	0.035%	Lower sulfur improves internal structure cleanliness.
Silicon (Si)	0.40% max	-	Silicon is used for deoxidization in structural steels.
Copper (Cu)	0.20% (if specified)	0.20% (if specified)	Added for atmospheric corrosion resistance.

Note: A1011 has various grades (SS, HSLAS, CS, DS). This table compares A36 against the most common A1011 grade, CS Type B.

3. Mechanical Properties and Strength

This section is critical for structural engineers. While A36 has a fixed minimum yield strength, A1011 varies significantly depending on the specific "Grade" selected within the standard.

Yield Strength and Tensile Strength

ASTM A36 takes its name from its mechanical requirement: a minimum yield strength of 36 ksi. It is a predictable, reliable standard for static loads.

ASTM A1011 focuses on the sheet's ability to deform. However, A1011 can be ordered as "Structural Steel" (SS) grades (e.g., Grade 36, Grade 45) which mimic the strength of A36 but in sheet form.

Table 2: Mechanical Properties Comparison

 

Property	ASTM A36	ASTM A1011 (CS Type B)	ASTM A1011 (SS Grade 36)
Yield Strength (min)	36,000 psi (250 MPa)	30,000 - 50,000 psi (Typical)	36,000 psi (250 MPa)
Tensile Strength	58,000 - 80,000 psi	-	53,000 psi (min)
Elongation (in 2")	20% - 23%	≥ 25%	≥ 22%
Hardness (Brinell)	119 - 160	-	-

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Alt Text: Stress-strain graph comparing the yield point of ASTM A36 structural steel versus the elongation curve of ASTM A1011 sheet steel.

4. Thickness and Dimensional Tolerances

One of the most frequent questions we receive at MWalloys involves thickness.

• A36 Territory: Typically starts at 3/16" (4.7mm) and goes up to very heavy plates (12" or more). It follows ASTM A6 tolerances, which are generally looser and allow for more variation in flatness and thickness.

• A1011 Territory: Typically covers thicknesses from 0.060" up to 0.230" (approx 6mm). It follows ASTM A568 tolerances. These tolerances are much tighter, ensuring precision for stamping dies and automated machinery.

If you order a 1/4" plate, you can technically get it in A36 or A1011 (as a heavy coil cut-to-length). However, the A1011 material will have a better surface finish and tighter gauge control.

5. Fabrication: Formability, Welding, and Machining

How the material behaves during manufacturing is often the deciding factor.

Formability (Bending and Stamping)

ASTM A1011 is the clear winner.

Because of its lower carbon content and processing method, A1011 (especially Commercial Steel or Drawing Steel grades) can be bent 180 degrees flat on itself without cracking.

ASTM A36 is rigid.

While A36 can be bent, it requires a larger bend radius (typically 1.5x to 2x thickness) to avoid fracturing along the outside edge. Attempting to deep draw A36 will result in immediate failure.

Weldability

Both grades are considered excellent for welding.

• A36: Highly weldable using all standard methods (Stick, MIG, TIG). Pre-heating may be required for sections thicker than 3/4".

• A1011: Exceptionally easy to weld. Due to thinner gauges, care must be taken to avoid burn-through.

Surface Finish (The HRP&O Factor)

A1011 is frequently sold as HRP&O (Hot Rolled Pickled and Oiled). This process removes the abrasive mill scale (magnetite/hematite) leaving a clean, grey surface ready for painting or plating.

A36 is typically sold "Black," covered in hard, flaky mill scale that destroys tooling and must be sandblasted before painting.

6. MWalloys Case Study: The Bracket Failure in Chicago

Project: Industrial HVAC Support Systems

Location: Chicago, Illinois

Time: March 2023

The Challenge:

A construction firm contacted MWalloys regarding a failure in their heavy-duty HVAC support brackets. The engineering prints specified "1/4 inch Hot Rolled Steel." The fabricator, defaulting to the most common structural grade, utilized ASTM A36 plate.

During the manufacturing process, the brackets required a tight 90-degree bend with a small inside radius. The A36 material, being harder and less ductile, developed micro-fractures along the bend line. Once installed in the oscillating environment of an HVAC rooftop unit, these micro-fractures propagated, leading to catastrophic failure of three supports during a wind event.

The mwalloys Solution:

Our team analyzed the failed parts. We recommended switching the material specification to ASTM A1011 HSLAS Grade 50.

1. Why: This grade maintained the high strength required for the load (50 ksi yield) but offered the tighter thickness tolerance and improved ductility of the A1011 standard.

2. Result: The fabricator was able to form the parts without surface cracking.

3. Outcome: Zero failures have been reported since the switch, and the client saved money on surface preparation because the A1011 material was supplied pickled and oiled.

7. Application Matrix: When to Use Which?

To simplify the decision process, consult the matrix below.

Table 3: Application Selection Matrix

Application	Recommended Grade	Reason
Heavy Structural Beams	A36	High load-bearing, standardized structural properties.
Automotive Body Parts	A1011	Requires complex stamping and drawing.
Base Plates for Columns	A36	Thickness usually exceeds A1011 limits; needs rigidity.
Ag Equipment Hoppers	A1011	Sheet metal that must be formed into cones/boxes.
Truck Frames	A1011 (HSLAS)	High strength-to-weight ratio needed in thinner gauges.
Machined Parts	A36	Generally easier to machine due to higher carbon/manganese.
Laser Cut Parts	A1011 HRP&O	Free of mill scale, allowing faster, cleaner laser cutting.

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8. Purchasing and Cost Considerations

Price volatility impacts both grades, but they generally track with the scrap metal market.

1. Base Price: A36 is often considered a "commodity" grade and may have a slightly lower base price per pound than A1011 CS Type B.

2. Processing Costs: This is where A1011 often becomes cheaper. Because A1011 is often pickled and oiled, you save the cost of sandblasting or grinding that A36 requires.

3. Availability: A36 is available everywhere in standard plate sizes (4x8, 5x10). A1011 is readily available in coils, which can be leveled to custom lengths, reducing scrap waste for large production runs.

9. FAQ: A1011 vs A36

1. Is A1011 stronger than A36?

Generally, no, but it depends on the grade. Standard A1011 CS Type B has a typical yield of 30-50 ksi, which overlaps with A36. However, A1011 can be ordered as High-Strength Low-Alloy (HSLAS) with yields up to 80 ksi, which is significantly stronger than standard A36.

2. Can I substitute A1011 for A36?

If you are working with sheet thicknesses (under 1/4 inch) and need weldability, you can often substitute A1011 IF you specify a Grade that meets the 36 ksi minimum yield strength (like A1011 SS Grade 36). Never substitute based on thickness alone without verifying strength requirements.

3. Does A1011 rust?

Yes. Both A1011 and A36 are carbon steels consisting mostly of iron. They will rust immediately if exposed to moisture/oxygen. A1011 HRP&O has a light oil coating that provides temporary rust protection during shipping and storage.

4. What is the difference between A1011 and A1008?

A1011 is Hot Rolled steel. A1008 is Cold Rolled steel. A1008 starts as hot rolled steel (A1011) but undergoes further processing (cold reduction) to achieve tighter tolerances and a smoother surface. A1011 is cheaper; A1008 is more precise.

5. Is A36 better for machining?

Yes. The slightly higher carbon content and consistent grain structure of A36 plate usually make it less "gummy" than low-carbon A1011 sheet, resulting in better chip formation during drilling or milling.

6. What does "Pickled and Oiled" mean for A1011?

Hot rolling leaves a crusty oxide layer called mill scale. "Pickling" involves running the steel through an acid bath to remove this scale. "Oiling" applies a rust inhibitor. This makes A1011 HRP&O ideal for laser cutting and painting. A36 is rarely pickled.

7. Can you galvanize A1011 and A36?

Yes, both can be hot-dip galvanized. However, the silicon content in A36 can sometimes cause a reaction called the "Sandelin Curve," leading to excessively thick or brittle galvanized coatings. A1011 usually galvanizes very consistently.

8. Why is my A36 plate warping when I cut it?

A36 hot rolled plates contain residual stresses from the cooling process. When you cut them (via laser or plasma), heat is introduced, and material is removed, causing the steel to spring back or warp. A1011, especially if "temper passed," tends to be flatter and more stable.

9. What is the density of A1011 vs A36?

For engineering calculations, they are identical. The density for both is approximately 0.2833 lbs/in³ (7850 kg/m³).

10. Does A1011 satisfy ASTM A36 requirements?

Not automatically. You must review the Mill Test Report (MTR). If an A1011 coil has a yield strength above 36 ksi and meets the chemical limits, it might be "dual certified," but they are distinct specifications.

10. The Evolution of Standards: Historical Context

Understanding the lineage of these metals helps in reading old blueprints.

• The A36 Legacy: Established in 1960, A36 replaced A7 structural steel. It has remained the dominant standard for construction for over 60 years.

• The A1011 Evolution: Previously, hot rolled sheet was covered under ASTM A569 (Commercial Quality) and ASTM A570 (Structural Quality). In the early 2000s, ASTM combined these into A1011 and A1018 to modernize the classification system. If you see a print calling for A569, A1011 CS Type B is the direct modern replacement.

11. Final Verdict: mwalloys's Recommendation

Selecting between a1011 vs a36 comes down to the "Form vs. Function" debate.

1. Choose ASTM A36 if: You are building a structure, a frame, or a base that requires thick plates, heavy angles, or channels. You prioritize stiffness and proven load-bearing data over surface finish.

2. Choose ASTM A1011 if: You are manufacturing parts that require bending, stamping, or laser cutting. You need material thinner than 1/4 inch with a clean surface (HRP&O) that extends tool life and reduces finishing costs.

At mwalloys, we advise our partners to stop treating "steel" as a generic term. Specificity in your prints saves money on rejected parts and failed welds.