A-286 yield strength depends on the material condition, test temperature and yield definition. For one solution-treated-and-aged bar condition, Carpenter reports a typical 0.2% offset yield strength of 655 MPa at 21.1°C and 607 MPa at 649°C. Those are reference values for the stated bar specimens, not minimum acceptance values for every A-286 bolt. [1, p.3]
Start with the temperature table below, then check the column heading before comparing a number with your purchase requirement. The separate A-286 heat-treatment guide explains route selection; this guide focuses on reading and using strength data.
A-286 yield strength at room and elevated temperatures
Condition for every row: 7/8-inch (22.2 mm) diameter bar, solution treated at 1800°F (982°C) for one hour and oil quenched, then aged at 1325°F for 16 hours and air cooled. Carpenter labels these as typical mechanical properties. The table selects the 0.2% offset yield column and seven reported temperatures; it does not reproduce the full property table. [1, p.3]
| Test temperature, °C | Source temperature, °F | 0.2% offset yield, MPa |
|---|---|---|
| 21.1 | 70 | 655 |
| 427 | 800 | 641 |
| 538 | 1000 | 603 |
| 593 | 1100 | 621 |
| 649 | 1200 | 607 |
| 704 | 1300 | 593 |
| 760 | 1400 | 427 |
The series does not fall at every temperature step: the reported 593°C value is slightly above the 538°C value. Keep that observation within this dataset; it does not establish a general strengthening mechanism. Do not force a straight declining curve through the points or interpolate an acceptance value for an unlisted temperature. A tensile result measured at 760°C also does not establish a 760°C service rating for a bolted joint.
Why 0.02% and 0.2% yield values differ
On a stress–strain plot, an offset line runs parallel to the initial elastic portion of the measured curve, starting at the specified strain offset on the strain axis. The stress at its intersection with the measured curve is the offset yield strength. A 0.2% offset starts at 0.002 strain; a 0.02% offset starts at 0.0002. Different offsets select different reported points. It is not a percentage of tensile strength or the elongation at fracture. The NBS guide to tensile-property data distinguishes offset yield from other yield measures and emphasizes recording the method and offset with the result. [2, pp.6–7]
Carpenter’s same 649°C row contains three different quantities:
| Column heading | Reported value, MPa | How to use the number |
|---|---|---|
| 0.02% offset yield strength | 431 | Keep the 0.02% definition attached. |
| 0.2% offset yield strength | 607 | Use this column when looking up the producer’s 0.2% value. |
| Tensile strength | 714 | This is ultimate tensile strength, a separate property. |
431 MPa cannot be relabelled as the 0.2% value. Nor can one offset result be converted to the other by multiplying by ten. If a report gives “yield strength” without its definition, ask the issuer which method and offset were used.
Match the condition before comparing reports
A-286 (UNS S66286) is an iron-based, precipitation-hardening alloy used for high-temperature components, including fasteners. The alloy designation leaves the processing condition open. [1] A solution-treated starting bar and an aged finished fastener are different test objects. Cold work, aging and the manufacturing sequence can also change the property being reported. Keep the approved condition and specimen basis alongside the strength requirement.
For a bolt order, identify the governing specification and edition, any required class, the final condition, and whether acceptance concerns the finished fastener or an agreed representative specimen. ASTM E8/E8M covers room-temperature tensile testing; ASTM E21 addresses elevated-temperature tension testing. Naming a test method does not supply the order’s acceptance limit. [3] [4]
ASTM also notes that tensile specimens taken from selected portions may not represent the entire product or its behavior in service. [3, §4.2] Use the producer table for an initial material review; use order-matching records to decide whether a delivered lot passes the specified test.
What is the maximum operating temperature for A-286 fasteners?
The yield table does not define a maximum operating temperature. A fastener must meet the joint’s load and life requirements at its actual metal temperature. A short tensile test cannot establish resistance to creep, stress rupture or loss of preload during a long hold. NASA’s historical fastener-material summary lists 1200°F (about 649°C) for A-286. Treat that as a selection reference, not unconditional approval for a particular bolt and joint. [1] [5]
Does A-286 resist stress relaxation at 600°C?
The yield data above do not establish how much clamp load an A-286 fastener will retain during sustained service at 600°C. For sustained service near 600°C, specify the service duration and required retained clamp load, then request evidence matching the proposed material condition, temperature, time and initial stress. Published A-286 relaxation experiments use defined processing and loading conditions; they do not supply a universal percentage of preload loss for finished bolts. [5] [6]
Include the nut, washer, gasket where used, clamped materials and temperature cycles in the joint review. Thermal expansion can change bolt load even when the material passes its hot-yield test. The preload and creep guide explains these separate mechanisms. For a material shortlist, the A-286 versus 718 guide compares producer hot-strength examples with their different bar sizes and treatment routes attached.
Worked example: which report answers the hot-yield requirement?
The following requirement and report values are fictional teaching examples, not ASTM limits, supplier results or a BYBOLT project. Assume an order requires a minimum 0.2% offset yield strength of 580 MPa at 649°C. The approved test object, final condition, sampling basis and lot identification are fixed by that order.
| Report entry | What the buyer can conclude | Next action |
|---|---|---|
| 660 MPa, 0.2% offset, tested at 21°C | The test temperature does not match the 649°C requirement. | Obtain the required elevated-temperature evidence; the larger room-temperature number does not close it. |
| 590 MPa, 0.02% offset, tested at 649°C | The reported yield definition differs from the specified 0.2% basis. That difference alone does not show lower material strength. | Clarify the report and obtain the specified result or an expressly approved acceptance basis; do not silently rename the value. |
| 600 MPa, 0.2% offset, tested at 649°C; all stated specimen, condition and lot requirements match | Meets this yield criterion by 20 MPa. | Close this test item, then complete the remaining drawing, test and document checks before release. |
A datasheet value above 580 MPa would not fill a missing lot-specific result. Conversely, passing this yield check does not settle rupture life, fatigue, corrosion or clamp-load retention.
What must accompany an A-286 strength requirement?
Name the standard, edition, product form and final condition. AMS 5731 and AMS 5737 are not interchangeable labels for the same treatment: SAE’s published titles identify 1800°F solution-treated, precipitation-hardenable material for AMS 5731, versus 1650°F solution-and-precipitation-treated material for AMS 5737. Those titles do not establish all finished-bolt requirements. [7] [8]
For ASTM A453/A453M Grade 660 bolting, state the required Class A, B, C or D and apply its class-specific requirements. Do not derive an ASTM class from an AMS number or a hardness reading. The A-286 heat-treatment and Grade 660 ordering guide covers the process and acceptance questions. [9]
Can a 3.1 certificate or PMI result prove the required condition?
An EN 10204 3.1 certificate reports specific inspection results against the order; check that its product, condition and test lot represent the delivered fasteners. Keep the chain from melt heat through manufacturing and heat-treatment batches to the shipped parts. A spectrometric PMI grade match verifies chemistry within the method’s capability; it does not prove the aging treatment or hot-yield strength. Agree any PMI coverage before ordering—100% PMI is not automatic. See the MTC, PMI and inspection-record guide for the receiving checks.
Put the required strength basis into the enquiry
For an A-286 hex-bolt enquiry, send the drawing, quantity and the requirement you already have. Include the property and offset definition, test temperature, required minimum, governing specification and final condition. Identify open items for review rather than choosing a datasheet value as a new requirement. The A-286 material page provides the grade and product-selection entry.
For custom hex bolts, A-286 studs or socket screws, confirm availability for the actual size, thread, final condition and test package. Available A-286 bar does not establish that finished, qualified parts are in stock. Ask the quotation to separate material availability, manufacturing, heat treatment and any additional testing.
Carpenter notes A-286’s rapid work hardening during cold working and recommends adjusting machining parameters to the workpiece. Agree the manufacturing route for the required final condition, then verify dimensions and threads after processing. For assembly, agree the mating materials, surface condition and lubricant or coating for the operating medium and temperature, then qualify the tightening procedure for that combination. The thread-galling guide explains why hardness alone cannot prevent seizure. [1] [10]
Every BYBOLT delivery includes an MTC / EN 10204 3.1 certificate, heat-number traceability and mechanical testing; threaded products include sampled GO / NO-GO gauging. Test objects, methods and acceptance follow the agreed order. Project-specific elevated-temperature testing and its reporting scope must be agreed during quotation. Send the drawing and test requirements for review.