Steel Sheets

ASTM A387 Grade 11 Class 1: keep the alloy and strength class together SHH STEEL's Grade 11 Class 1 product page concerns chromium- molybdenum pressure-vessel plate, not structural carbon plate and not stainless steel. The nominal alloy description is 1.25Cr-0.5Mo. ASTM's published A387/A387M scope identifies this family as plate intended primarily for welded boilers and pressure vessels designed for elevated-temperature service. A purchase inquiry should identify the complete designation, including Class 1, rather than stopping at “A387 Grade 11.” What distinguishes this plate Grade and class answer different questions. Grade 11 identifies the alloy family; Class 1 identifies the lower tensile-strength class within that grade. Class 2 is not an automatic upgrade, and Class 1 is not acceptable simply because its chemistry resembles the requested Class 2 material. The actual drawing, design calculation and purchasing specification determine which class is appropriate. For ASME equipment, state the required SA-387 designation and governing edition explicitly, and require the offered certification to match. The SHH STEEL page lists Grade 11 heat-analysis limits of chromium 1.00–1.50%, molybdenum 0.45–0.65%, carbon 0.05–0.17% and silicon 0.50–0.80%, by mass. These are heat-analysis limits, not the measured composition of a particular shipment. Product-analysis allowances are different and should be evaluated using the applicable standard rather than compared indiscriminately with the heat-analysis column. Grade 12 has a different chromium and silicon window; a general “Cr- Mo” description cannot establish equivalence. Strength values need the right context For Class 1, the company technical page lists tensile strength of 415–585 MPa and minimum yield strength of 240 MPa. Treat these as published material requirements to reconcile with the contractual edition, ordered thickness, test condition and certification. They are not allowable stresses for a pressure-vessel calculation or evidence of creep life. ASTM's scope states that maximum thickness is limited by the composition's ability to meet the specified mechanical properties; a single grade name therefore does not prove unrestricted thickness capability. Delivery condition is part of the purchase The product page describes thermally treated delivery, including annealed or normalized-and-tempered routes, with other permitted routes subject to the governing specification. Ask which route is proposed and require it to be recorded in the documentation. Where tempering applies, the page identifies 620°C as the minimum tempering temperature for Grade 11. This is not a universal fabrication PWHT instruction, and it should not be used to set a welding procedure without engineering review. Vessel fabrication can expose the plate to additional thermal cycles. If the design requires simulated post-weld heat treatment of test coupons, specify the cycle, number of cycles and acceptance basis before quotation. Otherwise, a satisfactory tensile result in the original delivered condition may not answer the buyer's actual question about performance after fabrication heat treatment. Applications and fabrication planning Possible uses include boiler shells and elevated-temperature pressure-vessel courses where the approved material specification calls for this exact grade and class. Service suitability also depends on pressure, temperature, corrosion allowance and the process environment. The alloy designation alone establishes neither sour- service qualification nor suitability for every hydrogen-containing process. Those requirements need a specific materials review. Welding should be covered by the fabricator's qualified procedure. The responsible engineer must establish preheat, interpass control, consumables and any PWHT against the construction code and component details. A procedure for ordinary carbon steel should not be assumed suitable merely because both products are plates. Inspection and inquiry checklist Request the required inspection document, such as EN 10204 3.1 where specified, heat-number traceability, heat analysis, mechanical results and delivered heat-treatment condition. If impact testing is required, define temperature, energy, orientation and specimen location. Specify ultrasonic testing with its method and acceptance level, and identify any third-party witness points. None of these additional services is implied as an automatic inclusion. Send nominal thickness, width, length, quantity, edge condition, tolerance basis and minimum-thickness constraints with the inquiry. Include the standard edition, Class 1 designation, intended service and fabrication heat-treatment requirements. Ask for confirmation of actual offered material, dimensions and schedule; no inventory, price, mill approval or blanket certification commitment is represented here. Product information: https://www.steelspecs.com/products/astm-a387- , grade-11-class-1-steel-plate/ Company website: https://www.steelspecs.com/