Gray cast iron

Material identity and specification

Dura-Bar G2 gray iron lists 40,000 psi minimum tensile strength on a separately cast ASTM B test bar. The producer treats tensile results cut from the continuous-cast stock as reference data because strength varies with diameter and section. Agree local-property verification when a thick casting section governs. Dura-Bar G2 test basis, ASTM A48/A48M scope

Gray cast iron contains flake graphite in a metallic matrix. Dura-Bar's gray-iron overview describes matrices ranging from pearlite to pearlite plus ferrite, with corresponding differences in machinability, strength, hardness and wear behavior. The family name therefore does not establish one set of engineering properties. Dura-Bar gray-iron grades overview

ASTM A48/A48M-22(2026) covers gray iron castings for general engineering use where tensile strength is a major consideration. Classification uses separately cast test bars and subordinates chemical composition to tensile strength. Its scope explicitly warns that strength in actual casting sections can differ from coupon values. ASTM publisher scope

What a grade and test bar establish

A separately cast tensile bar standardizes a test condition; it does not reproduce every cooling history or section of a complex component. Record the specified test-bar basis and its relationship to the delivered lot. Where local properties matter, agree any additional casting-specific verification with the foundry before ordering. ASTM A48/A48M scope, coupon and section distinction

Keep tensile acceptance separate from hardness, microstructure, soundness and dimensions. A satisfactory coupon cannot establish that a thick boss, thin wall, drilled passage and machined sliding surface all have the required local condition. State critical inspection locations and acceptance criteria on the drawing or purchasing documents.

A bounded continuous-cast example

Dura-Bar G2 is a pearlitic gray-iron product associated with ASTM A48 Class 40. Its 40,000 psi minimum tensile strength is determined using a separately cast ASTM B test bar; material removed from the continuous-cast bar provides reference data because strength varies with section thickness and diameter. The producer reports no minimum yield strength or elongation for this non-ductile product. Dura-Bar G2 technical specifications

The G2 page gives these hardness intervals across round bars, selected by nominal as-cast diameter. Rectangle/square values require their own height/width basis. Dura-Bar G2 hardness table

These intervals belong to that product and supplied geometry; they are not universal hardness limits for all Class 40 castings. Confirm current availability and the actual grade before applying a row.

Calculated conversion: 40,000 psi × 0.006894757 = 275.8 MPa. This only converts the named producer's tensile entry. ASTM A48/A48M treats SI and inch-pound systems independently; it warns against combining them into a new requirement. A conversion is not a declaration that another metric class or standard is equivalent. ASTM units clause

For a calculation model, do not invent a steel-style yield plateau or guaranteed plastic redistribution from this tensile figure. Use the accepted design method and material data for the actual application. Resolve modulus, thermal properties and fatigue inputs independently when they affect the result.

Stock allowances and machining

Dura-Bar states that G2 rounds include stock to clean up at nominal size, whereas rectangles and squares are cast to actual dimensions without the same added allowance. Its stock-allowance guidance must be checked for the particular section. Dura-Bar G2 stock guidance

Place finished geometry inside a verified cleanup envelope, including surface removal, out-of-round or other supplied variation relevant to the feature. Do not assume that nominal stock dimensions are finished dimensions. Confirm the inspection stage and datum scheme before machining fitted bores, slides or sealing faces.

The grade overview identifies machinability and vibration damping as reasons to consider G2. These are qualitative selection leads, not guaranteed cutting parameters or a specified machine's vibration response. Dura-Bar grades overview

Develop tooling and parameters for the actual stock, surface condition, operation and machine. Qualify dimensional stability and finish on representative parts. For a machine base or housing, assess the assembled structure, supports and excitation rather than assigning a damping guarantee from the material name.

Heat treatment, repairs and application limits

Dura-Bar offers G2P specifically for surface-hardening applications, emphasizing pearlite in the rim and response to flame or induction hardening. This illustrates why two gray-iron products with similar nominal tensile strength may be selected for different fabrication routes. Dura-Bar G2P description and heat-treatment response

Establish final condition, hardness location/depth and dimensional acceptance before choosing a thermal process. A surface reading cannot demonstrate a required through-section condition. Do not transfer a producer's hardening example to an arbitrary casting without qualifying the actual material and section.

For repair welding, brazing or local heating, require an accepted procedure and finished-area inspection suitable for the component's service. A tensile grade does not authorize an undocumented repair. Retain thermal and repair history with the material record where those operations affect acceptance.

Specify finished-part leak, fatigue or thermal-cycle tests where required.

Release and source versions

Connect the delivered lot and grade to the drawing, coupon/test basis, actual stock or casting used, processing history and final inspection. Resolve changes in grade, section, producer or manufacturing route before release. Preserve special soundness, local hardness and dimensional requirements rather than reducing the order to a class number.

The ASTM publisher identifies A48/A48M-22(2026); this page uses its public scope and abstract, not the full purchased standard. Dura-Bar's overview PDF prints Form 99-75-00-99-00, 0119, despite the download filename containing 0321. The code is retained without inferring a complete revision date. Live product pages have no technical revision dates used here. Sources reviewed 2026-11-01, America/Los_Angeles.

See grades, tempers and conditions.