Alloy Steel Flanges

Among other products, alloy steel flanges are primarily composed of chromium, molybdenum, and nickel. Corrosion and oxidation resistance are excellent on these flanges. In water pipelines, oil and gas fields, chemical plants, and food production systems, they are widely used.

Flanges made of high alloy steel are a key driver for the automotive industry. In this section, we will examine the current state of high alloy steel flanges and how they will be used in the future. The most commonly used flange in an automotive engine is a high alloy steel flange. 

A minimum of one piece is made from forged or extruded high-carbon tool steel. It is common for these flanges to have a two-piece inner tube, with the outer portion being welded to the inner tube. There are a number of performance and non-structure features that can be added to any high alloy steel flange, as well as structural features. 

This material’s strength and stiffness are entirely due to its rolled high carbon tool steel composition, not just welded together. Additionally, the properties that make these flanges ideal for this application are readily available in standard flange elements. A number of factors influence the engineering design and manufacture of high alloy steel flanges, including material cost, customer specifications, manufacturing technology, and 3D CAD modeling.

High AS 2129 Flanges Tolerance Formula

Alloys with the following tolerances:

Its components include the RA 253 MA, RA330, RA333, ZERON 100, AL-6XN, 304, 309, 316, 321, 347, 410, 446, 2205, 2507, 2101, 17-4, 15-5, and 800.

The tolerances listed were taken from ASTM A480

O.D. (Outside Diameter):

  • When O.D. (Outside Diameter) is less than 24″: ±1/16″ (1.6 millimeter)
  • When O.D. (outside diameter) exceeds 24 inches: 3.2 millimeters (1/8 inch).

Inside Diameter (I.D.):

  • 10″ and below: ±1/32″ (0.8 mm)
  • 12″ thru 18″: +1/8″ (3.2 mm)
  • 20″ and greater: -1/16″ (1.6 mm)

Diameter of contact face

  • 1/16″ recessed face: 1/32″ (0.8 mm)
  • 1/4″ RF (Raised Face), T/G (Tongue & Groove) (male & female), (m/f): 1/16″ (0.4 millimeters).

Diameter of hub at base

  • When the hub base is 24″ or smaller: 1/16″ (1.6 millimeters)
  • When hub base is more than 24″, add 1/8″ (3.2 millimeters).

Diameter of hub at point of welding

  • 5 pounds and smaller: 3/32″ (2.4 mm), 1/32″ (0.8 mm)
  • 6″ and larger: +5/32″ (4.0 mm) and -1/32″ (0.8 mm).


  • Bolts for circles: 1/16″ (1.6 mm)
  • Hole spacing for bolts: 1/32″ (0.8 mm)

Eccentricity of bolt circle with respect to facing

  • Up to 2 1/2″ and less than 1/32″ (0.8 mm)
  • 3″ and greater ±1/16″ (1.6 mm) maximum


  • Smaller than 18″: ±1/8″ (3.2 mm), -0″
  • Larger than 20″: ±3/16″ (4.8 mm), -0″

Length of hub

  • Smaller than 10″: ±1/16″ (1.6 mm)
  • 3.2 mm and larger: 1/8″
  • It is recommended to measure the thickness of the plate along the longitudinal edges at least 3/8 inch thick. A maximum of 3 inches is allowed, but not more than 9.52mm. From the edge, [76.20 mm].
  • Please note that this is only for plates up to 10 inches in diameter. A tolerance of 0.010 inches is allowed under the specified thickness of [254.0mm] inclusive. The thickness is 0.25 mm.
  • For circles, the over thickness tolerances in this table apply to the circle’s diameter corresponding to the width ranges. Plates with irregular shapes are subject to over thickness tolerances based on their greatest widths.

Based on ASTM A480, the following tolerances were determined

Table A2.20 Permitted Variations in Flatness of Plate Mill Plate (Quarto Plate)

  • Tolerances in this table apply to any length, not necessarily the rolling direction, up to 36 inches. [914mm] and to any 36-inch length. As measured on a flat surface with the concavity of the curvature upward, [914mm] of longer lengths in the plate plane.
  • The longer dimension must be less than 36 inches. There is a tolerance of 1/4 inch for [914mm]. 6.4 millimeters.
  • Plates with a minimum yield strength of 35 ksi [240MPa] are permitted to be modified.

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