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G2P Gray Iron

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G2 Gray Iron

Overview

Dura-Bar G2P is a highly pearlitic gray iron containing Type A graphite. It was developed to best suit surface-hardenability applications. G2P is made with a substantial amount of pearlite in the rim. This requires the least amount of stock removal necessary, in order to achieve a heat-treatable surface. Carbon-rich material is forced to the outer edges of the bars. This allows the surface hardening via heat treatment (induction and flame hardening) to be accomplished quickly, consistently, and effectively. To learn more, download the G2P Gray Iron Product Brief.

Microstructure

The microstructure will contain Type VII, A, size 4–6 graphite as defined in ASTM A247. The matrix is fully pearlitic. The edge or rim will consist of Type D, size 6–8 graphite in a matrix that is a combination of pearlite and ferrite. Chill carbides will be less than 5% in any field at 100x and are well dispersed.

Center Area

100x, etched in 5% Nital

Edge Area

100x, etched in 5% Nital

Heat Treat Response

Dura-Bar G2P can be hardened by fast methods, such as flame and induction hardening. Carbon-rich pearlite in the rim of the continuous cast bars will effectively transform to martensite (hard phase of iron). Contrasted with a more ferritic rim, continuous cast bars can result in untransformed microstructure and thus a less ideal material hardness after heat treatment.
In addition to surface hardening, Dura-Bar G2P can be heat treated by conventional quench and temper methods. Get more details including typical Jominy end quench curve, methods and cycle times, and temperature effects by downloading the Dura-Bar Heat Treating Guide.

Stock Sizes

Rounds

Size Range: 4.500" to 5.750"

As-cast round bars are made to clean up at the nominal size. Additional stock is added to allow for out-of-round and normal imperfections in the as-cast surface. Stock allowance is a function of the bar diameter - see Stock Allowances for details. Other finishes available are Centerless Grinding and Centerless Turning, for demanding tolerance applications.

Tubes

Size Range: 4.500" x 1.750" to 5.750" x 3.750"

Trepanned tubes are stocked in 72" lengths, but can be produced in longer lengths upon request. Tubes are stocked in grade G2 gray iron, but most stocked sizes and any grade of O.D. can be trepanned to the inside diameter listed. Tubes are sold with clean-up stock on the inside and outside diameters. See rounds Stock Allowances for O.D. The concentricity tolerance between the I.D. and O.D. is 0.250". See Services/Trepanning for details.

Technical Specifications

Chemical Composition

Carbon and silicon targets are specified for each bar size in order to control the size and shape of the graphite flake. Alloying elements are used to stabilize the pearlitic structure.

Mechanical Properties

Brinell hardness values for nominal as-cast diameters are shown in the table. Hardness properties listed are minimum and maximum across the bar. Hardness values for rectangles and squares are a function of the height and width ratios and will be supplied on request.

Tensile strength is determined from a separately cast, ASTM "B" test bar. Separately cast test bars will meet the minimum strength in pounds per square inch in the table. Additionally, a test bar is removed from the continuous cast bar for reference, since tensile strength varies with section thickness and bar diameter.

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