Flame harden

Fig. 3. Flame hardening (a) tempeiatuie—time heating curves of a 25 x 50 x 100 mm specimen at a feed of 75 mm /min and burner distance of 8 mm showing temperatures of A, surface B, 2 mm below surface and C, 10 mm below surface (b) hardness—depth curves for a 0.50% C steel 25 X 75 X 100 mm specimen at a feed of 50 mm /min, temperatures ia °C measured 10 mm below the surface, and burner distances ia mm, respectively, of A, 530 and 50 B, 540 and 12 C, 545 and 10 D, 550 and 8 and E, 565 and 6. Flame heating followed by water spray quenching. HV = Vickers hardness.

PISTON RINGS are normally cast-iron of the single-piece snap-ring type, although other materials may be used when conditions require. PISTON ROD is carbon-steel, flame-hardened over packing travel area. 

PISTON ROD is carbon-steel, flame-hardened over packing travel area unless otherwise specified. 

Flame hardened Heavy case depths with good capacity for contact loads, good bending fatigue resistance and fair dimensional control... 

The dies themselves are generally constructed of medium carbon alloy steels, with flame-hardened lips and chrome or nickel plating on the flow surfaces. Insulation of the die body Is common to prevent temperature variations that could result from air drafts. Dies can be electrically heated, or steam or oil heat can be used. Cooling is usually provided by natural convection, though forced air can also be used. 

Surface hardenability - laser hardening, flame hardening or inductive hardening,... 

FIGURE 4.90 Cracking during flame hardening due to excessively abrupt cooling conditions... 

Figure 4.90 shows an example of a plastic compression mold made of the prehardened plastic mold steel 1.2738 (40CrMnNiMo8-6-4). Cracking occurred during flame hardening of the parting lines due to the absence of pre-heating. 

FIGURE 4.91 Flame hardening a mold surface in a wear area... 

Selective hardening treatments, for example, flame hardening... 

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