The Differences Between Flame and Induction Hardening ...

The primary difference between flame and induction hardening in Gastonia, NC, lies in the final product of steel or alloy. Your choice of method mainly depends on the level of use and stress a component or item will face, as each offers distinct protective elements. Selecting the wrong method may lead to overkill, potentially damaging the item, or may result in inadequate surface hardening, leading to machinery failure. This explanation of induction and flame hardening will outline the differences, enabling you to make an informed decision.

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Induction hardening is a surface hardening process for steel and other alloy parts. Its goal is to create a hard shell that enables the item to endure pressure and use. This method is commonly applied to bearing races, pinion shafts, gears, crane wheels, treads, threaded pipe, and various components found in heavy machinery. For example, equipment used in oil patch drilling often relies on parts that have undergone induction hardening. While predominantly utilized for steel parts, this process also proves beneficial for copper alloys. Carbon and alloy steels with a carbon content between 0.40 and 0.45 percent are most suitable for induction hardening.

Initially, parts designated for induction hardening are placed in a water-cooled copper coil. They are heated to their transformation temperature using alternating current. This current heats the outer surface, alters its properties, and then hardens it to the desired depth. Once the appropriate temperature is reached, the part is quenched in oil or water, depending on the type of steel and the desired effects. The core remains unaffected by induction hardening, preserving the other properties of the steel.

Flame hardening is a more refined technique. It is particularly effective for flat surfaces, which is why plates and knives benefit greatly from this method. Like induction hardening, flame hardening produces a hard surface for alloys with sufficient carbon content, and the core remains unaffected as well.

During the flame hardening process, heat is applied using oxy-acetylene or another gas on the surface. The steel is heated to the upper-critical temperature before being quenched with water. This process tends to be quicker with less preparation for hardness. The outcome is a shallower hard shell; however, components treating with flame hardening typically do not encounter the same stress levels as those requiring induction hardening.

Essentially, both induction and flame hardening result in a harder surface for the item or component. The method you need depends on the item's purpose and the level of stress it will experience after completion. Generally, induction hardening is suited for industrial equipment and parts, while flame hardening is more appropriate for consumer products that need durability without facing the same stresses as machinery or equipment.

J.F. Heat Treating, Inc. offers both flame and induction hardening services in Gastonia, NC, suitable for multiple industrial or crafting applications. Contact us today to initiate the hardening process for your parts, flatware, or any items requiring a hardened surface, and benefit from our more than 30 years of industry experience.

The hardness and case depth of a workpiece are two crucial parameters indicating the quality and performance of surface hardening. Hardness measures a material's resistance to deformation or penetration, while case depth indicates the thickness of the hardened layer on a workpiece's surface.

Different methods and techniques exist for measuring hardness and case depth, depending on the material, the hardening process, and the required accuracy and precision. Some common methods include:

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• Vickers micro-hardness test: This test employs a diamond indenter in a pyramid shape to apply a small load on the workpiece's surface. The size of the indentation is measured under a microscope and converted to a hardness value using a table or formula. This test can also determine case depth by making multiple indentations along a workpiece's cross-section and plotting the hardness values against the distance from the surface.
• Rockwell hardness test: This test utilizes either a diamond cone or a steel ball as an indenter to apply a larger load on a workpiece's surface. The depth of penetration is measured by a dial gauge and converted to a hardness value using a scale or table. This method can also measure case depth by making multiple indentations along a cross-section and identifying where the hardness value drops below a specified level.
• Magnetic methods: These methods use electromagnetic sensors or probes to assess the magnetic properties of a workpiece, such as permeability, coercivity, or Barkhausen noise. These properties relate to the microstructure and hardness of the material and can be calibrated to estimate case depth.