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Work Hardening Austenitic Alloys |
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| This group includes Manganese and Stainless Steels. They have the unique capacity to work-harden under impact, and since this hardening effect is usually confined to the metal close to the surface, a part hardfaced with one of these materials will soon provide a hard, wear-resistant skin, while maintaining a strong, tough core. They have three main applications: | |||||||||||||||||||||||
| 1. | Used alone as an overlay. | ||||||||||||||||||||||
| 2. | Used as a build-up underneath more abrasion resistant hardfacing alloys. | ||||||||||||||||||||||
| 3. | Joining and fabricating carbon, alloy, stainless or manganese steels. | ||||||||||||||||||||||
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Group 1 - Austenitic Manganese |
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| 1. | Used as a manganese overlay, by itself, when the part will be subjected to a heavy metal-to-metal pounding such as occurs on railroad frogs or switches. | ||||||||||||||||||||||
| 2. | Use as a build-up, underneath more abrasion resistant chromium carbide overlays. | ||||||||||||||||||||||
| 3. | Used for fabricating and joining manganese or manganese to other steels, such as stainless, carbon and low alloy steel. | ||||||||||||||||||||||
| Cracking
and Spalling:
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| Precaution
when welding manganese - The heat from
welding can cause manganese to become embrittled, and because the
effects from welding are cumulative, this
can lead to further problems if the part is to be rebuilt over and over
again.
Never let the part get
over 500ºF(260ºC) for an extended period of time. Postalloy 2865-FCO wire or 207
electrode are an excellent heat insulator and ideal for use as a cushion
or buffer layer on manganese steel parts that must be rebuilt on a
repetitive basis. It will act as a heat insulator to the manganese
base metal helping it stay below 500ºF(260ºC) during the welding
operation. Spalling can also occur when welding on mild steel with standard 14% manganese steel welding alloys such as when applying manganese as a cushion layer on mild steel. This is due to the low carbon content of the mild steel and the carbon and alloy content of standard manganese hardfacing alloys, which because of dilution, produce areas of hard martensite in the weld zone. For such applications choose a manganese welding material with a high alloy content, such as Postalloy 285, a chromium-manganese alloy such as Postalloy 2865-FCO, or a nickel-chromium-manganese work-hardening stainless steel alloy, such as Postalloy 2866-FCO. These alloys have been formulated to remain austenitic in order to avoid this problem. |
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| Additional Comments: | |||||||||||||||||||||||
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When welding with austenitic manganese steel, use an alloy such as Postalloy 285 or 2850-FCO, if the weld deposit will later be flame-cut. Weld deposits of higher alloy content chrome-manganese alloys, such as Postalloy 2865-FCO, and stainless steel welding alloys cannot be cut with a torch. | ||||||||||||||||||||||
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Never use a manganese alloy in which the deposit will be machined. | ||||||||||||||||||||||
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Never use a manganese alloy for heat resistant applications. | ||||||||||||||||||||||
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Manganese steel is tough with excellent impact properties, however, it has only fair abrasion resistance. Therefore, for optimum wear resistance, deposits of manganese steel should be overlayed with a more wear resistant alloy such as chromium carbide. | ||||||||||||||||||||||
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Group 2 - Work-hardening Stainless Steel |
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This group of work-hardened alloys can be used for applications that involve heat (Postalloy 286-FCO only). | ||||||||||||||||||||||
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Also unlike manganese, deposits are machineable. | ||||||||||||||||||||||
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As a stainless steel they provide good corrosion resistance. | ||||||||||||||||||||||
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They
provide an excellent cushion for harder, more abrasion resistant hardfacing alloys.
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