Fabrication

Heating and Pickling

Nickel 200 may be annealed over a wide range of temperatures above its recrystallization temperature. For heavily coldworked material, temperature may be as low as 1100° to 1200°F (595° to 650°C), but from a practical viewpoint, the range is usually about 1300 to 1700°F (705° to 925°C).

Because of the absence of a quantity of residual elements and secondary phases that tend to inhibit grain growth in more complex alloys, grain growth is rather rapid in Nickel 200 at elevated temperatures. Figure 11 shows the effect of various annealing temperatures on grain size. At higher temperatures, time at temperature must be carefully watched in order to exercise control over grain size.

Batch annealing in box, retort, or open furnaces is usually performed in the range of 1300° to 1500°F (705° to 815°C) for about 30 minutes to 3 hours, depending on cross section and amount of contained cold work. Nickel 200 has relatively high thermal conductivity so that heating rate will be relatively rapid. Cooling rate is not critical, and quenching is not necessary except as a means to shorten the heat-treating cycle or to partially reduce any surface oxide developed during heating or cooling in an oxidizing atmosphere. This reduction is accomplished by quenching in water containing 2% alcohol.

A soft oxide will remain which can be easily removed in standard pickling solutions. Continuous annealing in pusher-type, roller-hearth and conveyor-belt furnaces is usually done between 1450° and 1750°F
(790° and 955°C) for about 15 to 45 minutes in the hot zone. Strip and wire may be strand-annealed at temperatures between 1600° and 1900°F (870° and 1040°C) from 5-10 minutes down to a few seconds in the hot zone.

The fabricator should establish empirically specific heat treatments to provide proper control of grain size and properties by selecting the proper temperature range and running trials within that range to obtain the desired set of properties. A fineto-medium grain necessary to maintain a smooth surface during forming is usually considered to be about 0.001 to 0.004 inch (0.025 to 0.10 mm), which corresponds to an ASTM grain size of 7½ to 3½.

Annealing for periods of 1 hour or more at temperatures above 1700°F (925°C) will result in hardnesses of approximately 20 to 40 Rockwell B. This treatment, commonly called a dead-soft anneal, is used only in specialized applications such as burst diaphragms because of the low mechanical properties and coarse grain structure produced. Annealing should be performed in a reducing atmosphere to retain bright finishes. Dry hydrogen and dissociated ammonia are preferred, but less expensive atmospheres like partially burned natural gas will also provide adequate brightness.

Heating in oxidizing atmospheres at high temperatures should be avoided because of the danger of intergranular oxidation. Nickel 200 is sensitive to intergranular attack from sulfur and metals such as lead, tin, zinc, and bismuth that have low melting points. Scrupulous care must be exercised to remove all traces of forming lubricants, marking paints and shop soil prior to heating.

Procedures for pickling Nickel 200 are dependent upon the condition of the metal. Appropriate solutions and guidelines are given in the Special Metals publication “Fabricating”, on the website, www.specialmetals.com.

MACHINING DATA
Carbide tools are suggested  for rates better than 50% of Type 304.
Machining Type	Suggested starting rates are:
Single Point turning :	Roughing - 0.15" depth, 0.015"/rev feed -175 SFM  Finishing - 0.025" depth, 0.007"/rev feed - 200 SFM
Drilling :	1/4" Dia hole - 0.004"/rev feed - 60 SFM  1/2" Dia hole - 0.007"/rev feed - 60 SFM  3/4" Dia hole - 0.010"/rev feed - 60 SFM
Reaming :	Feed - same as drilling - 100 SFM
Side and Slot Milling :	Roughing - 0.25" depth - 0.007"/tooth feed - 125SFM  Finishing - 0.050" depth - 0.009"/tooth feed - 140SFM
These rates are for carbide tools,  Type C-2 for roughing, drilling and reaming.  Type C-3 for finishing.

 

Capacity – All nickel alloys easily can face-turned and bored on any machine. These alloys are carrying all feature such as speed, feed, depth-of-cut and tooling, & because of all above we can do boring / machinery job. Drilling large holes and tapping also possible with all sturdy machinery with plenty of power.possible with all possible with all

Tooling – Due to the nature of the alloys being worked, tools will tend to dull fairly quick and the need to change tooling or re-sharpen tools will be frequent. Although expensive, C grade inserts should be used whenever possible.

Lubrication/Coolants – Lubricants/coolants are desirable. Good results can be obtained using water-miscible vegetable oil based fluids in CNC equipment and engine lathes.

Drilling – When using insert drills in CNC machines use the same speeds (SFM) for facing, turning and boring for the specific alloy.

Resources: www.specialmetals.com

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