| Machinability Rating |
| 27% of B-1112 |
Typical
Stock Removal Rate
|
45 surface feet/minute with high speed
tools, 125 surface feet/minute with
carbide.
|
| Comments: |
|
Care must be taken to make sure there
are rigid machine setup and sharp tools,
so that work hardening and surface
glazing do not occur.
|
|
HPAlloy X is machinable in both the
wrought and cast form. Low cutting
speeds and an ample flow of coolant are
required.
|
|
Suggested tool angles for single point
tungsten carbide tools are 8 to 10-Deg.
side-rake angle from cutting edge, 5 to 8
-Deg. back-rake angle, 5 to 7-Deg. end
relief angle, and 15 to 30-Deg. side
cutting-edge angle. Nose radius should
be 1/32 to 1/16 inch.
|
|
High-speed steel drills should be ground
to an included angle of 135 to 140 Deg.
with a clearance angle of 10 degrees.
The web should be thinned down to
about one-third the web-thickness of a
standard drill.
|
|
Better finishes can be obtained by
increasing the speed and decreasing the
feed. Automatic screw machines are not
recommended because speeds are
generally excessive and carbide-tipped
tools will not hold up.
|
|
A sulfur-base cutting fluid should be
used for machining this alloy. All traces
of cutting fluid should be removed prior
to heat-treatment or high temperature
service.
|
|
The table above may be used as a guide
in machining HPAlloy X. The figures
will be modified by such factors as tool
size and type, type of machining
equipment, size of stock, and nature of
cut.
|
|
| Welding |
| HPAlloy X can be welded by metallic-arc, inert-gas-shielded arc, submerged-melt, and SIGMA methods. |
| Cleaning |
|
The welding surface and adjacent area should be thoroughly cleaned down to bright metal before
welding. All grease, oil, crayon marks, and other foreign matter should be removed by scrubbing with
trichloroethylene or some other suitable solvent. The surface should be wiped clean before welding.
|
| Weld Joints |
|
Normally, a V joint is used for butt welds in plate thicknesses up 1/4 in. and a U joint for greater thicknesses.
The V or U joint is used where the welded material will be exposed to high stresses. These joints
will cause the stress to act axially. The lap or tee joint may be used for conditions of lower stress. The U
joint is preferred for material greater than 1/4 in. in thickness. While the cost of preparation may be
increased by this type of joint, the amount of welding materials and man-hours needed for welding will
be much less than if a V joint is used. The amount of residual stress will also be lower since less weld
material is required and less transverse shrinkage is incurred.
|
|
Usually, V joints should be beveled to 75- to 80° included angle; U joints beveled to 30° included
angle with a minimum bottom radius of 3/16 in. J grooves should have a 15° bevel with a minimum
bottom radius of 3/8 in. Tee joints between dissimilar material thicknesses should have a bevel of 45°.
The type of joint chosen will not necessarily be affected by a change of welding process since these joint
designs are standard. To make these joints suitable for automatic stressed material before welding
operations, such as inert-gas-shielded arc, certain slight modifications may be necessary.
|
| Edge Preparation |
|
Use of a machine tool in beveling is the surest way to obtain correct fits although hand grinding can also
yield satisfactory results. When sheared sheet or plate is used, the sheared edges should be ground back
approximately 1/16 in. to remove any stressed material before the edge is prepared for welding. In all
instances, the edges should be squared, aligned properly, and tacked before welding. Any misalignment
causes variation in gap width and bead contour, which results in stresses in the weld area. These factors
contribute to cracking in the weld joint. Careful preparation to assure good welds is well justified.
Thermal cutting and beveling of plates can be done, but, with the exception of HELIARC cutting, these
are not recommended procedures.
|
| Weld Penetration |
|
For good penetration, material 12-gage and heavier should be beveled and welded from both sides.
When joining material of dissimilar thicknesses, the heavier section should always be beveled for ease of
welding. Material thinner than 12-gage may be welded from one side by using proper edge spacing to
allow full penetration. Care should be exercised to eliminate non-uniform penetration. This condition
can leave undesirable crevices and voids in the underside of the joint which may contribute to areas of
accelerated corrosion. Non-uniform penetration in material used for high-temperature applications
creates stress raisers which may serve as focal points for mechanical failure.
|
|
Welding from both sides is recommended wherever possible. When this is not practical, the joint
spacing should be increased and copper backing bar used. Currents slightly higher than normal are then
used to obtain complete penetration. HPAlloy X does not have the same thermal conductivity as steel,
therefore, when using a standard groove, it is necessary to use a slightly larger clearance than would be
needed for steel. This larger clearance insures complete penetration of the weld.
|
| Jigs and Fixtures |
|
Proper jigging and clamping of the weld joint holds buckling and warping to a minimum. The use of a
backing bar helps to obtain a more uniform bead penetration. The bar also serves as a chill to the base
metal and helps prevent excessive bead penetration. When the arc process is used, the portion of the
fixture contacted by the arc should be copper. The bar should have a groove of the proper contour to
permit good penetration and bead contour. For arc welding, the grooves should be of a minimum depth,
usually from 1/16 to 3/32 in., and approximately 3/16 in. wide. The corners of the groove should be
rounded. Square corners cause poor bead contour, flux pockets, and non-uniform bead transfer. Jigs and
fixtures can be used to particular advantage when using the inert-gas-shielded arc process.
|
| Metallic-Arc Welding |
|
Direct current with reversed polarity produces the best mechanical properties. When joint design
permits, rapid travel with as little "weaving" as possible is preferred in order to minimize heat. To avoid
overheating when starting or stopping a bead, minimum currents that are consistent with the gage or size
of the parts should be used. To prevent crater-cracking it may be desirable to strike the arc on a tab
adjacent to the weld joint. The arc may be broken on a similar tab, however, doubling back on the bead
with a slant arc is the accepted practice. Because of the fluidity of the alloy, position welding is
somewhat difficult. Whenever possible, therefore, welding should be done in the flat position.
|
| Inert-Gas-Shielded Arc Welding |
|
In general, a minimum of heat input should be used, followed by a rapid cooling of the weld deposit. The
welding currents are dictated by the thickness of the sheet or plate to be welded, not by the wire
diameter. Use an electrode whose diameter is smaller than the thickness of the material to be welded.
This method is not recommended for welding plate over 3/8 inch thick.
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