HIFH03A_HeatTreatmentCurrMeter.pdf

HIF-H-03A

09-09-10

U.S. GEOLOGICAL SURVEY

WATER RESOURCES DIVISION

HYDROLOGIC INSTRUMENTATION FACILITY

SPECIFICATION

FOR

HEAT TREATMENT OF CURRENT METER PIVOTS

1. SCOPE

This specification provides information for heat treating the pivots on the USGS Price AA Current Meter and the USGS Price Pygmy Current Meter.

The pivots for both types of meters are made from the same type of material and are heat treated in the same manner.

2. MATERIALS

Carpenter #440C stainless steel.

3. REQUIREMENTS

Required Hardness: 87.4 - 89.8, measured on the Rockwell 15N scale, in the conical point and the adjacent reduced-diameter section of the pivot.

3. METHODS

There are two heat-treating methods that have been used in the past.

Experience has shown that the pivots can be treated to an acceptable value of hardness and toughness using either method.

Method #1

Heat: 1975 - 2000 degrees Fahrenheit in a dry hydrogen furnace Soak: For a period equal to the heating time Quench: In oil Deep Freeze: At -120 degrees Fahrenheit Draw: At 325-350 degrees Fehrenheit

Repeat the deep freeze and draw operation as necessary to produce a hardness in the upper end of the pivot, including all the portion above the shoulder, of 87.4 to 89.8 on the Rockwell 15N scale.

HIF-H-03A

09-09-10

Surface finish after heat treating:

Remove scale from the entire pivot.

Method #2

Heat: 1900 - 1925 degrees Fahrenheit in a vacuum furnace Soak: At 1900 - 1925 degrees Fahrenheit for 90 to 120 minutes Quench: Rapid nitrogen quench, pull parts from furnace at 115 degrees Fahrenheit Stress-relieve: Reheat to 280 degrees Fahrenheit for 30 to 60 minutes Deep Freeze: Hold at or below -120 degrees Fahrenheit for 4 hours Warm: To room temperature Draw: At 300 - 325 degrees Fahrenheit for two hours

This procedure will typically produce parts with the required hardness.

If the parts are harder than specified:

Repeat the draw operation, modifying the draw temperature as needed to produce the required hardness in the conical point and the adjacent reduced-diameter section of the pivot.

If parts are softer than specified:

Run a full cycle anneal process on the parts, then repeat the heat-treating process, modifying the draw temperature as needed to obtain the required hardness in the conical point and the adjacent reduced-diameter section of the pivot.

Surface finish after heat treating:

Remove scale from the entire pivot.