Manganese Steel Casting and Heat Treatment Procedure

1. Material Instruction

a. Control composition

i. Elements should be as follows:

• Carbon 1.20%
• Manganese 18.0%
• Phosphorous 0.05%
• Chrome 2.00%
• Si 0.50%
• Iron Balance (see comment on 1:b:i)

b. Keep Phosphorous levels controlled with the aid of new raw material (not scrap)

i. Scrap to virgin alloy steel to be controlled to about 50:50, not to exceed 60% scrap material to 40% virgin material (new)

c. If manganese level is below 18%, keep the carbon ratio consistent 1.2%

i. If there is an increase manganese content to 24%, Carbon not to exceed 1.3%

d. Assure mixture with Spectrochemical analysis while still in the furnace

2. Pouring Instruction

a. Heat mixture in the furnace to 1470 degrees Centigrade

b. Pour casting as cool as possible

i. Pour casting between 1380 and 1420 degrees Centigrade

3. Molding Instruction

a. Cool/Dwell newly poured casting slowly to 315 degrees Centigrade and remove from mold with rigging in tact

i. Dwell time is dependent on mold sand to metal ratio

4. Heat Treat & Quench Instruction

a. Move to the proper oven with expediency

i. Allowable range for the casting temperature versus the oven temperature is 90 degrees Centigrade

• Since the casting is 315 degrees Centigrade, the oven must be preheated to between 225 and 405 degrees Centigrade
• Preference is that the casting is warmer than the oven
• The ideal start point for the heat treat oven is 260 degrees Centigrade
• Oven must be ready for the casting

b. Heat slowly to avoid cracking

i. Move the temperature about 40 degrees Centigrade per hour until the casting reaches 650 degrees Centigrade

ii. Hold at 650 degrees Centigrade for as many hours as the casting is thick by a factor of 1.5 (at its thickest point (A))

iii. Move the temperature about 40 degrees Centigrade per hour until the casting reaches 1100 degrees Centigrade

iv. Hold at 1100 degrees Centigrade for as many hours as the casting is thick by a factor of 1.5 (at its thickest point (A))

• For example, a 4.25' Std Mantle with a 4" cross section on the seat should be held at 650 degrees Centigrade for 6 hours and again held at 1100 degrees Centigrade for 6 hours
• Reasonable allowable time for this example is about 36 hours (10+6+14+6)

c. Quench quickly

i. Quench at the desired point in time immediately

• Temperature reduction to about 38 degrees Centigrade

ii. Use a fresh and cold water supply, properly circulated

iii. Once cooled to a working temperature, remove the risers and rigging

• Reuse risers and rigging in next pour to help control Phosphorous levels
• Keep working temperatures thru the casting under 315 degrees Centigrade

5. Crack Repair Instruction

a. Identify subsurface cracks with the use of UT test equipment or Radiograph

b. If there is cracking use sound judgment in repair versus scrap

i. A long and deep crack on a relatively thin casting should not be repaired, but rather recast

• A long, shallow crack on the same casting could be repaired before final machining
• Keep repair temperatures thru the casting under 315 degrees Centigrade