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kovar sheet We are offering a wide range of superbly made kovar sheets. These sheets are made of high grade raw materials that are sourced from trusted vendors. Our team of expert professionals work with diligence to bring forth an engrossing assortment of products for esteemed clients. This sheet is used for making glass sealing of metal components. It mostly finds application where change in shape with the temperature is desired. With below given specifications kovar sheet can be availed.
Physical PropertiesSpecific gravity.......................................8.36 Curie temperature Density °F.................................................... 815 lb/cu in............................................... 0.302 °C.................................................... 435 kg/cu m............................................... 8359 Melting Point Thermal conductivity °F.................................................. 2640 Btu-in/ft²/hr/°F...................................... 120 °C................................................. 1450 W/m-K.................................................. 17.3 Modulus of elasticity Electrical resistivity psi x 10(6) ..................................... 20 ohm-cir mil/ft......................................... 294 MPa x 10(3) .................................. 138 microhm-mm......................................... 490
Thermal Expansion Properties
The following are the average coefficient of expansion properties after annealing in hydrogen for 1 hr at 1650°F (900°C) and 15 minutes at 2010°F (1099°C) and cooled to room temperature within 1 hr. Material heat treated using this procedure should not exhibit any transformation when cooled to -112°F (-80°C) for 4 hrs. This was determined by means of metallographic examination.
Mean coefficient of thermal expansion as annealed.
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Temperature
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Coefficient
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77°F to
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25°C to
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10(-6)/°F
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10(-6)/°C
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212
392
572
662
752
842
932
1112
1292
1472
1652
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100
200
300
350
400
450
500
600
700
800
900
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3.25
2.89
2.85
2.72
2.81
2.92
3.41
4.34
5.06
5.73
6.25
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5.86
5.20
5.13
4.89
5.06
5.25
6.15
7.80
9.12
10.31
11.26
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Preparation for Sealing
All degreased, fabricated Kovar alloy parts should be degassed and annealed in a wet hydrogen atmosphere. Atmosphere is to be made moist by bubbling the hydrogen through water at room temperature. Care must be taken to prevent surface carbon pickup. Furnace should have a cooling chamber provided with the same atmosphere.
Heating should be conducted within the 1540/2010°F temperature range. Time at temperature should be approximately two hours for lowest temperature to 20 minutes for the highest temperature. Parts should then be transferred to the cooling zone and held until below 570°F, then removed.
An oxide film on the metallic part is preferred for metal-to-hard glass sealing. The best oxide film is thin and tightly adhering. The film can be produced by heating the parts to 1200/1290°F in regular ambient atmosphere for a time sufficient to form a dark gray to slight brown oxide.
Workability
Forging
The principal precaution to observe in forging is to heat quickly and avoid soaking in the furnace. Long soaking may result in a checked surface due to absorption of sulfur from the furnace atmosphere and/or oxide penetration. A forging temperature of 2000/2150°F is preferred.
Coolant
It is important to control heat build up, the major cause of warpage. A suggested coolant would be Cool Tool. Cool Tool contains fatty esters to reduce friction in the cutting zone and a refrigerant to remove the heat generated by friction between the cutting tool and work place.
Tooling
T-15 Alloy, such as Vasco Supreme-manufactured by Vanadium Alloys Company. M-3 Type 2, such as Van Cut Type 2-manufactured by Vanadium Alloys Company. Congo manufactured by Braeburn.
For machining with carbide tools, a K-6 manufactured by Kennemetal, Firthie HA manufactured by Firth Sterling, or #370 Carboloy could be used, or a K2S manufactured by Kennemetal, or Firthie T-04 manufactured by Firth Sterling would be satisfactory. One thing of prime importance is that all feathered or wire edges should be removed from the tools. They should be kept in excellent condition by repeated inspection.
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