Kovar Product Material Supply Information

Kovar

Material:	Kovar
Other Brands:	4J29, kovar, K94610, FeNi29Co17, F15, 17745, 1.3981, Silvar 48, 29HK, Nilo K
Source Stock:	Customized
Supplier:	Shanghai Hite Special Alloy Co., Ltd.
Contacts:	Mr.KayDuan
Email:	sales02@hitealloy.com

Kovar Details

4J29 alloy, also known as Kovar alloy. This alloy has a linear expansion coefficient similar to that of borosilicate hard glass at 20-450 ℃, a high Curie point, and good low-temperature structural stability. The oxide film of the alloy is dense and can be well wetted by glass. And it does not interact with mercury, suitable for use in instruments containing mercury discharge. It is the main sealing structural material for electric vacuum devices.

Similar brands of Kovar
Technical standard YB/T 5231-1993 for J29 materials "Technical conditions for iron nickel cobalt glass sealing alloys 4J29 and 4J44".

Kovar Chemical Composition
Under the condition that the average linear expansion coefficient reaches the standard specified conditions, the nickel and cobalt content is allowed to deviate from the range specified in the table. The content of aluminum, magnesium, zirconium, and titanium should not exceed 0.10% each, and the total amount should not exceed 0.20%.

The performance test sample for the expansion coefficient and low-temperature structural stability specified in the 4J29 heat treatment system standard is heated to 900 ℃± 20 ℃ in a hydrogen atmosphere, held for 1 hour, then heated to 1100 ℃± 20 ℃, held for 15 minutes, and cooled to below 200 ℃ at a rate not exceeding 5 ℃/min.
The specifications and supply status of 4J29 varieties include wire, strip, plate, tube, and bar.
4J29 melting and casting processes are conducted using non vacuum induction furnaces, vacuum induction furnaces, or electric arc furnaces.
4J29 Application Overview and Special Requirements This alloy is a typical Fe Ni Co hard glass sealing alloy commonly used internationally. Stable performance after long-term use in aviation factories. Mainly used for glass sealing of electronic vacuum components such as emission tubes, oscillation tubes, ignition tubes, magnetrons, transistors, sealed plugs, relays, integrated circuit leads, chassis, casings, brackets, etc. In application, the expansion coefficient of the selected glass and alloy should be matched. Strictly inspect the low-temperature tissue stability according to the usage temperature. During the processing, appropriate heat treatment should be carried out to ensure that the material has good deep drawing and elongation performance. When using forged materials, their airtightness should be strictly inspected.

Kovar Physical and Chemical Properties
4J29 thermal performance.
The melting temperature range of 4J29 is approximately 1450 ℃.
The thermal conductivity of 4J29 is shown in the table.
When the specific heat capacity of 4J29 is 0 ℃, the specific heat capacity is 440J/(kg · C); At 430 ℃, the specific heat capacity is 649J/(kg · ℃).
According to the 4J29 line expansion coefficient standard, al (20~400 ℃)=(4.6~5.2) × 10-6 ℃ -1; Al (20-450 ℃)=(5.1-5.5) × 10-6 ℃ -1 (upper limit 5.6 when used for transistors × 10-6 ℃ -1).

Average linear expansion coefficient
Temperature coefficient of resistance

4J29 Curie point Tc=430 ℃

Magnetic Properties of 4J29 Alloy
At 4000A/m, the residual magnetic induction strength Br=0.98T, and the coercive force Hc=68.8A/m

4J29 Mechanical Properties
Performance specified in 4J29 technical standard.
The hardness of 4J29 deep drawn strip should comply with the specifications in the table. When the thickness is not greater than 0.2mm, no hardness test will be conducted.

The tensile strength of 4J29 wire and strip should comply with the specifications in the table.

The tensile properties of 4J29 tensile alloy (annealed state) at room temperature are shown in the table.

4J29 Organizational Structure
Thick strip with a cold strain rate of 60% to 70%, annealed at the temperature shown in the table for 1 hour, air cooled, and rated according to Appendix A of YB 027-1992

4J29 Process Performance and Requirements
The kovar alloy has good cold and hot working properties and can be made into various complex shaped parts. However, heating in sulfur-containing atmospheres should be avoided. During cold rolling, when the cold strain rate of the strip is greater than 70%, annealing will cause plastic anisotropy: when the cold strain rate is in the range of 10% to 15%, the alloy will cause rapid grain growth after annealing, which will also produce plastic anisotropy of the alloy. When the final strain rate is.

When the grain size is between 60% and 65%, and the grain size is between 7 and 8.5, the plastic anisotropy is the smallest.
4J29 welding performance: This alloy can be welded with copper, steel, nickel and other metals using methods such as brazing, fusion welding, and resistance welding. When the zirconium content in the alloy exceeds 0.06%, it will affect the quality of argon arc welding of the plate, and even cause weld cracking.
Before sealing the alloy with glass, it should be cleaned thoroughly, followed by high-temperature wet hydrogen treatment and pre oxidation treatment.
The heat treatment process of 4J29 parts can be divided into stress relief annealing, intermediate annealing, purification and degassing treatment, and pre oxidation treatment.

(1) Stress relief annealing is required to eliminate residual stresses in parts after mechanical processing: the relationship between outliers and thickness.
470-540 ℃, insulation for 1-2 hours, furnace cooled or air cooled.
(2) Intermediate annealing is used to eliminate the work hardening phenomenon caused by the alloy during cold rolling, cold drawing, and cold stamping processes, in order to facilitate further processing. The workpiece needs to be heated to 750~900 ℃ in dry hydrogen, decomposed ammonia, or vacuum, kept at a temperature of 14 minutes to 1 hour, and then furnace cooled, air cooled, or water quenched.
(3) After the purification and degassing treatment of parts, wet hydrogen treatment is required before pre oxidation treatment, and oil removal should be carried out before treatment. Work requires heating to 950~1050 ℃ in saturated wet hydrogen, holding for 10~30 minutes, and then furnace cooling.
(4) After wet hydrogen treatment, pre oxidation treatment is generally carried out on the alloy surface before melting and sealing, so as to generate a layer of uniform and dense oxide film on the alloy surface. The oxide film is firmly bonded to the substrate and can be well wetted with molten glass. After wet hydrogen treatment, the parts are oxidized in air at approximately 800 ℃. The weight gain of the parts should be within the range of 0.2~0.4mg/cm2 [10].

This alloy cannot be hardened by heat treatment.
The surface treatment process of 5.44J29 can include sandblasting, polishing, and pickling.
After sealing the parts with glass, in order to facilitate welding, the oxide film generated during sealing needs to be removed. The parts can be heated to 70 ℃ in a 10% hydrochloric acid+10% nitric acid aqueous solution.
Left and right, acid wash for 2-5 minutes.
This alloy has good electroplating performance, and its surface can be plated with metals such as gold, silver, nickel, chromium, etc. To facilitate welding or hot pressing bonding between parts, copper, nickel, gold, and tin coatings are often plated. To improve the conductivity of high-frequency current and reduce contact resistance to ensure normal cathode emission characteristics, gold and silver coatings are often plated. To improve the device.