4J33
Material grade: 4J33 precision alloy
Russian grade: 33HК/Ni33Co17
Japanese grade: KV-4/Ni33Co17
1.Overview of 4J33 precision alloy:
4J33 is a ceramic sealing alloy developed based on the characteristics of ceramics in our country. The alloy has a linear expansion coefficient similar to 95% Al2O3ceramics within the temperature range of -60℃ to 600℃. It is mainly used for matching seals with ceramics and is an important sealing structural material in the electric vacuum industry.
1. 4J33 material grade: 4J33.
2. Similar grades to 4J33: see Table 1-1.
Table 1-1^[1～3]

3. Technical standards for 4J33 material:
4. Chemical composition of 4J33: see Table 1-2.
Table 1-2                                                               %

Under the condition that the average linear expansion coefficient meets the standard requirements, deviations in nickel and cobalt content from the specified range in Table 1-2 are allowed.
5. Heat treatment system for 4J33: The performance test samples for the standard specified expansion coefficient and low-temperature microstructure stability are heated to 900℃±20℃ in a protective atmosphere or vacuum, held for 1 hour, and cooled to below 200℃ at a rate not exceeding 5℃/min.
6. Varieties, specifications, and supply status of 4J33: Varieties include wire, tube, plate, strip, and bar.
7. Melting and casting process of 4J33: Melted using non-vacuum induction furnace, vacuum induction furnace, or electric arc furnace.
8. Application overview and special requirements of 4J33: This alloy has been used for a long time in aviation factories, with stable performance. It is mainly used for sealing electric vacuum components with Al2O3ceramics. It is used to manufacture electrodes, lead frames, and lead wires for large electronic tubes and magnetrons. During use, the selected ceramics should match the expansion coefficient of the alloy. When selecting the alloy, the low-temperature microstructure stability should be strictly tested according to the usage temperature. Appropriate heat treatment should be carried out during processing to ensure that the material has good deep drawing and stretching performance. When using forged materials, their airtightness should be strictly tested.
2.Physical and chemical properties of 4J33:   
1. Thermal properties of 4J33:
(1) Melting temperature range of 4J33: The melting temperature of this alloy is about 1450℃^[1,2].
(2) Thermal conductivity of 4J33: The thermal conductivity of 4J33 alloy is λ=17.6W/(m•℃)^[1,2].
(3) Linear expansion coefficient of 4J33: The average linear expansion coefficient of the alloy as specified in the standard is shown in Table 2-1.
The average linear expansion coefficient of this alloy is shown in Table 2-2. The expansion curve of 4J33 alloy is shown in Figure 2-1.
Table 2-1 Table 2-2^[1]

2. Density of 4J33: ρ=8.27g/cm^3[1,4].
3. Electrical properties of 4J33:
(1) Resistivity of 4J33: ρ=0.46μΩ·m^[1,4].
(2) The temperature coefficient of resistance for 4J33: see Table 2-4.
Table 2-4^[1,2]

4. Magnetic properties of 4J33:
(1) Curie point of 4J33: Tc=440℃^[1,2].

(2) Magnetic properties of 4J33 alloy: see Table 2-6.
Table 2-6^[1,2]

At 4000A/m, the residual magnetic induction strength Br=1.06T, coercive force Hc=63.2A/m^[1,2].
5. Chemical properties of 4J33: This alloy has good corrosion resistance in the atmosphere, fresh water, and seawater.
Three,Mechanical properties of 4J33:
1. Performance specified by the technical standards for 4J33:
(1) Hardness of 4J33: The hardness of deep-drawn strip should meet the requirements of Table 3-1. Strips with a thickness not exceeding 0.2mm are not subjected to hardness testing.
Table 3-1

(1) Tensile strength of 4J33: The tensile strength of wire and strip should meet the requirements of Table 3-2.
Table 3-2

2. Mechanical properties of 4J33 at room temperature and various temperatures:
(1) Hardness of 4J33: The hardness of the alloy strip (annealed state) is shown in Table 3-3.
(1) Tensile properties of 4J33: The tensile properties of the alloy (annealed state) at room temperature are shown in Table 3-3.
Table 3-3^[1,2,4]

3. Durability and creep properties of 4J33:
4. Fatigue properties of 4J33:
5. Elastic properties of 4J33: Elastic modulus E=139GPa.
Four,Microstructure of 4J33:
1. Phase transformation temperature of 4J33: The γ→α phase transformation temperature of 4J34 alloy is below -80℃. 4J33 has a more stable structure than 4J34.
2. Time-temperature-structure transformation curve of 4J33
3. Microstructure of 4J33 alloy: The structure of this alloy is single-phase austenite.
When the alloy composition is improper, different degrees of austenite (γ) to needle-like martensite (α) transformation will occur at room temperature or low temperature. The phase transformation is accompanied by a volume expansion effect. The expansion coefficient of the alloy increases accordingly, leading to a significant increase in the internal stress of the sealing components, and even causing partial damage. The main factor affecting the low-temperature structural stability of the alloy is the chemical composition of the alloy. From the Fe-Ni-Co ternary phase diagram, it can be seen that nickel is the main element that stabilizes the austenite (γ) phase, and a higher nickel content is beneficial for the stability of the γ phase. As the total deformation rate of the alloy increases, its structure tends to become more stable. The segregation of the alloy composition may also cause local γ→α phase transformation. In addition, coarse grains can also promote the γ→α phase transformation.^[2,5,6].
4. Grain size of 4J33: The standard stipulates that the grain size of deep-drawn strip should not be less than grade 7, and the grains smaller than grade 7 should not exceed 10% of the area. For strips with a thickness of less than 0.13mm, when estimating the average grain size, the number of grains along the thickness direction of the strip should not be less than 8.
A 1mm thick 4J33 strip with a cold strain rate of 60% to 70% is annealed at the temperatures shown in Table 4-1, and after air cooling, the grain size rating is conducted according to YB 027-1992 Appendix A, with results shown in Table 4-1.
Table 4-1

Five,4J33 process performance and requirements:
1. 4J33 forming performance: This alloy has good cold and hot working performance and can be made into various complex shapes of parts. However, heating in a sulfur-containing atmosphere should be avoided. During cold processing, the cold strain rate of the strip is greater than 70%, which can cause plastic anisotropy after annealing. When the strain rate is within 10% to 15%, the alloy will cause rapid grain growth during annealing, which will also produce plastic anisotropy of the alloy. When the final strain rate is 60% to 65% and the grain size is 7 to 8.5, the plastic anisotropy is minimized.
2. 4J33 welding performance: This alloy can be welded to metals such as copper, steel, and nickel 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, even causing cracks in the weld.
The parts of this alloy should be annealed, cleaned, and nickel-plated before sealing with ceramics. They should be sealed with silver solder to ceramics that have been metallized and then nickel-plated.
3. 4J33 parts heat treatment process: Heat treatment can be divided into: stress relief annealing and intermediate annealing.
(1) Stress relief annealing: To eliminate the residual stress in the parts after machining, stress relief annealing should be performed at 470 to 540℃, holding for 1 to 2 hours, followed by furnace cooling or air cooling.
(2) Intermediate annealing: To eliminate the work hardening caused by cold rolling, cold drawing, and cold stamping of the alloy, facilitating further processing. The workpiece needs to be heated in dry hydrogen, decomposed ammonia, or vacuum to 750 to 900℃, holding for 15 minutes to 1 hour, then furnace cooling, air cooling, or water quenching.
This alloy cannot be hardened by heat treatment.
4. 4J33 surface treatment process: Surface treatment can be done by sandblasting, polishing, and pickling. This alloy has good electroplating performance and can be plated with metals such as gold, silver, nickel, and chromium.
5. 4J33 cutting and grinding performance: The cutting characteristics of this alloy are similar to those of austenitic stainless steel. High-speed steel or carbide tools should be used for low-speed cutting processing. Coolants can be used during cutting. This alloy has good grinding performance.
Six,4J33 varieties, specifications, and supply status:
1. Variety classification: Seamless pipes, steel plates, round steel, forgings, flanges, rings, welded pipes, steel strips, wires, and matching welding materials.
2. Delivery status: Seamless pipes: solid solution + acid white, length can be customized; plates: solid solution, pickled, trimmed; welded pipes: solid solution acid white + RT% flaw detection, forgings: annealed + turned; bars in forged state, surface polished or turned; strips delivered after cold rolling, solid solution soft state, and descaling; wires delivered in solid solution pickled coil or straight bar form, solid solution straight bar fine polished state.