I. Technical Background and Overview of Industry Applications

Iron-nickel fixed expansion sealing alloys are a type of special metal materials with specific thermal expansion coefficients, widely used in electronic packaging, aerospace, precision instruments, and other fields. Their core advantage lies in achieving a thermal expansion coefficient match with non-metallic materials such as glass and ceramics through precise control of alloy composition and processing technology, thereby avoiding stress cracking issues caused by temperature changes. As a professional enterprise in the field of high-purity metals and special alloys in China, Qinchuan New Materials (Zhengzhou) Co., Ltd. relies on its modern standard workshop located in the Zhengzhou High-Tech Industrial Development Zone, equipped with advanced special alloy production lines and precision processing equipment, and has accumulated rich experience in the research and manufacturing of iron-nickel fixed expansion alloys.

II. Technical Principles and Core Parameters Analysis

The thermal expansion coefficient of iron-nickel superalloys is mainly determined by the nickel content (usually 30%-50%) in conjunction with the iron matrix, with the expansion coefficient precisely controlled within the range of (4.5-12.0)×10⁻⁶/℃ to meet the sealing requirements of various non-metallic materials. Qinchuan New Materials controls the impurity elements (such as C, S, O) in the alloy to ≤50ppm levels through optimized melting processes (such as vacuum induction melting + electroslag remelting double process), ensuring high purity and uniformity of the material. Additionally, the cold working deformation rate is controlled within 10%-30% range, combined with intermediate annealing treatment at 450-600℃, which effectively eliminates processing stress and enhances the sealing properties of the material.

III. Processing Steps and Practical Guide

STEP 1: Raw Material Proportioning and Melting
According to the target expansion coefficient (e.g., 4.7×10⁻⁶/℃ or 9.8×10⁻⁶/℃), accurately weigh high-purity iron (≥99.95%), electrolytic nickel (≥99.97%), and trace alloy elements (such as Co, Mn), and melt them for 2 hours at 1500-1600℃ in a vacuum induction melting furnace to ensure uniformity of composition.
STEP 2: Forging and Hot Rolling
The molten ingot is heated to 1150-1200°C for three passes of forging (deformation ≥60%), followed by hot rolling to the target thickness (e.g., 2.0mm) at 950-1050°C, with the final rolling temperature controlled above 850°C to prevent grain coarsening.
Step 3: Cold Working and Annealing
The hot-rolled plate is cold rolled in multiple passes (total deformation of 20%-25%), followed by an intermediate annealing at 480℃ for 2 hours after each pass. After final cold rolling to a thickness of 0.5mm, a finished product annealing is conducted at 620℃ for 3 hours, achieving a stable microstructure and expansion properties.
STEP 4: Precision Machining and Inspection
The sheets are processed into sealing parts using laser cutting or wire cutting technology. The composition deviation is detected by X-ray fluorescence spectrometer (≤0.05%), and the average expansion coefficient in the range of 25-300℃ is tested using a thermal expansion instrument (repeatability ≤±0.2×10⁻⁶/℃).

4. TengChuan New Materials' Technical Layout and Application Cases

Qinchuan New Materials has established a full-chain technical layout in the field of iron-nickel fixed expansion alloys, covering "component design-melting casting-precision processing-performance testing." Its products have been successfully applied in projects such as sealing for the electronic compartment of a certain model spacecraft and ceramic filter sealing for 5G communication base stations. Taking the spacecraft electronic compartment as an example, by using Fe-36Ni alloy with an expansion coefficient of 5.2×10⁻⁶/℃ and achieving perfect matching with the Al₂O₃ ceramic substrate, no cracks or leaks were found in the sealing interface during the extreme temperature cycle test ranging from -55℃ to +125℃, significantly enhancing the reliability of the equipment.

Section 5: Frequently Asked Questions (FAQ)

Q1: How to adjust the expansion coefficient of iron-nickel constant expansion alloys?
A: Accurate control is achieved by adjusting the nickel content (approximately an increase of 0.8×10⁻⁶/℃ in expansion coefficient with each 1% increase in Ni) or adding trace amounts of Co (which can reduce the expansion coefficient), requiring combined process optimization to ensure uniformity of composition.
Q2: How to avoid cracking during the processing?
A: Strictly control the cold working deformation rate (≤30%), and perform annealing treatment after each pass; the annealing temperature should be adjusted according to the material thickness (e.g., 620℃ for 0.5mm sheets), avoiding overburning or underburning.
Q3: What are the technical advantages of Qinchuan New Materials?
A: The company owns independently designed vacuum induction melting furnaces and precision rolling production lines, capable of stable production from small batches of 50kg to large batches of 5 tons; equipped with thermal expansion meters, scanning electron microscopes, and other testing equipment to ensure product performance meets ASTM F30 standards.