It is suitable for manufacturing low-thermal expansion structural parts, precision instrument parts, measurement reference parts, optical equipment parts, electronic packaging components, and high-precision metal parts that require dimensional stability under temperature changes.
Invar usually refers to Inwa alloy, often corresponding to 4J36, a low-expansion iron-nickel alloy material. Its main feature is its extremely low coefficient of thermal expansion within a certain temperature range, making it suitable for parts that require high dimensional stability, deformation control under temperature changes, and precision assembly. It is commonly used in precision instruments, optical equipment, measurement reference parts, electronic packaging, aerospace parts, low-expansion structural components, and high-precision tooling fixtures. The core value of Invar is not high strength or wear resistance, but dimensional stability under temperature changes.
By focusing on application scenarios, boundaries of advantages, and non-recommended scenarios, it helps sales, customer service, and quoting staff quickly determine whether the material meets current part requirements.
Low coefficient of thermal expansion, good dimensional stability, suitable for precision structures, temperature variation environments, optical and measuring equipment, CNC machining, weldable and brazed, suitable for low-expansion matching structures.
Precision instrument structural parts, optical platform parts, measurement reference parts, standard rulers, positioning seats, sensor housings, electronic packaging parts, low-expansion brackets, aerospace precision parts, laser equipment structural parts, precision fixtures, low-expansion connectors, temperature-sensitive components, scientific instrument parts.
Low-cost ordinary structural parts, high-strength load-bearing parts, high-hardness wear-resistant parts, high thermal conductivity and heat dissipation parts, high electrical conductivity parts, highly corrosive environment parts, lightweight structural parts, large-size low-budget parts, high-elasticity snap-fit parts, ordinary appearance decorative parts, and conventional metal parts that do not require dimensional stability.
The following parameters come from product information and material knowledge fields, used for design review, quotation communication, and preliminary judgment before material selection.
| Material positioning | It is suitable for manufacturing low-thermal expansion structural parts, precision instrument parts, measurement reference parts, optical equipment parts, electronic packaging components, and high-precision metal parts that require dimensional stability under temperature changes. |
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| Precision performance | Invar suitable for CNC turning, milling, drilling, tapping, grinding, wire cutting, and precision machining. Since its application is mostly related to low expansion and high dimensional stability, in actual machining it should focus on controlling machining stress, clamping deformation, thermal deformation, and post-processing dimensional changes. Precision positioning surfaces, reference planes, hole positions, assembly surfaces, and optical-related structures should be individually controlled for tolerances, flatness, perpendicularity, coaxiality, and surface roughness. |
| Dimensional tolerances | The standard dimensional tolerances for CNC machined Invar can be evaluated as ± 0.02mm to ±0.10mm, while ordinary structural parts can be evaluated at ± 0.05mm to ±0.20mm. Precision reference planes, positioning holes, optical mounting surfaces, and measurement structures can be further controlled according to machining capabilities. This value is a standard reference range and does not guarantee the absolute tolerance of all structures; For parts involving low expansion and high stability, final tolerances should be confirmed based on material condition, heat treatment, processing flow, and temperature detection. |
| Minimum Wall Thickness | The wall thickness of ordinary CNC machined structures is recommended to be no less than 0.8mm-1.0mm. Since Invar is mostly used for precision structures, thin-walled parts need to focus on machining deformation, clamping deformation, and dimensional changes after stress release. Positions requiring welding, tapping, bearing assembly forces, or serving as precision references should be appropriately thickened to ensure structural stability and machining reliability. |
| Recommended wall thickness | For ordinary precision structural parts, 1.5mm-3.0mm is recommended; positioning seats, mounting seats, reference plates, optical brackets, and other positions requiring positional stability are recommended to be at least 2.0mm; for large-size low-expansion structural parts, design should be based on rigidity, thermal stability, weight, and machining deformation, and if necessary, add reinforcing ribs or use split assembly structures. |
| Minimum aperture | CNC drilling can achieve smaller hole diameters, but deep holes, precision holes, and low deformation require focused control of tool rigidity, chip evacuation, burrs, and stress at the hole position. For general designs, the recommended aperture is no less than 1.0mm. It is recommended to reserve machining allowance for positioning holes, threaded holes, pin holes, and assembly holes, and if necessary, use drilling, reaming, boring, or grinding methods to ensure accuracy. |
| Assembly clearance | For precision metal assembly, 0.02mm-0.10mm per side can be reserved according to fitting requirements; for ordinary assembly, 0.10mm-0.30mm per side is recommended. If subsequent nickel plating, gold plating, passivation, or other surface treatments are needed, additional gaps should be reserved according to the thickness of the coating. For assembly structures with large temperature fluctuations, the gap should be designed based on the thermal expansion differences of the Invar and the mating material to avoid overtightness, looseness, or stress concentration caused by temperature changes. |
| Detailed performance | Invar suitable for machining holes, grooves, steps, chamfers, threads, positioning surfaces, reference surfaces, assembly surfaces, and precision structural details. CNC machining and grinding can achieve better detail quality. Small text, logos, and markings are recommended to be achieved through laser marking, engraving, or etching. It is not recommended to design unnecessary decorative textures in the precision reference area to avoid affecting inspection, assembly, and stability. |
| Surface effect | Invar raw processed surface usually has a silver-gray or gray metallic texture. After grinding and polishing, a relatively smooth metal surface can be obtained, and sandblasting produces a uniform matte finish. As a precision alloy material, Invar usually focus more on dimensional stability, surface roughness, and rust resistance rather than decorative appearance. If corrosion resistance or soldering performance is needed, nickel plating, gold plating, passivation, or other surface protection treatments can be performed. |
Based on material characteristics and suitable product ranges, customer needs are broken down into easier application directions to determine.
Precision instrument structural parts, optical platform parts, measurement reference parts, standard rulers, positioning seats, sensor housings, electronic packaging parts, low-expansion brackets, aerospace precision parts, laser equipment structural parts, precision fixtures, low-expansion connectors, temperature-sensitive components, scientific instrument parts.
It is suitable for manufacturing low-thermal expansion structural parts, precision instrument parts, measurement reference parts, optical equipment parts, electronic packaging components, and high-precision metal parts that require dimensional stability under temperature changes.
The main feature of Invar is its very low coefficient of thermal expansion, allowing it to maintain good dimensional stability under temperature changes, making it suitable for precision instruments, optical systems, metrology equipment, and packaging structures. Compared to ordinary steel, stainless steel, aluminum alloys, and copper alloys, Invar shows smaller dimensional changes under temperature changes; However, its material cost, processing difficulty, and specialized applications are higher, making it unsuitable for use as ordinary structural steel or low-cost metal parts.
Based on wall thickness, hole position, assembly clearance, dimensional tolerances, and material usage risks, determine in advance whether the part structure is suitable for Invar.
Post-processing of Invar affects appearance, dimensions, hole position, assembly clearance, and usage validation results, and should be explained in advance during quotation, DFM review, and sample confirmation stages.
Post-processing should focus on appearance display, dimensional fitting, connection assembly, and testing verification. Parts involving assembly positions need to be reserved in advance for machining, coating, and trial assembly allowances.
For common issues such as threads, snaps, strength, temperature resistance, and weather resistance, identify in advance whether the material needs to be replaced or if another processing method should be used.
When customer demand exceeds Invar material boundaries, it is necessary to combine strength, temperature resistance, toughness, long-term stability, and mass production goals to promptly recommend alternative materials or processing technologies.
If lower expansion and greater dimensional stability are required, 4J36 Invar alloys can be further selected; If glass or ceramic sealing and matching are needed, Keva alloy 4J29 or other fixed-expansion alloys can be selected; If only ordinary strength structural parts are needed, carbon steel,304 Stainless Steel, or 6061 Aluminum Alloy can be chosen; If higher corrosion resistance is required,316L Stainless Steel or TC4 Titanium Alloy (Ti-6Al-4V) can be chosen; If higher thermal conductivity is required, Pure CopperT2, TU2 Oxygen-Free Copper, or aluminum alloys can be chosen.
If the customer's core requirements are dimensional stability under temperature changes, low thermal expansion, precise positioning, or optical measurement structures, Invar is the right choice. If customers only need ordinary brackets, shells, machined parts, or low-cost structural components, it is not recommended to prioritize Invar; stainless steel, aluminum alloy, or ordinary carbon steel can be used. If the part requires both low expansion and sealing or airtightness, further confirmation should be made to determine whether 4J36, 4J29, or other precision alloy grades are needed.
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