Iron Metal’s “Transformation”: The Industrial Magic Around You
When you cook in an iron pot, drive across a sea bridge, or undergo an MRI, you may not realize that these scenes are all backed by the “72 transformations” of iron metal.
Figure 1: “Iron Metal” in Daily Life
From the kitchen to space stations, iron takes on different “forms” and performs magical material feats in the industrial world.
I. Pure Iron: The Secret Behind Flying Phone Signals
Your phone signals and hospital MRIs rely on “the purest iron.”
Pure iron, with the highest purity among iron metals, boasts a series of characteristics as shown in Table 1.
Table 1: Key Technical Parameters of Pure Iron
| Performance Indicator | Value | Comparison Reference |
| Permeability | 10⁵ H/m | 100 times that of regular silicon steel sheets |
| Coercivity | 0.8 A/m | 1/5000 of the Earth’s magnetic field |
| Resistivity | 9.7×10⁻⁸ Ω·m | 6 times higher than that of copper |
Pure iron is like a “top student” in the metal world, with a purity of up to 99.997% (equivalent to only 0.003 grams of impurities in 100 grams of iron). This extreme purity endows it with super abilities:
Pure iron is used in MRI magnets to generate a magnetic field 100,000 times stronger than the Earth’s.
Figure 2: Pure Iron Coils in MRI Magnets
In 5G base stations, micro inductors made of carbonyl iron powder, finer than flour, are 3D printed to enable phone signals to penetrate reinforced concrete.
Fig.3 Miniature Inductors Made of Carbonyl Iron (a) and Their Application (b)
In quartz clocks, pure iron sheets in electromagnetic valves ensure precise vibrations of 32,768 times per second.
Figure 4: Electromagnetic Valve in a Quartz Clock
In industrial production, zone melting is used. A moving heating coil allows impurities to move with the melt zone. After 20 repetitions, ultra-pure iron is obtained. This process is like filtering soybean paste with a rake to remove impurities layer by layer.
Figure 4: Schematic Diagram of the Zone Melting Process
If iron is likened to a student, pure iron is a genius who scores full marks in every subject, specializing in solving “high-difficulty problems” that require extreme precision.
II. Steel: The “King of Versatility” From Kitchen Knives to Skyscrapers
Why does Mom complain about rusty kitchen knives? How can Tesla car bodies be light yet strong? How does the roof of the Winter Olympics speed skating have an impressive span? Steel, one of the iron metals, plays a key role.
The properties of steel depend on the distribution of carbon and the synergistic effects of alloy elements:
Different carbon contents lead to different steel properties, as shown in Table 2.
Table 2: Properties of Steels with Different Carbon Contents
| Carbon Content | Crystal Structure | Typical Properties | Real-life Application |
| 0.1% (Low) | Ferrite + Pearlite | High tensile strength, Deep drawable | Aluminum cans |
| 0.4% (Medium) | Pearlite-dominated | High strength, Wear-resistant | Automotive transmission gears |
| 0.8% (High) | Pearlite + Cementite | Hard, Brittle | Surgical knives |
| 1.2% (Ultra-high) | Net-like Cementite | Extremely hard, Brittle | Files |
Alloy elements can optimize performance boundaries by regulating carbon distribution, reflecting the “composition-structure-property-application” design logic.
Fun fact: The Eiffel Tower’s steel contains 0.4% carbon, resisting Paris’s rain while being lightweight—equivalent to distributing the weight of 320 African elephants evenly on four “iron legs.”
Figure 5: The Solid Structure of the Eiffel Tower
III. Cast Iron: The “Tough and Tender Man” That Lasts for Millennia
Consider the cast iron Buddha statue at Tang Dynasty’s Iron Buddha Temple, still intact after 12 centuries; your cast iron pan becoming non-stick with use; and high-speed train brake discs stable at 300℃.
Figure 6: High-Speed Train Brake Disc in Operation
Cast iron’s magic lies in graphite morphology:
Like a thousand-layer,pismatic graphite absorbs vibrations. Old sewing machine bases use it to eliminate 80% of noise.
Figure 7: Grey Cast Iron
Cast iron’s strength rivals steel. Modern manhole covers are unbreakable thanks to spheroidal graphite.
High thermal conductivity and heat resistance: German high-end gas stove burners use vermicular graphite.
Figure 9: Compacted Graphite Iron
The strength and toughness of cast iron depend on graphite morphology, which is controlled by cooling speed and alloy elements.
Different cast iron types have different properties. Grey cast iron has good vibration damping; ductile cast iron has high tensile strength; and vermicular cast iron has a high thermal conductivity and heat fatigue resistance, as shown in Table 3.
Table 3: Comparison of Three Types of Cast Iron
| Type of Cast Iron | Graphite Morphology | Key Process | Performance Characteristics |
| Grey Cast Iron | Flake-like | Natural cooling | Good vibration damping, compressive strength 250MPa |
| Ductile Iron | Spherical (magnesium treatment) | Spheroidizing treatment + rapid cooling | Tensile strength 600MPa, elongation 3% |
| Compacted Graphite Iron | Worm-like | Titanium + rare earth元素 control | Thermal conductivity 45W/(m·K), heat fatigue resistance |
In life, cast iron pans are non-stick because a carbide layer forms on the surface, with hardness comparable to sapphire.
Figure 10: Carbide Layer on the Surface of a Non-Stick Pan
IV. Cast Steel: The “Transformer” of Heavy Industry
Cast steel transforms liquid metal into rigid industrial “bones” through precise solidification.
In industrial cast steel production, 3D printing and casting are often combined. 3D printers stack special sand materials layer by layer to form sand molds. Metal liquid is poured into the mold, and after cooling and solidification, the sand mold is removed to obtain the desired castings.
Figure 11: Green Casting Sand Mold Made by 3DP Sand Printing Process
This technology integrates 3D printing with traditional casting and is suitable for complex metal parts.
Figure 12: Cast Steel Component
The process seems simple ,but involves a microscopic “fast-paced race.” Engineers must control temperature gradients, cooling speeds, and alloy element diffusion within milliseconds to avoid defects like pores and cracks. Different cast steel materials have different properties, as shown in Table 4.
Table 4: Core Properties of Different Cast Steels
| Performance Aspect | Typical Material | Application Scenario | Scientific Principle | Everyday Analogy |
| High Strength and Toughness | ZG20Mn (Low-alloy Cast Steel) | Wind Turbine Hubs, High-speed Railway Gearboxes | Annealing refines grain structure, forming Ferrite + Pearlite matrix | Material the size of a fingernail withstands truck roll-over |
| Wear Resistance | ZGMn13 (High-manganese Cast Steel) | Jaw Plates of Ore Crushers, Railway Switches | Impact load induces work hardening with martensite formation on the surface | Like fitting metal with “self-hardening armor” |
| Corrosion Resistance | ZG06Cr13Ni4Mo (Stainless Steel) | Seawater Pump Valves, Nuclear Power Plant Pipelines | Chromium (Cr) forms a dense 2nm oxide film (Cr₂O₃) | Comparable to metal having built-in “invisible rust-proof coating” |
Cast steel is used for ship anchor chains due to its good corrosion resistance. Its integrated casting process ensures integrity, making it suitable for large hydropower station blades.
Figure 13: (a) Cast Steel Anchor Chain and (b) Cast Steel Turbine Blades for a Hydropower Station
Fun analogy: Casting a train wheel is like building an Eiffel Tower model on a football field with sand, where every grain must be precisely placed.
The process involves digital sand mold casting, directional solidification control, and material gene design. 3D printing fixes each sand grain; electromagnetic stirring directs steel crystallization for wear-resistant properties; and finally, vibration stress relief and laser quenching are applied. This is an industrial miracle of taming chaotic steel water.
The Future of Iron Metals: Sci-Fi Becoming Reality
The differences among pure iron, cast iron, steel, and cast steel stem from carbon content and processing. Pure iron, with low carbon, is used for electromagnetic materials. Cast iron, high in carbon, is for complex parts. Steel, with moderate carbon, offers good strength and toughness. Cast steel, similar to steel in composition, is for large complex parts, as shown in Table 5.
Table 5: Comparison of Four Major Types of Metals
| Category | Carbon Content | Core Structure | Performance Advantage |
| Pure Iron | ≤0.02% | α-Fe single-phase body-centered cubic structure | Extreme magnetic permeability (saturation magnetization 2.15T) |
| Cast Iron | 2.1%-4.3% | Graphite flakes/spheres + pearlite matrix | High wear resistance, low cost |
| Steel | 0.02%-2.1% | Ferrite/pearlite/martensite | Strong and tough, programmable (tensile strength 250-2000MPa) |
| Cast Steel | 0.1%-0.5% | Dendritic + equiaxed mixed structure | Complex large-scale integrated forming |
From programmable degradable smart materials to lunar steel furnaces, iron metal innovation transcends single material evolution. It is building a self-repairing, zero-carbon, and interstellar industrial ecosystem. When Thyssenkrupp’s hydrogen steel plant resonates with SpaceX’s Starship, we witness not just technological breakthroughs but humanity’s journey from Earth to the universe.
Embark on Your Metal Fabrication Journey Today
The transformative potential of iron metals knows no bounds—what truly matters is partnering with a team that combines mastery of materials science and craftsmanship excellence. At SafeWell Solution, we specialize in delivering precision-engineered solutions. Don’t let your metal fabrication vision remain a concept—turn it into a reality with SafeWell Solution. Contact us today and discover how our expertise in iron metal transformation can elevate your next project.
