Soft Iron Base Alloys

Soft Iron Base Alloys
Soft magnetic alloys are ferromagnetic materials that are easily magnetized and de-magnetized. To provide optimal magnetic performance, these alloys possess very low levels of carbon, nitrogen, and oxygen. They rely on various additions of phosphorus, nickel, and silicon to optimize magnetic induction, permeability, and coercive force. The magnetic properties of all of these alloys benefit from high temperature sintering (HT) above 2200 F (1200 C) in hydrogen, as compared to the standard PM sintering process (ST) in metal mesh belt furnaces at nominally 2050 F (1120 C). Density and grain size increases, while residual levels of carbon, oxygen, and nitrogen are reduced. Typical applications include tone wheels, relays, cores, sensor probes, armatures, solenoid components, and pole pieces.

SUY-1 is a soft steel with ultra-low carbon and low impurities.
The grade is defined in the standard, “JIS C 2504 Soft Magnetic Iron,” and is generally referred to as “pure iron.”
There are four SUY grades from SUY-0 to SUY-3. The suffix indicates the material’s magnetic properties with grade 0 providing the best magnetic properties.
SUY-1 has less carbon content and lower impurities than carbon steel. It also features good drawability and good properties as a soft magnetic material. SUY-1 is mainly used in motor applications, but is recently being used more and more as magnetic shielding.
It has high flux density and coercive force, and these magnetic properties can be maximized if the material is re-subjected to magnetic annealing after the cold-rolling process.

High purity soft iron suitable for the manufacture of frames, yokes, armatures, cores etc in telephone relays, solenoids, magnetic clutches, magnetic brakes and all stationary parts of magnetic circuits carrying a direct flux.
Many other applications in the electrical and electronic equipment industry.
Also used for Sacrificial Anodes, for example in the protection of condensers and pumps for the electricity generation and shipping industries and in water de-salination plants.
Whilst strategic stock sizes are held, semi finished material is always available to enable further processing to satisfy individual customer requirements.

Heat Treatment
The heat treatment required to produce these typical electromagnetic properties, consists of full annealing from 920ºC (ie 920º C soak, furnace cool at 50º C/hour max to 600º C, furnace cool to room temperature).
In order to avoid scaling, this treatment should be carried out in a neutral or slightly reducing atmosphere. Typical hardness after annealing 95-110 B.H.N. Annealing is normally done after any significant machining work, but can be arranged on request.

Electromagnetic Properties
Normally conforming to MoD specifications DTD 5092 and DTD 5102, which although obsolete, are commonly used as a basis for the typical electromagnetic properties which are expected to be achieved following the annealing process.
In order to develop the optimum electromagnetic properties, the material must be subjected to the above annealing treatment, preferably after rough machining.

The purity of a metal determines its electrical conductivity. This is why materials that are as pure as possible are used for all conducting parts. Electrical conductivity is affected even by very low proportions of C, Si, P, S, Mn and Cu, and these proportions are higher in the usual commercial grades of steel. PURE IRON FE, on the other hand, is sure to provide significantly better conductivity than other soft, unalloyed types of steel. Experience has shown that the specific resistance of PURE IRON FE, at 20° C temperature of the material, is ≈ 0.11 Ohm x mm²/m. Because of its high magnetic permeability, PURE IRON FE is also a material of choice for DC magnetisation of solid parts. It has a saturation of approx. 21,000 Gauss, and can thus be used wherever maximum induction is required. Particularly noteworthy characteristics of the pure and soft PURE IRON FE are its high permeability and very low coercive force.
It also has outstanding magnetic properties, such as high magnetic saturation, low coercivity, high permeability, as well as excellent conductivity, especially in medium induction ranges.
Each cold working process leads to stresses in the microstructure of the material, and thus to a deterioration of its magnetic properties. That is why finished parts generally need to undergo annealing when they are in final form. You will find an example on the following pages. However, our experience shows that PURE IRON FE reaches the magnetic values required by customers even without a final annealing in various applications. This is due to its high grade of purity. Precise values for specific applications can be demonstrated in experiments.
The following values should be taken as guidelines:
Initial permeability: 300-500, Max. permeability: 2.000-20.000, Coercive force: 15-160 A/m, Saturation induction: 2.15 T.

The purer the iron, the greater its resistance to electrolytic self-destruction, which occurs at the interfaces between the iron crystals and the accumulated alloying elements.
Chemical interactions
PURE IRON FE is partially resistant to acids, bases, and salt solutions, which react with the element Fe. Although PURE IRON FE cannot completely replace other rust- and acid-resistant materials, it offers advantages where certain chemical degradation of unalloyed metallic materials is acceptable. Compared to unalloyed steels, the homogeneous structure and high purity of PURE IRON FE makes it more resistant to many corroding chemicals.
he purer the iron, the better its oxidation behavior (scaling). It plays a major role particularly in thermal processing and other thermal applications. Oxidative scaling not only prevents the transfer of heat; it also has a destructive effect by reducing the thickness of the material.
PURE IRON FE features increased resistance due to its firmly adhering, protective layers of scale.

Because of its 99,9% pure iron PURE IRON FE can be used in a large scope of application. From high-technology up to various handcrafts.
PURE IRON FE can be machined using both high-speed steel tools and carbide tools. It is extremely important that the tools are sharpened and the cutting data is carefully selected, otherwise PURE IRON FE will lubricate. Small feed rate and deep cutting will ensure most efficient rough turning. With fine turning, the feed rate should not exceed 0.1 mm if optimal surface quality and dimensional accuracy are required. When cutting data is properly selected, the turned surface appears bright; otherwise it is matt. Extremely fine-grained cutting surface is also important. Tip: Generous cooling and lubrication are essential to protect the tool and the workpiece. It is recommended to use a mineral oil with 1-1.5% sulphur and 5% grease.
For a fine surface, use hobbing cutters with lead angles of 45-52°. Radial rake angle: 30°. For optimal cutting speed of 25 – 45 m/min at 19 – 32 mm/min feed rate. Radial rake angle when working with side milling cutters: 10°. Tip: Check that the clearance hole of the tools is correct. For cooling and lubricating, observe the same instructions as for turning.
Generally, high-speed steel drills with an acute angle of 100° provide satisfactory results. Lead angle at the cutting edge: approx. 12°. Cutting speed 20-30 m/min at a feed rate of 0.02-0.1 mm/revolution.
Tip: Select a slightly larger core diameter of the thread than usual. This will greatly reduce the risk of taps breakage, and ensure a clean thread. Non-cutting thread forming is recommended. Rake angle: approx. 15-20° Cutting speed: 4 6 m/min.
Non-cutting forming
Due to its mechanical properties, PURE IRON FE offers exceptional advantages in cold working with a high degree of deformation. During there is minimal compressive stress and resistance to deformation. That ensures high levels of deformation. With a controlled deformation, the tensile strength can reach twice the initial value.
Tip: Hot working by rolling, forging, bending, flanging, and pressing must not take place in the red-short area from 850 to 1.050°.

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