AISI 4130 • 25CrMo4 • JIS SCM430 Steel

What Is 4130 Steel?

AISI 4130 steel also can be called JIS SCM430 steel, 25CrMo4(1.7218) steel. 4130 alloy steel has high strength and toughness and the hardenability is high. And the hot strength of AISI 4130 is good by hardening in the oil. At the temperature of lower than 500℃, it will get enough strength. But if the temperature is 550℃, that will get decrease markedly. If you feel interested in it, you can check 4130 steel heat treatment, properties and chemical composition as below.

By the way, at the level of Alloy structure steel, they have good hardenability. After the good heat treatment, the sorbite and bainite of microstructure will be uniform. So they will get higher tensile strength, yield ratio, toughness and fatigue strength. So they are good material for machine fittings with a big size of cross-section.

25CrMo4 Steel Characteristics

  1. It is easier to get welded if the alloy elements at the lower limit. But if the alloy elements are closed to the higher limit, the weldability is at the medium level. And this situation, must preheat it up to 175℃ before the welding.
  2. And its machinability is good. During the cold deformation, its plasticity is medium.
  3. If the temperature is 300℃-350℃ on the heat treatment processing, get the flake is a tendency.
  4. It is medium-Carbon alloy steel which can be oil quenched to attain a maximum as-quenched hardness of approximately 48HRC. Its hardenability is significantly higher than that of the carbon-molybdenum(40xx) grades.

4130 Alloy Steel Applications

This type of steel usually is used after the quenching and tempering. Because after that, it can get high properties to satisfy the needs of the industry.

  1. It is a good choice for the fittings which has a big size of cross-section and works on the high-stress condition of the machine-building industry. Such as the shaft, steering wheel which sustain high load capacity, screw bolt, gear wheel and etc.
  2. And it is used to make fastening pieces, flange and blind flange of the production of boilers.

4130 Steel Forging

Aisi 4130 steel must be forged at the condition of the temperature at the range of 1230º C to 950º C.The 1230º C is maximum. And do not forge after the temperature of forging stock drops below approximately 870℃. If the finishing temperature of forging is lower, then the grain size will decrease. But if the temperature of forging is too lower, the risk of the formation of a non-uniform structure in certain areas of the forged part will get raise. So it is necessary to do the normalizing treatment after the forging.

4130 Steel Heat Treatment

Does the special heat treatment according to the requirements of different fields after the forging, it can make steel properties satisfy the needs of the industry. And the annealing, normalizing, hardening, tempering are parts of it. Let’s figure it out as below.

Annealing

At the processing of annealing, the temperature is the most important thing. The biggest thing is to maintain the temperature around 1575 º F (860º C) for annealing. Keep it for a suitable time and then furnace cooling. Use this way, the steel structure will be more suitable for machining. That is a wonderful way for fittings with simple shapes. If the temperature of steel for the different sections is different, that means the uniform structure will not be obtained. To change that, the only way is spheroidizing anneal at around 1380 º F (750 º C).

Normalizing

Heat to 900º C (1650 º F). Cool 4130 steel in air. Actually, when forgings are normalized before, say, carburizing or hardening and tempering, the upper range of normalizing temperatures is used. When normalizing is the final heat treatment, the lower temperature range is used.

Hardening

Austenitize at 870º C (1600 º F), and quench in oil. The hardening will cause the martensite to be made after quenching. So hardness and tensile strength get raise dramatically and with some brittleness. Smaller sections of 4130 might be quenched in oil, bigger sections in water.

Tempering

Reheat to the temperature which will result in the required hardness. The impact of tempering is to relieve stress from the hardening processing, but the most important point is to get required mechanical properties of the industrial production and application.

steel making

What Are The Consequences For Bad Heat Treatment?

Overheating

If AISI 4130 steel is overheating, its retained austenite will be more, and the stability for size is decreased. Due to the quenched structure is overheating, so the crystalloid of it will be bigger. That will make the toughness and shock resistance of fittings get the drop.

Out of Shape

During the heat treatment processing of 25CrMo4 steel, the heat stress and transformation stress out there. Those interior stress can overlay or partially offset each other. It is complicated. Because it will change depending on different heating temperature, heating speed, cooling method, cooling speed, the size and shape of fittings. So the deformation of steel is ineluctable.

Soft Point

Because the heating is not enough, bad cooling and etc, the hardness of the steel surface is not enough. And the wear resistance and fatigue strength of steel will get down.

4130 Steel Mechanical Properties

PropertiesMetricImperial  
Tensile strength, ultimate560MPa81200psi
Tensile strength, yield460MPa66700psi
Modulus of elasticity190-210GPa27557-30458ksi
Bulk modulus (Typical for steel)140GPa20300ksi
Shear modulus (Typical for steel)80GPa11600ksi
Poissons ratio0.27-0.300.27-0.30
Elongation at break (in 50 mm)21.50%21.50%
Reduction of area59.659.60%
Hardness, Brinell217217
Hardness, Knoop (Converted from Brinell hardness)240240
Hardness, Rockwell B (Converted from Brinell hardness)9595
Hardness, Rockwell C (Converted from Brinell hardness, value below normal HRC range, for comparison purposes only.)1717
Hardness, Vickers (Converted from Brinell hardness)228228
Machinability (Annealed and cold drawn. Based on 100% machinability for AISI 1212 steel.)7070

4130 Steel Physical Properties

PropertiesMetricImperial
Density7.85 g/cm³0.284 lb/in³
Melting point1432°C2610°F
Steel Packing

4130 Steel Chemical Composition

STANDC(%)Mn(%)P(%)S(%)Si(%)Cr(%)Mo(%)Ni(%)Cu(%)
ASTM A29/A29M-050.28-0.330.40-0.60MAX 0.035MAX 0.0400.15-0.350.80-1.100.15-0.25//
EN 10083/3-20060.22-0.290.60-0.90MAX 0.025MAX 0.035MAX 0.400.90-1.200.15-0.30//
JIS G4053-20080.28-0.330.60-0.90MAX 0.030MAX 0.0300.15-0.350.90-1.200.15-0.30MAX 0.25/
TOCT 4543-710.26-0.340.40-0.70MAX 0.025MAX 0.0250.17-0.370.80-1.100.15-0.25//

4130 Steel Grade Equivalent Chart

CountryUSAGermany/UK/FranceJAPANRussia
StandardASTM A29/A29M-05EN 10083/3-2006JIS G4053-2008TOCT 4543-71
Grades413025CrMo4 (1.7218)SCM43030XMA

4130 Steel Supply

We have our own cutting and processing equipment. Specifications can be cut and customized according to your requirements.
We are a professional special steel stockist and supplier with a high-quality stand for many years. As a professional 4130 steel supplier, please contacts us for any request for it. Songshun Steel always with you.

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