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4130 25CrMo4 1.7218 SCM430 30XM Alloy Steel Round Bar

4130 Steel Introduce
AISI or SAE 4130 grade is a low-alloy steel containing chromium and molybdenum as strengthening agents. The steel has good strength and toughness, weldability and machinability. AISI/SAE 4130 grade is a versatile alloy with good atmospheric corrosion resistance and reasonable strength. It shows good overall combinations of strength, toughness. and fatigue strength.
AISI 4130 Steel Specification and Relevant Standards
| Country | USA | BS | BS | Japan |
| Standard | ASTM A29 | EN 10250/EN10083 | BS 970 | JIS G4105 |
| Grades | 4130 | 25CrMo4/1.7218 | 708A25/708M25 | SCM430 |
ASTM 4130 Steels And Equilvalents Chemical Composition
| Standard | Grade | C | Mn | P | S | Si | Cr | Mo |
| ASTM A29 | 4130 | 0.28-0.33 | 0.40-0.60 | 0.035 | 0.040 | 0.15-0.35 | 0.80-1.10 | 0.15-0.25 |
| EN10250 /EN10083 | 25CrMo4/ 1.7218 | 0.22-0.29 | 0.60-0.90 | 0.025 | 0.035 | <=0.40 | 0.90-1.2 | 0.15-0.30 |
| JIS G4105 | SCM430/ SCM2 | 0.28-0.33 | 0.60-0.85 | 0.030 | 0.030 | 0.15-0.35 | 0.90-1.2 | 0.15-0.30 |
AISI 4130 Materials Mechanical Properties
| Properties | Metric |
| Tensile strength, ultimate | 560 MPa |
| Tensile strength, yield | 460 MPa |
| Modulus of elasticity | 190-210 GPa |
| Bulk modulus (Typical for steel) | 140 GPa |
| Shear modulus (Typical for steel) | 80 GPa |
| Poissons ratio | 0.27-0.30 |
| Elongation at break (in 50 mm) | 21.50% |
| Reduction of area | 59.6 |
| Hardness, Brinell | 217 |
| Hardness, Knoop (Converted from Brinell hardness) | 240 |
| Hardness, Rockwell B (Converted from Brinell hardness) | 95 |
| Hardness, Rockwell C (Converted from Brinell hardness, value below normal HRC range, for comparison purposes only.) | 17 |
| Hardness, Vickers (Converted from Brinell hardness) | 228 |
| Machinability (Annealed and cold drawn. Based on 100% machinability for AISI 1212 steel.) | 70 |
Forging
Type 4130 steel should be forged between 2250 and 1750 º F (1230 and 950 º C.) The lower the finishing temperature from forging, the finer will be the grain size. If the alloy is forged at too low a temperature, there is a risk of the formation of a non-uniform structure in certain areas of the forged part, necessitating a normalizing treatment - prior to further heat treatment - after forging.
Annealing
Annealing of 4130 forgings may be carried out by transferring the part straight from the forging operation to a furnace held at a suitable temperature, around 1575 º F (860º C) for annealing, holding for a suitable time then furnace cooling. In this way a structure suitable for machining may be obtained. This treatment is best used for parts with simple shapes. If the forging is such that some sections (of the forging) will finish much colder than others then a uniform structure will not be obtained and for best results a spheroidizing anneal at around 1380 º F (750 º C) may be used. It is safe to say that experience alone will decide the best type of annealing treatment to be used prior to machining.
Normalizing
This process is defined as heating a steel to a temperature above the ferrite to austenite transformation temperature, then cooling in air to a temperature well below this transformation temperature. The treatment may be carried out on forged or rolled products as a conditioning treatment prior to final heat treatment. Normalizing also serves to refine the structure of forgings that might have cooled non-uniformly from their forging operation. The nominal normalizing temperature for 4130 grade is 1650 º F (900 º C), but production experience may necessitate a temperature either 50 º F (10 º C) above or below this figure. In fact 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
This heat treatment results in the formation of martensite after quenching, thus a great increase in hardness and tensile strength, together with some brittleness. The steel should be austenitized - i.e. all micro constituents transformed to austenite - at 1500 to 1600 º F (815 to 870 º C). The actual austenitizing temperature is a function of chemical composition within the analysis range, section size and cooling method. Smaller sections of 4130 might be quenched in oil, heavier sections in water.
Tempering
Tempering is carried out to relieve stresses from the hardening process, but primarily to obtain mechanical properties required for the final application. The actual tempering temperature will be chosen to meet the required properties, and in many cases will be a matter of trial and error.
Machinability
The alloy is readily machinable. Simple shapes might be machined following a normalizing treatment, whereas more complex shapes will require annealing. For optimum machinability a coarse pearlitic structure with minimum ferrite is normally recommended.
Welding
AISI 4130 steel is also good in weldability, and the 4130 alloy may be welded by any commercial method. The material may require a post-weld stress relief heat treatment in certain instances. Low-hydrogen electrodes are recommended together with preheat at 150 - 260 º C (300 - 500 º F) to be maintained during welding, Cool slowly and stress relieve where possible.
Application of 4130 Steel
AISI 4130 steel alloy is used primarily in the construction of commercial and military aircraft and ground support systems. Alloy steel 4130 is an intermediate strength material. Lighter gauges offer lighter weight but still maintain great strength, making it excellent for auto racing and aerospace. This low alloy 4130 steel is widely used in many applications, and some typical application areas are as follows: Commercial aircraft, aircraft engine mounts Military aircraft Automotive Machine tools Hydraulic tools Auto racing Aerospace Oil and gas industries - as forged valve bodies and pumps Agricultural and defense industries etc. Alloy steels are designated by AISI four-digit numbers. They are more responsive to mechanical and heat treatments than carbon steels. They comprise different types of steels with compositions which exceed the limitations of B, C, Mn, Mo, Ni, Si, Cr, and Va in the carbon steels. AISI 4130 alloy steel contains chromium and molybdenum as strengthening agents. It has low carbon content, and can be welded easily. The datasheet below provides further detail.

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