4130 alloy steel

• Annealing of 4130 steels

Annealing of 4130 steel forgings may be carried out by transferring the part straight from the forging operation to a furnace held at a suitable temperature, around 860º C (1575 º F) 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 4130 forging is such that some sections will finish much colder than others then a uniform structure will not be obtained and for best results a spheroidizing anneal at around 750 º C (1380 º F) 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.

It should then be cooled in the furnace at a rate of less than 50 F per hour down to 900 F, followed by air cooling from 900 F.

• Normalizing of Alloy Steel 4130

The nominal normalizing temperature for 4130 is 900 º C (1650 º F) followed by the 1600 F soak and oil quench, 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, for example, 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 of AISI 4130 Alloy Steel

The steel 4130 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 of 4130 Steel

The actual tempering temperature will depend on what required properties are needed. Alloy steel 4130 is tempered at between 398 ºC -565 ºC (750 F and 1050 F), depending upon the strength level desired. The lower the tempering temperature the greater the strength. However, tempering should not be carried out between 200 – 420 ºC (400 – 790 º F) to avoid the danger of embrittlement.

Machinability

The AISI 4130 alloy is readily machinable by conventional methods. Simple shapes might be machined following a normalizing treatment, whereas more complex shapes will require annealing. However, machining becomes difficult when the hardness of the 4130 steel is increased.

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.