SAE4130 steel, which also goes by the classification AISI4130, is a low-alloy steel that gets its strength from molybdenum and chromium. It is a strong and tough type of steel that also offers excellent weldability and machinability. A very versatile alloy, the 4130 steel has good atmospheric corrosion-resistance and fairly good strength, including fatigue strength. It is used frequently in various applications for industries such as agriculture, automotive, and defense. It is also used as forgings in the oil and gas and the aerospace industries, being used as forged valve bodies and pumps.

What About Forging?

The 4130 type of alloy steel should be forged between 1750° and 2250° Fahrenheit, and the lower your finishing temperature is from forging, the finer the grain size will be. You have to be careful not to forge the alloy at temperatures that are too low; otherwise, you might get a nonuniform structure in certain areas of the forged part. This, in turn, may result in having to execute a normalizing treatment after forging but prior to more heat treatment.

Heat Treatment for SAE4130

Heat treatment after the steel is forged is done for it to be suitable for machining and to meet the mechanical property limits specified for its applications. There are actually several ways to heat-treat certain parts of this type of steel. 

Composition for the SAE4130:

0.035 max.
0.040 max.

Naturally, you should find out more and get answers to your questions before you decide for sure what to buy.