Technical Memo

4330 VANADIUM MODIFIED for Open Gearing

There wouldn't be an HMC Difference if we didn't select the best materials for your Replacement Part Designs!

Large Mechanical Components are normally designed around the readily available less expensive Shelf Steels; 1045, 4140, 4130, 4340, or 4350. We use Materials made up with Special Alloys and or Special Alloy Combinations; Nickel, Chromium, Vanadium, and Molybdenum. That is why our Forged and Cast Steel Open Gearing has always passed the True Test - The Test of Time.

Our Gears, Pinions, and other Critical to Process Products are designed to offer increased Tensile and Yield Strengths, and Improved Wear Resistance, without sacrificing any of the materials ability to Deform and Absorb Stress, (Impact Values). This is especially achievable through our 4330 Vanadium Modified. In fact 4330 VM with comparable hardness can offer 100% more Impact Values over 1045, 4140, 4130, 4340, or 4350. 4330 VM will safely test at 25 foot lbs. Impact Values at operating temperatures of - 40 Degrees Fahrenheit.

We have many years experience with the Design and Manufacturing of Large Critical to Process Mechanical Components. This experience has taught us to be very selective with the materials for these applications. That is why we do not design Component's around the common 4000 Series Shelf Steels when heavy loading and hostile environments exist.

For example 4350 would be a very poor selection because of the segregation of the carbon caused by the slow solidification rate in large 4350 forgings. The below graph illustrates the actual carbon content across a large forging as compared to the nominal (ladle) carbon content. Near the center of the forging, the carbon level can more than double due to segregation. Once the local carbon level exceeds approximately 0.7% you enter a condition called hypereutectoid, where brittle carbides begin to form in the material. This can lead to microcracking of the forging as well as producing poor mechanical properties. To prevent this, it is preferred to limit the carbon content of the alloy to around 0.35% or less when making large forgings. Clearly 4350, with 0.50% carbon, will pose a problem. 4340 with 0.40% carbon offers some improvement, however the best alloy for large forgings is the 4330 Vanadium Modified with 0.34% nominal carbon content.

The second concern is to develop appropriate mechanical properties. In general all three materials (4330 Vanadium Modified, 4340, and 4350) can meet the required surface hardness. Since tensile and yield strength relate directly to surface hardness all three materials are essentially equivalent assuming that the surface hardness is the same. The primary difference will be in ductility, % elongation, % reduction of area, and toughness - (Impact Values). The table below shows comparative tensile and impact properties for all three materials at the same hardness. All of these samples were taken in the transverse direction from a ~30" thick disk. The 4330 VM provides vastly superior properties.

The other significant advantage to 4330 VM for Large Open Gearing, Pinions, and other Critical to Process Machine Parts is its user friendliness during welding. This material is not as Carbon Migration Sensitive as other Gear Materials and does not require nearly as high Pre and Post Heat temperatures during a required Welding Process.

Chemical and Alloy Composition Range

Impact Values - The Steels ability to Deform and Absorb Stress without Cracking and or Breaking.

4330 mod             impact values up to 25 ft-lbs at -40 degrees

4340                     impact values up to 12 ft-lbs at 70 degrees F

4140                     impact values up to 15 ft-lbs at 70 degrees F

Open Gearing and other large critical to process mechanical components intended for heavy loading require design by Experience. HMC has that experience. And our Unsurpassed Warranties speak for themselves.