| What is Chrome Moly anyway? Well first off, If you | | | | last 2 digits indicate 0.3% carbon. |
| just searched the internet for chrome moly, I have to | | | | The reason 4130 chromoly is so freakin strong and the |
| tell you that the correct spelling is actually Chromoly. | | | | reason it performs so well when used in airplanes, |
| Chromoly is like steel on steroids. It contains Chromium | | | | bicycles, dragsters, etc. is because the combination of |
| and molybdenum a splash of carbon and mostly iron. | | | | chromium, molybdenum, and carbon, along with proper |
| The most popular grade of chromoly tubing is 4130. | | | | normalized heat treatment , give 4130 chromoly tubing |
| Here is what 4130 means: The American Iron and | | | | a combination of strength, toughness, and ductility. |
| Steel Institute (AISI) has a numbering system that uses | | | | 4130 chromoly tubing has great properties and great |
| 4 numbers to categorize steels. | | | | strength to weight ratio. The trick is not to screw that |
| The first number indicates the major alloying element. | | | | up when you weld it. |
| Take 1010 plain carbon steel, for example. The 1 | | | | There are some purists out there who insist that gas |
| denotes plain carbon steel. The second number | | | | welding is the only way to go for welding chromoly |
| indicates the approximate percentage of the major | | | | tubing for small airplanes. The idea is that the slow |
| alloying element. In the case of plain carbon steel the | | | | heating and slow cooling that is part of the gig with gas |
| number is a zero because there is no major alloying | | | | welding, is necessary and when 4130 tubing is gas |
| element. The third and fourth numbers indicate the | | | | welded, it kind of gets stress relieved at the same |
| carbon content of the steel. | | | | time. |
| In the case of 1010 steel They indicate that the steel | | | | But with all the data available on TIG welding 4130 |
| contains approximately 0.1% carbon, that's 0.1% or point | | | | chromoly tubing without the need for stress relief in |
| one percent carbon. | | | | enough for me to feel good about TIG welding it. Even |
| OK lets look at 4130 chromoly. | | | | for small aircraft |
| The 41 in 4130 indicate the main alloying elements are | | | | I just make sure to only weld within established |
| chromium and molybdenum and that the steel contains | | | | guidelines and I don't use 4130 filler rod. |
| about 1% chromium and molybdenum combined. The | | | | |