North America uses two "numbering" systems for identifying metals types, the first being SAE (Society of Automotive Engineers) and the second being AISI (American Iron and Steel Institute). AISI designations often include a "letter", making them alphanumeric in appearance.
Metals and alloys thereof is a very broad subject, so I will tend to "simplify" this response in the interests of brevity. We will give a breakdown of the SAE numbering system and how it works, specifically on the examples of "1020" and "4130" and how their metallurgy differs.
The first number in an SAE code refers to the basic material primary composition. The second number refers to the PRIMARY alloying element added to the base material. The third and forth digits are not really individual numbers, together they stipulate the carbon content of the material in HUNDRETHS of a percent. Carbon content is assigned "ranges" which determine "low", "medium", or "high" carbon content. Ferrous materials with a very high carbon content such as cast iron will actually have a five-digit SAE code, the last *three* numbers being the carbon content when it exceeds one percent. Most materials, including the bulk of what are classed "high carbon steels" DO NOT exceed 1% carbon content!
"1020" can be broken down as follows:
1 - plain carbon steel 0 - no "significant" alloying element 20 - 0.18 to 0.23 % carbon content (that's about 1/5 of 1 percent)
While there is no significant alloying element in 1020 steel, be aware that it DOES contain 0.30-0.60% manganese. Manganese gives steel ductility, or the ability to be shaped , formed, or "worked" without fracturing.
"4130" can be broken down as follows:
4 - molybdenum group of steels 1 - chromium is the main alloying element 30 - 0.28 to 0.33 % carbon content
Typically, 4130 steel alloy has 0.15-0.25% molybdenum, 0.80-1.10% chrome, and 0.40-0.60% manganese.
Obviously from the numbers above, it only takes very small amounts of alloying elements to make dramatic changes in the characteristics of a steel. Equally critical is the carbon content and it's effects, because while "1020" is technically classed as a low-carbon steel, "1040" is recognized as a medium-carbon steel!
As far as framebuilding goes, low carbon content is beneficial. While carbon adds hardness to a steel, it also carries the penalty of enhancing brittleness - or propensity towards cracking. The framebuilders on this list can attest to the criticality of temperature while brazing so as NOT to induce carbon-related problems that can result from the metallurgical reactions carbon creates as its' temperature becomes elevated.
For the record, "1020" steel is only one step above the absolute "bottom of the barrel" material in the steels realm.... "1018" is the lowest commonly used mild-steel in industry where low-stress capable material will suffice.
Should anyone be interested in more details, ask away.... on or off-list, I'll try to respond.
Brad Orr Alberta, Canada [please see last post for more detailed "location".... ;^) ]
At 05:00 PM 1/1/03 -0800, Brandon Ives wrote:
>The 1020 stuff was a Hi-Ten (High Tensile) steel, I believe, which is
>quite different from the 4130 steel. It's been a while since I learned
>this stuff.
>enjoy,
>Brandon"monkeyman"Ives
>SB, CA
>
>On Wednesday, January 1, 2003, at 04:31 PM, Raoul Delmare wrote:
>
>> I completely agree with Mr. Ives . And besides , he knows way more
>> than I do .
>>
>> But , was Raleigh's usual "1020" steel really the exact same
>> chemical formula as the U.S.A. 4130 chromium molybdenum steel ?
>>
>> Raoul Delmare
>> Marysville Kansas