c-g-designs

·         METALS 1.

·         CONSTRUCTION AND TOOL STEELS.

            I have read with a certain consternation an article on the metals used in arms making. This article appeared to me so much basic that I thought I should bring my modest contribution and rectify some errors.

            There will be 3 chapters, this one covering the construction and tool steels. Next will be  on Stainless Steels, and last on Light Metals….Maybe also a  succinct one one later on Titanium…

First, the steels :

            All the informations on the subject of the steels used by US industrial and custom actions manufacturers use the same steel grades. It is either the 4140 and 4350 in the AISI/ASTM american nomenclature, 42CrMo4 and 42CrMoV4 in the european nomenclature.

            Those two grades are really quite basic, often supplied in pre-hardened condition, 100-110kgs/mm² (32 to 36 HRC).

            To simplify, the two important steels classes are :

            -The construction low alloyed steels , able to be heat treated. The grades 4140 and 4350 enter in this class and are the most used in general engineering.

            -The high-alloyed tool steels, shock and wear-resistant.

            Without entering in the american nomenclature,rather complex,  we will give here the signification of the european norm :

            -For the low-alloyed steels (for instance 42CrMo4), the first group of figures represent the carbon content multiplied by 100 (42=0,42%C).

            -The symbols (Cr Mo) are the additive in their order of content

            -The last number represent the content of the major addition multiplied by 4 ( 4=1%Cr).

            In what concerns the highly-alloyed tool steels, for instance  36NiCrMo16, the first 2 digits also the Carbon content (0,36%) and the last group the major component content multiplied by 4 (16= 4% Ni). Usually, the other components are in order ½ and ¼ of the main one (2%Cr and 1%Mo).

            The carbon content condition the quenching ability.

            Theadded elements improve the mechanical characteriistics and/or increase hardness obtained by the heat treatment.

            In the tool steel range, it is also to note the high-carbon and Chromium content such as the X100Cr12 (ASTM= A2) and 155CrV12 (ASTM= D2) , both at 12%Cr and at high quenching ability  (62HRC). They find their place for the highly loaded parts such as extractors, bolt stops,etc…

R.G.C