In Reply to: Re: Cracked 9N Axle Housing, cast iron or cast steel? posted by JP on April 12, 2019 at 17:42:58:
Steel is cast into ingots and then goes to the rolling mill where bars, slabs, blooms, billets, squares, rounds, and sheets are forged into parts like plow frames, tools, and pipe. Some simple parts can be cast too like motor casings. Cast iron is easier to cast into complicated shapes -engine blocks, axle trumpets, rear ends and center housings, and various other parts for example, into mold boxes called cope & drags that contain the part shape, cooled and cured for 30 days, then machined. Spark test should show white for steel, red for iron. You can also identify by the type of chip each forms when machined. Cast iron will be flakes, steel will be more solid, curly-Q type, in little 6's and 9's. FWIW: Steel is a material composed primarily of iron. Most steel contains more than 90% iron. Many types of carbon steel contain more than 99% iron. All type s of steel contain a second element -carbon. The different grades of the steels contain various other alloying elements such as chromium, nickel, and molybdenum, but the only elements found in all steel is carbon and iron. The percentage of carbon in steel ranges from just above 0% to about 2%. Most steel has between .15% and 1.0% carbon. When steel is made, the iron dissolves the carbon. The numbering system for steel is usually four digits. The first two define the alloy content. The last two (or three) digits define the percentage of carbon in the steel. For example, in 5147 steel, the '51' identifies chromium as a key alloying element. In 2517 steel, the '25' indicates that there is an unusual amount of nickel in that grade. In 1040 steel, the '10' indicates that this steel has very little alloy content except carbon. For the last two digits, the '40' defines that there is 0.40% carbon in the steel. Cast iron is a material that uses iron as its primary ingredient. It contains between 2% and 6% carbon and small amounts of silicon. Wrought iron contains essentially no carbon. At about 6% carbon content, the material is virtually useless as it becomes too brittle. The terms "cast iron" and "iron" are two very different animals. It is only a coincidence that both use the word 'iron' in each. Basic differences are that steel is produced when the carbon is that is added to the iron dissolves and disappears. It's like adding a small amount of sugar to a glass of water. The sugar dissolves and becomes invisible. If you keep adding a lot more sugar, eventually the water will not dissolve all the sugar and will precipitate out and it becomes visible. Steel is iron with the carbon in solution, which occurs below 1.6 to 2%. Cast iron is iron in which some of the carbon has precipitated out and appears as flakes like in gray cast iron, the most common. The industry has a special chart with all the steel grades listed in detail. The foundry steel and cast iron process is very interesting and if you ever get the chance take a tour. When I was in the 7th grade we toured the Ford Rouge Plant and saw steel being made on the one end and at the other end brand newly built 1968 Ford Mustangs came rolling off the line. I'm not sure if the Rouge still operates blast furnaces/foundries but the TIMKEN Company does.