the basic building material of modern industry i or the most useful of all metals everywhere we look we see iron it services to mankind are limitless iron is the basis of the new over both forms of metals in one form it is used quest strength is required in another beauty is an important factor or iron is used in beams that must be rigid as well the most common commercial source of iron is iron or iron which is found in the earth's interior in the form of the red dust that is one of man's most valuable possession huge masses of this or are transported from the mines to the blast furnaces in the blast furnace the process of changing the iron ore into wire and it is carried out on a tremendous scale the iron ore is mixed with coke and limestone and then loaded into the top of the furnace this tolling structure holds many many tons of the red door which is soon to become iron a blast of super heated air forced into the furnace sweeps up through the raw materials the air heat the coke until it burns out the heat drives most of the impurities from the arno or leaving liquid iron in a pool at the bottom of the furnace in the laboratory weekends the how the or is converted into iron liquid iron the iron is poured into the flaming furnace is where most of the impurities are burned out the process of removing the impurities changes the iron interest eal the steel is drawn from the furnace and poured into a mold forming in gets the most are stripped off the ingots after the steel is not and the huge blocks of steel weighing several tons are placed in a circular or open furnace the massive groans exert terrific pressure on the hot steel needing it then threatening it until at last it can be worked into well most any desired shape and thickness steel is strong hard enduring but the strenuous use to which steel is proto day demands many special characteristics more different kinds of steel are needed to meet the high manufacturing and engineering standards of the automobile for any other purpose and so the modern automobile makers have laboratories for testing and improving the quantities of steel in the laboratory for an we see how steel can be after a careful blending the mixture is poured into a mold and then scientifically brought to a normal room temperature the hardness of steel to which chromium as been added is measured by getting it small extremely hard pull its force down to the steel test specimen the size of the dancer or impression is measured under the microscope the smaller the dent not harder the steel microscope isn't needed to compare the size of the dents made in hard chromium steel and ordinary steel some years of steel required to be extremely strong own able to withstand tremendous strains the strength of metals is measured by pulling test pieces apart in a powerful machine the dial of the testing machine shows the tremendous force used in pulling apart a piece of plain steel more and more force is used the steel stretches under the load and then finally snaps more than thirteen thousand pounds of force are required plain steel can be made stronger by adding nickel in addition to a small amount of chromium then let's see what happens when the chromium nickel steel is tested in the stretching machine the bob breaks chromium nickel steel test piece is more than twice as strong as common steel  common steel but some steels today have to stand up under great heat and still look at all their good qualities steel can be given an ability to resist great heat by the addition of little chromium and laboratory the pretty extract of metal just measured by placing a test bar in a machine which in a short time duplicates the effect of years of use by adding a little bit of nickel and a small amount of the metal a we can see what happens to a piece of steel when it is completely surrounded by small particles of carbon bearing material when heated the steel slowly soaks up the carbon to form an extremely hard guinea's all these top trends have improved the usefulness of steels but all of these different ally steels must be put through a process called a heat treating the we must select the best metal to give us the finest performance and the greatest dependability with safety and blowing the life force with crawling of the rig brake drums of perfected hydraulic brak