May's Shop Talk began a series on the materials used in our industry. The series continues with stainless steel. Stainless steel: Most people have heard of, and even used, stainless steel. This material is used for many things from table flatware to aircraft parts. Stainless steel is so called because of its resistance to corrosion. There are two broad groups of stainless steel. Like other types of steel, these groups are classified according to the chemical composition of the material. 400 series: One group is called 400 series stainless steel. This group is coded by the Society of Automotive Engineers (SAE) as 51403-51502, where the American Iron and Steel Institute uses the final three digits and calls these steel 403-502. The first digit (5), indicates a chromium steel and the additional digits indicate varying additional elements which determine the characteristics of the material. Turn over a fork or spoon. Unless you're using grandmother's silver, it probably says "stainless." Flatware is the most recognizable use of 400 series stainless steel. Machining 400 series stainless: 400 series steel are used in a wide variety of machining applications. It has better machining characteristics than the 300 series steel. When drilling and tapping 400 series stainless steel, cobalt tooling works well. For rough and finish turning, carbide tooling is sufficient at speeds of 300 to 700 SFPM. Lower SFPM should be selected with this harder material. Overall, 400 stainless steel is machined similar to a preheat-treated alloy steel. 400 series steel can be supplied in a heat-treated condition resulting in reduced cutting speeds. The 400 series stainless is magnetic and allows for heat treatment procedures. It does not possess the high corrosion resistance of 300 series steel but it can be hardened to 50 Rc. Escalating steel prices seen as a reason to reduce the supply base and seek out substitute materials. Value analysis was initiated in late 2005 for the half-dozen metalworking companies under the United Technologies Corp. umbrella when it became apparent this year's corporate cost of stainless steel sheet was heading for an increase of 35% and maybe higher. 'There are lots of opportunities for value analysis within the commercial group that would both reduce future cost and increase the functionality of our metals buys,' says Troy McFarlane, commodity manager for commercial metals at UTC in Farmington, Conn. 'We decided to go with stainless steel, first, because of the volume of the total buy (around 20,000 tons/year on average) and the inflation rate our businesses were trying to handle individually. Also because of the possible use of duplex, martensitic and ferritic grades of stainless steel in which nickel plays a lesser role than in austenitic and precipitation hardening stainless steel.' All metals are targeted Stainless steel is just the first of what will be a corporate value analysis project for all production metals sponsored by senior management at each metal-using division. The idea is to eventually consolidate purchasing of a slimmed-down family of steel, aluminum and copper products used by the commercial and industrial firms of Otis Elevator, Carrier, UTC Fire & Security and Hamilton Sundstrand Industrials' units of Sullair, Sundyne and Milton Roy. 'First, even before we delved into the VA (value analysis) process,' says McFarlane, 'we had to complete due diligence about just what stainless steel our companies bought, why they bought those specific grades and who they bought them from.' Since all the UTC metalworking companies use some form of stainless steel sheet, the project took on a degree of urgency when it became obvious that buyers of stainless steel were watching a pricing tidal wave approach their shores this year.
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