 
Used in applications where extreme shock and abrasive wear are the primary cause of failure. Excellent weldability, formability, and
Welding Guidelines EB-450 is a high strength alloy steel readily weldable by following basic guidelines for good welding technique. The following procedure will prevent cracking from the three most common causes of weld related crack problems. Three areas to be controlled for crack-free welding of EB-450 are:
Joint preparation
Filler Material
Heat Input
Welding
Machining EB-450 plates are typically cut to size with flame cutting or plasma cutting. these cutting procedures leave a hardened edge, which in plates 3 inches and over will be considerably harder than the bulk of the plate. If machining at or within about 3/8 inch of these flame cut edges is planned, some shops prefer to allow a larger positive cutting tolerance, e.g. 1/2" over nominal size rather than 1/4" over so that deeper cuts can be taken on the edge miller to get underneath the hardened edge. On flame cut beveled cutting edges, the hardened zone of the flame cut edge is used to great advantage in service. Cutting blade customers typically use only a light hand grinding to sharpen the beveled edge. Details on specific machining processes are given below: Milling For optimum metal removal in interrupted machining (i.e. milling), best results are also accomplished using negative rake, mechanically clamped, tungsten carbide inserts. Recommended feed rate is 0.003" per tooth. Total cutting rate therefore, equal 0.003 time number of inserts in cutter times rpm. Uniform distribution of feed is working beyond the zone work hardened by the preceding insert. For plates at hardness of 350 BHN or less, 150 sfm is reasonable, with slower speeds for higher hardness and higher speeds for lower hardness. For cutting keyways in material less than 350 BHN hardness, use a three or four fluted high-speed cobalt end mill. Run at 12 to sfm with 0.003 chip load. Use a good coolant to keep the cutter and steel cool. The great majority of fatigue failures in shafting made from any steel can be traced back to sharp corners and notches like those found at the base of a square cornered keyway. To greatly increase your shafting life, put a small radius at the corners of the keyway and put a corresponding radius at the corners of the keyway. To greatly increase your shafting life, put a small radius at the corners of the keyway and put a corresponding radius on the matching corners of the key. Suggested minimum radius is 1/16" EB-450 is commonly drilled at full hardness following the general guidelines suggested below:
If you have any questions, or need further information concerning machining of EB-450, please contact Inside Sales, Technical Services or the Machine Shop Supervisor at Astralloy Wear Technology. Forming Cold Forming EB-450 Plate The high inherent toughness of EB-450 makes it possible to cold form the steel at full hardness. EB-450 is best formed with the bend axis transverse to the grain direction of the original mill plate. Press brake bending should be reformed to a minimum inside radius of 5T across the grain and of 12T with the grain direction. Astralloy Steel Products indicates the grain direction on plates by painting a white arrow. Cold forming to a 90° bend in a single stroke is generally not recommended. In cold forming that requires bending 90° or more, incremental bending techniques are best. For incremental bending, a 1/2" thick plate for example would be cold formed in a press brake using a 4" diameter bottom die and a 5/8" radius punch. The punch would be impressed upon the plate along parallel forming sites approximately 1-1/8" apart. In this manner, the forming stresses are more uniformly distributed throughout the bend area. For workpiece sections with less that 12" of bend length, reduced forming radii may be used. The high yield strength of EB-450 requires that allowance for "spring-back" must be a consideration in cold forming. All flame cut edges should be ground and corners removed before bending. Hot Forming EB-450 Plate Hot forming of EB-450 can be performed for bends too severe to be cold formed. Hot forming may be done in rolls or by press brake. he steel should be heated to 1600°F minimum before forming. Since EB-450 is not air hardenable, full hardness will not be regained after forming without requenching and tempering. For this reason, Astralloy-V® plate is normally recommended for tight bends. If EB-450 is quenched, prolonged heating in the austenitizing temperature region should be avoided or a protective environment should be used to prevent excessive decarburization. Excessive decarburization reduces wear resistance. In order to estimate the hardness to be expected after hot forming EB-450 plate without reheat treating, Astralloy Steel Products performed a study. A 1-1/2" thick sample of EB-450 was heated to 1650°F and held for 1-1/2 hours and still air cooled. The resulting hardness was measured to be 341 BHN on the surface and 331 BHN throughout the section. Heat Treating EB-450 plate is normally used in the as-received, quenched and tempered, full hardness condition. Occasionally, customers want to temper the plate to a reduced hardness specification. In this case, the graph below will give an indication of the appropriate tempering temperature to specify. If, due to hot forming, requenching is required
for EB-450, the formed part should be soaked at 1650°F for 1 hour per inch minimum. To reduce the likelihood of cracking, plates should also be tempered at 450°F. Fixturing may be considered to reduce distortion due to the quenching operation.
In order to estimate the hardness to be expected after hot forming and air cooling EB-450 plate, Astralloy Steel Products performed a heat treat study. A 1-1/2" thick sample of EB-450 was heated to 1650°F and held for 1-1/2 hours and cooled in still air. The resulting hardness was measured to be 341 BHN on the surface and 331 BHN throughout the section. Cutting The most common method of cutting steel plate is thermal cutting, especially oxy-acetylene and plasma. These methods provide an accuracy of +1/8" on length and width, which is suitable for most industrial wear plate applications. For applications requiring tighter tolerances on cutting and reduced heat affect on the edges, alternate methods are available including friction sawing, water jet cutting and laser cutting. The various cutting methods are described below. One consideration in selection of cutting method is the effect on the hardness of the edge. The cutting operation creates a heat affected zone (HAZ), similar to that created in welding. Generally, the depth of this zone is related to the amount of heat input into the plate during cutting. On the surface of the cut edge, EB-450 hardens, and effect similar to flame hardening. Behind this hardened zone is a tempered zone where the hardness decreases below the base metal hardness. The depth of the hardened zone varies from about 1/8" to about 3/16". The full HAZ, including the softened region may be up to 1/2" in thick plates. The EB-450 steel in the HAZ softens because steel is "tempered" when its temperature rises above about 400°F. This is evident in the graph of hardness versus tempering temperature for furnace tempering heat treatments. This graph show that for short heating times typical of thermal cutting, that the plate temperature needs to reach about 600°F to reduce the hardness of the steel below advertised hardness. During the cutting operation the temperature of
the plate edge varies from the melting point at the cutting line to ambient (room) temperature some distance away. The exact temperature profile depends on the travel speed of the cutting torch. Astralloy Steel Products conducted a study during a typical oxy-acetylene cutting operation of a 3/8" thick EB-450 plate using tempil
sticks crossing the cutting path ahead of the torch. The melting of the various tempil sticks indicated a temperature profile as shown in the following table.
The study above shows that the steel exceeds 400°F only within 0.5 inches of the edge, which corresponds roughly to the maximum extend of the HAZ as measured by metallographic examination or hardness measurements. The hardness profile of two 3/8" thick EB-450 plates are shown in the graphs below. Consistent with the tempil stick study, the heat affected zone is restricted to within about 0.5 inches of the cutting edge.  Thermal Cutting - Oxy-fuel Common methods include oxygen-fuel and plasma cutting. the common fuel used with oxygen is acetylene because it yields the hottest flame. Other fuels used successfully include natural gas and chemolene Plasma cutting achieves an even higher temperature, which will melt steels without reliance on combustion of the carbon dissolved in the steel. Paradoxically, the hotter the cutting flame, the less heat is transferred into the plate. The cutting proceeds faster with a hotter flame. Thus the plate is exposed to the flame's heat for a shorter time. Prior to cutting, preheating is recommended. A pre-heat of 250°F for plates up to 1 inch thick and of 300°F for plates over 1" is recommended. In warm weather, EB-450 can often be successfully cut without preheat. Astralloy has had good experience with the following settings:
Thermal Cutting - Plasma The hottest cutting method is plasma cutting. This method uses an electric arc, like welding, to heat a gas, such as nitrogen, to a plasma state. The level of heat generated is sufficient to melt the steel plate. Plasma cutting can be specified for applications, such as ballistic test plates, where full hardness is required to the edge. For industrial applications where the edge will be welded and a HAZ will be obtained anyway, oxyacetylene is entirely satisfactory. Water Jet Cutting Steel plate can be cut by directing a small stream of water, containing fine abrasive particles, at high velocity. The water cools the plate as the abrasive particles cut the steel; therefore eliminating heat affected zone. Water jet cutting can hold a dimensional tolerance of 0.001";therefore, it can be used in lieu of conventional edge milling and hole drilling. Water jet cutting is not limited by plate thickness; however, cutting speed is reduced as plate thickness increases. for example, cutting speed may be 20 inches per minute for a thin plate, but may only proceed at 1/4" per minute on a 12" plate. Laser Cutting Laser cutting is another thermal process, but cuts at such a high temperature that the HAZ is quite small. Laser cutting can hold tolerances comparable or better than water jet cutting. |
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