Grain, in metallurgy, any of the crystallites (small crystals or grains) of varying, randomly distributed, small sizes that compose a solid metal . ... Grains of a metal ingot can be elongated and locked together by rolling to improve the mechanical properties in the direction of grain length.
What is grain of a material?
Grains, also known as crystallites, are small or even microscopic crystals which form, for example, during the cooling of many materials (crystallization). A very important feature of a metal is the average size of the grain. The size of the grain determines the properties of the metal.
Does steel have grain?
Once all the steel has solidified , the microstructure has formed. Some grains are small, some are large. Small grains will strengthen the steel—the grain boundaries intersect with neighboring grains to add strength, while the inner portion of the grains remain soft.
What is mean by grain structure?
The grain structure refers to the arrangement of the grains in a metal , with a grain having a particular crystal structure. The grain boundary refers to the outside area of a grain that separates it from the other grains. ... The size of the grain determines the properties of the metal.
What is the grain size of steel?
The higher the grain-size number, the smaller the average grain size. HSLA steels often have grain-size numbers ranging from 10 to 12. Traditional low-strength forming steels have grain-size numbers around 6 or 7 . Grain-size numbers of 5 and lower can have visual surface problems like cracks, tears, and orange peels.
How do you tell the direction of steel grain?
Look at the surface of sheet metal through a microscope or a magnifying glass , and you should see the grain direction. Movement takes place along the cleavage planes of the crystals and not within the boundary areas between them.
Does stainless steel have a grain?
Go with the Grain. Believe it or not, stainless steel has a grain . You should be able to see lines in the stainless steel and feel the grain with your fingers. Start at the top of your appliance and wash in the direction of the grain.
What is difference between crystal and grain?
A crystal has a unique arrangement of molecules or atoms an a lattice showing a symmetry and long range order (usually a three-dimensional arrays of atoms). ... A grain is a bunch of crystals (rather than a unit lattice) arranged in a same direction.
Is polycrystalline a steel?
Most inorganic solids are polycrystalline , including all common metals, many ceramics, rocks, and ice. The areas where crystallites meet are known as grain boundaries.
How does grain boundary occur?
Grain boundaries are usually the result of uneven growth when the solid is crystallizing . Grain sizes vary from 1 μm to 1 mm. Most grain boundaries are preferred sites for the onset of corrosion and for the precipitation of new phases from the solid. They are also important to many of the mechanisms of creep.
How is grain formed?
The grains are formed from the molten material when it solidifies, interact with one another and with other ingredients , like phases and contaminations. Typically, the grain structure is adapted to the technical application.
What is grain structure in stainless steel?
In general, solid metals and alloys consist of randomly oriented grains that have a well-de- fined crystalline structure, or lattice, within the grains. In stainless steels, the crystalline structures within the grains have been given names such as ferrite, austenite, martensite, or a mixture of two or more of these .
What is fine grain structure?
Fine grain steels have good cold formability and toughness. They have fine grain structure due to the low carbon content and micro-alloying elements (e.g. titanium and niobium). ... The higher yield strengths of PERFORM® steels can be achieved by rapid cooling after hot rolling.
How do you reduce the grain size of steel?
Grain size is reduced by controlled cooling , by adding alloying elements like grain refiners.
How the size of grain is determined?
The average grain size is found by dividing the number of intersections by the actual line length . Average grain size =1/(number of intersections/actual length of the line).
Why are smaller grains stronger?
Smaller grains have greater ratios of surface area to volume , which means a greater ratio of grain boundary to dislocations. The more grain boundaries that exist, the higher the strength becomes. ... The smaller grain has a surface area of 6 square units.
