Spark Testing of Steel
Spark testing is a widely used quality control technique to quickly identify the presence of any foreign material in steel. This test is also used to distinguish between different grades of steel and to detect the presence of any alloying elements. The test involves creating an electric arc between the specimen and a reference electrode, and then evaluating the shape, length and intensity of the sparks generated.
The spark test is usually done on a carbon steel. To conduct the test, the specimen is held by tongs or any other grip mechanism in hand and the reference electrode is placed against it. An electric current is then applied to the specimen which creates an arc. The arc produces sparks due to the oxidization of steel and alloying elements in the specimen.
The sparks produced by the arc vary in color and intensity depending on the composition of the specimen. Sparks are mostly white in color for pure carbon steel whereas sparks with a yellow tinge indicate the presence of alloying elements such as nickel, chrome or molybdenum. Higher intensity sparks are expected from the more highly alloyed steels. Thus, the arc and the produced sparks aid in identifying the composition of the steel.
The shape and length of the produced sparks also help in material identification. The sparks produced by pure carbon steel are short and spread out, while the sparks produced by alloy steels will be longer and of a narrower in shape. In this way, the material can be identified due to the differences in spark characteristics.
It is important to note that the spark test cannot accurately determine the exact composition of steel. It is only used to provide a qualitative indication of the composition and strength of the steel. Another disadvantage of the spark test is that it can be tedious and time-consuming, especially when the materials have a large number of alloying elements. Nevertheless, it is an economical and reliable testing method for relatively small samples.
In conclusion, spark testing is a widely used and cost-effective quality control technique to identify different grades of steels and the presence of any foreign material in steel. The test is based on the qualitative evaluation of the sparks produced from the arc. Although the spark test cannot accurately detect all alloying elements in advanced steel, it is still an effective method for quick material identification.
