The European Commission passed a resolution to amend the RoHS directive on August 18, 2005 (2005/618 / EC), which clearly set the upper limit of the concentration of six harmful substances in homogeneous materials, and the content of lead must not exceed 1000 ppm. Article 6 of Annex Article 4 (1) of the RoHS Directive (2002/95 / EC) specifies that when lead exists as an alloying element in steel, aluminum, and copper alloys, it is present in steel, aluminum, and copper alloys. The permissible weight content in can reach 0.35%, 0.4% and 4% respectively.
Manufacturers and users of many of these alloy materials have different perceptions. Some believe that as long as the content of lead in the above alloys does not exceed the upper limit of exemption specified in the Annex of the RoHS Directive (2002/95 / EC); some believe that it depends on the specific situation. To analyze this problem, we must first understand the concept of alloy elements.
The alloy element refers to a chemical element specially added to a metal or an alloy in order to ensure that the required microstructure, physical chemistry, and mechanical properties are obtained. Therefore, the exemption condition set by the RoHS directive is that when lead is used as an alloy element, the content of steel, aluminum, and copper alloys is allowed to reach the corresponding exemption value. However, when lead is present as an impurity, its concentration must not exceed 1000 ppm. Generally speaking, lead will always reduce the performance of steel, or lead incorporation is not beneficial to steel. At this time, lead is an impurity, and its weight content in steel cannot exceed 1000 ppm. However, in special cases, for example, in order to increase the easy cutting performance of steel, an appropriate amount of lead can be added to the steel, so that the chips are easily broken, and at the same time, it acts as a lubricant. At this time, lead exists as an alloying element, which is in the steel The weight content can be allowed to reach 0.35%. Adding lead to some aluminum is beneficial to its casting process and wear resistance, such as lead in the aluminum alloy of sliding bearings. At this time, lead exists as an alloying element in aluminum, and its weight content in aluminum can allow 0.4%. When lead is present as an impurity in aluminum, its content cannot exceed 1000 ppm.
Adding lead to copper can enhance the smoothness of copper liquid, increase toughness, lubricity and wear resistance. For example, lead in a bronze bearing alloy is added to copper as an alloy element, and its weight content in copper can reach 4%; and when lead is present as an impurity in copper, its content cannot exceed 1000 ppm. .
In summary, to determine whether the lead content in the alloy can reach the corresponding exemption value, it is necessary to first determine whether lead exists in these alloys as an alloying element. Considering the current level of industrial smelting, generally speaking, if the alloy raw materials used in the industry are qualified and there are no wrong materials, and the lead content test result is relatively high (over 1000ppm), it is likely to fall into the scope of exemption.
