Measuring tools generally use stainless steel, generally 7Cr17, which has the characteristics of high hardness, good toughness, good corrosion resistance, and excellent mechanical properties. For details, please refer to GB/T 1220-1993. Although most measuring tools are not made of stainless steel, it does not mean that they are not stainless materials. There are also a few measuring tools made of stainless steel on the market, but even so, they must be maintained with anti-rust oil.
The reasons why most measuring tools use iron or alloy materials are nothing more than the following:
1. Stainless steel is not really rustless, and its processed surface may still rust due to the destruction of martensite. Especially in places with harsh working conditions such as workshops.
Then surface reprocessing is also required, so there is no reason to use such expensive materials, after all, stainless steel is more than 4 times more expensive than ordinary iron raw materials.
2. The anti-rust performance of iron materials or alloy materials after corresponding heat treatment and surface treatment is very excellent, not necessarily worse than ordinary stainless materials
3. Stainless materials, most of which contain high nickel content and low carbon content. The phenomenon of thermal expansion and contraction is more obvious than ordinary iron products, and measurement errors are prone to occur.
4. Many tools not only have the measurement function, but also have the function of marking and marking. Since stainless steel and other materials are plastic materials, and iron is a rigid material, then the hardness must be better than iron products.
5. Also because stainless steel is a plastic material and iron is a rigid material, iron products are not easily deformed although they are fragile. For measuring tools, we would rather it be destroyed than an inaccurate number, so we would not use plastic stainless steel.
6. There is another reason. The measuring tools are all precision processed products. The stainless steel material is dense and hard, and it is not easy to process. It consumes a lot of machining equipment and is easy to deform during processing. The processing performance of iron products is very good, and the accuracy is also high. Higher, so in terms of processing capacity, stainless steel will not be used.
At present, high-carbon steel is generally used-the carbon content is greater than 0.55%, or refers to steel with a carbon content of about 0.7 to 1.4%. This kind of steel is used for tools, moulds and measuring tools with different requirements, such as T7 and T7A (median carbon content 0.7%), T8 and T8A (median carbon content 0.8%), T13 and T13A (median carbon content) 1.3%) and other types of steel.
Alloy tool steel-measuring tool steel with a carbon content of less than 1% can also be used. For example, 3Cr2W8V, 9Mn2V, 5CrMnMo, 5CrNiMo, 4Cr5W2VSi, etc.