Do you also often screw stainless steel screws? Or do you simply often have to deal with stainless steel components? Do you sometimes ask yourself what "V2A" and "V4A" actually mean and how they differ?
We get such questions quite often in everyday life and want to give a very rough and simple answer to them here:
Origin of terms
Steel is named according to material numbers, which is why today a distinction is made between V2A and V4A, for example. The V in the designation stands for trial, as different alloys were tried out. The A stands for austenite, this element is responsible for the non-rusting of steels. The difference between V2A and V4A therefore lies in the alloy. Both have a chromium and nickel content, but in the case of V4A steel, other elements are then added.
Let's take a closer look at the differences and what they are good for!
V2A
V2A stands for "experimental melt 2, austenite".
The original steel material 1.4300 (material number). The alloy code is X12CrNi18-8 and states that it contains 17-19% chromium, 7-9% nickel and a maximum of 0.12% carbon. In addition, there are elements such as manganese, phosphorus and sulphur in smaller (defined) quantities. In the meantime, this original steel material is no longer used. Nowadays, V2A includes the material 1.4301 (X5CrNi18-10), the material 1.4307 ( X2CrNi18-9) and the material 1.4305 (X10CrNiS18-9 and X8CrNiS18-9). The material 1.4305, also known as AISI 305, has a higher sulphur content. The materials 1.4301 and 1.4307, on the other hand, have a higher proportion of nickel and a lower proportion of carbon. The steel with the material number 1.4301 is also called AISI 304 and should only be welded using the electric method. Under no circumstances should the gas fusion welding process be used here.
The V2A steels can withstand a temperature of up to 600° Celcius. However, if the steel is to be exposed to an even higher temperature, for example up to 900° Celcius, the steel with the material number 1.4541 (X6CrNiTi18-10) should be used. This alloy includes titanium as well as the usual elements. It is resistant to steam, combustion gases and petroleum products, among other things. The steel can be welded well with all welding methods and thermal post-treatment is not necessary.
These steels are particularly well suited for polishing and processing. This is why they are used for the production of household appliances and other household items such as cutlery. But also in the construction of vehicles, sinks and railings, as well as for use within the pharmaceutical and cosmetics industries.
The disadvantage of V2A steel is its non-resistance to chlorides. Therefore, the V4A steel was alloyed.
- can withstand a temperature of up to 600° Celcius .
- Titanium-based material 1.4541 can be welded well with all welding methods.
- Good formability, even when cold.
- These steels are particularly well suited for polishing and processing.
- For the manufacture of household appliances and other household items such as cutlery, as well as the construction of vehicles, sinks and railings, and for use within the pharmaceutical and cosmetics industries.
V4A
V4A steel stands for "experimental melt 4, austenite".
This is alloyed with molybdenum and makes up a component of about 2%. The addition of molybdenum makes the steel more resistant than V2A steel. This means that it offers particular protection against corrosion in combination with chloride. The V4A steel is marked with the tool number 1.4401 (X5CrNiMo17-12-2).
The alloy of this steel can also be changed further. If the material is to be even more corrosion-resistant, the steel with the number 1.4571 (X6CrNiMoTi17-12-2) is used. Titanium is added to this steel, which is also called AISI 316, just like the temperature-resistant V2A steel. It can be welded well with all welding methods and heat treatment after welding is not necessary. For the use of V4A steel at lower temperatures, the material number 1.4404 (X2CrNiMo17-12-2) is recommended. This steel is less expensive. Most corrosion-resistant and stainless steels are called Alloy. They can be recognised by the alloy number X1NiCrMoCuN25-20-7.
Like V2A steel, V4A steel can be easily formed, even when cold. It can therefore also be stamped, deep-drawn and bent. The disadvantage of this steel is its machinability, which is why, in contrast to V2A steel, it is not suitable for the production of milled and turned parts.
It is therefore not surprising that this steel is mainly used in salt water, in the chemical industry and in swimming pools.
- Good formability, even when cold.
- Titanium-based material 1.4571 can be welded well with all welding methods.
- Alloy steel with alloy number X1NiCrMoCuN25-20-7 most corrosion resistant and stainless steel.
- This steel is mainly used in salt water, in the chemical industry and in swimming pools.
Why can VA2 or A4 steel still rust?
Despite the special steel, it is possible for it, and the products made from it, to rust.
This happens when the external influences are too strong. Then the actually impermeable layer of chromium oxide is no longer sufficient to protect against rust.
When surfaces made of stainless steel are welded, a high temperature load (oxidation) occurs, which is shown by the typical blue discolouration. The chromium around the welding area is degraded and a consequently higher iron concentration remains. If this is observed, the susceptible and unprotected areas should be reworked and maintained so that rust protection can reappear. (Reference to pickling)
Even if the V2/4A steel comes into contact with conventional steel made of carbon or similar, the rust protection can be impaired. The rust protection can also be lost if uncleaned (already rusting) tools are used during production. Surface rust then develops, as the smallest steel particles settle due to mechanical abrasion.
V2/4A steel screws
By the way, the stainless steel described is also used for ordinary screws.
These stainless steel screws are rust-free due to the alloys of the steel and are therefore more resistant and durable than conventional screws made of other materials such as zinc. Stainless steel screws made of V4A steel are also resistant to acids. This is why stainless steel screws are used especially outdoors, where they are exposed to all these materials and substances.
However, it should also be noted that the material is not hardenable due to its composition. Therefore, it cannot be processed with as high a torque as the conventional galvanised screw with higher strength.
Do you have further questions on the topic?
We at WEWO see ourselves as problem solvers and are at your side with help and advice for all your stainless steel questions. You not only have the option of purchasing your stainless steel products from us, we also offer solutions for your application problems.
For our customers we offer a special surface treatment that reduces cold welding (galling). Did you know that we also sell special screws made of V4A and V2A steel? In addition, we also offer fastening technology, tools, factory equipment and other industrial supplies made of this steel.
Feel free to contact us!