What are the materials of screw & bolt? (Part 2)

You may have some ideas about materials for screw and bolt production from our perious article now,
So now we are getting deeper about it,
Since we have the basic understanding of materials, about the quality of material,
We are getting about the "quality of material process"!
Let me clarify here that I am not taking about the process quality, which is related to ISO 9001 or IATF 16949.
Due to the "cost", which is the most important thing upon all the business activities,
The qualtiy of material process comes up,
What is the quality of material process exactly?
After we refine the steel from the basic material like iron ore,
We will get wire rod after the previous processes,
Before we manufacture the screw and bolt,
We will need to have suitable wire diameter to produce the specific products,
Therefore, we will take the wire rod and put them in the "wire-drawing machine" to achieve it,
And it is clear that not everything are perfect,
During the processes, the surface of steel might have some "wounds",
We could "heal" the wounds by regrinding them,
But sometimes, we might just leave it there because it cause money,

So if we do this process of "healing" on the steel wire we made,
We call it "CHQ, Cold Heading Quality", because the material is suitable for cold heading production,
If there is cost limitation, some people might just choose"MQ, Merchandise Quality",
Actually, both of them are able to produce screw and bolt,
But it will affect the consistency of screw & bolt product and the general qulaity.
At the moment, most of Taiwanese screw & bolt manufacturers are quite experienced and good at improvement of production,
Therefore, for some product ranges, MQ level is good to work,
Normally, the product without recess could work with MQ level.

But for some specific prodcts, CHQ is the basic level of material using.
There are 3 categroies under CHQ level,
1. HCWQ, Heavy Cold Work Quality
2. SCWQ, Special Cold Work Quality,
3. GCWQ, General Cold Work Quality,

For GCWC level quality,
it is normally used on general bolts and nuts,
Normally Grade 8.8 bolt are using GCWQ level material to produce,

For SCWQ level qualtiy,
It has better grinding level of surface,
So it can perform and form better than normal GCWQ material,
Normally it is used for specific request of bolt and nut,

For HCWQ level quality,
Normally it is required to test under normal temperature, high temperature and cold temperature.
High quality of rimmed nut or elevator bolt are generally using HCWQ level of material.

Hope you can have basic ideas about the material now,
We will take more about wire drawing on next part of article!

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