Fastener screws are small and inconspicuous, but without countless
screws connecting and fixing, machines and equipment cannot form a
solid whole and cannot operate.
It can be said that screws are indispensable for everything from national
heavy equipment to various daily necessities, and their role is crucial.
So, how is a qualified fastener screw made?
Many people may know that screws need to undergo hot and cold
treatment and strict testing before they can leave the factory.
This understanding is correct, but the production process of screws
cannot be covered by simple hot and cold treatment.
It takes 6 processes to transform wire into qualified fastener screws.
1. Wire processing
Fastener screws generally use wire with a diameter of 5-19㎜ as raw material. The materials are mainly carbon steel, stainless steel, and copper. Each
category is divided into many different models, which will not be described here.
2. Rough drawing processing
In order to remove the oxide skin produced during the production and storage of the wire, rough drawing is required. After the treatment, the surface of
the wire will show the original color of the metal.
(1) Annealing. After the wire is selected, it should be heated for a period of
time and then slowly cooled. This can adjust the crystal structure, reduce the
hardness of the wire, eliminate particles, and improve the room temperature
processability of the wire.
(2) Pickling and phosphating. Pickling and phosphating remove the oxide film
on the surface of the wire and form a phosphate film on the metal surface, so
that the wire will be easier to process and shape. This step can also reduce
the scratches and wear of the tooling during subsequent processing such as
wire drawing and cold heading.
3. Precision drawing processing
This step is relatively easy to understand. It is to draw the wire to the corresponding wire diameter according to different product requirements and
specifications, so as to facilitate further processing and forming.
4. Forming process：This step is divided into three steps:
(1) Cold heading. The wire is cut into the required length by the cold heading machine, and the nut and mark are punched.
(2) Tail clamping. Through this step, the wire can be made into a dovetail shape that can penetrate the steel plate.
Thread rolling, that is, grinding the threads. After the head and tail of
the screw are completed by cold heading and tail clamping, the semi-
finished product that has been formed is threaded through the
interaction of the movable tooth plate and the fixed tooth plate. In
this way, a screw is basically formed.
5.Heat treatment
This step is divided into five steps
Cleaning
Remove grease from the surface of the screw.
01
High-temperature carburizing
This is the core step of heat treatment, which allows carbon atoms to penetrate into the surface layer of the screw and increase the hardness of the screw.
02
Quenching
The screws after high-temperature carburizing are quenched at high temperature to form a layer of crystals on the surface of the screw to achieve the final hardness requirement.
03
Cleaning the quenching oil
Clean the quenching oil on the surface of the screw.
04
Low-temperature tempering
Low-temperature tempering can reduce the core hardness of the screw, making the screw more resilient and avoiding the situation where the screw breaks due to excessive hardness of the core.
05
After the first five processes are completed, the screws will be sent to the
laboratory for strict testing. After all parameters are tested and qualified,
the last process: electroplating will be carried out.
Everyone should know that the role of electroplating is to prevent screws
from rusting, extend their service life, and make them more beautiful.
Electroplating mainly uses the principle of electrochemistry to generate
screw body by the outside world, such as the common zinc plating, chrome
plating, nickel plating, copper plating, etc.
Finally, after about 2 hours of electroplating, qualified screws are made and
can be packaged and shipped out of the factory.
