aluminum
2)
N2 can lengthen the gouging parts life time, and get acceptable gouging groove surface on carbon steel
and stainless steel
3)
Ar/H5 mixed gas can get best metal remove without slag on the gouging surface. It can get clear and
smooth quality on aluminum and stainless steel gouging groove surface
Cutting technology instruction
The related main technical parameters
1)
Cutting material and thickness
The selection of cutting technical parameters is based on the cutting material and thickness. If the material is thick,
it should adopt large current and nozzle with big aperture. For different material under the same thickness, the
parameter should also be different.
2)
Nozzle selection
The three main dimension of nozzle are the diameter of nozzleφ, the hole pass length ι and the compacted angle α,
they all can affect the cutting. There should be a certain proportion between ι and φ, the value is usually lower than 2,
and it usually takes
, the compact angle usually takes α
＝
30°
～
60°, and now it usually takes α
＝
30°.
3)
Cutting current and arc voltage
The selection of cutting current should be according to the diameter of the nozzle, the relationship between the
two should be as: I(current A)
＝
(70
～
100)×φ(mm). As the increase of the metal thickness, the influence of arc current
to the cutting speed will become less. But as the increase of current, the burning damage will be worse for the
electrode and the nozzle. So when cutting a thick metal work-piece, usually the increase of cutting speed is made by
increasing arc voltage. The actual arc voltage is decided not only by the gas type but also by the air flux and nozzle
shape. Working voltage increases with the increase of gas flux.
4)
Gas flow Q
The arc voltage increases as the increase of air flow, that is, the arc power, the cutting speed, as well as the cutting
capacity and quality is improved accordingly. Because the arc compression level increases, the energy is more
concentrated, the arc beam temperature, the arc spraying speed, as well as the arc current impulsion increases. But
overlarge current may cause the instability of the plasma arc. Usually no change is made to air flow for one torch. But
it can be adjusted a little when the cutting torch or cutting thickness is different.
5)
Electrode
inner contraction ΔL
y
When electrode inner contraction
ΔL
y
is so small that electrode extends into spray hole, electrode is damaged
seriously by air flow impact and the combination function between high temperature gas and electrode. This leads to
the instability of plasma arc, weak compression effect, and weak cutting penetration ability that cutting cannot be
proceeded. If ΔL
y
is too big, the arc is so unstable that the cutting ability is weakened. The electrode end should be
placed within siphoning zone of gas current under a relative vacuum condition, and it will difficult to damage
electrode by burning, as well as this is beneficial for compression of arc.
ΔL
y
is about 2-4mm.
6)
The distance between the nozzle and the work-piece (d)
If the d is too big, the blow power of plasma arc for molten metal decreases, so does the cutting ability, and the
burr on the bottom increases, meanwhile the instability of the arc increases. However, if the d is too small, it increases
the possibility of short circuit between the nozzle and the work-piece. Usually d should be as small as possible on
condition that no short circuit is caused between nozzle and work-piece. The d under normal cutting of air plasma is
usually 2
～
5mm. The work-piece can also contact with the nozzle during air plasma cutting, that is, the nozzle glide on
the surface of the work-piece. This cutting method is called contact cutting, and the cutting thickness is the half as the
ordinary cutting.
7)
Open circuit voltage