JPS5949286B2 - Oxidation-free continuous heat treatment method for metal strips and wires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of heating a metal while preventing or deoxidizing it.

In order to process metal and finish it into the desired shape and characteristics,
Heat treatment for refining is usually performed during intermediate or finishing processing.

If the metal is oxidized during this heat treatment, it will affect the properties, surface condition, shape, etc., so the heat treatment is often performed in an inert or reducing atmosphere.

Nitrogen gas is generally used as the inert gas due to its cost.

However, industrial nitrogen gas often contains oxygen as an impurity.

In addition, oxygen may be mixed in from the middle of the piping.

Therefore, in a mass production factory, it is difficult to heat-treat metals in an inert gas without causing surface oxidation.

One way to prevent this oxidation is to use a reducing gas such as hydrogen or ammonia decomposition gas instead of an inert gas.

However, this method requires expensive structural equipment such as a furnace and piping, since an explosion occurs when the reducing gas mixes with the atmosphere at high temperatures.

As an intermediate method, there is also a method of mixing a reducing gas into an inert gas at a ratio below the explosion limit.

This method is also effective in preventing oxidation because the oxygen in the inert gas is consumed by combustion with the mixed reducing gas, but a mixer is used to ensure that both gases are mixed stably at a predetermined ratio. This makes the equipment expensive and complicated.

The present invention provides a continuous furnace filled with gas of industrially available purity without using expensive furnaces, piping structures, or equipment such as gas mixers to achieve complete airtightness as described above. In this method, a non-oxidizing heat treatment is easily performed by applying a combustible organic solvent to the metal strip or wire to be heated in advance.

Details are shown below.

As already mentioned, in order to perform non-oxidizing heat treatment on metals in an inert gas furnace that contains oxygen as an impurity, it is necessary to make the oxygen react with other substances in some way before the metal oxidizes. .

An easy way to do this is to apply a liquid organic substance such as oil or liquid paraffin to the metal surface.

When the applied organic solution is charged into a continuous furnace together with the metal, it is gradually heated as it reaches the high temperature section.
Eventually, it reacts with the oxygen in the furnace.

Oxygen in the furnace only contains impurities, so it can be removed sufficiently by applying organic matter, but depending on the concentration, the amount of surface application and
Adjustment by changing the type of organic matter is also possible.

Incidentally, the organic solution that is applied in excess and does not react with oxygen is decomposed during heating and is therefore harmless to the metal to be heated.

Therefore, when coming out of the furnace, the metal has an oxidized-free surface.

Note that a more complete non-oxidized state can be obtained when the metal and gas are sent in the same direction, but the effect is great even when the metal and gas are sent in the opposite direction.

Embodiments of the present invention are illustrated using figures.

γ is the continuous furnace main body, 10 is a pipe for feeding nitrogen gas 9, and 8.14 is the continuous furnace inlet and outlet, both of which are slit-shaped to minimize the inflow and outflow of gas.

2 is a guide roll, and 11 is a drawer roll that also serves as speed adjustment.

1 and 6 are materials to be heat treated. When performing heat treatment,
In the present invention, the metal strip 6 is once sent into a tank 3 in which liquid paraffin 4 is stored.

Next, the paraffin on the surface is squeezed out, the remainder adheres to the metal surface, and is fed into the furnace T.

As the inert gas 9 and the metal strip 6 move through the furnace in the direction of the arrow 13, they are gradually heated, and eventually the active paraffin on the surface vaporizes and reacts with the oxygen in the inert gas.

Therefore, as the metal progresses through the furnace toward the exit, the oxygen in the furnace disappears, and the metal is heated without oxidation.
It cools down and comes out.

Reference numeral 12 denotes a metal strip wound on a winding device after completion of heat treatment.

Although a strip was used in this example, a wire rod can also be subjected to the same heat treatment.

Of course, argon may be used instead of nitrogen gas, and the organic solution does not have to be liquid paraffin, but has a boiling point of 10
It can be used if the temperature is 0°C or higher and 300°C or lower.

The reason why the minimum boiling point is set at 100°C is because if it is lower than this, there is a risk that organic matter will vaporize from the metal surface or catch fire before entering the furnace.

The reason why the upper limit is set at 300° C. is to avoid a situation where, in the case of low-temperature heating such as in strain relief baking, the heat treatment temperature becomes T1 below the boiling point and oxidation cannot be prevented.

[Brief explanation of drawings]

The figure is a processing system diagram showing an outline of an apparatus implementing the present invention. 2...Guide roll, 3...Organic solution storage tank, 4...Liquid paraffin, 5...
- Squeezing roll, 6... Heated metal strip, T...
...Continuous furnace main body, 8...Inlet, 10...
...Gas inlet pipe, 11... Speed adjustment and pull-out roll, 14... Outlet.

Claims (1)

[Claims] 1. When continuously heat-treating a metal strip or wire in a furnace while continuously feeding an inert gas into the furnace, the surface of the metal to be heated must have a boiling point of 100°C or more and 30°C before entering the furnace.
A non-oxidizing continuous heat treatment method characterized by applying an organic substance at a temperature of 0°C or lower.