JPS5913570B2 - Annealing method for strip welds - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for annealing a weld after a strip welding process using a combustion burner.

In the manufacturing process of strips, for example cold-rolled stainless steel sheets, multiple hot-rolled coils are usually welded (
There is a coil build-up process in which the coils are connected by TIG or MIG to form a large diameter coil.

The welded parts welded in this process are usually annealed by a boss annealer using a combustion type burner.

However, in annealing using the combustion type burner, the flame ejected from the nozzle through the header from the supply port is biased in the longitudinal direction of the nozzle due to the flow direction from the supply port, and the upper middle part directly below the nozzle is Since the weld is heated locally compared to the intermediate part, the weld is heated non-uniformly in the longitudinal direction.

As a result, corrugated nails were generated in the welded part, making it difficult to perform bead cutting in the next process.Furthermore, annealing failures occurred due to uneven heating, which could lead to plate breakage during rolling in the next process.

Further, in conventional combustion, only air is generally supplied as an oxygen source, but it is effective to use only oxygen or enrich oxygen in order to shorten the time.

However, this method has the drawback that it promotes a temperature difference (uneven baking) between the area immediately below the nozzle and the area between the nozzles, and furthermore, it is extremely difficult to maintain the temperature during soaking.

In other words, supplying oxygen alone or enriched with oxygen causes the flame temperature to rise rapidly and achieve the goal in terms of rapid heating, but between the nozzle and the area directly below the nozzle where the flame collides, a temperature difference that cannot be used is created. , it is not practical, especially for thin plates.

In addition to the above-mentioned temperature raising process, if the flame temperature is increased in the soaking process, the upper limit of the allowable temperature range will be exceeded, and the purpose of annealing will not be achieved.

One way to deal with this problem is to detect the temperature and control the amount of combustion, but generally speaking, annealing furnaces for welded parts perform a series of multi-functional functions such as coil build-up (welding) and side trimming. In many cases, it is installed in a continuous processing line, and a simple open type furnace is used so as not to impair workability. It cannot be applied due to accuracy problems.

Furthermore, it is not appropriate to use an additional temperature control device and the furnace structure because it requires a tight structure that allows temperature control, which increases the investment amount.

The present invention solves these drawbacks in a method of annealing the welded part after strip welding using a combustion burner, and the annealing is performed while the burner body is oscillated in the width direction of the strip (longitudinal direction of the weld length). It is characterized by:

Figure 1 shows an example of the swinging of the burner main body when a strip weld is annealed by a combustion burner, where 1 is the strip, 2 is the welded part of the strip, and 3 is arranged close to the front and back surfaces of the strip in the width direction. This is a combustion type burner in which a large number of nozzles 4 are arranged in the longitudinal direction of the welding length.

Such a combustion type burner 3 is also arranged on the lower surface side of the strip.

When annealing the welded part 2, combustion gas and air are supplied to the supply port 5.
The flame is injected from the nozzle 4 through the header 6 onto the front and back surfaces of the welded portion 2, but in this case, the zero point directly below the nozzle 4 is locally heated as described above.

Also, the flame distribution is uneven in the longitudinal direction of the burner body.

Therefore, the combustion type burner 3 is oscillated.

That is, by reciprocating in the width direction of the strip [in the direction of arrow 45], the zero point at the center of the flame and the distribution of flame intensity in the longitudinal direction of the nozzle move in the longitudinal direction of the welding length, so that the welded area is uniform. It is heated.

It is preferable that the distance of the reciprocating movement be appropriately adjusted depending on the interval between the nozzles 4 and the uneven distribution of the flame, and the period of the oscillation may be set at a relatively gentle speed.

The effect of the present invention is particularly great when annealing is performed in a short time using a combustion type burner because uniform heating is achieved as described above.

That is, since the flame distribution from the plurality of nozzles is spread, even if rapid heating is performed, uneven heating will not occur.

In addition, in the oscillating annealing of strip welds using the combustion burner, only oxygen is supplied to the combustion gas, or the supply air is enriched with oxygen to rapidly raise the temperature until the weld reaches the required soaking temperature range. By supplying only air to lower the flame temperature once the soaking temperature range is reached, even if rapid heating is performed, uniform heating in the longitudinal direction of the welded length can be achieved.

Figure 2 shows the heating range from the start of heating to the end of annealing during annealing of a welded part of a hot-rolled ferritic stainless steel plate (thickness: 40 mm) using a gas-fired annealing device using a combustion burner.
In the case where only air is supplied to the fuel gas through the soaking temperature range (■) and in the heating temperature range up to the predetermined soaking temperature (750°C), only oxygen is supplied instead of the supply air.
0 to 850°C), the temperature rise curve of the welded part (3) is shown when the supply of oxygen is stopped and air is supplied instead.

As is clear from FIG. 2, annealing takes 3 minutes in the case of ①, whereas it takes only 1.5 minutes in the case of ②.

In other words, to shorten the annealing time, it is possible to increase the flame temperature and shorten the heating time by using only oxygen in the combustion gas or enriching the supplied air with oxygen from the start of heating until the predetermined soaking temperature range. It is.

Next, it is necessary to stably maintain the welding part temperature within a predetermined temperature range in the soaking temperature range.

For this purpose, it is possible to spread the temperature of the weld zone over the entire area by stopping the enriched supply of oxygen and supplying only air.

By implementing the present invention, rapid heating is possible and during annealing in a continuous strip processing line, the line stop time can be shortened, so the welding process can be incorporated into the continuous processing line and the process can be omitted, resulting in a more favorable effect. It is something that demonstrates the.

Next, a practical example of the present invention will be shown.

Table 1 shows the TI of SUS 430 hot-rolled plate (thickness 4.0).
The results are shown for /161~N in which annealing according to the present invention was performed using a combustion type burner after G welding and for AIV~■ in which annealing outside the present invention was performed as a comparative example.

In the method of the present invention, the shape of the welded part after annealing is better than that of the comparative example, and no cracking of the welded part occurs during rolling.

Further, the annealing time required for method ii of the present invention was 1.9 minutes, whereas the time required for annealing was 3 minutes for the comparative example scrap (2), which was shortened to about 2/3.

Therefore, if the method of the present invention is applied to a continuous processing line, the loop amount can be reduced to 2/3, which is convenient for incorporating into the continuous processing line.

[Brief explanation of the drawings] Figure 1 is a diagram illustrating the swinging state of the burner body when a strip weld is annealed using a combustion burner.
is a front view, and b is a side view. FIG. 2 is a graph showing a temperature rise curve of a welded part during annealing of a welded part of a hot rolled ferritic stainless steel plate using a gas-fired annealing apparatus using a combustion type burner. In the figure, 1 is a strip, 2 is a welded part, 3 is a combustion burner, 4 is a nozzle, 5 is a combustion gas and air supply port, and 6 is a header.

Claims (1)

[Claims] 1. A method of annealing a strip weld using a combustion type burner in which a plurality of nozzles are arranged in the longitudinal direction of the weld length, in which annealing is performed while the burner body is oscillated in the longitudinal direction of the weld length. A method for annealing a strip weld characterized by: 2. Until the welding part reaches the required soaking temperature range, only oxygen is supplied to the combustion gas or the supply air is enriched with oxygen to rapidly raise the temperature, and once the soaking temperature range is reached, only air is supplied. 2. The method of annealing a strip weld according to claim 1, wherein the flame temperature is lowered by the step of reducing the flame temperature.