EP3789130B1 - Method for the continuous production of at least one steel profile hardened in at least one section - Google Patents

Description

The invention relates to a method for the continuous production of at least one steel profile hardened at least in one section.

Continuously producing steel profiles with hardened sections is, for example, from the EP 3159419 A1 known. In this process, a steel slit strip is roll formed into a profile strand, the profile strand is hardened in predetermined sections and the steel profiles with the hardened sections are then separated from the profile strand.

The profile strand is hardened in three stages. First, in the first heating step, the profile strand is heated homogeneously to below Ac1. In the subsequent, second heating step, the profile strand is heated in the specified section via Ac3 - with the aid of second gas burners, which are appropriately positioned opposite the profile strand. The third step is the accelerated cooling of the profile strand.

The disadvantage, for example, of geometrical changes to the steel profile, requires a comparatively high level of effort to readjust the position, location and control of the gas burners in order to match them exactly to the subsections to be hardened. Known methods are therefore comparatively inflexible - which, when adapted, leads to a relatively high loss of productivity and consequently to increased production costs.

The invention has therefore set itself the task of increasing the flexibility of a method of the type described at the outset without jeopardizing the reproducibility of producing exactly hardened sections on the steel profile.

The invention solves the problem posed by the features of claim 1.

If, in the second heating step, the second gas burners are arranged in rows along the profile strand and in columns across the profile strand, a heating field can be formed with which a universal reaction can be made to subsections that are differently arranged on the profile strand. This is done by activating the second gas burners in order to heat the section on the profile strand via Ac3. The latter can also bring about a particularly controlled process management on the section, which can lead to precisely hardened steel profiles. The method according to the invention can therefore, for example, ensure a high level of reproducibility regardless of the number, size, position, etc. of the subsections on the profile strand, and can therefore also be used extremely flexibly to produce hardened steel profiles. The second heating step preferably immediately follows the first heating step.

Furthermore, the second gas burners provided according to the invention do not cause any loss of accuracy in the formation of the subsection, in that the second gas burners are controlled as a function of at least one mark on the profile strand. This makes it possible to better control and precisely adjust the second heating of the profile strand continuously passing the second gas burners. For example, the control of the second gas burners can be better synchronized on the basis of the mark provided on the profile strand, which, for example, has positive effects on the contour accuracy of the subsection heated via Ac3. In contrast to the prior art, the partial sections can be heated with sharp delimitations.

The method according to the invention can therefore be flexibly adapted to a wide variety of subsections and, moreover, harden these exactly in a reproducible manner.

In general, it is mentioned that activation of the gas burner, for example its ignition, switching off and / or temperature setting, etc., can be understood, for example, by regulation or control, etc.

With the help of the mark on the profile strand, the position of the subsection on the profile strand to be heated via Ac3 is preferably determined, which can be used for a precisely positioned second heating step. This is because the second gas burners heat the determined section on the profile strand via Ac3 and thus produce hardened sections on the steel profile with tight tolerances.

The rows and columns of the second gas burners preferably form a matrix arrangement with, preferably equal, distances between the rows and / or between the columns. This can, for example, improve the process control on the subsection. Preferably, a matrix arrangement with equal distances between the rows and columns can facilitate the handling of the method.

If the second gas burners are controlled separately from one another, this can make the method more flexible, since the reaction to different belt speeds is correspondingly improved.

The contour accuracy of the hardened sections on the steel profile can always be maintained even over a long process if the profile strand has a regularly repeated mark.

The activation of the second burner can be further simplified if a hole in the profile strand forms the mark. Among other things, such a mark can be comparatively resistant to soiling and, as a result, also guarantee short cycle times.

Scaling of the profile strand can be avoided if the second gas burners each heat the profile strand with a combustion air ratio (λ) of ≤ 1.3. This can be of particular advantage in the case of a galvanized slit strip in order to avoid Zn combustion in the process.

The second heating step can be carried out in a particularly reproducible manner if the second gas burners each have a combustion air ratio (λ) of 0.9 λ 1.3.

The control of the second gas burners can be improved if each column of the second gas burner is assigned at least one pilot burner which ignites the second gas burner.

A pilot burner is preferably assigned to each column of the second gas burner at its opposite column ends, as a result of which the second gas burners in this column can be activated particularly quickly. In this way, particularly high belt speeds can be permitted in the process, which among other things further increases the productivity of the process.

The handling of the method can be made easier if, in the first heating step, several first gas burners are arranged in rows along the extruded profile and in columns across the extruded profile.

The rows and columns of the first gas burners preferably form a matrix arrangement with, preferably equal, distances between the rows and / or between the columns. This can, for example, improve the process control on the subsection. Preferably, a matrix arrangement with equal distances between the rows and columns can facilitate the handling of the method.

The first gas burners each preferably have a combustion air ratio (λ) of 1 λ 1.4 in order to heat the profile strand comparatively quickly.

This heating rate is to be increased if several first gas burners arranged in a column are activated to jointly heat the section to below Ac1.

Preferably, all of the first gas burners arranged in a column heat the extruded profile at the same time in order to enable, for example, homogeneous heating of the extruded profile.

Fig. 1

eine Vorrichtung zur Durchführung des erfindungsgemäßen Verfahrens,

Fig. 2a

eine Draufsicht auf eine Härteinrichtung der Vorrichtung nach Fig. 1 zur Durchführung des ersten und zweiten Erwärmungsschritts und

Fig. 2b

eine Seitenansicht der Fig. 2a.

In the figures, for example, the subject matter of the invention is shown in more detail on the basis of an embodiment variant. Show it

Fig. 1

a device for carrying out the method according to the invention,

Fig. 2a

a plan view of a hardening device of the device according to Fig. 1 for performing the first and second heating steps and

Figure 2b

a side view of the Fig. 2a .

The after Fig. 1 The device 1 shown for example comprises a strip preparation device 2, a roll profiling device 3, an embossing device 4, a cleaning device 5, a hardening device 6 and a cutting device 7.

In the strip preparation device 2, the flat steel slit 8 is unwound from a coil 9 and fed into the continuous conveyance of the device 1.

The slit strip 8 is then continuously rolled into a profile strand 10 by means of the roll profiling device 3.

The embossing device 4, which is preferably flying, is then used to make beads and / or embossments and / or depressions in the extruded profile.

The extruded profile 10 is then cleaned with a cleaning device 5 and thus prepared for hardening of subsections 10.1, 10.2 on the extruded profile 10.

For this purpose, the extruded profile 10 runs into a hardening device 6, which consists of several stations, namely two heating devices 11, 12 and a subsequent quenching device 13.

With the first heating device 11, the extruded profile 10 is heated homogeneously to below Ac1 in a first heating step, for example to 650 to 720 ° C., in particular to <680 ° C.

With the second heating device 12, the subsection of the profile strand 10 to be hardened is heated in a subsequent second heating step via Ac3, for example to 720 to 920 ° C. Second gas burners 14 are used for this purpose.

After the second heating step 12, the extruded profile 10 is cooled in an accelerated manner in order to complete the hardening of the subsections 10.1, 10.2 on the extruded profile 10.

After the partial sections 10.1, 10.2 have hardened on the profile strand 10, the latter arrives in a cutting device 7, by means of which steel profiles 15 are cut, which steel profiles 15 each have hardened partial sections 10.1, 10.2.

According to the invention, in the second heating device 12, the second gas burners 14 are arranged in rows r1, r2, r3, r4 along the extruded profile 10 - that is, in the direction of belt travel 16 of the extruded profile 10 - and in columns s1, s2, s3, s4 transversely to the extruded profile 10 - that is, transversely to the strip running direction 16 of the profile strand 10 - arranged, as shown in FIG Fig. 2a can be seen. This creates a field of second gas burners 14 with which extremely flexible - even different - partial areas 10.1, 10.2 of the profile strand 10 can be heated to above Ac3.

For example, the second gas burners 14 in rows r1, r2, r3 and column s1 are activated for subsection 10.1, with the second gas burners 14 in rows r3, r4 of columns s3, s4 being activated for heating for subsection 10.2.

These rows r1, r2, r3, r4 and columns s1, s2, s3, s4 of the second gas burners 14 form a matrix arrangement M with equal distances between the rows and between the columns.

In order to achieve high belt speeds, this control must be precise. This is ensured in that this control takes place as a function of, in particular machine-detectable, marks 17 on the profile strand 10.

These marks 17 are detected on the passing profile strand 10 via one or more - not shown - sensors so that the position of the subsections 10.1, 10.2 to be heated is precisely determined and the respective gas burners 14 are precisely timed to be sharply delimited by subsections 10.1, 10.2 Ac3 to heat. This ensures hardened subsections 10.1, 10.2 on the steel profiles 15, which are precisely positioned and designed with exact dimensions.

The second gas burners 14 are controlled separately from one another as seen in the direction of belt travel 16. For example, the gas burners 14 of the columns s3, s4 are controlled one after the other to heat the subsection 10.2 - as in FIG Fig. 2a can be seen, for example. The subsection 10.2 of gas burners 14 offset in the strip running direction 16, namely in the gaps s3, s4, is thus heated to above Ac3, which rules out overheating of the subsection 10.2.

The second heating step preferably immediately follows the first heating step.

In addition, the profile strand 10 has a regularly repeating mark 17 so that the accuracy of the hardening of the profile strand 10 is maintained even with long cycle times.

How also the Fig. 2a to be seen, holes 17.1 in the extruded profile form the mark 17 which, for example, can be introduced into the extruded profile 10 with the embossing device 4, for example stamped. Other marks 17 are conceivable, for example embossings, depressions, optical markings such as lines, stitches, etc.

Overheating of the sub-areas 10.1, 10.2 is avoided by the second gas burners 14 each heating the profile strand 10 with a combustion air ratio (λ) of 1.3, in particular a combustion air ratio (λ) of 0.9 λ 1.3 exhibit.

In general, it is mentioned that the second gas burners 14 can be post-mixing, in particular externally mixing, gas burners 14 which mix the gas and the oxygen before exiting the burner nozzle. Active water cooling of the gas burners 14 can be provided in order to ensure a continuous process.

In order for the second gas burners 14 to be able to react quickly, provision is made for two pilot burners 18.1, 18.2 to be assigned to each column s1, s2, s3, s4, namely at the opposite column ends of the respective column s1, s2, s3, s4.

The first heating device 11 has first gas burners 19 which are likewise arranged in rows r1, r2, r3, r4 along the profile strand 10 and in columns c1, c2 transversely to the profile strand 10. Here, too, these rows r1, r2, r3, r4 and columns c1, c2 of the first gas burner 19 form a matrix arrangement M with equal distances between the rows and between the columns.

The first gas burners 19 also each have a combustion air ratio (λ) of 1 λ 1.4 and are designed as post-mixing, in particular externally mixing, gas burners 19; these are preferably the same as the first gas burners 14.

In addition, in the first heating step, all of the first gas burners 19 arranged in the gaps c1, c2 simultaneously heat the extruded profile 10, which enables homogeneous heating to below Ac1.

In that the gas burners are arranged at regular intervals in columns and rows, the extruded profile 10, for example, can also be hardened in subsections 10.1 with a small area. It can also contribute if the gas burners 14 and / or 19 are actuated via solenoid valves 20. The solenoid valves 20 preferably have a switching time of less than or equal to 300 ms.

In addition, the gas burners 14 can be activated sufficiently quickly to switch off when embossed in the subregions 10.1, 10.2 to avoid overheating, as this overheating inevitably occurs in the prior art with inductive heating.

The first gas burners 14 and / or second gas burners 19 are preferably post-mixing, in particular externally mixing, gas burners.

The respective first gas burners 14 and / or second gas burners 19 are preferably purged with purging gas (e.g. N2 as inert gas) in the fuel gas line (e.g. to carry CH4) after being switched off. A solenoid valve is used for purging to switch between fuel gas and purging gas. The purge gas prevents reignition in the nozzle and also ensures sufficient cooling of the nozzle.

The first gas burners 14 and / or second gas burners 19 preferably heat the respective subsections 10.1, 10.2 of the profiled strand 10, which subsections 10.1, 10.2 have embossings, on the side of the profiled strand 10 with the back of the embossing.

This activation or deactivation of individual first gas burners 14 and / or second gas burners 19 in the areas with geometries pushed out of the strip can prevent overheating due to the reduced distance between gas burners 14, 19 and profile strand 10, among other things. Overheating, for example on an outer edge of the embossing, can thus be avoided in a reproducible manner.

Claims (16)

1. Method for the continuous production of at least one steel profile (15) hardened at least in a subsection (10.1, 10.2), in which
   a slit strip (8) of steel is roll-formed into a profile strand (10) and the profile strand (10) is hardened in the subsection (10.1, 10.2), for which purpose the profile strand (10) is heated in a first heating step to below Ac1, more particularly homogeneously, and the subsection (10.1, 10.2) of the profile strand (10) is heated in a subsequent second heating step with the aid of a plurality of second gas burners (14) to above Ac3 and then cooled at an accelerated rate, and the steel profile (15) hardened in the subsection (10.1, 10.2) is separated from the profile strand (10),
   characterized in that
   in the second heating step, the second gas burners (14) are arranged along the profile strand (10) in rows (r1, r2, r3, r4) and transversely to the profile strand (10) in columns (s1, s2, s3, s4) and are actuated in order to heat the subsection (10.1, 10.2) on the profile strand (10) above Ac3.
2. Method according to claim 1, characterized in that the actuation of the second gas burners (14) is performed depending on at least one mark (17) on the profile strand (10).
3. Method according to claim 2, characterized in that the position of the subsection (10.1, 10.2) to be heated to above Ac3 on the profile strand (10) is determined with the aid of the mark (17) on the profile strand (10).
4. Method according to claim 2 or 3, characterized in that the second gas burners (14) are actuated separately from each other.
5. Method according to claim 2, 3 or 4, characterized in that the profile strand (10) comprises a regularly repeating mark (17).
6. Method according to one of claims 2 to 5, characterized in that a hole (17.1) in the profile strand (10) forms the mark (17).
7. Method according to one of claims 1 to 6, characterized in that the rows (r1, r2, r3, r4) and columns (s1, s2, s3, s4) of the second gas burners (14) form a matrix arrangement (M) with, preferably equal, distances between the rows and/or between the columns.
8. Method according to one of claims 1 to 6, characterized in that the second gas burners (14) each heat the profile strand (10) with a combustion air ratio (λ) of ≤1.3.
9. Method according to one of claims 1 to 8, characterized in that the second gas burners (14) each have a combustion air ratio (λ) of 0.9 ≤ λ ≤ 1.3.
10. Method according to one of claims 1 to 9, characterized in that at least one pilot burner (18.1, 18.2) is associated with each column of second gas burners (14) for igniting the second gas burners (14).
11. Method according to claim 10, characterized in that each column (s1, s2, s3, s4 or c1, c2) of second gas burners (14) is associated with a respective pilot burner (18.1, 18.2) at its opposite column ends.
12. Method according to one of claims 1 to 11, characterized in that, in the first heating step, a plurality of first gas burners (19) are arranged in rows (r1, r2, r3, r4) along the profile strand (10) and in columns (c1, c2) transversely to the profile strand (10).
13. Method according to claim 12, characterized in that the rows (r1, r2, r3, r4) and columns (c1, c2) of the first gas burners (19) form a matrix arrangement (M) with, preferably equal, distances between the rows and/or between the columns.
14. Method according to claim 12 or 13, characterized in that the first gas burners (19) each have a combustion air ratio (λ) of 1 ≤ λ ≤ 1.4.
15. Method according to claim 12, 13 or 14, characterized in that a plurality of first gas burners (19) arranged in a column are actuated to jointly heat the subsection (10.1, 10.2) to below Ac1.
16. Method according to one of claims 12 to 15, characterized in that all first gas burners (19) arranged in a column (s1, s2, s3, s4) heat the profile strand (10) simultaneously.

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