JP4958514B2 - Austenitic stainless steel continuous hot-rolled shear joining method and continuous hot-rolling equipment - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a continuous hot rolled material shear joining method and continuous hot rolling equipment for continuously hot rolling by joining hot rolled materials to each other in a hot rolling process, and more specifically, austenitic stainless steel. In continuous hot rolling, a method for shear joining continuous hot rolled material that can be passed through without controlling the joining conditions of the hot rolled material, etc., and causing plate breakage in the finish rolling stage, and continuous for the same It relates to hot rolling equipment.

In the technical field of producing metal sheet materials by hot rolling, there is a strong demand for improving productivity and quality through continuous finishing rolling and automating operations.
An important point in the field of such continuous hot rolling is a metal bar joining technique in which a rear end of a preceding hot-rolled sheet (hereinafter referred to as “metal bar”) and a subsequent metal bar are joined to each other.

  In the hot rolling process, the joining of the metal bars is performed between the roughing mill and the finishing mill, and if the metal bars are joined in the process after the roughing mill, the finishing rolling process is performed. It becomes possible to continuously roll the metal bar that is rolled in step (b).

Therefore, in order to perform finish rolling continuously, it is necessary to join the running metal bar and the metal bar at high speed, and various techniques have been proposed for such joining.
The bonding techniques known so far can be broadly classified into a melt bonding method and a solid phase bonding method.

  When the metal bars are joined together by the melt joining method, the melted joint is softened due to the fact that the temperature of the melted joint is higher than the temperature of the adjacent part, and the joint strength of the joint is higher than that of the base metal part. There is a disadvantage of being inferior.

As a technique known in the solid phase bonding method, there is a metal plate bonding method disclosed in Patent Document 1.
The invention of this Patent Document 1 is generated in a shearing process by overlapping the rear end portion of the preceding metal bar and the front end portion of the subsequent metal bar vertically and shearing the two superimposed metal bars simultaneously. This is a technique in which the shear surfaces of two metal bars are directly contacted and joined.

  Since the invention of Patent Document 1 is joined by shearing, it is simple and can be joined in a short time, and the required space is small and the temperature drop during finish rolling is small. As having many advantages.

  However, the invention of Patent Document 1 has a disadvantage in that the shape of the joined part is non-uniform and the surface scale is mixed into the joined surface, thereby significantly reducing the joint strength of the joined part. .

  In addition, when the metal bar is joined by applying the invention of Patent Document 1, unjoined portions are generated at the upper and lower portions of the joint section and both ends in the width direction, and there are portions where the joining force is weak. In addition to the problems, there is a problem that the surface strength is mixed into the bonding surface and the bonding strength is lowered.

On the other hand, the austenitic stainless steel has an austenitic microstructure almost non-magnetic and has a low thermal conductivity, excellent toughness, softness and corrosion resistance, building materials, kitchen equipment, industrial equipment, electronic components, And it is widely used for parts for vehicles.
When continuous hot rolling is performed by applying a joining technique to such austenitic stainless steel, there are many advantages such as increased productivity and reduced thickness.

  However, such austenitic stainless steel produces scales at high temperatures. Although the thickness of the scale is relatively thin, it is very dense, so that it is very difficult to remove the scale in the rolling process, and there are many problems in applying continuous hot rolling.

  As known joining techniques for continuous rolling, there are an induction heating method (see Patent Document 2 and Patent Document 3) and a laser welding method (see Patent Document 4 and Patent Document 5) which are fusion joining.

  In continuous rolling by induction heating, the plate material is heated and pressed, and then the process proceeds in the order of removing the beads, and the scale existing on the joint surface where the preceding and subsequent plate materials are abutted is placed on the outside of the joint in the crimping process. Extruded as a bead.

  However, the stainless steel scale is easy to adhere to the base material and the scale itself is soft and difficult to remove. As a result, there is a problem that the scale remaining in the induction heating joint portion significantly reduces the joint strength.

  In order to prevent this, it is possible to look at the method of induction heating in a reducing atmosphere, but in this case, only a specific part of the hot rolling line exposed to the atmosphere is controlled to the reducing atmosphere. Must. It is not only very difficult to control the atmosphere of only a specific line with a large facility, but it is also a major cause of cost increase from the aspect of production unit price.

  In the case of laser welding, since the laser beam is very small, bonding cannot be performed unless the surfaces to be bonded are in close contact.

  For this purpose, the method of using a welding material can be considered. However, in the method using the welding material, it is important to control the gap between the surfaces to be joined.

  In order to control the gap between the surfaces to be joined, the precision of cutting the material to be joined by the crop shear located in front of the joining machine is very important. It is very difficult to ensure the precision of the cut surface of the material to be joined because of its unique characteristics and the unique properties of austenitic stainless steel, such as its softness and toughness.

  Because of the above problems, continuous hot rolling is hardly applied in the case of austenitic stainless steel.

Japanese Patent Laid-Open No. 9-174117 JP-A-5-000202 JP-A-9-314216 Japanese Patent Laid-Open No. 7-024504 JP-A-9-010803 JP 2005-46661 A

  Accordingly, the present invention is for solving the conventional problems as described above, and an object of the present invention is to provide a shear bonding method capable of applying continuous hot rolling to austenitic stainless steel. And providing a continuous hot rolling facility.

  Another object of the present invention is that when joining austenitic stainless steel metal bars, the joint of the metal bars can sufficiently bear the load of finish rolling in the finish rolling process, and the tension between finish rolling stands To provide a shear bonding method and continuous hot rolling equipment that ensure tensile properties capable of withstanding tension.

The austenitic stainless steel continuous hot rolled material shear joining method according to the present invention for achieving the above object includes 12 to 26 mass (wt)% Cr, 6 to 22 mass% Ni, and other inevitable. An austenitic stainless steel metal bar consisting of various impurities and the remaining Fe, or Cr, 12 to 26 mass%, Ni to 6 to 22 mass%, Si, Mn, P, S, Cu, Mo, Al elements or V An austenitic stainless steel metal bar containing at least one special element of Nb, Ti, B, the content of each element being 3.00% by mass or less, and other inevitable impurities and the remaining Fe, descaling apparatus for descaling by water pressure predetermined joining portions are trailing superposed and joined metal bar and the preceding leading end of the trailing metal bar in a hot rolling mill train By utilizing descaling at pressures 50 MPa, and shear-joining using a bonding machine for bonding overlapping the rear end of the metal bar and the preceding leading end of the trailing metal bar in the hot rolling mill train The metal bars are joined to each other so that the joining surfaces of the joined metal bars are inclined from the thickness direction of the metal bars.

  Further, in the shear joining method of the austenitic stainless steel continuous hot rolled material according to the present invention for achieving the above object, when the metal bar is shear joined, the upper blade and the lower blade of the joining machine overlap each other. Provided is a method for shear joining of an austenitic stainless steel continuous hot-rolled material that is shear-joined by setting the range of a lap as a distance to 3 mm or more and 19 mm or less.

  Further, in the shear joining method of the austenitic stainless steel continuous hot rolled material according to the present invention for achieving the above object, when the metal bar is shear joined, the upper blade and the lower blade of the joining machine move. A method for shear joining austenitic stainless steel continuous hot-rolled material is provided in which the stroke ratio obtained by dividing the sum of the distances by the thickness of the metal bar is 1.30 or more and 1.65 or less.

  And in the shear joining method of the austenitic stainless steel continuous hot rolled material according to the present invention for achieving the above object, when the metal bar is shear joined, both the upper blade and the lower blade of the joining machine are simultaneously used. Provided is a method for shear joining an austenitic stainless steel continuous hot rolled material in which shear joining is performed while moving up and down, or only one of an upper blade and a lower blade is shear joined.

Further, the continuous hot rolling facility according to the present invention for achieving the above object comprises 12 to 26% by mass of Cr and 6 to 22% by mass of Ni, and is composed of other inevitable impurities and the remaining Fe. Austenitic stainless steel, or Cr 12-26 mass%, Ni 6-22 mass%, Si, Mn, P, S, Cu, Mo, Al elements or special elements V, Nb, Ti, B A rough rolling machine for rough rolling an austenitic stainless steel slab comprising at least one element and a content of each element of 3.00% by mass or less and comprising other inevitable impurities and the remaining Fe; and a coil box metal bar wound into a coil, to descaling by water pressure at pressures 50MPa the predetermined joining portion of the metal bars to be unwound from the coiler of the coil box de A pair of a cauling device and the descaled metal bar are shear-bonded while being pressed and sheared from both sides in a state where the rear end of the preceding metal bar and the front end of the subsequent metal bar are overlapped and the overlapped portion is sandwiched therebetween Characterized in that the austenitic stainless steel metal bar is continuously hot-rolled, and has a shear joining device provided with a shearing blade and a finish rolling mill for finish rolling the sheared metal bar. And

  The method for shear joining of austenitic stainless steel continuous hot-rolled material according to the present invention is that hot-rolled material of austenitic stainless steel, which has not been applied so far, can be joined by shear joining to enable continuous hot rolling. Has a technical effect.

  Further, when joining austenitic stainless steel metal bars according to the present invention, the joint of the metal bars can sufficiently bear the finishing rolling load in the finishing rolling process, and withstands the tensile tension between the finishing rolling stands. There is a technical effect of providing shear bonding conditions that ensure tensile properties.

  Furthermore, the present invention provides a process variable capable of continuously performing rolling without sheet breakage in the subsequent finish rolling process even when metal bars are joined together, when austenitic stainless steel is continuously hot rolled. There is a technical effect.

  As described above, if the process condition range of the present invention is applied, the joint portion of the metal bar is sufficiently resistant to the strong compressive load due to finish rolling and the tensile load applied between the stands even if it is austenitic stainless steel. It has performance, and continuous hot rolling becomes possible without causing plate breakage, that is, joint breakage in finish rolling.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

  The austenitic stainless steel in the present invention includes 12 to 26 mass (wt)% of Cr (% means mass% unless otherwise specified), 6 to 22% of Ni, other inevitable impurities and the remaining It means mainly Fe-Cr-Ni stainless steel made of Fe. And the austenitic stainless steel has an austenite structure almost at the normal temperature, and Mn, N, etc. may be added to replace expensive Ni.

  Therefore, in the present invention, the austenitic stainless steel means that any stainless steel having an austenitic structure with an Fe—Cr—Ni system as a basic component system is included. Therefore, Fe—Cr—Ni system is used as a basic composition, and there is at least one element such as Si, Mn, P, S, Cu, Mo, Al or special elements such as V, Nb, Ti, B. However, until it is contained (in this case, the content of each element is not limited, but is preferably 3.00% or less), it is assumed that all are contained in the austenitic stainless steel.

  The shear bonding in the present invention is a plastic flow deformation generated by the pressure at which the shearing surfaces of the metal bars are pressed against each other in the process of shearing with the shearing blades, where the shearing blades facing the joints of the stacked metal bars are positioned. This means that the metal bars are joined to each other, and the joint surface of the joint at this time is formed so as to be inclined from the thickness direction of the metal bar.

First, a hot rolling facility for carrying out continuous hot rolling by shearing the austenitic stainless steel according to the present invention, and a method for shearing the austenitic stainless steel using this facility are shown in FIGS. Will be described with reference to FIG.
FIG. 1 is a configuration diagram showing a basic configuration of an austenitic stainless steel continuous hot rolling facility according to an embodiment of the present invention.

  Referring to FIG. 1, the austenitic stainless steel continuous hot rolling facility according to the present invention is roughly divided into a rough rolling mill 10, a coil box 20, a joining device 30, and a finishing rolling mill 40 including a plurality of rolling mills from the upstream side. , And a down coiler 50.

  The austenitic stainless steel metal bar produced by rolling the austenitic stainless steel slab with the roughing mill 10 is wound around the coiler of the coil box 20 in a coil shape. Such a coil box 20 adjusts the speed difference between the roughing mill 10 and the metal bar running on the finishing mill 40.

  The trailing metal bar 60 unwound from the coiler of the coil box 20 is cut by the partial descaling device 81 with the partial descaling device 81 after the tip of the trailing metal bar 60 is cut by the inlet-side crop shear 70. It is scaled and overlapped on the rear end of the preceding metal bar 90 by the overlapping device 80 of the joining device 30. At this time, the end of the preceding metal bar can be cut by the inlet side crop shear 70 as necessary.

  The leading end of the trailing metal bar 60 and the trailing end of the preceding metal bar 90 are joined by the joining machine 100 of the joining device 30, and the crop at the joined portion is cut by the crop processing device 120. The metal bar 110 joined by the joining device 30 and brought into a continuous state is transferred to the finishing mill 40.

Here, the joining device 30 is equipment for joining the rear end of the preceding metal bar 90 and the front end of the following metal bar 60 in a traveling state, and is a short-time joining device capable of shear joining in a short time. .
And in order to carry out the shearing joining of the metal bar in the running state, the joining machine 30 can move following the running of the metal bar, and the joining machine 30 swings following the running of the metal bar. Can be additionally installed.

  For example, as will be described later, the joining device 100 of the joining device 30 is press-fitted from both sides with an overlapped portion where the rear end of the preceding metal bar 90 and the front end of the succeeding metal bar 60 are sandwiched. A pair of shearing blades that are sheared while being sheared are provided.

  Then, the metal bar 110 transferred to the finishing mill 40 is sequentially hot-rolled through a plurality of rolling mills to be manufactured to a desired thickness, and is then wound around the down coiler 50.

  Here, in FIG. 1, reference numerals 130 and 140 indicate levelers installed on the respective outlet sides of the coil box 20 and the joining device 30, and reference numeral 150 indicates a crop shear installed on the inlet side of the finishing mill 40. Reference numeral 160 represents an edge heater disposed between the leveler 140 and the crop shear 150, and reference numeral 170 represents a bar heater disposed in front of the edge heater 160.

  The levelers 130 and 140, the crop shear 150, the edge heater 160, and the bar heater 170 can be selectively arranged depending on the material to be hot rolled and the hot rolling conditions. In FIG. The installation or non-installation is shown as an example, and can be variously changed.

  The crop shear 70 that cuts the rear end of the preceding metal bar 90 and the front end of the subsequent metal bar 60 is necessary when the metal bars are butted and joined. In the case of shear bonding, it may be omitted when not necessary.

Next, the joining machine 100 and the austenitic stainless steel metal bar in the shear joining process according to the present invention will be described in detail with reference to FIGS.
Referring to FIG. 2, the joining machine 100 according to the present invention includes an upper blade assembly 180, a lower blade assembly 190, and a housing 101 that movably supports them.

  Here, the upper blade assembly 180 includes an upper blade 181, an upper clamp 182, and an upper support device 183, all of which are integrally formed. The lower blade assembly 190 includes a lower blade 191, a lower clamp 192, and a lower support device 193, all of which are integrally formed.

  The upper blade assembly 180 and the lower blade assembly 190 are guided by a post portion (not shown) of the housing 101, and the thickness direction of the leading metal bar 90 and the trailing metal bar 60 (direction perpendicular to the rolling surface). ) To be able to move in a direction inclined in the metal bar traveling direction. Further, the upper blade assembly 180 and the lower blade assembly 190 are configured to be able to approach and separate by a link mechanism (not shown). Note that the inclination direction is a case where the embodiment shown in FIG. 2 is a cross section along the metal bar traveling direction, and may be inclined in another direction.

  Such a joining machine 100 according to the present invention is guided in a state in which the leading end of the trailing metal bar 60 is superimposed on the trailing end of the leading metal bar 90 made of austenitic stainless steel.

  As a result, the leading edge 61 of the trailing metal bar 60 is superimposed on the trailing edge 91 of the preceding metal bar 90 made of austenitic stainless steel, and the portion where the leading edge 61 and the trailing edge 91 overlap is the protrusion of the upper blade. 184 and the protrusion 194 of the lower blade. In other words, the upper blade protrusion 184 and the lower blade protrusion 194 come into contact with the surfaces of the front end 61 and the rear end 91.

  The upper clamp 182 and the lower clamp 192 are in contact with the portion where the rear end 91 of the preceding metal bar 90 and the front end 61 of the subsequent metal bar 60 are overlapped. The upper clamp 182 is supported by the upper support device 183 with hydraulic pressure, and the lower clamp 192 is supported by the lower support device 193 with hydraulic pressure.

  If the upper blade 181 and the lower blade 191 shear the leading metal bar 90 and the trailing metal bar 60 in such a state, the shear surfaces of the leading metal bar 90 and the trailing metal bar 60 are shear-bonded to each other by plastic flow deformation. Thus, the metal bar 110 is integrally connected.

  Thus, if the end of the austenitic stainless steel is shear-joined, the upper crop separated from the tip 61 of the trailing metal bar 60 is located at the joined portion of the connected metal bar, A lower crop separated from the rear end 91 of the preceding metal bar 90 is located. When the metal bars are joined to each other, the upper blade 181 and the lower blade 191 retreat so as to be separated by a certain distance.

  The upper and lower crops cut by the metal bar shearing are removed by the crop processing device 120 shown in FIG. 1, and the connected metal bars 110 are continuously transferred to the finishing mill 40.

When the joint portion of the metal bar passes through the finishing mill 40, strong compressive stress, bending during finish rolling, and external force such as bending or tension acts between each stand of the finishing mill, so the joint portion Will be subjected to harsh process conditions.
At this time, the joining portion of the austenitic stainless steel metal bar needs to maintain a joining strength that can pass through the finishing mill 40 without breaking.

  Hereinafter, when the austenitic stainless steel metal bar is shear bonded by continuous hot rolling, process variables of the bonding process for controlling the bonding strength of the bonded portion will be described in detail.

First, with reference to FIG. 4, the process of solid-phase joining two metal bars will be described in terms of metal thermodynamics.
Solid state bonding can be said to be a process in which two free surfaces become one interface. In this case, when the change of the free energy γ in the solid phase bonding process is calculated thermodynamically, it is as shown in Equation 1.

In Equation 1, since the interfacial energy has a value of 30% or less of the _{free surface} energy, the change in free energy can be represented by -1.7γ _{free surface} . And since γ _{free surface} has a positive value, the change in overall energy has a negative value. This means a spontaneous reaction, that is, the two surfaces are naturally joined without any external force.

  However, in reality, the two surfaces are not naturally joined without any external force in the atmosphere. This is because the unevenness and scale on the surface of the plate obstruct the joining of the two surfaces.

  In order for two metal bars to be joined together, an attractive force must act between the atoms on the surface of the metal bars to be joined. In order for the attractive force between atoms to work, the interatomic distance must be Å class.

  However, since the surface of the metal bar is uneven even after machining, the interatomic distance between the surfaces of the two metal bars is far greater than the soot class. Considering this point, a strong pressure (compressive force) is applied in normal solid-phase bonding, and a very large force is required at room temperature, so the metal bar is heated to a high temperature.

  However, even if such a strong pressure is applied, the scale existing on the surface of the metal bar or generated on the surface of the metal bar when the metal bar is heated reduces the bonding force. Therefore, in order to ensure a sufficient joint strength at the time of continuous hot rolling of austenitic stainless steel, the scale must be reduced.

  In some cases, the conventional solid-phase bonding method in which two metal bars are bonded can extremely exceptionally prevent bonding of scale. However, in this case as well, since hot rolling is performed at a high temperature of about 1,000 ° C., scale due to high-temperature oxidation naturally occurs on the surface where two metal bars are to be stacked, and descaling is performed to remove this. Even if you do, a scale is generated on the surface instantly.

  Moreover, since the softness of the material is very high at a high temperature, scales existing on the surfaces to be stacked are mixed into the joint. Such scale contamination acts as a cause of reducing the bonding strength.

  Hereinafter, with reference to FIG. 5, in the case where two metal bars are bonded in a hot state as described above, a bonding rate and a bonding strength ratio of the bonding portion will be described.

  In FIG. 5, the solid line (straight line) shows the relationship between the bonding rate and the bonding strength when it is assumed that no scale is mixed in the bonded portion and there is theoretically no bonding force between the scales. As described above, theoretically, the bonding rate and the bonding strength are shown as a linear relationship. Therefore, if the bonding rate increases, the bonding strength ratio must also increase. Here, the joining rate is expressed as a percentage obtained by dividing the length of the joined portion that is completely scaled without the scale by the entire length of the joined portion. This indicates that the greater the amount of scale mixed in the joint, the lower the joining rate, and thus the lower the joint strength ratio.

  However, due to the high temperature conditions in the actual hot rolling process, scales are always generated, and there is a weak bonding force between the scales, so the bonding strength ratio is slightly higher than the solid line (straight line), that is, the dotted line. To show a good relationship.

Next, when the austenitic stainless steel metal bar is shear bonded by continuous hot rolling, the bonding conditions for controlling the bonding strength of the bonded portion will be described.
A shear joining process of the joining machine 100 according to the present invention will be described with reference to FIG.

As shown in FIG. 6A, the force for joining two metal bars by shear joining is a force in a direction perpendicular to the joining portion of the compression loads pressed by the upper blade 181 and the lower blade 191. Further, the friction between the two new surfaces generated by shearing here improves the bondability.
Such a force causes opposing pressures to act as shown in FIG.

  At this time, this force is a function of the bonding machine 100 and the process conditions, and if this is insufficient, the bonded portion cannot have sufficient bonding strength. On the other hand, the protrusions 184 and 194 existing on the upper blade and the lower blade play a role of preventing the metal flow when the metal bar is sheared, thereby strengthening the joining force.

  Further, as shown in FIG. 7, in the width direction of the metal bar, the central portion has no problem with the surrounding restraint, but the both end portions are in a free surface state without any restraint.

In this way, the ends in the free surface state at the time of joining the metal bars have a gap in the outer direction as shown in FIG.
As a result, the joining strength of both ends of the metal bar is reduced, and as shown on the right side of FIG. This causes cracks during the subsequent finish rolling, and if the cracks become large, continuous part breakage of the continuous steel sheet occurs.

  The shape of the joint also affects the joint strength. When shear bonding is applied, unbonded portions exist at the upper and lower portions of the cross section of the bonded portion due to the characteristics of the bonding method, and the bonding strength varies depending on the position and size of the unbonded portion.

  Considering the above explanation, various control factors that affect the performance of the joint are arranged as shown in FIG.

  As shown in FIG. 8, it can be seen that the material characteristics, process variables, and joining device all affect the joint strength of the metal bar joint performance.

  However, it is difficult to control the material properties and the joining device here, so when actually joining metal bars, it is easy to adjust the process variables to control the joining conditions, and the effect is certain. It is.

Such process variables include descaling conditions and joining conditions.
As the descaling condition, the temperature and pressure at the time of descaling can be controlled to suppress the scale mixture. As the joining conditions, the joining force and shape of the joint can be adjusted by controlling the temperature, lap, and stroke rate during joining of the metal bars.

  By appropriately adjusting the five process variables as described above, it is possible to control the mixing of scale, insufficient bonding force, and the shape of the bonded portion, which are factors that decrease the bonding strength. Moreover, the strength reduction of the metal bar joint can be suppressed by controlling such process variables.

Here, the definition of the stroke rate and the lap, which are the joining conditions of the process variables, will be described with reference to FIG.
The stroke rate is obtained by dividing the total distance (Δl _U + Δl _L ) moved up and down after contacting the metal bar where the upper blade 181 and the lower blade 191 of the joining machine 100 overlap with each other by the thickness (t) of the metal bar. Value.

Therefore, as the stroke rate = ((Δl _U + Δl _L ) / t) increases, the relative thickness of the joint decreases.

  The lap is a distance at which the upper blade 181 and the lower blade 191 overlap. However, the shearing blade (the upper blade and the lower blade) has a predetermined angle, and after the shearing blade is sheared, a slight difference from the set value may occur depending on the stroke rate. Therefore, when the metal bar is actually shear-joined, actual measurement is impossible. Therefore, it is preferable to control the set value of the joining machine.

  Since the hot rolling equipment and the joining method using the same according to the present invention described above perform shear joining, there is no scale that can be generated simultaneously with shearing. Accordingly, since only the new surfaces due to the shearing are joined, there is no scale, and problems in subsequent processes such as plate breakage that can occur due to this can be prevented. In addition, since the precision of the cut surface does not have to be taken into consideration at all, it can be applied to austenitic stainless steel.

  Furthermore, since the joining method according to the present invention is solid phase joining, shear joining is performed within the temperature range of the metal bar itself heated to a hot state without supplying a separate heat source on the hot rolling equipment line. It can be carried out. Therefore, preheating and post-heating are unnecessary, and cracking of the metal bar joint can be prevented without introducing a separate heat source.

  Further, unlike the conventional welding joining method, only the shearing force is used, so that there is a technical effect capable of fundamentally preventing not only the scale mixing problem but also the pore mixing problem in the joining process of the austenitic stainless steel.

  Therefore, the shear joining method according to the present invention is a very useful method for joining austenitic stainless steel in a continuous hot rolling process, and if only process variables are appropriately controlled, the finish rolling plateability of the joint is ensured. be able to.

  Hereinafter, considering such points, process variables and process conditions at the time of shear bonding of austenitic stainless steel will be examined through evaluation.

[Evaluation]
Experiments were carried out using austenitic stainless steel metal bars having the compositions shown in Table 1 below with the continuous hot rolling equipment shown in FIGS.

  Hereinafter, the experimental graphs shown in FIGS. 10 to 15 show the all-type average experimental values of the steel types shown in Table 1. As a result of various experiments as shown in FIGS. 10 to 15 for typical austenitic stainless steels such as STS304, STS316, and STS304L shown in Table 1, characteristics such as a bonding strength ratio (described later) are obtained. Since similar patterns are represented, the drawings described below and the physical characteristics of the austenitic stainless steel are shown as average values for the steel types shown in Table 1.

FIG. 10 shows the relationship between descaling temperature, joint strength ratio and crack rate (joint strength ratio and crack rate of metal bar edge) by a joining machine provided in an austenitic stainless steel continuous hot rolling facility according to an embodiment of the present invention. It is a graph which shows the influence of the descaling temperature with respect to.
Here, the joint strength ratio is expressed by the following mathematical formula 2.

  And the edge crack rate is like the following numerical formula 3.

  As shown in FIG. 10, in the case of austenitic stainless steel, it can be seen that if the metal bar is shear bonded, the influence of the descaling temperature variable on the bonding strength ratio and the edge crack rate is not large.

  During finish rolling, if the bond strength ratio is low, the plate breaks in the first or second pass, and if the edge crack rate increases, the plate breaks in the subsequent stage.

FIG. 11 shows the relationship between the descaling pressure, the joint strength ratio, and the crack rate by the joining machine provided in the austenitic stainless steel continuous hot rolling facility according to one embodiment of the present invention (with respect to the joint strength ratio and the crack rate of the metal bar edge). It is a graph which shows the influence of a descaling pressure.
As shown in FIG. 11, when the joined metal bars are finish-rolled with a finish rolling mill and the sheet-passability is tested, if the joining strength ratio is 52% or more, finish rolling without breaking the joints of the metal bars is performed. It is understood that is possible. In the case of the edge crack rate, up to 30% could be passed.

  Further, as shown in FIG. 11, as the descaling pressure increases, the amount of scale mixed into the joint portion decreases, so the joint strength of the joint portion increases and the area of the unjoined portion at both ends in the width direction increases. The edge crack rate is also reduced.

  However, if the descaling pressure is too high, the amount of water injection increases and the temperature of the joint portion decreases significantly, making it difficult to secure the temperature required for finish rolling, which is a subsequent process.

  Moreover, the base material of the metal bar having a weak high-temperature strength is significantly damaged due to excessive descaling pressure, and many irregularities are generated on the surface of the joint portion, thereby deteriorating the bondability.

As a result of the above experiment, it can be seen that when austenitic stainless steel is shear-joined with a joining machine, the descaling pressure in the descaling device 81 immediately before the joining machine 100 is preferably controlled to 50 MPa or less.
As described above, austenitic stainless steel has a high temperature strength and a small decrease in bonding strength and a small increase in edge crack rate even at a high pressure of about 50 MPa.

  Further, in the case of austenitic stainless steel, descaling may be omitted because a joining strength and a low edge crack rate that can be passed through in the finish rolling process can be obtained even when the descaling pressure is 0 MPa.

FIG. 12 shows the relationship between the joining temperature and joining strength ratio by the joining machine provided in the austenitic stainless steel continuous hot rolling facility according to one embodiment of the present invention (corresponding to the joining temperature when austenitic stainless steel is shear-joined). FIG.
As shown in FIG. 12, it can be seen that the joining temperature when the austenitic stainless steel is shear-joined hardly affects the joining strength ratio. Although not shown, it can be seen that the edge crack rate is not affected.

FIG. 13 shows the relationship between the lap and the joining strength ratio by the joining machine provided in the austenitic stainless steel continuous hot rolling facility according to one embodiment of the present invention (joining due to changes in lap when austenitic stainless steel is shear-joined. Intensity ratio).
As shown in FIG. 13, it can be seen that the lap and the bonding strength ratio show a Gaussian distribution, that is, a parabolic relationship.

  This is because the lap increases, that is, if the overlap length when the upper blade 181 and the lower blade 191 are in contact with the upper surface or the lower surface of the metal bars 60, 90 is increased, the bonding strength ratio is increased. (After-mentioned) began to be satisfied, and when it exceeded 16 mm, it began to decrease again, and if it exceeded 19 mm, the sheet passing standard could not be satisfied. Note that the overlap length is determined by the inclination angle of the bonding machine 100.

The reason why the lap range is 3 mm or more and 19 mm or less and satisfies the sheet passing standard is as follows.
In other words, the reason why the bonding strength increases as the lap increases is that the rising angle of the bonding surface from the rolling surface becomes smaller as the wrap increases, thereby the bonding surface of the pressing force of the shearing blade. This is because the component force in the vertical direction increases, and if the wrap amount is larger than a predetermined value, the necessary load increases, so that the bonding strength decreases.

  Therefore, the wrapping range is preferably 3 mm or more and 19 mm or less.

  Since the austenitic stainless steel has a high high-temperature strength of the material itself, the lower limit value range of the lap appears relatively high.

  On the other hand, the edge crack rate was greatly influenced by the descaling pressure, but almost no influence by wrapping was observed. This is because the bonding force increases due to the increase of the wrap, but the bonding force decreases or oxidation occurs at the edge portion, and the effect becomes extremely small.

  The more the shear blade is used, the more wear it takes. The lap amount changes with time, and it is difficult to measure with an actual hot rolling line. Therefore, the lap amount in the present invention is the set value in the bonding machine 100. means.

FIG. 14 shows the relationship between the stroke rate and the breaking load by the joining machine provided in the austenitic stainless steel continuous hot rolling facility according to one embodiment of the present invention It is a graph which shows a load.
As shown in FIG. 14, the breaking load of the joint portion gradually increases as the stroke rate increases, and the passing plate standard is satisfied at 1.30, and almost the saturation phenomenon is exhibited at 1.30 or more. However, it decreased again above 1.60. However, it can be seen that the plate passing standard is satisfied up to 1.65.

  Therefore, in the case of austenitic stainless steel, it is preferable that the stroke rate of the joining machine 100 is 1.30 or more and 1.65 or less during shear joining.

  At this time, the stroke rate can be sheared by moving the upper blade and the lower blade of the bonding machine 100 up and down simultaneously, and only one of the upper blade and the lower blade is moved and sheared. You can also

  Unlike other joining conditions, the stroke rate affects the thickness of the joint. That is, if the stroke rate increases, the thickness of the joint becomes thinner. As a result, even if the joining strength increases, the breaking load may decrease, so the relationship between the stroke rate and the breaking load at the joint was investigated. As can be seen from FIG. 14, when the stroke rate is increased, the breaking load is increased even though the thickness of the joint portion is reduced, and this indicates that the joint strength ratio is significantly increased as the stroke rate is increased. Means.

  In addition, the stretch rate increased as the stroke rate increased, but the effect on the edge crack rate was not significant. The phenomenon that the breaking stress and breaking load increase as the stroke rate increases in this way is that the joining force increases as the stroke rate increases, and the position and shape of the unjoined part at the upper and lower parts in the thickness direction of the plate differ. It is caused by appearing.

  FIG. 15 shows the result of a sheet passing experiment using a finishing mill after shear joining the austenitic stainless steel according to the present example to a hot rolling facility, and FIG. 15 confirms the sheet passing standard according to the present invention. it can.

FIG. 15 is a graph showing the result of shear joining using an austenitic stainless steel material having the composition shown in Table 1 and then rolling the joined metal bars with a finishing mill at a hot rolling mill.
The experimental material shown in the graph of FIG. 15 is obtained by shear-bonding an austenitic stainless steel metal bar having a width of 450 mm, then welding the two sets of the experimental material joined to each other to obtain a width of 840 to 900 mm, and then back and forth. A metal bar having a length of 9000 mm made by welding bars having the same thickness. FIG. 15 shows the result of finishing rolling after heating such a metal bar in a heating furnace.

  As a result of such an experiment, all of the metal bars having a bonding strength ratio of less than 52% were ruptured by finish rolling, and the metal bars having a bonding strength ratio of 52% or more were successfully passed (FIG. 15 (a)). )reference).

  Thus, the joint edge crack of the metal bar which was successfully passed through the finish rolling was 20% or less.

  On the other hand, if the stroke rate is fixed, there is no problem even if the threading standard is set by the joint strength ratio, but if the stroke rate changes, the thickness of the joint will change. Is shown in FIG. Here, the bonding load ratio is as shown in Equation 4 below, and the threading plate standard for such a bonding load ratio is 31.5%.

  As described above, as shown in FIG. 15, the sheet passing standard in the finish rolling stage means that the joining strength ratio and the breaking load of the finish rolling are satisfied without breaking the metal bar.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to the joining conditions in the junction part at the time of continuous hot rolling of the above austenitic stainless steel, Such an austenite type | system | group It can be applied to various joining methods necessary for shear joining of continuous hot rolling of stainless steel.

  Accordingly, the present invention can be variously modified and implemented within the scope of the claims and the detailed description of the invention, and these also belong to the scope of the present invention.

It is a block diagram which shows the basic composition of the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention. It is a joining machine with which the austenitic stainless steel continuous hot rolling facility which concerns on one Example of this invention comprises, Comprising: It is a block diagram which shows the metal bar by which joining was completed. It is a conceptual diagram which shows the state of the metal bar completed by the joining machine which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention comprises. It is a conceptual diagram which shows the change of the free energy of the solid phase junction by one Example of this invention. It is a graph which shows the relationship between the joining rate at the time of the solid-phase joining by one Example of this invention, and joining strength ratio. It is explanatory drawing which shows the joining force which acts on the joining surface by the joining machine with which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention comprises. It is explanatory drawing which shows the cause of the joining strength fall of the edge part of a metal bar by a joining machine, and crack generation. It is a block diagram explaining the correlation of the joining variable which acts on the junction part performance of the metal bar by a joining machine, and each joining variable. It is a conceptual diagram explaining the definition of a stroke rate and a lap. It is a graph which shows the relationship between the descaling temperature by the joining machine with which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention comprises, joining strength ratio, and a crack rate. It is a graph which shows the relationship between the descaling pressure by the joining machine with which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention comprises, joining strength ratio, and a crack rate. It is a graph which shows the relationship between the joining temperature by the joining machine with which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention comprises, and joining strength ratio. It is a graph which shows the relationship between the lap | lap | lap by the joining machine with which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention, and joining strength ratio. It is a graph which shows the relationship between the stroke rate by the joining machine with which the austenitic stainless steel continuous hot rolling facility which concerns on one Example of this invention comprises, and a fracture | rupture load. It is a graph which shows the plate test result of the joint finish rolling by the joining machine with which the austenitic stainless steel continuous hot rolling equipment which concerns on one Example of this invention comprises.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Coarse rolling mill 20 Coil box 30 Joining apparatus 40 Finishing mill 50 Downcoiler 60 Trailing metal bar 61 Trailing metal bar tip 70 Entrance side crop shear 80 Stacking device 81 Descaling device 90 Leading metal bar 91 Leading metal bar Rear end 100 Joiner 101 Housing 110 Metal bar 120 Crop processing device 130, 140 Leveler 150 Exit side crop shear 160 Edge heater 170 Bar heater 180 Upper blade assembly 181 Upper blade 182 Upper clamp 183 Upper support device 184 Projection 190 Lower blade assembly Body 191 Lower blade 192 Lower clamp 193 Lower support device 194 Projection

Claims (6)

An austenitic stainless steel metal bar containing 12 to 26% by mass of Cr, 6 to 22% by mass of Ni, and other inevitable impurities and the remaining Fe, or 12 to 26% by mass of Cr and Ni 6-22 mass% contains at least one element of Si, Mn, P, S, Cu, Mo, Al or a special element of V, Nb, Ti, B, and the content of each element is 3.00 mass%. An austenitic stainless steel metal bar consisting of other inevitable impurities and the remaining Fe is superposed on the tip of the following metal bar and the trailing end of the preceding metal bar in the hot rolling equipment row. and descaling at pressures 50MPa using a descaling apparatus for descaling by water pressure predetermined joining portion to be joined, and the tip of the metal bars to be trailing in the hot rolling mill train The metal bars are shear-bonded by using a joining machine that overlaps and joins the rear ends of the metal bars so that the joining surfaces of the joined metal bars are inclined from the thickness direction of the metal bars. A method for shear joining of austenitic stainless steel continuous hot-rolled materials characterized in that they are joined together. 2. The austenitic system according to claim 1, wherein when the metal bar is subjected to shear bonding, the lap range, which is a distance at which the upper blade and the lower blade of the bonding machine overlap, is set to 3 mm or more and 19 mm or less. Shear joining method for stainless steel continuous hot rolled material. When the metal bar is subjected to shear bonding, shear bonding is performed by setting the stroke rate obtained by dividing the total distance traveled by the upper blade and lower blade of the bonding machine by the thickness of the metal bar to 1.30 to 1.65. The shear joining method of the austenitic stainless steel continuous hot-rolled material according to claim 1 or 2, characterized by the above. The austenitic stainless steel according to any one of claims 1 to 3, wherein when the metal bar is shear-joined, both the upper blade and the lower blade of the joining machine are shear-joined while simultaneously moving up and down. Shear joining method for continuous hot rolled material. The austenitic system according to any one of claims 1 to 3, wherein when the metal bar is subjected to shear bonding, only one of the upper blade and the lower blade of the bonding machine is moved to perform shear bonding. Shear joining method for stainless steel continuous hot rolled material. Austenitic stainless steel containing 12 to 26% by mass of Cr, 6 to 22% by mass of Ni, and other inevitable impurities and the remaining Fe, or 12 to 26% by mass of Cr and 6 to 22% by mass of Ni Contains at least one element of Si, Mn, P, S, Cu, Mo, Al or at least one special element of V, Nb, Ti, B, and the content of each element is 3.00% by mass or less. A rough rolling machine for rough rolling an austenitic stainless steel slab composed of the inevitable impurities and the remaining Fe,
A coil box that winds the roughly rolled metal bar into a coil;
A descaling device for descaling the metal bar unrolled from the coil box coiler by water pressure at a pressure of 50 MPa or less;
A pair of shearing blades that shear-join the descaled metal bar while being sheared by press-fitting from both sides in a state where the rear end of the preceding metal bar and the front end of the subsequent metal bar are overlapped to sandwich the overlapped portion. A shear bonding device provided; and
A finish rolling mill for finishing and rolling the shear bonded metal bar,
A continuous hot rolling facility characterized in that austenitic stainless steel metal bars are continuously hot rolled.

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