JP4917980B2 - Hot rolling method for wire and bar - Google Patents

Description

  The present invention relates to a rolling method for improving the surface quality of a wire rod and steel bar by reducing the twist of the rolled material generated in the hole die during the hot hole rolling process of the wire rod and the steel bar.

  In hot hole rolling of wire rods and steel bars, the heated material billet is usually cut in a rhombus-horn-rhombus-hole or rhombus-horn-hole pattern in a rough rolling mill row. The area is reduced sequentially and rolled into a square hole type as a rolled material immediately after it is caught in the next oval hole type, and the cross-sectional area is further reduced by the subsequent hole type series such as a round-oval, so that the rolled material is required. Finished with product dimensions. In this hot hole rolling process, when the radius r of the rolled material arc portion (top) C in contact with the bottom of the groove groove on the exit side of the square hole die is small, as shown in FIG. When rolled by an oval hole mold in a twisted state, the torsion recovery force of the rolled material itself is large, and the oval shape on the exit side of the hole mold is in a good state, but the arc portion (top) radius r is small. In the oval hole mold, the compressive strain in the circumferential direction of the rolled material in the vicinity of the arc portion becomes large and surface flaws are generated. In order to suppress the occurrence of such surface flaws, there is a method of increasing the radius r of the arc portion (top portion) C of the rolled material on the exit side of the square hole die as shown in FIG. When the rolled material is twisted in a state where the arc portion (top portion) radius r is large and twisted into the oval hole mold, the torsional recovery force is small compared to the case where the arc portion (top portion) radius r is small, and the twist is twisted. As the rolling deformation progresses in this state, the cross-sectional shape of the rolled material on the outlet side of the oval hole mold becomes asymmetrical, and it is folded near the arc (top) when rolling with the subsequent round hole type. Is likely to cause surface flaws. For this reason, in order to maintain an appropriate shape without causing the cross-sectional shape of the rolled material to be asymmetric at the outlet side of the oval hole mold and to prevent surface flaws, the radius r of the arc portion of the rolled material at the outlet side of the square hole mold It is important to increase the width so that the oval hole mold is properly bitten, that is, to reduce the twist of the rolled material on the entry side of the oval hole mold.

As means for properly biting into the oval hole mold, conventionally, a roller guide is installed on the roll hole mold entry side of the rolling mill, and the rolling material is fixedly supported by the guide roller, and the rolling material is introduced on the hole mold entry side. A rolling method for correcting twist is used. For example, in Patent Document 1, a guide device provided with a twister guide having a guide body rotatably supported is installed on the entrance side of a pair of vertical rolls of a finishing stand for steel bar rolling, and a product (bar steel) that comes out of the finishing stand. ) Has been disclosed that corrects the product twist by imparting rotation in the opposite direction to the twist. In addition, in the Japanese Patent Application No. 2006-120898, the present applicant adjusts the perforated rolling roll in the roll axial direction without using a twister guide or a roller guide in continuous rolling of the steel slab using the perforated rolling roll. A rolling method was proposed to eliminate twisting of the rolled material.
JP 2000-176529 A

  However, in the method of fixing and supporting the rolled material with the roller guide described above, if the rolled material is forcibly fixed and supported, it will come into strong contact with the guide roller due to twisting of the rolled material, and surface flaws may occur, Excessive force was applied, causing the bearing to break and the guide roller to stop, causing problems such as seizure. Further, if the roller guide has already been largely twisted before entering the roller guide, the roller guide itself will be damaged, and the twisting problem cannot be fundamentally improved by installing the roller guide. Further, in the rolling apparatus disclosed in Patent Document 1, surface flaws that occur when the rolled material comes into contact with the twister guide cannot be avoided. On the other hand, according to the rolling method proposed by the present applicant, the continuous rolling of the steel slab does not impair the finished cross-sectional shape of the steel slab, and avoids the occurrence of surface flaws due to contact with the twister or twisting. It is possible to eliminate twisting of a piece, but in hot rolling of wire rods and steel bars, an oval hole type rolling roll is used when the rolled material is already twisted on the entrance side of the oval hole mold. Even if the twist is reduced by adjusting the roll axis in the roll axis direction, the cross-sectional shape of the rolled material on the outlet side of the oval hole mold becomes asymmetric, and the occurrence of surface flaws can be avoided in the roll hole mold after the next rolling mill. Can not.

  Therefore, the subject of the present invention is that, in hot hole rolling of wire rods and steel bars, the radius of the arc portion of the rolled material that is in contact with the bottom of the square hole type groove groove is not supported by the twister or the roller guide. By providing a rolling method in which the twist is restored by the rolling deformation itself in the square hole mold and the oval hole mold is properly bitten in a state where surface flaws are not generated in the immediately subsequent oval hole mold. is there.

  In order to solve the above problems, the present invention employs the following configuration.

  That is, the hot rolling method of the wire rod / steel bar according to claim 1 includes a rhomboid-diamond-diamond hole type series or rhomboid-diamond-corner series provided on a roll of a plurality of rolling mills from a heated material billet. This is a hot rolling method for wire rods and bar steels in which the cross-sectional area is sequentially reduced by the hole series and the oval hole form immediately thereafter, and the cross-sectional area is further reduced by the subsequent hole series to finish the rolled material to the required product dimensions. When the radius of the arc portion of the free surface of the rolling material on the exit side of the rhomboid type that bites into the square hole type immediately before the oval hole type is r and the reduction amount in this square hole type is a, the rhomboid The width dimension W of the rolled material on the mold side and the arc radius r of the free surface thereof are associated in advance, and the arc radius r is predicted from the width dimension W, and the ratio r / a is 0.1 or more and 0.3. The rhomboid-diamond-square hole type series or rhomboid-diamond-hole type series low so as to fall within the following range: Adjust the gap, characterized in that the rolled material was such that meshed properly into the oval hole type.

  The inventor of the present invention has a square hole type by reducing the radius of the arc portion of the free surface of the rolled material on the exit side of the rhombus type immediately before the square hole type even in a state where the top (groove bottom) radius of the square hole type is large. Attention was paid to a rolling method in which the torsional recovery force of the rolled material is increased and the stability of the rolled material in the square hole mold is improved, so that the rolled oval mold is properly bitten. That is, by reducing the radius of the arc of the free surface that is not in contact with the hole wall surface of the rolled material rolled in the rhombus type immediately before the square hole type, the torsional recovery force in the square hole type is increased. I came up with it.

When the rolling material on the rolling mill entrance side is twisted and rolled in a roll hole mold, as shown in FIGS. 1 and 2, the radius r of the top portion of the inlet rolling material that receives the rolling at the bottom of the hole groove (the immediately preceding hole mold) Using the deformation analysis means (rigid plastic 3D full model FEM software) developed by the present applicant for the effect of the arc radius of the free surface of the rolled material on the exit side on the twist recovery rate Rt on the exit side of the roll hole mold The deformation analysis was performed. As shown in FIG. 1, the deformation analysis is performed when the entrance-side rhombus DS is rolled with a square hole type SG having an opposite side dimension Gt of about 50 mm. The definition of the reduction amount a in the type SG is shown in the figure. In the deformation analysis, as shown in FIG. 3A, the number of element divisions in the cross section of the rolled material is divided into four for each corner portion (arc portion) C, six for each surface portion P, and between opposite sides (PP). As shown in FIG. 4, the number of divisions in the longitudinal direction of the rolled material was 5 divisions at the entrance side and the exit side portion of the roll hole mold, and 10 divisions within the roll bite. The coefficient of friction between the roll and the rolled material was μ = 0.5. The twist angles θ (θ1, θ2) of the rolled material on the entry side and the exit side of the roll hole mold are shown in FIG. 3 (the measurement positions (L1 and L2) on the entrance side and the exit side of the roll hole mold shown in FIG. The angles shown in b) and (c). That is, in FIG. 3B, the entry side twist angle θ1 is the top of the entrance side diamond rolled material DS with respect to the line segment SS connecting the centers C1 and C2 of the groove bottom part of the square hole type SG, that is, the arc of the free surface. This is the inclination angle θ1 of the line segment DD connecting the centers C1d and C2d. Further, in FIG. 3C, the outgoing twist angle θ2 is a line connecting the centers C1s-C2s of the top of the outgoing rolled corner SR (groove bottom contact portion of the square hole type SG) with respect to the line segment SS. The minute inclination angle θ2. The twist recovery rate Rt was calculated by the following equation (1). As shown in FIG. 4, the entry side measurement position is a position (L1 = Ld / 2) that is separated from the biting start position (roll contact start portion) B0 by Ld / 2 (Ld: contact arc length). The output side measurement position is a position (L2 = Ld / 2) away from the roll bite output side position B1 by Ld / 2. In the deformation analysis, both L1 and L2 are within the range of 67 to 72 mm.
Twist recovery rate Rt (%) = ((input side twist angle θ1 (deg) −output side twist angle θ2 (deg)) / input side twist angle θ1 (deg)) × 100 ---------- ---------------------- (1)

  FIG. 5 shows the effect of the ratio r / a between the top radius r of the entry-side rolled material and the reduction amount a in the hole mold G on the twist recovery rate Rt based on the above deformation analysis result. Is shown. Although the torsion recovery rate Rt varies depending on the size of the top radius r of the entry-side rolled material, it can be seen that when r / a is 0.3 or less, a torsion recovery rate of a certain value, that is, 30% or more is obtained.

  In FIG. 6, the entrance material (material, material: SCM435) finished into four types of square shapes having a side of 60 mm, 62 mm, 65 mm, and 68 mm and a corner portion R of 12 mm by heating is heated to 1100 ° C. After that, four hole types of rhombus type-square hole type-oval hole type-round hole type with a roll diameter of 490 to 430 mm were finished into a round shaped outlet material with a diameter of 22 mm by four-pass experimental rolling. From the result of investigating the occurrence of surface flaws in the cross section of the round shaped exit side material with an optical microscope, the ratio r / a (r: the top radius r of the rhombus shaped entrance side material, a: the amount of reduction in the square hole type, FIG. (Reference)), the incidence (%) of surface flaws having a depth of 0.02 mm or more is plotted using the same standard as the surface flaw depth of a product (finished rolled material) described later. Generation of surface defects of 0.02 mm or more is suppressed by setting the ratio r / a to 0.3 or less. However, when the ratio r / a is 0.1 or less, surface defects having a depth of 0.02 mm or more are suppressed. Can be seen again. From this experimental result, it can be seen that by adjusting the ratio r / a to 0.1 or more and 0.3 or less, it is possible to suppress the generation of surface flaws having a depth of 0.02 mm or more. It shows that the square material on the exit side of the square hole mold is properly bitten into the oval hole mold by rolling, that is, the twist of the rolled material on the entry side of the oval hole mold is effectively reduced. As described above, the reason why surface flaws having a ratio r / a of 0.3 or more and a depth of 0.02 mm or more is generated is that the top radius r of the entrance rhombus material is smaller than the reduction amount a in the square hole type. Because of its large size, the torsional recovery in the square hole type was not sufficient and the oval hole type was not properly bitten. It is thought that the surface flaws occurred. In addition, when the ratio r / a is smaller than 0.1, a surface flaw having a depth of 0.02 mm or more is generated because the apex radius r of the entry side diamond material is smaller than the reduction amount a in the square hole type. 14, in the “square-oval” path shown in FIG. 14, a phenomenon similar to the case where the top (arc portion) radius rs of the square rolled material is small, that is, in the vicinity of the top of the entrance side rhombus material in the square hole mold. It is considered that the compressive strain in the circumferential direction of the material increases and surface flaws are generated, which are promoted by the oval hole mold followed by the surface flaws and remain in the round experimental rolled material on the outlet side of the round hole mold.

  Accordingly, as described above, the width dimension W of the rolled material on the rhomboid-type outlet side and the arc radius r of the free surface thereof are associated in advance, and the arc radius r is predicted from the width dimension W, and the ratio r By rolling the roll gap so that / a is 0.1 or more and 0.3 or less, the twist of the rolled material is restored by the rolling deformation itself in the square hole mold, and the twister guide or the roller guide The oval hole is in a state where the radius of the arc of the rolled material that is in contact with the bottom of the square hole type groove groove without supporting the rolled material is large enough to cause no surface flaws in the immediately subsequent oval hole type. It is possible to properly bite the mold.

In the hot rolling method for a wire rod / steel bar according to claim 2, the width dimension W of the rolled material on the rhomboid-type outlet side is associated in advance with the hole-shaped roll gap s immediately before the rhomboid-type, and during rolling, Measure (measure) the width dimension W of the rolled material on the exit side of the rhomboid type, and calculate the radius r of the arc portion of the rolled material free surface previously associated with the measured width dimension W, When the ratio r / a is not in the range of 0.1 or more and 0.3 or less, the ratio r / a is adjusted to 0.1 or more and 0.3 or less by adjusting the hole roll gap s immediately before the rhombus type. The hot rolling method according to claim 1, wherein the hot rolling method is performed within a range .

The radius r (corresponding to the apex radius r of the aforementioned entrance rhombus material) is controlled by adjusting the roll gap sd of the rhombus type DG. In this case, the dimension of the rolling material on the exit side of the rhomboid type changes, and this greatly affects the dimensional accuracy of the rolled material on the exit side of the square hole type. For this reason, the roll gap s (see FIG. 2 (a)) of the roll hole type FG of the rolling mill immediately before the rhombus type and the width dimension W (see FIG. 2 (b)) of the rolled material DS on the exit side of the rhombus type. Further, the width dimension W of the rolled material on the rhombus type outlet side and the arc portion radius r of the free surface of the rolled material on the rhombus type outlet side are associated in advance. By associating in this way, the arc surface radius r of the free surface is calculated based on the width dimension W of the rolling material on the rhomboid-type exit side measured during rolling, and the ratio r / a is the above When it is outside the range, the radius r of the arc of the free surface of the rolled material is adjusted so as to be within the above range by adjusting the roll gap s of the rolling mill immediately before the rhomboid type shown in FIG. Can be controlled. In this way, since the radius r of the arc portion can be controlled without adjusting the rhombus type roll gap immediately before the square hole mold, the required dimensional accuracy of the rolled material on the square hole mold outlet side is maintained. The oval hole mold can be properly bitten by increasing the twist recovery force of the rolled material in the square hole mold.

  According to the present invention, the rhomboid of the hole type schedule comprising the rhomboid-diamond-diamond hole type series or the rhomboid-diamond-square hole type series and the oval hole type immediately after the hot-hole rolling of the wire rod / bar In the mold-square hole type-oval hole type, the width dimension W of the rolled material on the exit side of the rhombus type to be engaged with the square hole type immediately before the oval hole type is associated with the arc radius r of the free surface in advance. The radius r of the arc portion is predicted from the width dimension W, and the roll gap is set so that the ratio r / a between the arc portion radius r and the subsequent roll-down amount a in the square hole mold is 0.1 or more and 0.3 or less. Since the twist of the rolled material is restored by rolling deformation in the square hole mold, the radius r of the rolled material arc portion (top) C that is in contact with the bottom of the groove groove on the exit side of the square hole mold Even if the oval hole type is large enough not to cause surface flaws, the twister guide or roller guide Without the need for support of the rolled material by de so caught properly the rolled material into oval hole type, i.e. it is possible to reduce the twisting of the rolled material in the oval hole type entry side.

  In addition, the width dimension W of the rolling material on the exit side of the rhomboid mold and the roll gap s of the roll hole mold of the rolling mill immediately before the rhombus mold are associated in advance, and based on the width dimension W measured during rolling. By adjusting the roll gap s of the rolling mill immediately before the rhomboid type, the arc radius r of the free surface can be controlled so that the ratio r / a is within the above-mentioned required range. As a result, the required dimensional accuracy of the rolled material on the exit side of the square hole mold can be maintained, and the oval hole mold can be properly bitten, the occurrence of surface flaws can be suppressed, and the surface quality of the rolled material can be improved. Can contribute.

  Hereinafter, embodiments of the present invention will be described with reference to FIGS.

  FIG. 7 schematically shows a heating furnace 1, a rough rolling mill row 2 and an intermediate rolling mill row 3 of a wire rod and bar rolling line. A plurality of horizontal rolling mills 1H to (RF-1) H and vertical rolling mills 2V to RFV are alternately arranged, and the material billet 4 (pressured material 4a) heated in the heating furnace 1 includes the rolling mill rows. While rolling without twisting 90 ° between the rolling mills 2 and 3, the roll hole molds are alternately pressed down from different directions by 90 ° to fill each roll hole mold, Are gradually decreasing. In the rough rolling mill row 2, a hole-type roll in which a rhombus type or a square hole type is processed so that a rhombus-square-diamond-hole type series or a rhombo-diamond-type hole type series is formed. The roll hole type of the final rolling mill RFV of the rough rolling mill row 2 is a square hole type. Further, in the intermediate rolling mill line 3, the oval hole type, the round hole type, and the round hole type are processed so that an oval (elliptical) -round hole type series or an oval-square hole type series is usually formed. A hole-type roll is incorporated, and the roll hole type of the first rolling mill RM1 in the intermediate rolling mill row 3 is an oval hole type. In this way, a hole schedule of rhombus type-square hole type-oval hole type is formed from the exit side of the rough rolling mill row 2 to the entry side of the intermediate rolling mill row 3. Between this rhombus type and the square hole type, that is, between the rolling mills (RF1-1) H and RFV, a dimension for actually measuring the width dimension W of the rolled material on the exit side of the rhombus type (RF-1). A measuring device 5 is installed. The material billet 4 (pressured material 4a) heated in the heating furnace 1 is subjected to a roughing mill after the surface scale is removed by a descaling device (not shown) installed on the entry side of the roughing mill row 2. While proceeding between the rolling mills in row 2, the roll hole molds are alternately rolled down from different directions by 90 ° to fill the roll hole molds, and the cross-sectional areas thereof are sequentially reduced. The corners of the final rolling mill RFV The square rolled material 4b is formed by the hole mold. This square rolled material 4b is squeezed in the opposite direction by the oval hole type of the entry side rolling mill RM1 of the intermediate rolling mill row 3 (see FIG. 14 and FIG. 15) to fill the hole type, and thereafter this rolling mill row 3 Due to the hole type series between the rolling mills and the subsequent rolling mill row (not shown), the (rolled material) cross-sectional area is further reduced to finish the wire or bar with the required product size. And corresponding to the hole type schedule of the rough rolling mill row 2, as shown in FIG. 8 and FIG. 9 as an example, the diamond of the rolling mill (RF-1) H just before the final rolling mill RFV (square hole type). The rolled material width dimension W on the exit side of the hole mold, the arc radius r of the free surface thereof, and the (hole mold) roll gap s of the rolling mill (RF-2) V immediately before the diamond hole mold are associated in advance. And stored in a storage device of a process computer that controls the rolling process in the form of a table value or a mathematical expression. In addition, the arrangement | positioning of the rolling mill of the said rough rolling mill row | line | column 2 can also be alternately arrange | positioned in order of a vertical rolling mill-a horizontal rolling mill.

  FIG. 10 shows that the roll gap is adjusted so that the ratio r / a is 0.1 or more and 0.3 or less, and the rolling material is twisted by rolling deformation in a square hole shape over the entire length from the front end to the rear end of the rolled material. The form performed by the roll clearance setting for obtaining the action of restoring the shape is shown. The following roll gap setting steps (S10 to S110) can be executed by a process computer that controls the rolling process described above. First, based on the rolling plan, necessary rolling information such as material billet dimensions, product dimensions, and hole schedule is read for the rolled material (rolling lot) (S10), and the rolling mill RM1 (see FIG. 7, see below). ) Of the square rolled material immediately before the oval hole mold, that is, the vertical dimension Hs of the square hole SG of the rolling mill RFV (see FIG. 1; S20). Next, the width dimension W of the rolling material on the exit side of the rhomboid DG of the rolling mill (RF-1) H immediately before this square hole mold is assumed (S30), and the reduction amount a (FIG. 1) in the square hole SG. Reference) is calculated (S40). Then, using the relationship between the width dimension W of the rhomboid exit side rolled material DS and the arc radius r of the free surface, which has been associated in advance in the form of a table value or a mathematical formula (S50), this rhombus rolling The arc portion radius r of the material DS is calculated (S60). When the ratio r / a is within the range of 0.1 to 0.3 (S70), the width dimension W of the rhombus type outlet side rolled material DS, which is associated in advance in the form of a table value or a mathematical expression, etc. The roll gap sd of the rhombus type DG is set (S100) using the relationship between the roll gap Sd of the rhombus type DG (see FIG. 2B) (S90). Hereinafter, the roll gap of the rolling mill (RF-2) V immediately before the rhombus type DG and the hole mold of the rolling mill on the upstream side thereof are set (S110). When the ratio r / a is not within the range of 0.1 to 0.3, the width dimension W of the diamond rolled material DS is corrected (S90), and the ratio r / a is 0.1 to 0.3. Steps S40 to S80 are repeated until it falls within the range. In this way, the rhombus-angle-diamond-angle ratio is set so that the ratio r / a in the square hole shape of the rolling mill RFV immediately before the oval hole shape of the rolling mill RM1 falls within the range of 0.1 to 0.3. It is possible to set a roll gap of a hole type series or a rhomboid-square hole type series.

  FIG. 11 shows that the rolling process after setting the above-mentioned roll gap is performed so that the ratio r / a falls within the range of 0.1 to 0.3 when the dimensional variation of the diamond rolling material DS occurs. The flow which controls the width dimension of material DS is shown. After the start of rolling, the width dimension W of the rolling material DS on the exit side of the rhomboid DG is measured by the dimension measuring device 5 installed on the exit side of the rolling mill (RF-1) H (see FIG. 7, the same applies hereinafter) ( S10a). Using this actually measured width dimension Wa, an actual reduction amount a in the square hole type SG of the rolling mill RFV is calculated (20a). Using the relationship between the aforementioned width dimension W of the rolled diamond DS and the arc portion r of the free surface (S30a), the arc portion radius r is calculated from the actually measured width dimension Wa (S40a). When the ratio r / a is not within the range of 0.1 to 0.3 (S50a), the rolling mill (RF-2) immediately before the rhomboid DG of the rolling mill (RF-1) H associated in advance. ) Using the relationship between the V-hole-shaped roll gap s and the width W of the rolled material on the exit side of the rhomboid DG (S60a), the hole of the rolling mill (RF-2) V immediately before the rhomboid-type DG The roll gap s of the mold is adjusted (S70a), and steps S10a to S60a are repeated until the ratio r / a falls within the range of 0.1 to 0.3. When the ratio r / a is within the range of 0.1 to 0.3, the rolling of the rolled material is continued (S80a), and after the rolling is finished, the width of the diamond rolled material DS of the next rolled material The dimension W is controlled (S90a). In this way, the ratio r / a can be kept in the range of 0.1 to 0.3 from the front end to the rear end of the rolled material, and the twist of the rolled material in the square hole type SG is restored. It becomes possible to properly bite the oval hole mold of the rolling mill RM1.

  When a 155 mm square billet (material: SCM435) was heated to 1100 ° C. and rolled into a wire with a diameter of 10 mm in the hot rolling line shown in FIG. 7, first the product dimensions (Φ10 mm) were supported. The rhomboid type shown in Table 1 (Roller (RF-1) H) is shown in Table 1 for the required rolling material dimensions (square dimension: 50 mm square) on the exit side of the square hole mold of the final rolling mill RFV of the rough rolling mill row 2. ) And the arc surface radius r of the free surface in correspondence with each other, the rhomboidal exit side of the rolling hole (RF-1) H immediately before the rolling amount a in the square hole type (rolling machine (RF-1) H). Rolling was carried out after setting each roll gap of the rough rolling mill row 2 so that the ratio r / a of the arc portion radius r of the free surface of the rolled material was 0.1 or more and 0.3 or less. During this rolling process, the dimension measuring instrument 5 (see FIG. 7) is used to measure the width dimension W of the rolled material on the rhomboid exit side and calculate the arc portion r of the free surface using the table in Table 1. When the ratio r / a is out of the range of 0.1 to 0.3, the rolling mill (RF-2) V immediately before the rhomboid type is used by using the table in Table 1 so that the ratio r / a falls within this range. The roll gap s was controlled and the surface flaw occurrence state of the product (Φ10 mm wire) was investigated. On the other hand, each roll gap of the rough rolling mill row 2 is set so that the ratio r / a does not fall within the range of 0.1 to 0.3, and the rolling mill (RF-2) V immediately before the rhombus type in the rolling process. The surface flaw occurrence state was investigated also about the product ((PHI) 10mm wire rod) rolled without controlling the roll gap s.

  The surface flaw occurrence state investigation was conducted by winding the coil, sampling at 10 positions from the front end side of the coil to the rear end side, removing the surface scale by pickling, and then visually observing the surface. The cross-section of the portion where the generation of wrinkles was observed was measured for the wrinkle depth by microscopic observation, and the ratio (%) of the number of wrinkles having a depth of 0.02 mm or more to the total number of wrinkles was obtained. FIG. 12 shows the results of investigation of the surface flaw occurrence state. From FIG. 12, it can be seen that the generation of surface defects having a depth of 0.02 mm or more is suppressed by adjusting the ratio r / a to be within the range of 0.1 to 0.3. On the other hand, when the ratio r / a is not within the range of 0.1 to 0.3, it can be seen that surface defects having a depth of 0.02 mm or more are generated.

  The present invention can be applied not only to the above-described wire rod rolling but also to the case where the product is rolled into a bar steel. The technical idea of the present invention can also be applied to a square-oval-square hole type series. That is, as shown in FIG. 13, the width dimension W of the oval rolled mold exit side oval rolled material OS and the arcuate radius r of the free surface in the square-oval-square hole type series are associated in advance. The radius r of the arc portion is predicted from the above, and the roll gap of the square hole type immediately before the oval hole type is adjusted, so that the ratio r / a is kept within the required range, and the right square hole type SG is properly bitten. You can also make it happen.

It is explanatory drawing which shows the top part radius r of the free surface of a diamond rolling material, and the amount of reduction a in a square hole type | mold. (A) It is explanatory drawing which shows the width dimension W of the rolling material of a rhombus type exit side, and the circular arc part radius r of a free surface. (B) It is explanatory drawing which shows the hole-shaped roll gap s immediately before a rhombus type. It is explanatory drawing which shows the element division in the rolling material cross section of a deformation | transformation analysis. It is explanatory drawing which shows the element division in the rolling material vertical cross section of a deformation | transformation analysis. It is explanatory drawing which shows the influence which the ratio r / a of the top part (free surface circular arc part) radius r of a entrance side rolling material and the amount of reduction a in a hole shape has on the twist recovery rate Rt. It is explanatory drawing which shows the generation | occurrence | production rate (%) of the surface flaw with respect to ratio r / a when it finishes in a round-shaped exit side material by three-pass experimental rolling of a square hole type-oval hole type-round hole type. It is explanatory drawing which shows typically the principal part of a wire and a bar rolling line. It is explanatory drawing which shows an example which matched the rolling material width dimension W of the rhombus type | mold exit side, and the circular arc part radius r of the free surface. It is explanatory drawing which shows an example which matched the roll gap of the hole type just before a rhombus type | mold, and the rolling material width dimension W of the rhombus type exit side. It is explanatory drawing which shows the flow of the roll clearance setting in embodiment. It is explanatory drawing which shows the flow of width dimension control of the rolling material of the rhombus type | mold exit side in embodiment. It is explanatory drawing which shows the generation | occurrence | production condition of the surface flaw with respect to ratio r / a in actual machine rolling. It is explanatory drawing which shows the top part (arc part) radius r of the free surface of an oval rolling material, and the reduction amount a in a square hole type | mold. It is explanatory drawing which shows typically the case where the rolling material with a small top radius of a square hole type | mold exit side is rolled in the state twisted by the oval hole type | mold. It is explanatory drawing which shows typically the case where the rolling material with a large top radius of the square hole type | mold exit side is rolled in the state twisted by the oval hole type | mold.

Explanation of symbols

1: Heating furnace 2: Rough rolling mill row 3: Intermediate rolling mill row 4: Material billet (rolled material) 5: Dimension measuring device DS: Rhombus rolled material SR: Square rolled material OS: Oval rolled material DG: Rhombus type Hole type SG: Square hole type

Claims (2)

  From the heated material billet, the cross-sectional area is sequentially reduced by the rhomboid-diamond-diamond hole type series or rhombo-diamond-square hole type series provided on the rolls of a plurality of rolling mills and the oval hole type immediately thereafter. A hot rolling method for wire rods and steel bars, in which the cross-sectional area is further reduced by the subsequent hole mold series to finish the rolled material to the required product dimensions, and the diamond hole that engages with the square hole mold immediately before the oval hole mold When the radius of the arc portion of the free surface of the rolled material on the mold exit side is r and the amount of reduction in this square hole mold is a, the width dimension W of the rolled material on the exit side of the rhomboid mold and the arc portion of the free surface thereof The radius r is associated in advance, the arc radius r is predicted from the width W, and the rhombus-angle-diamond-angle hole is set so that the ratio r / a falls within the range of 0.1 to 0.3. Adjust the roll gap of the die series or the rhomboid-square hole type series to make the rolled material suitable for the oval hole type. Hot rolling method of wire-bars, characterized in that so as to incorporated seen. The width dimension W of the rolled material on the exit side of the rhombus type is previously associated with the hole type roll gap s immediately before the rhombus type, and the width dimension W of the rolled material on the exit side of the rhombus type is measured during rolling. Then, the radius r of the arc portion of the free surface of the rolled material, which is associated in advance, is calculated from the measured width dimension W, and the ratio r / a is not in the range of 0.1 to 0.3. 2. The wire rod according to claim 1 , wherein the ratio r / a is adjusted to fall within a range of 0.1 to 0.3 by adjusting the hole roll gap s just before the rhomboid mold. -Hot rolling method for steel bars.

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