CN111191338A - Method for preventing transverse rib in equal-rib-height steel bar from cracking due to stress concentration - Google Patents
Method for preventing transverse rib in equal-rib-height steel bar from cracking due to stress concentration Download PDFInfo
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- 238000005336 cracking Methods 0.000 title claims abstract description 14
- 238000003754 machining Methods 0.000 claims abstract description 8
- 230000007704 transition Effects 0.000 claims abstract description 8
- 229910001294 Reinforcing steel Inorganic materials 0.000 claims description 2
- 238000005452 bending Methods 0.000 abstract description 18
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- 238000005096 rolling process Methods 0.000 description 2
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- 239000004566 building material Substances 0.000 description 1
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Abstract
the invention discloses a method for avoiding cracking of a transverse rib in a steel bar with equal rib height due to stress concentration, which is characterized in that the arc transition at the intersection of the transverse rib and the inner diameter surface of the steel bar is increased by reducing the oblique angle α of the transverse rib in the steel bar with equal rib height and reducing the distance between the tail sections of the transverse rib, and simultaneously, the stress condition of the root of the transverse rib of steel can be effectively improved and the bending property of the steel is improved by optimizing a hole pattern system and improving the machining mode of the transverse rib.
Description
Technical Field
The invention relates to the field of small-sized section steel, in particular to a method for preventing transverse ribs in steel bars with equal rib height from cracking due to stress concentration.
Background
The steel bars with equal rib height are mainly used for reinforced concrete structural engineering of highways, railways, bridges, hydropower, houses, municipal construction and the like, are important building materials, and are firmer than the combination of common square steel and round steel. Cracks which cannot be found by naked eyes of the steel bars with equal rib height are an important parameter of cold bending, and the steel bars with equal rib height are easy to form macroscopic transverse cracks at the roots of the transverse ribs due to the unique transverse rib shapes, so that the quality stability of products is reduced, and the cost is obviously increased.
Disclosure of Invention
the technical problem to be solved by the invention is to provide a method for avoiding the cracking of the transverse rib in the steel bar with equal rib height due to stress concentration, aiming at the defects of the prior art, the method for avoiding the cracking of the transverse rib in the steel bar with equal rib height due to stress concentration enables the arc transition at the intersection of the transverse rib and the inner diameter surface of the steel bar to be increased by reducing the oblique angle α of the transverse rib of the steel bar, reducing the distance between the tail sections of the transverse rib and optimizing the hole pattern processing of the finished steel bar with equal rib height, thereby increasing the fracture resistance of the transverse rib, reducing the probability of the root crack of the transverse rib and obviously improving the product quality.
In order to solve the technical problems, the invention adopts the technical scheme that:
a method for avoiding transverse rib cracking in steel bar with equal rib height due to stress concentration comprises the steps of processing and optimizing a finished hole pattern of the steel bar with equal rib height by reducing an oblique angle α of the transverse rib in the steel bar with equal rib height and reducing the distance between the tail sections of the transverse rib, so that the arc transition at the intersection of the transverse rib and the inner diameter surface of the steel bar is increased, the fracture resistance of the transverse rib is increased, and the probability of the occurrence of cracks at the root of the transverse rib is reduced, wherein the data after the oblique angle α of the transverse rib and the distance between the tail sections of the transverse rib are reduced are as follows:
wherein, the distance between the tail ends of the transverse ribs refers to the projection distance of the tail ends of the two corresponding transverse ribs on a plane vertical to the axis of the reinforcing steel bar.
the selection method of the specific value of the adjusted transverse rib oblique angle α comprises the steps of drawing a steel bar model with the same rib height of the related specification and a corresponding adjusted transverse rib tail end distance range by using modeling software, and selecting the transverse rib oblique angle α as small as possible under the conditions that the transverse rib tail end distance range and machining allowance are met.
The modeling software is AutoCAD.
The formula for calculating the end-to-end distance E of the cross rib is as follows:
E＝C-L
wherein, L is 2H/tan α + B
0.5D≤C≤0.7D
wherein C is the distance between the transverse ribs, α is the bottom width of the transverse ribs, H is the height of the transverse ribs, B is the top width of the transverse ribs, alpha is the oblique angle of the transverse ribs, and D is the diameter of the steel bars with equal rib height.
when the specific value of the oblique angle alpha of the transverse rib is adjusted, the range of the distance E between the tail ends of the transverse rib is met, and meanwhile, the distance C between the transverse ribs is in a positive tolerance.
The invention has the following beneficial effects:
(1) the transverse rib oblique angle α in the steel bars with equal height has close relation with the stress concentration degree, the positive pressure value N acting on the side surface of the transverse rib is reduced along with the reduction of the angle α, the bending stress value delta f is reduced, and the stress concentration trend is relieved along with the reduction of the angle α.
(2) By optimizing the hole type system and improving the transverse rib processing mode, the stress condition of the root of the steel transverse rib can be effectively improved, and the bending performance of the steel is improved. The method is suitable for the bending processing environment of the steel bars in the market, and avoids improving the bending performance of the steel materials by increasing alloy components and improving the cooling control temperature. Therefore, the investment of alloy elements can be reduced, and the method has great practical significance for reducing the production cost of enterprises and improving the market competitiveness.
Drawings
Fig. 1 is a picture showing the cracking of a cross rib due to stress concentration in a prior art medium rib steel bar.
FIG. 2 shows a schematic representation of the relationship between cross-rib angle and cross-rib tip spacing.
Figure 3 shows a cross rib force analysis diagram.
Fig. 4 shows a picture of a cross rib in a steel bar with equal rib height after the method of the invention is adopted.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific preferred embodiments.
In the description of the present invention, it is to be understood that the terms "left side", "right side", "upper part", "lower part", etc., indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and that "first", "second", etc., do not represent an important degree of the component parts, and thus are not to be construed as limiting the present invention. The specific dimensions used in the present example are only for illustrating the technical solution and do not limit the scope of protection of the present invention.
A method for preventing transverse rib in steel bar with equal rib height from cracking due to stress concentration includes such steps as reducing the oblique angle alpha of transverse rib and the distance between tail sections of transverse rib, optimizing the finished hole pattern of steel bar with equal rib height, increasing the arc transition at the intersection between transverse rib and internal diameter surface of steel bar, increasing the anti-breaking power of transverse rib and decreasing the crack probability of root of transverse rib.
The transverse rib spacing C should meet the design requirements of ISO6935-2 standard, and the current specification and the corresponding finished hole type parameters are shown in Table 1.
TABLE 1 Current Specifications and corresponding finished hole pattern parameters
the relevant specifications and corresponding transverse rib spacing values are drawn by modeling software such as AutoCAD and the like, and the transverse rib oblique angle alpha is reduced as far as possible within the range conforming to the transverse rib spacing and the condition line allowed by machining.
when the oblique angle alpha of the transverse rib is reduced, machining factors comprise the influence of forward sliding on the distance, the reduction of the roll diameter after the groove worn roll is repaired and the like.
The control method for avoiding the reduction of the roll diameter of the repaired groove worn roll comprises the following steps: under the condition that the number of the transverse rib grooves is unchanged, the transverse rib spacing is reduced, but the spacing value does not exceed the negative deviation value after the transverse rib spacing value is reduced. When the roller is turned to a certain size, the transverse rib spacing exceeds the negative deviation value, at the moment, all the grooves are required to be turned, and the number of the transverse rib grooves meeting the spacing tolerance requirement is selected again. Therefore, in order to prolong the service life of the roller as much as possible and reduce the roller consumption and the production cost, a certain degree of positive deviation value is selected to increase the heavy turning times when the distance value of the transverse ribs is selected; the limit value of the distance deviation value is that the distance increase value caused by forward slip during rolling is smaller than the distance positive deviation value, and meanwhile, a negative deviation value exceeding the distance cannot be generated in the process of heavy vehicle.
the adjusted cross rib oblique angle alpha and the cross rib end section distance are shown in table 2.
TABLE 2 adjustment of the bevel angle of the front and rear transverse ribs and the distance between the end sections of the transverse ribs
the specific value of the adjusted transverse rib oblique angle α is selected by drawing the equal rib height steel bar model of the related specification and the corresponding adjusted transverse rib tail end distance range by modeling software again, and selecting the transverse rib oblique angle α as small as possible under the condition of meeting the transverse rib tail end distance range and the practical machining allowance of a user.
The distance between the tail ends of the transverse ribs refers to the projection distance of the tail ends of the two corresponding transverse ribs on a plane vertical to the axis of the steel bar. The value of which directly affects the relative rib area of the equal-height rib steel bars. The maximum distance value of the transverse rib ends is specified in the standard, but in the machining of the transverse ribs, the transverse ribs and the longitudinal ribs are crossed, and the gap value of the transverse rib ends is artificially increased, so that the reasonable distance value of the transverse rib ends is ensured from the design and machining links to meet the requirement of the relative rib area. In actual production, since a certain roll gap exists between the rolls and is ensured, the roll gap value is generally designed according to the standard longitudinal rib width, and the roll gap value is contained in the range of the distance between the tail ends of the transverse ribs, the roll gap value is generally adjusted to be equal to or slightly smaller than the width of the longitudinal ribs in operation, and further, the distance between the tail ends of the transverse ribs is ensured not to be increased and exceed the maximum gap value.
As shown in fig. 2, the formula for calculating the distance E between the ends of the ribs is as follows:
E＝C-L
wherein, L is 2H/tan α + B
0.5D≤C≤0.7D
wherein C is the distance between the transverse ribs, α is the bottom width of the transverse ribs, H is the height of the transverse ribs, B is the top width of the transverse ribs, alpha is the oblique angle of the transverse ribs, and D is the diameter of the steel bars with equal rib height.
As shown in fig. 3, the force analysis of the transverse rib shows that:
δf＝M/W＝(Nsinα+Nmcosα)l/W
wherein M is bending moment, W is bending section modulus, α is transverse rib oblique angle, l is action moment, M is friction coefficient, N is positive pressure borne by the transverse rib, and delta f is bending stress value.
In the prior art, when the steel bars with equal height ribs are subjected to cold bending, bending stress is generated under the action of bending moment, so that the tensile force of the outer surface of the bent part of the steel bar is increased, the plasticity and the toughness of the root of the transverse rib are far smaller than those of the base circle part, and the cracking probability of the root of the transverse rib is greatly increased.
The arc transition at the intersection of the transverse rib and the inner diameter surface of the steel bar is smaller by observing the surface shape of the steel bar and the surface quality of a roller, uneven deformation is easy to generate during rolling, so that the root of the transverse rib and the surface of a matrix generate tensile stress, the steel bar is influenced by the bending stress in the cold bending process, the bent part of the steel bar is always in a tensile stress state, and the plasticity and the toughness of the root of the transverse rib are smaller than those of the base circle part under the influence of the residual tensile stress, so that the fracture resistance of the steel bar is reduced.
according to the invention, the distance C between the tail ends of the transverse ribs is redesigned and reduced, so that the oblique angle α of the transverse ribs is reduced, the residual stress at the transition position is reduced, the contact area between the root part and the base circle is increased, and the bending stress delta f is generated between the root part of the transverse ribs and the surface of the base circle.
after the new process method is executed, the generation rate of the cold bending cracks at the root part of the transverse rib of the steel bar is basically eliminated, and the optimization of the process finds that the method for reducing the oblique angle α of the transverse rib of the steel bar, reducing the distance between the tail sections of the transverse rib and optimizing the finished hole pattern of the steel bar with equal rib height increases the arc transition at the intersection of the transverse rib of the steel bar and the inner diameter surface, increases the fracture resistance, can reduce the probability of the cracks at the root part of the transverse rib compared with the traditional finished hole pattern, obviously improves the product quality, and shows specific experimental results as table 3, and shows the surface condition of the steel bar after the cold bending test as shown.
TABLE 3 test Steel Cold bending results
Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the details of the embodiments, and various equivalent modifications can be made within the technical spirit of the present invention, and the scope of the present invention is also within the scope of the present invention.
Claims (5)
1. A method for avoiding cracking of a transverse rib in a steel bar with equal rib height due to stress concentration is characterized in that a finished hole pattern of the steel bar with equal rib height is processed and optimized by reducing a transverse rib oblique angle α in the steel bar with equal rib height and reducing the distance between the tail sections of the transverse ribs, so that the arc transition at the intersection of the transverse rib and the inner diameter surface of the steel bar is increased, the fracture resistance of the transverse rib is increased, and the probability of crack generation at the root of the transverse rib is reduced, wherein the data after the transverse rib oblique angle α and the distance between the tail sections of the transverse rib are reduced are as follows:
wherein, the distance between the tail ends of the transverse ribs refers to the projection distance of the tail ends of the two corresponding transverse ribs on a plane vertical to the axis of the reinforcing steel bar.
2. the method for avoiding the cracking of the cross rib in the steel bar with equal rib height due to the stress concentration as claimed in claim 1, wherein the specific value of the adjusted cross rib bevel α is selected by using modeling software to draw a model of the steel bar with equal rib height of the related specification and a corresponding adjusted end distance range of the cross rib, and selecting the cross rib oblique angle alpha as small as possible under the conditions of conforming to the end distance range of the cross rib and the allowance of machining.
3. The method for preventing the transverse rib of the steel bar with equal rib height from cracking caused by stress concentration according to claim 2, wherein the method comprises the following steps: the modeling software is AutoCAD.
4. The method for preventing the transverse rib of the steel bar with equal rib height from cracking caused by stress concentration according to claim 2, wherein the method comprises the following steps: the formula for calculating the end-to-end distance E of the cross rib is as follows:
E＝C-L
wherein, L is 2H/tan α + B
0.5D≤C≤0.7D
wherein C is the distance between the transverse ribs, α is the bottom width of the transverse ribs, H is the height of the transverse ribs, B is the top width of the transverse ribs, alpha is the oblique angle of the transverse ribs, and D is the diameter of the steel bars with equal rib height.
5. the method of claim 4, wherein the specific value of the bevel angle α of the rib is adjusted to fit the range of the end distance E of the rib and to maintain the rib spacing C within a positive tolerance.
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110899327A (en) * | 2019-11-20 | 2020-03-24 | 盐城市联鑫钢铁有限公司 | Process method for solving problem that maximum clearance at tail end of transverse rib of phi 8mm spiral shell exceeds standard |
| CN112588820A (en) * | 2020-12-25 | 2021-04-02 | 首钢长治钢铁有限公司 | Production method of hot-rolled mining anchor rod steel |
| CN112858623A (en) * | 2021-01-04 | 2021-05-28 | 广西柳钢华创科技研发有限公司 | Method for judging whether ribbed steel bar is reasonable in appearance and reinforcing strength of ribbed steel bar |
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| US4895027A (en) * | 1988-01-19 | 1990-01-23 | Battelle Development Corporation | Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens |
| CN102168473A (en) * | 2011-01-30 | 2011-08-31 | 莱芜钢铁股份有限公司 | Large-specification ribbed reinforcing steel bars and machining process thereof |
| CN108714623A (en) * | 2018-05-14 | 2018-10-30 | 盐城市联鑫钢铁有限公司 | A kind of process for solving the problems, such as large gauge ribbed bar clod wash and splitting |
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4895027A (en) * | 1988-01-19 | 1990-01-23 | Battelle Development Corporation | Determining plane strain fracture toughness and the J-Integral for solid materials using stress field modified miniature specimens |
| CN102168473A (en) * | 2011-01-30 | 2011-08-31 | 莱芜钢铁股份有限公司 | Large-specification ribbed reinforcing steel bars and machining process thereof |
| CN108714623A (en) * | 2018-05-14 | 2018-10-30 | 盐城市联鑫钢铁有限公司 | A kind of process for solving the problems, such as large gauge ribbed bar clod wash and splitting |
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110899327A (en) * | 2019-11-20 | 2020-03-24 | 盐城市联鑫钢铁有限公司 | Process method for solving problem that maximum clearance at tail end of transverse rib of phi 8mm spiral shell exceeds standard |
| CN112588820A (en) * | 2020-12-25 | 2021-04-02 | 首钢长治钢铁有限公司 | Production method of hot-rolled mining anchor rod steel |
| CN112588820B (en) * | 2020-12-25 | 2022-10-28 | 首钢长治钢铁有限公司 | Production method of hot-rolled mining anchor rod steel |
| CN112858623A (en) * | 2021-01-04 | 2021-05-28 | 广西柳钢华创科技研发有限公司 | Method for judging whether ribbed steel bar is reasonable in appearance and reinforcing strength of ribbed steel bar |
| CN112858623B (en) * | 2021-01-04 | 2022-11-18 | 广西柳钢华创科技研发有限公司 | Method for judging whether ribbed steel bar is reasonable in appearance and reinforcing strength of ribbed steel bar |
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Address after: 215600 Shagang Science and Technology Building, Jinfeng Town, Zhangjiagang City, Suzhou City, Jiangsu Province Patentee after: Jiangsu Shagang Steel Co.,Ltd. Country or region after: China Patentee after: JIANGSU SHAGANG GROUP Co.,Ltd. Address before: Suzhou City, Jiangsu province 215625 Zhangjiagang City Jin Fengzhen Shagang Technology Building Patentee before: ZHANGJIAGANG HONGCHANG STEEL PLATE Co.,Ltd. Country or region before: China Patentee before: JIANGSU SHAGANG GROUP Co.,Ltd. |