阅读说明：本技术 一种含铌微合金化hrb400e钢筋的控轧控冷生产工艺 (Controlled rolling and controlled cooling production process of niobium-containing microalloyed HRB400E steel bar ) 是由 赵璟珠 于 2020-05-27 设计创作，主要内容包括：本发明属于轧制工艺领域,具体涉及一种含铌微合金化HRB400E钢筋的控轧控冷生产工艺,工艺过程为：粗轧→中轧→冷却→精轧→分级冷却→冷床控温；钢坯加热温度控制在1070～1120℃,开轧温度控制在1000～1050℃,精轧温度控制在850～950℃,上冷床温度控制在850～900℃,通过本工艺批量生产的含铌微合金化HRB400E钢筋,其力学性能稳定,抗震性能优良,且强屈比较钒微合金化钢筋稍高,钢筋中的铌含量较低,降低了生产成本。(The invention belongs to the field of rolling process, and particularly relates to a controlled rolling and controlled cooling production process of niobium-containing microalloyed HRB400E steel bars, which comprises the following process steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the heating temperature of a steel billet is controlled to be 1070-1120 ℃, the initial rolling temperature is controlled to be 1000-1050 ℃, the finish rolling temperature is controlled to be 850-950 ℃, the temperature of an upper cooling bed is controlled to be 850-900 ℃, and the niobium-containing microalloyed HRB400E steel bar produced in batches by the process has stable mechanical property, excellent anti-seismic property, higher yield ratio than that of a vanadium microalloyed steel bar, lower niobium content in the steel bar and reduced production cost.)

1. A controlled rolling and controlled cooling production process of niobium-containing microalloyed HRB400E steel bars is characterized in that a billet with the section of 160 x 160mm is heated by a heating furnace and then rolled, and the rolling process comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the heating temperature of the steel billet is controlled to be 1070-1120 ℃, the initial rolling temperature is controlled to be 1000-1050 ℃, the finish rolling temperature is controlled to be 850-950 ℃, the temperature of the upper cooling bed is controlled to be 850-900 ℃, the chemical components of the steel billet comprise, by weight, 0.19-0.23% of C, 1.40-1.60% of Mn, 0.60-0.70% of Si, 0.010-0.015% of Nb, less than or equal to 0.04% of S and less than or equal to 0.04% of P.

2. The controlled rolling and controlled cooling production process of the niobium-containing microalloyed HRB400E steel bar as claimed in claim 1, wherein the rolled steel bar is a hot rolled ribbed steel bar with a diameter of 12-25 mm.

3. The controlled rolling and controlled cooling production process of the niobium-containing microalloyed HRB400E steel bar as claimed in claim 2, wherein the steel billet is rolled in a continuous rolling mill group, and the continuous rolling mill group comprises a roughing mill group (1), a middle mill group (2), a cooling water tank (3), a finishing mill group (4), a direct injection type grading and controlled cooling water tank (5) and a cooling bed (6) which are sequentially arranged according to the steel passing sequence.

4. The controlled rolling and controlled cooling production process of the niobium-containing microalloyed HRB400E steel bar as claimed in claim 3, wherein the roughing mill group (1) comprises four 550 model rolling mills and two 450 model rolling mills, the intermediate mill group (2) comprises four 450 model rolling mills and two 350 model rolling mills, and the finishing mill group (4) comprises six 350 model rolling mills.

5. The controlled rolling and controlled cooling production process of the niobium-containing microalloyed HRB400E steel bar as claimed in claim 4, wherein the cooling bed (6) is a stepping cooling bed, the cooling bed (6) is provided with a heat preservation device, and the phase change cooling speed can be controlled to be below 4 ℃/s.

Technical Field

The invention belongs to the field of rolling processes, and particularly relates to a controlled rolling and controlled cooling production process of niobium-containing microalloyed HRB400E steel bars.

Background

At present, HRB400E reinforcing bars are the mainstream of reinforcing bars for buildings, the production mode of HRB400E reinforcing bars is single for a long time, and the mode of ferrovanadium and vanadium-nitrogen microalloy is mainly adopted, so that the vanadium resource is in shortage and price is increased, the balanced use of the resource is not facilitated, the sustainable development concept is not met, and meanwhile, the production cost is too high.

From the perspective of reasonably and uniformly utilizing resources, the niobium (Nb) microalloying technology is a better choice for producing the 400 MPa-level reinforcing steel bar. When the past attempts at producing the niobium-containing HRB400E steel bar are made at home and abroad, the weight percentage of niobium in the steel bar needs to be 0.03-0.05% in order to ensure the performance of the steel bar. The higher niobium content not only increases the cost, but also causes problems, and in order to ensure that the carbonitride of niobium is fully dissolved into austenite, the steel billet needs to be heated to a higher temperature in the production, so that the probability of occurrence of cracks of the continuous casting billet is increased; a large-proportion bainite structure is easy to appear, and the problems of unobvious yield point of the steel bar, low elongation after fracture, brittle fracture and the like exist; therefore, a production process of niobium-containing microalloyed HRB400E steel bars, which is simple and feasible and has stable product performance, needs to be developed.

Disclosure of Invention

The invention overcomes the defects in the prior art and provides the controlled rolling and cooling production process of the niobium-containing microalloyed HRB400E steel bar, which has simpler process and more stable product performance.

In order to solve the technical problems, the invention adopts the technical scheme that:

a billet with a section of 160 x 160mm is heated by a walking beam type heating furnace and then enters a continuous rolling mill set for rolling, the heating temperature of the billet in the heating furnace is controlled to be 1070-1120 ℃, niobium is dissolved in austenite to form carbon and nitride at a higher temperature, the alloy in a solid solution state at a soaking temperature can play a role in preventing recrystallization, and when the soaking temperature is lower, partial undissolved microalloy carbonitrides exist and cannot prevent austenite from recrystallizing. Therefore, the heating temperature of the steel billet needs to be increased; the alloy elements can be dissolved by increasing the heating temperature, but too high soaking temperature can cause excessively large grains, which is unfavorable for the mechanical property of the product, and the niobium content is lower due to the design of the components of the steel billet, and the soaking temperature is comprehensively considered to be controlled to be 1070-1120 ℃.

The chemical components (weight percent) of the steel billet are 0.19-0.23 percent of C, 1.40-1.60 percent of Mn, 0.60-0.70 percent of Si, 0.010-0.015 percent of Nb, less than or equal to 0.04 percent of S, less than or equal to 0.04 percent of P, and the balance of iron element.

The continuous rolling unit comprises a roughing mill unit, a middle rolling mill unit, a cooling water tank, a finishing mill unit, a direct-injection type graded cooling water tank and a cooling bed which are sequentially arranged according to the steel passing sequence, and the rolling process comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the initial rolling temperature is controlled to be 1000-1050 ℃, the finish rolling temperature is controlled to be 850-950 ℃, and the temperature of the upper cooling bed is controlled to be 850-900 ℃.

The initial rolling is carried out according to a normal hot rolling process, the initial rolling temperature is higher than the austenite recrystallization temperature, so the initial rolling temperature is controlled to be 1000-1050 ℃; in the controlled rolling process, niobium has 2 functions, namely, the growth of austenite grains is prevented, and the recrystallization of austenite is inhibited; the process mainly relates to the control of deformation temperature, the temperature is controlled by using a cooling water tank between a middle rolling mill group and a finishing mill group in a continuous rolling mill group, so that the finish rolling meets the condition of low-temperature rolling, the rolling is carried out when austenite is not recrystallized at 850-950 ℃, the austenite is repeatedly deformed, crystal grains are elongated and generate a large number of deformation zones, favorable conditions are provided for nucleation of solid phase change, and niobium is precipitated in a crystal boundary, a subcrystal boundary and crystal grains in the cooling process after the rolling, so that the growth of ferrite after the phase change is prevented, the distribution in the crystal grains is more uniform, and the ferrite after the phase change is refined.

In order to prevent the deformed austenite grains from growing rapidly after rolling, the austenite grains after finish rolling enter a water tank for cooling, and meanwhile, in order to prevent the appearance of a super-cooled structure, three groups of graded cooling are carried out after rolling, the temperature of an upper cooling bed is controlled to be 850-900 ℃, and after cooling control, the fine austenite grains can effectively inhibit the generation of a bainite structure; in the north, because the environmental temperature is low in winter, in order to prevent the niobium-containing steel bar from generating bainite due to the excessively high cooling speed, certain heat preservation measures can be taken after the niobium-containing steel bar is put on a cooling bed during production, the phase change cooling speed is controlled below 4 ℃/s, and the requirement that the structure is pearlite and ferrite can be met.

Compared with the prior art, the invention has the following beneficial effects: the HRB400E steel bar produced in batch by the process has stable mechanical property and excellent shock resistance, the yield ratio is slightly higher than that of the vanadium microalloyed steel bar, the crystal grains of the product are fine, uniform and equiaxial, and the grain size is 9.5 grade; and microscopic metallographic analysis is carried out on the product, the matrix structure of the product is pearlite + ferrite, the obtained result meets the requirements on the metallographic structure in the GB/T1499.2-2018 standard, the process flow is simpler and easier to implement, the niobium content in the steel bar is lower, and the production cost is reduced.

Drawings

The invention is further described below with reference to the accompanying drawings.

Fig. 1 is a schematic view of the structure of the continuous rolling mill train of the present invention.

In the figure: 1 is a rough rolling unit, 2 is a middle rolling unit, 3 is a cooling water tank, 4 is a finishing rolling unit, 5 is a direct-injection type graded cooling water tank, and 6 is a cooling bed.

Detailed Description

The present invention is further illustrated by the following specific examples.

Example 1

A billet with a section of 160 multiplied by 160mm is heated by a walking beam type heating furnace and then enters a continuous rolling mill set for rolling, and the chemical components (weight percent) of the billet are C:0.19%, Mn:1.40%, Si:0.60%, Nb:0.010%, S: 0.04%, P: 0.04% and the balance mainly comprising iron.

The continuous rolling unit comprises a roughing rolling unit 1, a middle rolling unit 2, a cooling water tank 3, a finishing rolling unit 4, a direct injection type graded control cold water tank 5 and a cooling bed 6 which are sequentially arranged according to the steel passing sequence; the roughing mill group 1 comprises four 550-model rolling mills and two 450-model rolling mills, the intermediate mill group 2 comprises four 450-model rolling mills and two 350-model rolling mills, and the finishing mill group 4 comprises six 350-model rolling mills; the cooling water tank 3 can realize the rolling control function, and the direct-injection type graded rolling control water tank 5 is arranged into five groups, so that the requirements of graded cooling after rolling can be met.

The rolling process of the steel billet comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the steel rolling temperature is controlled to be 1000-1050 ℃, the cooling water tank 3 arranged between the middle rolling mill group 2 and the finishing mill group 4 can control the steel finishing rolling temperature to be 850-950 ℃, after the steel is finished, the direct-injection type graded control cold water tank 5 is used for graded cooling, the temperature of a steel upper cooling bed can be controlled to be 850-900 ℃, the cooling bed 6 is a stepping cooling bed, the cooling bed 6 is provided with a heat preservation facility, and the phase change cooling speed can be controlled to be below 4 ℃/s; the steel bar produced by the process is hot-rolled ribbed steel bar with phi 12-phi 25 mm.

Example 2

A billet with a section of 160 multiplied by 160mm is heated by a walking beam type heating furnace and then enters a continuous rolling mill set for rolling, and the chemical components (weight percent) of the billet are C: 0.20%, Mn: 1.50%, Si: 0.65%, Nb: 0.013%, S: 0.03%, P: 0.03 percent, and the balance of iron element.

The continuous rolling unit comprises a roughing rolling unit 1, a middle rolling unit 2, a cooling water tank 3, a finishing rolling unit 4, a direct injection type graded control cold water tank 5 and a cooling bed 6 which are sequentially arranged according to the steel passing sequence; the roughing mill group 1 comprises four 550-model rolling mills and two 450-model rolling mills, the intermediate mill group 2 comprises four 450-model rolling mills and two 350-model rolling mills, and the finishing mill group 4 comprises six 350-model rolling mills; the cooling water tank 3 can realize the rolling control function, and the direct-injection type graded rolling control water tank 5 is arranged into five groups, so that the requirements of graded cooling after rolling can be met.

The rolling process of the steel billet comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the steel rolling temperature is controlled to be 1000-1050 ℃, the cooling water tank 3 arranged between the middle rolling mill group 2 and the finishing mill group 4 can control the steel finishing rolling temperature to be 850-950 ℃, after the steel is finished, the direct-injection type graded control cold water tank 5 is used for graded cooling, the temperature of a steel upper cooling bed can be controlled to be 850-900 ℃, the cooling bed 6 is a stepping cooling bed, the cooling bed 6 is provided with a heat preservation facility, and the phase change cooling speed can be controlled to be below 4 ℃/s; the steel bar produced by the process is hot-rolled ribbed steel bar with phi 12-phi 25 mm.

Example 3

A billet with a section of 160 multiplied by 160mm is heated by a walking beam type heating furnace and then enters a continuous rolling mill set for rolling, and the chemical components (weight percent) of the billet are C: 0.21%, Mn: 1.60%, Si: 0.70%, Nb: 0.015%, S: 0.02%, P: 0.02% and the balance mainly iron.

The continuous rolling unit comprises a roughing rolling unit 1, a middle rolling unit 2, a cooling water tank 3, a finishing rolling unit 4, a direct injection type graded control cold water tank 5 and a cooling bed 6 which are sequentially arranged according to the steel passing sequence; the roughing mill group 1 comprises four 550-model rolling mills and two 450-model rolling mills, the intermediate mill group 2 comprises four 450-model rolling mills and two 350-model rolling mills, and the finishing mill group 4 comprises six 350-model rolling mills; the cooling water tank 3 can realize the rolling control function, and the direct-injection type graded rolling control water tank 5 is arranged into five groups, so that the requirements of graded cooling after rolling can be met.

The rolling process of the steel billet comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the steel rolling temperature is controlled to be 1000-1050 ℃, the cooling water tank 3 arranged between the middle rolling mill group 2 and the finishing mill group 4 can control the steel finishing rolling temperature to be 850-950 ℃, after the steel is finished, the direct-injection type graded control cold water tank 5 is used for graded cooling, the temperature of a steel upper cooling bed can be controlled to be 850-900 ℃, the cooling bed 6 is a stepping cooling bed, the cooling bed 6 is provided with a heat preservation facility, and the phase change cooling speed can be controlled to be below 4 ℃/s; the steel bar produced by the process is hot-rolled ribbed steel bar with phi 12-phi 25 mm.

Example 4

A billet with a section of 160 multiplied by 160mm is heated by a walking beam type heating furnace and then enters a continuous rolling mill set for rolling, and the chemical components (weight percent) of the billet are C: 0.22%, Mn:1.40%, Si:0.60%, Nb:0.010%, S: 0.04%, P: 0.04% and the balance mainly comprising iron.

The continuous rolling unit comprises a roughing rolling unit 1, a middle rolling unit 2, a cooling water tank 3, a finishing rolling unit 4, a direct injection type graded control cold water tank 5 and a cooling bed 6 which are sequentially arranged according to the steel passing sequence; the roughing mill group 1 comprises four 550-model rolling mills and two 450-model rolling mills, the intermediate mill group 2 comprises four 450-model rolling mills and two 350-model rolling mills, and the finishing mill group 4 comprises six 350-model rolling mills; the cooling water tank 3 can realize the rolling control function, and the direct-injection type graded rolling control water tank 5 is arranged into five groups, so that the requirements of graded cooling after rolling can be met.

The rolling process of the steel billet comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the steel rolling temperature is controlled to be 1000-1050 ℃, the cooling water tank 3 arranged between the middle rolling mill group 2 and the finishing mill group 4 can control the steel finishing rolling temperature to be 850-950 ℃, after the steel is finished, the direct-injection type graded control cold water tank 5 is used for graded cooling, the temperature of a steel upper cooling bed can be controlled to be 850-900 ℃, the cooling bed 6 is a stepping cooling bed, the cooling bed 6 is provided with a heat preservation facility, and the phase change cooling speed can be controlled to be below 4 ℃/s; the steel bar produced by the process is hot-rolled ribbed steel bar with phi 12-phi 25 mm.

Example 5

A billet with a section of 160 multiplied by 160mm is heated by a walking beam type heating furnace and then enters a continuous rolling mill set for rolling, and the chemical components (weight percent) of the billet are C: 0.23%, Mn: 1.50%, Si: 0.65%, Nb: 0.013%, S: 0.03%, P: 0.03 percent, and the balance of iron element.

The continuous rolling unit comprises a roughing rolling unit 1, a middle rolling unit 2, a cooling water tank 3, a finishing rolling unit 4, a direct injection type graded control cold water tank 5 and a cooling bed 6 which are sequentially arranged according to the steel passing sequence; the roughing mill group 1 comprises four 550-model rolling mills and two 450-model rolling mills, the intermediate mill group 2 comprises four 450-model rolling mills and two 350-model rolling mills, and the finishing mill group 4 comprises six 350-model rolling mills; the cooling water tank 3 can realize the rolling control function, and the direct-injection type graded rolling control water tank 5 is arranged into five groups, so that the requirements of graded cooling after rolling can be met.

The rolling process of the steel billet comprises the following steps: rough rolling → medium rolling → cooling → finish rolling → graded cooling → cooling bed temperature control; the steel rolling temperature is controlled to be 1000-1050 ℃, the cooling water tank 3 arranged between the middle rolling mill group 2 and the finishing mill group 4 can control the steel finishing rolling temperature to be 850-950 ℃, after the steel is finished, the direct-injection type graded control cold water tank 5 is used for graded cooling, the temperature of a steel upper cooling bed can be controlled to be 850-900 ℃, the cooling bed 6 is a stepping cooling bed, the cooling bed 6 is provided with a heat preservation facility, and the phase change cooling speed can be controlled to be below 4 ℃/s; the steel bar produced by the process is hot-rolled ribbed steel bar with phi 12-phi 25 mm.

The above embodiments are merely illustrative of the principles of the present invention and its effects, and do not limit the present invention. It will be apparent to those skilled in the art that modifications and improvements can be made to the above-described embodiments without departing from the spirit and scope of the invention. Accordingly, it is intended that all equivalent modifications or changes be made by those skilled in the art without departing from the spirit and technical spirit of the present invention, and be covered by the claims of the present invention.