Production method and process of hot-rolled ribbed steel bar

Production method and process of hot-rolled ribbed steel bar

Background technique:

In the current rebar market, hrb400e accounts for more. The microalloy strengthening method is the main way to produce hrb400e in the world. The microalloy is mainly vanadium alloy or niobium alloy, which consumes a lot of alloy resources every year. Due to limited mineral resources containing vanadium and niobium, the supply of these alloying elements is tight. Therefore, if the alloy content of hrb400e steel bar can be reduced, it will produce huge economic and social benefits.

In the existing technology, the double-wire rolling production line without reducing and sizing rolling mill generally adopts vanadium alloy strengthening to produce hrb400e, and the mass percentage content of vanadium is 0.035% to 0.045%.

Chinese patent cn104357741a discloses a kind of hrb400e high-strength earthquake-resistant steel coil and its production method. Through the method, the finished product is produced by a reducing and sizing rolling mill, which can ensure that the finishing rolled steel is rolled at a low temperature of 730~760 ℃ to obtain For finer grains, this method is not suitable for production lines without reducing sizing mills. Chinese patent cn110184516a discloses a preparation method of high wire φ6mm~hrb400e coiled screw. With the help of the strong rolling capacity of the equipment, low temperature rolling starts from the heating temperature, and the production without microalloying is realized. The disadvantage of this method is that The requirements for the strength and motor performance of the rough and medium rolling equipment are relatively high, especially for the production line of torsion rolling, which reduces the experimental life of the equipment and increases the maintenance cost of the equipment, and the yield strength of the high wire φ6mm~hrb400e coil produced by this method is surplus. Insufficient quantity, it is difficult to guarantee the performance qualification rate.

Technical implementation elements:

The present invention aims to provide a method for producing hot-rolled ribbed steel bars, particularly a method for producing hot-rolled coiled snails for high wire φ8~φ10mm~hrb400e, which overcomes the above-mentioned deficiencies of the prior art and reduces production costs.

Technical scheme of the present invention:

The production method of hot-rolled ribbed steel bar, the specification of ribbed steel wire rod is φ8~φ10mm, and the technological process includes heating – billeting – rough rolling – medium rolling – cooling – pre-finishing – cooling – finishing – cooling – spinning – Air-cooled roller table—coil collection—slow cooling; the chemical composition mass percentage of steel is c=0.20%~0.25%, si=0.40%~0.50%, mn=1.40%~1.60%, p≤0.045%, s ≤0.045%, v=0.015%~0.020%, the rest are Fe and unavoidable impurity elements; the key process steps include: the furnace temperature is 1070~1130℃, the prefinishing rolling temperature is 970~1000℃, and the finishing rolling temperature is 840~1000℃. 880℃; laying temperature 845~875℃; final rolling temperature is below the recrystallization temperature of austenite zone; rapid cooling by fan on air-cooled roller table, air volume is 100%; The temperature of the cover is 640~660℃, the temperature of the heat preservation cover is 600~620℃, and the time in the heat preservation cover is 45~55s.

The principle of the invention: in the temperature range of 840-880 ℃, the austenite grains are elongated by rolling deformation, but recrystallization does not occur. However, deformation bands are generated in the austenite grains, and the ends of the deformation bands are generally at the grain boundaries, and there are also deformation bands in the grains as apparent grain boundaries to divide the elongated austenite grains. During the transformation from austenite to ferrite, both the elongated austenite grain boundaries and the apparent grain boundary deformation zone act as nucleation sites for ferrite, resulting in the refinement of ferrite after transformation. Low temperature rolling in the finishing mill reduces the rolling load of the roughing and intermediate rolling mills and pre-finishing mills and increases the service life of the equipment.

The beneficial effects of the invention are as follows: by adding a small amount of v for microalloy strengthening, the yield strength is improved, v and c form carbides, which are precipitated during the cooling process after rolling, and play the role of precipitation strengthening. The hot-rolled wire rod of the invention has a tensile strength of 600-700mpa, a yield strength of 420-500mpa, an average yield strength of about 450mpa, and agt>10%, which ensures a sufficient margin. The yield strength is stable, and the performance qualification rate is above 99%. The invention technically solves the problem that the twist rolling mill is difficult to perform low-temperature rolling, reduces the cost on the premise of ensuring that the production capacity is not reduced, and brings about higher economic benefits.

Detailed ways

The content of the present invention is further described below in conjunction with the embodiments.

The production method of a group of high wire φ8mm~φ10mmhrb400e coiled snails. The rolling process is: outgoing temperature: 1080~1120℃, entering pre-finishing rolling 1030~1060℃, entering finishing rolling temperature: 850~870℃, spinning temperature: 850~870℃, fan air volume 100%, entering insulation cover temperature 640~660℃, 600~620℃ out of the heat preservation cover, the time in the heat preservation cover is 45~55s, and it cools naturally. The chemical composition of the wire rod of the embodiment of the present invention is shown in Table 1, and the mechanical properties of the wire rod of the embodiment of the present invention are shown in Table 2.

Chemical composition (wt%) of the wire rod of the table example

Table 2 Mechanical properties of example wire rods

The yield strength of the high wire φ8mm~φ10mmhrb400e coiled snails produced by the method of the invention is in the range of 420~500mpa, the agt is above 10%, the strength yield ratio is above 1.35, and the metallographic structure is mainly ferrite and pearlite. , stable performance, sufficient yield strength and agt margin, the success of this process is of great significance to reducing production costs and increasing profits for dual-line torsion rolling production lines with relatively old equipment.

Technical Features:
1. The production method of hot-rolled ribbed steel bar, the wire rod specification is φ8mm~φ10mm, and the technological process includes heating – billeting – rough rolling – medium rolling – cooling – pre-finishing – cooling – finishing – cooling – spinning – air Cold roller table—collecting coil—slow cooling, characterized in that: the chemical composition mass percentage of steel is c=0.20%~0.25%, si=0.40%~0.50%, mn=1.40%~1.60%, p≤0.045 %, s≤0.045%, v=0.015%~0.020%, the rest are fe and unavoidable impurity elements; the key process steps include: the tapping temperature is 1070~1130 °C, the pre-finishing temperature is 970~1000 °C, and the finishing rolling is carried out. The temperature is 840~880℃; the spinning temperature is 845~875℃; the final rolling temperature is below the recrystallization temperature of the austenite zone; it is rapidly cooled by the fan on the air-cooled roller table, and the air volume is 100%; the roller table is insulated by closing the insulation cover , the temperature of entering the insulation cover is 640~660℃, and the temperature of exiting the insulation cover is 600~620℃, and the time in the insulation cover is 45~55s.

Technical summary
The production method of hot-rolled ribbed steel bar, the spring steel hot-rolled wire rod specification is Φ8mm~Φ10mm, the chemical composition mass percentage content of the steel is C=0.20%~0.25%, Si=0.40%~0.50%, Mn =1.40%~1.60%, P≤0.045%, S≤0.045%, V=0.015%~0.020%, the rest are Fe and unavoidable impurity elements; the rolling process is: the furnace temperature is 1070~1130℃, and the pre-finishing is carried out. The rolling temperature is 970~1000℃, the finishing rolling temperature is 840~880℃; the spinning temperature is 845~875℃; the final rolling temperature is below the recrystallization temperature of the austenite region; %; After closing the insulation cover of the roller, the temperature of entering the insulation cover is 640~660℃, and the temperature of exiting the insulation cover is 600~620℃, and the time in the insulation cover is 45~55s. By adding a small amount of V alloy and finishing rolling at low temperature, the invention not only ensures the stable operation of the equipment, but also reduces the alloy content and the cost.