CN103225044B - Steel for vanadium micro alloying low temperature steel bar and process for rolling steel - Google Patents

Abstract

The invention discloses a vanadium microalloyed steel for low-temperature reinforcement and a rolling process thereof. The steel for low-temperature reinforcement has a chemical composition ratio of C: 0.05-0.15% and Si: 0.15-0.40% in weight percentage. , Mn: 1.40-1.60%, P≤0.010%, S≤0.010%, Ni: 0.50-2.00%, Cu: 0.10-0.80%, V: 0.020-0.080%, the rest is Fe and unavoidable impurities; the low temperature The rolling process of steel for steel bars, the rolling process parameters are: the billet is heated to 1100-1250°C, the rolling start temperature is 900-1060°C, the final rolling temperature is 900-1100°C, water cooling after rolling, the temperature of the upper cooling bed It is 500～650℃. The steel for low-temperature hot-rolled ribbed steel bars and its rolling process can meet the requirements of LNG and other low-temperature construction engineering reinforced concrete structures by adopting the alloying principle of multiple elements and controlled rolling process, and reasonably reducing the nickel content. The steel used for low temperature hot-rolled ribbed steel bars has good low temperature resistance performance and is safe and reliable because of the low temperature requirement of 165°C.

Description

A kind of vanadium microalloyed steel for low-temperature reinforcement and its rolling process

technical field

The invention relates to low-temperature steel and its production process, in particular to vanadium microalloyed steel for low-temperature hot reinforcement and its rolling process.

Background technique

The hot-rolled ribbed steel bar is the skeleton material of the concrete structure. It bears various stresses in the structure and is sometimes used in a certain low temperature environment. Therefore, not only the steel bar is required to have high strength and process performance, but also high The functionality - the ability to resist low temperature.

A typical example that requires the use of low-temperature steel bars is the low-temperature-resistant steel bars used in the construction of liquefied natural gas storage tanks (LNG for short) in the petrochemical industry. The basic requirements and characteristics are:

(1) High strength, yield strength ≥ 400MPa or ≥ 500MPa;

(2) The production process is not limited, and it can be produced by waste heat quenching process;

(3) There are certain requirements for low-temperature performance, which are agreed between the project buyer and the supplier. The minimum storage temperature is -165°C, and there are certain requirements for low-temperature tensile plasticity and notch sensitivity.

But so far, there is no disclosed technology about the specific composition of steel for low-temperature hot-rolled ribbed steel bars and its rolling process parameters.

Generally, steel used at low temperatures from -10 to -196°C is called low-temperature steel, and steel used at low temperatures below -196°C is called ultra-low temperature steel. Low temperature steel can be roughly divided into 4 categories: low carbon aluminum killed steel, low temperature high strength steel, nickel steel and austenitic stainless steel.

(1) Low carbon aluminum killed steel. This type of steel is a low-temperature steel with silicon-manganese as the main element. In order to improve the low-temperature toughness of steel, from the chemical composition point of view, it is necessary to reduce the carbon content in the steel as much as possible, increase the Mn/C ratio, reduce sulfur, phosphorus and other harmful elements, add an appropriate amount of aluminum, refine the grain, and fix the steel. Nitrogen increases the toughness of steel and improves aging properties. The low-temperature steel on the market basically belongs to this category, which is specified in GB3531-83. Low-carbon aluminum-killed steel, the yield strength is about 290MPa, and the impact energy at low temperature is 21-28J. The main grades are 16MnDR, 09Mn2VDR, 09MnTiCuXtDR, 06MnNbDR.

(2) Low temperature high strength steel. This type of steel is based on carbon-manganese, adding a small amount of nickel and chromium to improve the low temperature toughness of the steel, and adding a small amount of molybdenum and vanadium to improve the strength of the steel itself. When the strength requirements are met, the carbon content should be reduced as much as possible to improve the toughness of the steel. , improve weldability, and obtain good self-integration performance through quenching and tempering treatment. It not only has high strength, but also has good low-temperature toughness, so it is a material with both strength and toughness. It is mainly used for coal pressurization and the manufacture of spherical tanks for various large-scale ethylene projects, and is widely used in the manufacture of high-pressure cryogenic pressure vessel.

(3) Nickel-based low-temperature steel. This type of steel is low temperature steel with nickel as the main alloying element. Nickel is the most effective element to improve the low-temperature toughness of steel. With the increase of nickel content in steel, the low-temperature toughness increases and the minimum service temperature decreases. It is mainly used to manufacture low-temperature equipment used at -40～-196°C.

(4) Austenitic stainless steel. The most important feature of this type of steel is that it has no ductile-brittle transition phenomenon. Excellent low-temperature toughness is obtained through solution treatment, and there is almost no loss of toughness even at a low temperature of -196°C, so austenitic stainless steel is mainly used below ultra-low temperature (-196°C).

At present, there are no reports of the above-mentioned 4 types of low-temperature steels being used as low-temperature steel bars for low-temperature construction projects such as LNG. The construction of LNG and other low-temperature construction projects urgently needs -165°C-resistant, nickel-saving high-strength low-temperature hot-rolled ribbed steel bars.

Contents of the invention

The object of the present invention is to provide a kind of -165 ℃ resistant, nickel-saving type high-strength vanadium microalloyed steel for low-temperature reinforcement and its rolling process.

In order to achieve the above object, the technical scheme adopted in the present invention is:

The steel for vanadium microalloyed low-temperature steel bars of the present invention has the following chemical composition ratios by weight percentage: C: 0.05-0.15%, Si: 0.15-0.40%, Mn: 1.40-1.60%, P≤0.010%, S≤ 0.010%, Ni: 0.50-2.00%, Cu: 0.10-0.80%, V: 0.020-0.080%, and the rest are Fe and unavoidable impurities.

The steel for vanadium microalloyed low-temperature steel bars of the present invention has carried out countless tests based on the alloying principle of multiple elements and a small amount, and obtained a reasonable chemical composition ratio. Compared with the prior art, the functions and effects of each composition are as follows:

Carbon: At present, the C content of general hot-rolled ribbed steel bars is 0.18-0.25%. Considering the performance requirements and the amount of other alloy elements, the C content is 0.05-0.15%. Reducing the C content is conducive to improving welding performance, plasticity and toughness .

Silicon: Si can promote the precipitation of pro-eutectoid ferrite, has little effect on the formation of pearlite, and is cheap. Si can increase the critical point of A ₃ and A ₁ and has a strong solid solution strengthening effect, but too high Si has a negative effect on steel The ductility and toughness of silicon are unfavorable, and the silicon content range is preferably 0.15-0.40%.

Manganese: Mn can lower the critical point of A ₃ and A ₁ , delay the ferrite transformation while delaying the pearlite transformation, Mn has the effect of solid solution strengthening and improving hardenability, the range of Mn content is selected as 1.40-1.60%.

Sulfur and phosphorus: S and P are harmful elements in this steel. The lower the requirement, the better. After comprehensive consideration, it should be controlled at ≤0.010%.

Nickel: Ni has the functions of refining the structure of steel, improving the low-temperature performance of steel, solid solution strengthening and improving hardenability, but it is expensive. After rational adjustment, the Ni content range is preferably 1.40-1.60%.

Copper: Cu is similar to Ni in terms of solid solution strengthening and hardenability improvement. Cu replaces a part of Ni, and Cu also has the effect of improving the corrosion resistance of steel.

Vanadium: As a microalloying element, V can improve the strength of steel bars and ensure the strength performance of steel bars, and V is a rich resource in my country. V dissolved in austenite can significantly increase the hardenability of steel. In ferrite Precipitated carbides or carbonitrides of V have significant dispersion strengthening effects.

The rolling process of vanadium microalloyed steel for low-temperature steel bar, steel for low-temperature hot-rolled ribbed steel bar according to the above-mentioned composition range, steel billet is smelted in converter, electric arc furnace or other smelting furnace and refined outside the furnace, continuous casting, and then rolled The rolling process parameters are as follows: the billet is heated to 1100-1250°C, the rolling start temperature is 900-1060°C, the final rolling temperature is 900-1100°C, water is cooled after rolling, and the temperature of the upper cooling bed is 500-650°C. The steel bars are bundled and stacked after natural cooling on the cooling bed. During the rolling process, the billet line speed is above 100m/s. The rolling process can ensure that the performance of the steel bar meets the requirements.

The advantages of the present invention are: the steel for low-temperature hot-rolled ribbed steel bar and its rolling process, by adopting the principle of alloying with multiple elements and a small amount, under the condition of reasonably reducing the nickel content, the room temperature performance of the low-temperature hot-rolled ribbed steel bar can reach: Yield strength R _eL (R _p0.2 ) ≥ 500MPa, strength-to-yield ratio ≥ 1.15, uniform elongation A _gt ≥ 5%; low temperature performance at -165°C: yield strength R _eL (R _p0.2 ) ≥ 575MPa (ie 1.15 times the design yield strength), uniform elongation A _gt ≥ 3%.

The steel for low-temperature hot-rolled ribbed steel bars can meet the use requirements of reinforced concrete structures in low-temperature construction projects such as LNG for low temperature resistance of -165°C, and the steel type has low nickel content. The steel for low-temperature hot-rolled ribbed steel bars has good low-temperature resistance ,Safe and reliable.

The rolling process of steel for low-temperature hot-rolled ribbed steel bars can ensure the performance of low-temperature hot-rolled ribbed steel bars by controlling the rolling temperature and cooling through water after rolling.

Detailed ways

The specific implementation manner of the present invention will be further described in detail through the description of the best embodiment below.

Example 1

The vanadium microalloyed steel for low-temperature steel bars has the following chemical composition ratios by weight percentage: C: 0.11%, Si: 0.32%, Mn: 1.57%, P: 0.008%, S: 0.005%, Ni: 0.53% , Cu: 0.72%, V: 0.028%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ12mm as an example, the rolling process of the φ12mm vanadium microalloyed low-temperature steel steel is based on the above composition range, smelted in an electric arc furnace and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill Made into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1110-1187°C, the rolling start temperature is 953-982°C, the final rolling temperature is 916-958°C, water is cooled after rolling, the temperature of the upper cooling bed is 632-645°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 2

The vanadium microalloyed steel for low-temperature reinforcement, the chemical composition ratio, by weight percentage: C: 0.12%, Si: 0.31%, Mn: 1.49%, P: 0.006%, S: 0.007%, Ni: 0.87% , Cu: 0.11%, V: 0.035%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ16mm as an example, the rolling process of the φ16mm vanadium microalloyed low-temperature steel bar is based on the above composition range, smelted in a converter and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1118-1205°C, the rolling start temperature is 971-1021°C, the final rolling temperature is 1018-1062°C, water is cooled after rolling, the temperature of the upper cooling bed is 611-623°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 3

The vanadium microalloyed steel for low-temperature reinforcement, the chemical composition ratio, calculated by weight percentage: C: 0.13%, Si: 0.19%, Mn: 1.52%, P: 0.007%, S: 0.008%, Ni: 0.89% , Cu: 0.12%, V: 0.043%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ20mm as an example, the rolling process of the φ20mm vanadium microalloyed low-temperature steel bar is based on the above composition range, smelted in a converter and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1152-1179°C, the rolling start temperature is 1008-1045°C, the final rolling temperature is 1021-1059°C, water is cooled after rolling, the temperature of the upper cooling bed is 590-617°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 4

The vanadium microalloyed steel for low-temperature steel bars has the following chemical composition ratios by weight percentage: C: 0.07%, Si: 0.28%, Mn: 1.51%, P: 0.006%, S: 0.008%, Ni: 1.73% , Cu: 0.12%, V: 0.048%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ20mm as an example, the rolling process of the steel billet for vanadium microalloyed low-temperature steel bars with a diameter of φ20mm, the steel type is smelted in a converter and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill according to the above composition range into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1133-1171°C, the rolling start temperature is 1003-1038°C, the final rolling temperature is 1047-1070°C, water is cooled after rolling, the temperature of the upper cooling bed is 552-565°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 5

The vanadium microalloyed steel for low-temperature steel bars has the following chemical composition ratios by weight percentage: C: 0.12%, Si: 0.27%, Mn: 1.49%, P: 0.006%, S: 0.007%, Ni: 0.77% , Cu: 0.39%, V: 0.053%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ25mm as an example, the rolling process of the φ25mm vanadium microalloyed low-temperature steel steel is based on the above composition range, smelted in an electric arc furnace and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill Made into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1144-1201°C, the rolling start temperature is 963-1011°C, the final rolling temperature is 1055-1079°C, water is cooled after rolling, the temperature of the upper cooling bed is 578-589°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 6

The vanadium microalloyed steel for low-temperature steel bars has the following chemical composition ratios by weight percentage: C: 0.09%, Si: 0.29%, Mn: 1.55%, P: 0.007%, S: 0.006%, Ni: 1.03% , Cu: 0.17%, V: 0.061%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ25mm as an example, the rolling process of the φ25mm vanadium microalloyed low-temperature steel steel is based on the above composition range, smelted in an electric arc furnace and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill Made into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1145-1193°C, the rolling start temperature is 928-990°C, the final rolling temperature is 1033-1078°C, water is passed through and cooled after rolling, the temperature of the upper cooling bed is 535-555°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 7

The vanadium microalloyed steel for low-temperature reinforcement, the chemical composition ratio, by weight percentage: C: 0.08%, Si: 0.30%, Mn: 1.44%, P: 0.004%, S: 0.005%, Ni: 1.08% , Cu: 0.16%, V: 0.072%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ25mm as an example, the rolling process of the φ25mm vanadium microalloyed low-temperature steel steel is based on the above composition range, smelted in an electric arc furnace and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill Made into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1153-1196°C, the rolling start temperature is 1007-1033°C, the final rolling temperature is 1048-1055°C, water is cooled after rolling, the temperature of the upper cooling bed is 543-561°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

Example 8

The vanadium microalloyed steel for low-temperature reinforcement, the chemical composition ratio, calculated by weight percentage: C: 0.07%, Si: 0.27%, Mn: 1.49%, P: 0.008%, S: 0.009%, Ni: 1.29% , Cu: 0.12%, V: 0.078%, and the rest are Fe and unavoidable impurities.

Taking a steel billet with a diameter of φ32mm as an example, the rolling process of the steel billet for vanadium microalloyed low-temperature steel bars with a diameter of φ32mm, the steel type is smelted in a converter and refined outside the furnace, continuous casting, and rolling on a continuous bar rolling mill according to the above composition range into hot-rolled ribbed steel bars.

The rolling process parameters are as follows: the billet is heated to 1148-1183°C, the rolling start temperature is 1018-1033°C, the final rolling temperature is 1037-1058°C, water is cooled after rolling, the temperature of the upper cooling bed is 508-523°C, and the steel bar is Bundled and stacked after natural cooling on the cooling bed.

The product performance of the steel for the low-temperature hot-rolled ribbed steel bar of above embodiment rolling is as follows:

The steel products for low-temperature reinforcement obtained in the above examples can all meet the requirements of LNG and other low-temperature construction engineering reinforced concrete structures for low temperature resistance of -165°C, and the nickel content of the steel type is low, and the steel for low-temperature reinforcement has good low-temperature resistance and is safe. reliable.

The present invention has been exemplarily described above, and it is obvious that the specific implementation of the present invention is not limited by the above-mentioned manner, as long as the various insubstantial improvements of the method concept and technical solutions of the present invention are adopted, or the present invention is implemented without improvement. The ideas and technical schemes directly applied to other occasions are within the protection scope of the present invention.

Claims (4)

1. a vanadium micro-alloying low temperature reinforcing bar steel, it is characterized in that: by weight percentage, chemical composition proportioning is: C:0.05-0.09%, Si:0.15-0.40%, Mn:1.40-1.60%, P≤0.010%, S≤0.010%, Ni:0.50--1.29%, Cu:0.10-0.72%, V:0.020-0.048%, all the other are Fe and inevitable impurity.

2. vanadium micro-alloying low temperature reinforcing bar steel as claimed in claim 1, it is characterized in that: wherein the content of C, Si, Mn, Ni, Cu and V is: by weight percentage, C:0.05-0.09%, Si:0.15-0.28%, Mn:1.40-1.49%, Ni:0.50-1.03%, Cu:0.10-0.39%, V:0.020-0.048%.

3. vanadium micro-alloying low temperature reinforcing bar steel as claimed in claim 1, it is characterized in that: wherein the content of C, Si, Mn, Ni, Cu and V is: by weight percentage, Si:0.19-0.27%, Mn:1.49-1.57%, Ni:1.08-1.29%, Cu:0.39-0.72%, V:0.035-0.048%.

4. the rolling technology of vanadium micro-alloying low temperature reinforcing bar steel described in an any one of claims 1 to 3, it is characterized in that: rolling technological parameter is: heating steel billet to 1100 ~ 1250 DEG C, start rolling temperature is 900 ~ 1060 DEG C, finishing temperature is 900 ~ 1100 DEG C, roll rear Water cooling, temperature on cooling table is 500 ~ 650 DEG C.