CN103981461B - A kind of production method of X90 pipe line steel Wide and Thick Slab - Google Patents

Abstract

An X90 pipeline steel wide and thick plate and a production method thereof belong to the technical field of low-carbon micro-alloy steel. Composition by weight percent: C: 0.06‑0.10%, Si: 0.20‑0.50%, Mn: 1.50‑1.80%, P≤0.010%, S: ≤0.003%, Nb: 0.04－0.06%, V: 0.04－ 0.06%, Ti: 0.010-0.020%, Ni: 0.15-0.30%, Cr: 0.15-0.30%, Mo: 0.10-0.30%, Als: 0.020-0.05%, and the balance is Fe and unavoidable impurities. The process includes: blast furnace molten iron→pre-desulfurization of molten iron→converter smelting→LF+RH refining→slab continuous casting→slab heating→4300 rolling mill rolling→ACC rapid cooling→stack cooling→sampling, inspection→storage and shipment. The advantage is that the steel plate has high strength, excellent low temperature toughness and dynamic tear resistance.

Description

A production method of X90 pipeline steel wide and thick plate

technical field

The invention belongs to the technical field of low-carbon micro-alloy steel, and in particular relates to a wide and thick plate of X90 pipeline steel and a production method thereof.

Background technique

Oil and natural gas are important strategic materials for the national economy. Energy growth coupled with structural optimization and adjustment has driven the overall development of the oil and gas industry. Pipeline transportation is an important way to transport oil and gas from remote mining sites to end users over long distances. High-pressure and large-diameter long-distance pipelines have become the most economical and safest transportation method for oil and gas transportation. The data show that the increase of the delivery pressure can be achieved by increasing the strength level of the pipeline steel pipe and increasing the wall thickness, and the increase of the wall thickness will inevitably lead to the increase of the weight of the steel pipe and the increase of the construction cost. In this case, only by increasing the steel grade of the pipeline can the wall thickness of the steel pipe be reduced, steel materials can be saved, and the cost of pipeline construction can be reduced. Under normal circumstances, the cost of steel pipes accounts for 25%-30% of the entire pipeline investment.

In recent years, with the successive construction of my country's West-East Gas Pipeline and Central Asia Pipeline and other projects, my country has made remarkable achievements in the development of X70/X80 high-strength pipeline steel, and has become one of the world's advanced pipelines. At present, my country has initially formed an energy pipeline network that spans east and west, runs north and south, covers the whole country, and connects overseas. With the continuous increase of my country's oil and gas demand, compared with my country's energy demand and the pipeline level of advanced countries, my country's pipeline construction still has huge demand and potential. At the same time, in order to reduce land occupation and construction costs as much as possible, the research and development of ultra-high-strength economical pipeline steel makes it possible to transport pipelines with higher pressure.

In 2014, China National Petroleum Corporation organized domestic pipeline and metallurgical industry experts to hold an economical X90 seminar, at which the chemical composition requirements, performance index adjustment, procurement mode, girth weld and economic feasibility of economical X90 pipeline steel were discussed. The development of economical X90 pipeline steel is not only an upgrade and replacement of existing X80 pipeline steel and low-cost promotion and use, but also can accumulate relevant practical data for higher-grade X100/X120 pipeline steel, which is of great significance to China's pipeline construction. The difficulty in the development of economical X90 pipeline steel wide and thick plates is to achieve a comprehensive increase in the strength and toughness of the steel plate under the premise that the cost is less than that of X80, and it has excellent weldability and crack arrest toughness.

Contents of the invention

The purpose of the present invention is to provide a X90 pipeline steel wide and thick plate and its production method. Through reasonable composition design and rolling process, 300mm continuous casting billet is used to produce economical X90 pipeline steel hot-rolled flat plate, not only the comprehensive performance of the product meets the requirements , and has excellent low temperature toughness and welding performance. The structure of the steel plate is mainly bainite structure + martensite + a small amount of M-A components, the structure is uniform and fine, and the grain size is above 13 grades.

The composition (by weight percentage) of steel plate of the present invention is:

C: 0.03-0.09%, Si: 0.10-0.40%, Mn: 1.30-2.0%, P≤0.015%, S: ≤0.003%, Nb: 0.05-0.10%, V: ≤0.06%, Ti: 0.010-0.040 %, Ni: 0.10-0.50%, Cr: ≤0.50%, Mo: ≤0.50%, Al: 0.010-0.040%, and the balance is Fe and unavoidable impurities.

The composition design of the present invention is based on following understanding:

C: In order to ensure that the economical X90 pipeline steel has excellent welding performance and good low-temperature toughness, the carbon content must be strictly controlled below 0.09%.

Si is an effective deoxidizing element and can also play a strengthening role, but too high Si content will reduce the plasticity and toughness of steel, so the range is set at 0.15% to 0.40%.

Mn is an important solid solution strengthening element in steel, which can reduce the phase transition temperature, refine the microstructure substructure, improve the toughness while strengthening the steel plate; at the same time, it can improve the hardenability.

P and S are harmful impurity elements. Calcium treatment and pure steel production technology are adopted to strictly control inclusions such as phosphorus and sulfur in steel.

Nb and Ti are both solid solution strengthening elements and carbonitride forming elements. During the billet heating and rolling process, they pin the austenite grain boundaries and prevent the austenite grains from growing excessively, but their content is too high Will affect toughness and weldability.

Cr can effectively increase the hardenability of the steel and improve the mechanical properties, but too high a content will have an adverse effect on the weldability of the material.

Ni and Cu act as solid solution strengthening, and can also improve corrosion resistance, while Ni can also improve the low-temperature toughness of steel.

Mo can improve the low temperature toughness of steel, and it is a strong bainite transformation control element. In high-strength microalloy steel, adding an appropriate amount of Mo element can obtain obvious bainite structure, and at the same time, due to the transformation to low temperature, the phase transformation structure can be further refined, and the strength and toughness of the steel can be greatly improved. It can also effectively reduce the yield-to-strength ratio. Since Mo is a noble metal element, the content of Mo in the present invention is controlled within the range of 0.10-0.25%.

The presence of N will deteriorate the toughness of the base metal and the heat-affected zone of welding, and its content should not exceed 0.006%.

The production of the steel plate of the present invention includes: blast furnace molten iron→pre-desulfurization of molten iron→converter smelting→LF+RH refining→slab continuous casting→slab heating→4300 rolling mill rolling→ACC rapid cooling→stack cooling→sampling, inspection→storage , Shipping.

In the process of slab casting + controlled rolling + controlled cooling, the control parameters in the process are:

(1) Cast molten steel smelted according to the chemical composition of the steel plate into a 300mm thick continuous casting slab;

(2) Heating the billet to a set temperature of 1150-1200°C in a walking beam heating furnace for a heating time of 280-350 minutes to ensure that the billet is fully austenitized;

(3) After the steel billet comes out of the furnace, it enters the 4300mm rolling mill for rolling. During rolling, two-stage rolling is adopted in the recrystallization zone + non-recrystallization zone. The temperature control thickness is 2-4 times the thickness of the finished product. The parameters of the rough rolling stage and the finishing rolling stage are as follows :

Rough rolling stage: start rolling temperature: 1000-1100℃, rolling speed: 1.0-3.5m/s, rolling torque: 2000-3200kNm; in order to obtain fine and uniform microstructure, rough rolling needs to ensure single-pass deformation Rate 10-35%.

Finishing rolling stage: low temperature starting rolling, starting rolling temperature: 760-820°C, finishing rolling temperature: 720-800°C, rolling speed: 2.0-4.0m/s.

(4) After rolling, the steel plate is cooled by ultra-fast cooling UFC + laminar flow ACC. The initial cooling temperature is controlled at 730-790°C, and the final cooling temperature is controlled at 200-350°C. The cooling equipment capacity is fully utilized, and the cooling rate is 25-40°C/ s, fully refine the grains at a high cooling rate, and improve the strength and toughness of the steel plate;

(5) After the steel plates are cooled, they are stacked and cooled slowly, and the stack cooling time is 12-24 hours.

The economical X90 pipeline steel produced through the above process has high strength, excellent low temperature toughness and dynamic tear resistance.

Description of drawings

Figure 1 shows the optical electron microscope structure of X90 pipeline steel wide and thick plate.

Figure 2 is the scanning electron microscope structure of X90 pipeline steel wide and thick plate.

detailed description

According to the economical X90 pipeline steel wide and thick plate and its manufacturing method of the present invention, it is smelted on a 100-ton converter, cast into a continuous casting slab of 300mm×2400mm×2700mm, and rolled on a 4300mm wide and thick plate production line. The chemical composition is shown in Table 1, the process system is shown in Table 2, and the mechanical properties of the steel plate are shown in Table 3.

Table 1 Chemical composition wt% of steel plate

Example o Si mn P S al Nb Ni Ti Cr Cu Mo N h Example 1 0.045 0.25 1.80 0.011 0.0013 0.034 0.078 0.175 0.014 0.21 0.20 0.15 0.004 0.0001 Example 2 0.056 0.24 1.79 0.010 0.0008 0.036 0.063 0.175 0.014 0.19 0.21 0.12 0.003 0.0001 Example 3 0.060 0.22 1.75 0.009 0.0011 0.03 0.055 0.172 0.015 0.23 0.19 0.18 0.002 0.0001 Example 4 0.070 0.23 1.70 0.008 0.0009 0.035 0.050 0.170 0.015 0.20 0.21 0.13 0.004 0.0002

Table 2 Process system

The economical X90 pipeline steel produced by the invention has a lath structure with small spacing, fine M-A islands are distributed between the laths, and has high-density dislocations. Figure 1 and Figure 2 are X90 metallographic photographs under optical and scanning electron microscopes, respectively.

Table 3 Mechanical Properties of Steel Plate

The present invention fully refines the phase transition structure by adopting ultra-low temperature phase transformation of low temperature and high pressure and ultrafast cooling + laminar cooling, and ensures that the phase transition structure of X90 pipeline steel is fine bainite structure + martensite structure after deformation, It ensures that the steel plate can have high strength, and at the same time has excellent low-temperature impact toughness and low-temperature dynamic tear resistance. The economical X90 pipeline steel of the invention can be widely used in the construction of petroleum and natural gas pipeline projects, and has obvious effect on reducing the construction cost of transmission pipelines.

Claims (1)

1. a production method for X90 pipe line steel Wide and Thick Slab, technique includes: blast-melted → molten iron pre-desulfurization → converter smelting → LF+RH refine → sheet billet continuous casting → heating of plate blank → 4300 mill milling → ACC quickly cools down → and heap is cold → samples, check → enter Storehouse, shipping；It is characterized in that, the technical parameter controlled in slab casting+controlled rolling and controlled cooling technical process is:

(1) 300mm thickness continuous casting billet will be poured into by the chemical composition smelting molten steel of steel plate；

(2) by walking beam heating furnace by heating steel billet 1150～1200 DEG C, heat time heating time 280-350min, it is ensured that steel billet is difficult to understand Family name's body；

(3) enter 4300mm mill milling after steel billet is come out of the stove, during rolling, use recrystallization zone+Unhydrated cement two-phase control rolling, Holding gauge is 2-4 times of finished product thickness, and rough rolling step is as follows with finish rolling stage parameter:

Rough rolling step: start rolling temperature: 1000-1100 DEG C, mill speed: 1.0-3.5m/s, roll torque: 2000-3200kNm； Roughing need to ensure single pass deformation rate 10-35%；

The finish rolling stage: start rolling temperature: 760-820 DEG C, finishing temperature: 720-800 DEG C, mill speed: 2.0-4.0m/s；

(4) roll rear steel plate and combine cooling by ultrafast cold UFC+ laminar flow ACC, begin to cool down temperature and control at 730-790 DEG C, the coldest Temperature controls at 200-350 DEG C, cooldown rate 25-40 DEG C/s, with crystal grain thinning, improves steel plate obdurability；

(5) stacking slow cooling after steel plate cooling, heap cool time 12-24 hour；

Described X90 pipe line steel Wide and Thick Slab, it is characterised in that component weight percentages is:

C:0.03-0.09%, Si:0.10-0.40%, Mn:1.30-2.0%, P≤0.015%, S :≤0.003%, Nb: 0.05-0.10%, V :≤0.06%, Ti:0.010-0.040%, Ni:0.10-0.50%, Cr :≤0.50%, Mo :≤ 0.50%, Al:0.010-0.040%, surplus is Fe and inevitable impurity；

Steel plate is organized as bainite structure+martensite+a small amount of M-A constituent element, and even tissue is tiny, and grain size is more than 13 grades.