CN103725988A - Hot-rolled flat plate for production of high-grade thick specification pipe fitting from continuous casting billet and preparation method of hot-rolled flat plate - Google Patents

Abstract

The invention discloses a hot-rolled flat plate for production of high-grade thick specification pipe fitting during continuous casting billet and a preparation method of the hot-rolled flat plate and belongs to the technical field of low-carbon microalloyed steel. The hot-rolled flat plate comprises the following components in percentage by weight: 0.07-0.10 percent of C, 0.10-0.35 percent of Si, 1.20-1.60 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.003 percent of S, 0.02-0.07 percent of Nb, less than or equal to 0.06 percent of V, 0.010-0.020 percent of Ti, 0.15-0.40 percent of Ni, 0.10-0.2 percent of Cr, 0.10-0.30 percent of Mo, 0.020-0.05 percent of Als and the balance of Fe and inevitable impurities. The production method comprises the following steps: blast furnace molten iron, performing preliminary desulphuzation on the molten iron, performing converter smelting, performing LF+RH refining, performing continuous casting on slab, heating the slab, rolling through a 4300 rolling mill, performing ACC rapid cooling, cooling in heap, sampling and checking, warehousing and delivering. The hot-rolled flat plate has the advantages that the mechanical property index of the steel plate is stable, the intensity index of the steel plate is good, and the plasticity and toughness are well matched.

Description

Continuously cast bloom is produced high-grade thick specification pipe fitting hot rolled slab and manufacture method thereof

Technical field

The invention belongs to low-carbon micro steel-alloy field, particularly relate to a kind of continuously cast bloom and produce high-grade thick specification pipe fitting hot rolled slab and manufacture method thereof, use continuously cast bloom to produce the high-grade thick specification pipe fitting hot rolled slab of X70, X80, the pipe line steel thickness of production is 30-60mm.

Background technology

Along with the fast development of world economy, global energy, environment face increasing challenge.Various countries increase day by day to the demand of hydrocarbon resources, adopt high-grade long distance to carry oil gas to obtain in the world great development, high grade pipe line steel research, the development and application such as X70 and X80 have been promoted, pipe line steel and pipeline steel tube have become an important branch of the richest vigor of Hi-Stren steel and micro-alloyed steel field, tool achievement in research, and its research, development and production level have become the important symbol of a national metallurgical industry level and equipment process industry level.

Because the demand of world energy sources constantly increases, people remote districts find and develop new oil field, gas field, and the pipeline adapting is therewith many in awful weather, the area construction that meagrely-populated, geology and geomorphology condition is extremely complicated.For example, the pipeline of Alaska crosses in the U.S., and by way of frost region, temperature is low reaches-70 ℃; Be positioned at the pipeline of Russian West Siberia, accumulated snow 70-90cm along the line, temperature is low reaches-63 ℃.Along with the reduction of service temperature, the mechanism of fracture of pipeline steel tube gathers type from micropore and becomes transcrystalline cleavage type, and Fracture Characteristics is from the fibrous crystalloid that becomes, and toughness obviously declines, and material becomes brittle state from tough sexual state.For the safety meeting under this cold condition, be on active service, pipe line steel must have large toughness deposit.

Large wall thickness X70/X80 low temperature pipe fitting is mainly used in low temperature and specific geologic condition area, not only requires high strength, high tenacity and good welding property, more will have good very low temperature impelling strength.Stretching and impact experiment all require the sampling in steel plate heart portion, and the refinement of the thicker core structure of steel plate is more difficult, how to be quickly cooled to steel plate heart portion after controlled rolling, prevents grain growth, to water-cooled condition, are also greatly challenges.Steel plate is made after pipe, also needs through multiple tracks moulding process and thermal treatment, thereby, make pipe fitting there is larger added value and the market requirement.

Summary of the invention

The object of this invention is to provide a kind of continuously cast bloom and produce high-grade thick specification pipe fitting hot rolled slab and manufacture method thereof, adopt continuously cast bloom to produce the high-grade thick specification pipe fitting hot rolled slab of X70, X80.By reasonable component, design and rolling technology, use 300,400mm continuously cast bloom are produced the high-grade thick specification pipe fitting hot rolled slab of X70, X80, not only product over-all properties foot requirement, and and tradition to use ingot casting production heavier walled fitting to compare production efficiency with hot rolled slab high, steel plate loss is little.The steel plate of producing can reach the performance requriements of X70, X80 pipe line steel completely.

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

C:0.07-0.10%, Si:0.10-0.35%, Mn:1.20-1.60%, P≤0.015%, S :≤0.003%, Nb:0.02-0.07%, V :≤0.06%, Ti:0.010-0.020%, Ni:0.15-0.40%, Cr:0.10-0.20%, Mo:0.10-0.30%, Als:0.020-0.05%, surplus is Fe and inevitable impurity.

The production of steel plate of the present invention comprises: blast-melted → molten iron pre-desulfurization → converter smelting → LF+RH refining → sheet billet continuous casting → heating of plate blank → 4300 mill milling → ACC cooling → cooling in heap → sampling fast, check → warehouse-in, shipping.

In slab casting+controlled rolling and controlled cooling technological process, controlling parameter is:

(1) the chemical composition smelting molten steel by steel plate is poured into 300, the thick continuously cast bloom of 400mm;

(2) by walking beam heating furnace by heating steel billet to 1170～1220 ℃ of design temperatures, heat-up time, 280-450min, guaranteed the abundant austenitizing of steel billet;

(3) steel billet enters 4300mm mill milling after coming out of the stove, and adopts two stage rolling during rolling, and doubly, rough rolling step and finish rolling stage parameter are as follows for the 2-3 that holding gauge is finished product thickness:

Rough rolling step: start rolling temperature: 1000-1100 ℃, end temp: >=980 ℃, roll speed: 1.0-4.5m/s, rolling torque: 2000-3200kNm;

Finish rolling stage: start rolling temperature: 760-820 ℃, finishing temperature: 750-800 ℃, roll speed: 2.0-5.0m/s.

(4) rolling rear steel plate, to enter ACC laminar flow cooling, begins to cool down temperature and be controlled at 740-790 ℃, and final cooling temperature is controlled at 400-500 ℃, and rate of cooling is controlled at 7-20 ℃/s;

(5) the cooling rear stacking slow cooling of steel plate, heap cool time >=24 hour.

The thick specification X70 producing by above-mentioned operation, X80 pipe fitting pipe line steel, steel plate thickness specification covers 30mm～60mm; Mechanical property of steel plate index is more stable, and armor plate strength index is good, and plasticity, toughness coupling better.

Accompanying drawing explanation

Fig. 1 is the 1/2 place metallographic structure of 32mmX70 hot-rolled steel sheet thickness;

Fig. 2 is the 1/2 place metallographic structure of 38mmX70 hot-rolled steel sheet thickness;

Fig. 3 is the 1/2 place metallographic structure of 48mmX70 hot-rolled steel sheet thickness;

Fig. 4 is the 1/2 place metallographic structure of 58mmX70 hot-rolled steel sheet thickness;

Fig. 5 is the 1/2 place metallographic structure of 36mmX80 hot-rolled steel sheet thickness;

Fig. 6 is the 1/2 place metallographic structure of 43mmX80 hot-rolled steel sheet thickness;

Fig. 7 is the 1/2 place metallographic structure of 46mmX80 hot-rolled steel sheet thickness;

Fig. 8 is the 1/2 place metallographic structure of 54mmX80 hot-rolled steel sheet thickness.

Embodiment

According to Composition Design provided by the invention and production method, in 100 tons of converters, smelt 300,400mm continuously cast bloom, rolling 30～60mm steel plate respectively on 4300mm wide and heavy plate mill, its chemical composition is in Table 1, rolling technological parameter in Table 2, table 3 and table 4, hot-rolled steel sheet performance situation is in Table 5.

Table 1 chemical composition

The heating of table 2 steel plate, rolling and water-cooling process parameter

Table 3 different thickness X70 hot-rolled steel plate parameter

Table 4 different thickness X80 hot-rolled steel plate parameter

Table 5 hot-rolled steel sheet performance

Note: stretch, impact sample and take from steel plate thickness 1/2 place.

Claims (2)

1. continuously cast bloom is produced a high-grade thick specification pipe fitting hot rolled slab, it is characterized in that, composition is by weight percentage: C:0.07-0.10%, Si:0.10-0.35%, Mn:1.20-1.60%, P≤0.015%, S :≤0.003%, Nb:0.02-0.07%, V :≤0.06%, Ti:0.010-0.020%, Ni:0.15-0.40%, Cr:0.10-0.20%, Mo:0.10-0.30%, Als:0.020-0.05%, surplus is Fe and inevitable impurity.

2. a production method for pipe fitting use hot rolled slab described in claim 1, comprising: blast-melted → molten iron pre-desulfurization → converter smelting → LF+RH refining → sheet billet continuous casting → heating of plate blank → 4300 mill milling → ACC cooling → cooling in heap → sampling fast, check → warehouse-in, shipping; It is characterized in that, the technical parameter of controlling in slab casting+controlled rolling and controlled cooling technological process is:

(1) the chemical composition smelting molten steel by steel plate is poured into 300, the thick continuously cast bloom of 400mm;

(2) by walking beam heating furnace by heating steel billet to 1170～1220 ℃ of design temperatures, heat-up time, 280-450min, made steel billet austenitizing;

(3) steel billet enters 4300mm mill milling after coming out of the stove, and adopts two stage rolling during rolling, and doubly, rough rolling step and finish rolling stage parameter are as follows for the 2-3 that holding gauge is finished product thickness:

Rough rolling step: start rolling temperature: 1000-1100 ℃, end temp: >=980 ℃, roll speed: 1.0-4.5m/s, rolling torque: 2000-3200kNm;

Finish rolling stage: start rolling temperature: 760-820 ℃, finishing temperature: 750-800 ℃, roll speed: 2.0-5.0m/s;

(4) rolling rear steel plate, to enter ACC laminar flow cooling, begins to cool down temperature and be controlled at 740-790 ℃, and final cooling temperature is controlled at 400-500 ℃, and rate of cooling is controlled at 7-20 ℃/s;

(5) the cooling rear stacking slow cooling of steel plate, heap cool time >=24 hour.

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