CN103725988B - Continuously cast bloom produces high-grade think gauge pipe fitting hot rolled slab and manufacture method thereof - Google Patents

Abstract

A kind of continuously cast bloom produces high-grade think gauge pipe fitting hot rolled slab and manufacture method thereof, belongs to technical field of low-carbon micro-alloy steel. 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. Production comprises: blast-melted �� molten iron pre-desulfurization �� converter smelting �� LF+RH refining �� sheet billet continuous casting �� heating of plate blank �� 4300 mill milling �� ACC cools �� pile cold �� sampling, inspection �� warehouse-in, shipping fast. Advantage is, mechanical property of steel plate Indexes Comparison is stablized, and armor plate strength index is good, and plasticity, toughness coupling is better.

Description

Continuously cast bloom produces high-grade think gauge pipe fitting hot rolled slab and manufacture method thereof

Technical field

The invention belongs to field of low-carbon micro-alloy steel, particularly relate to a kind of continuously cast bloom and produce high-grade think gauge pipe fitting hot rolled slab and manufacture method thereof, namely using continuously cast bloom to produce the high-grade think gauge 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 more and more challenges. The demand of hydrocarbon resources is increased by various countries day by day, high-grade long distance delivery oil gas is adopted to obtain great development in the world, facilitate high grade pipe line steel research, the development and application such as X70 and X80, 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, most achievement in research, and its research, development and production level have become the important symbol of a national metallurgical industry level and equipment manufacturing industrial level.

Owing to the demand of world energy sources constantly increases, people find and develop new oil field, gas field in remote districts, build with the many areas severe at weather, meagrely-populated, that geology and geomorphology condition is extremely complicated of this pipeline adapted. Such as, the pipeline of Alaska crosses in the U.S., and by way of freezing area, temperature is low reaches-70 DEG C; The pipeline being positioned at Russia's West Siberia, accumulated snow 70-90cm along the line, temperature is low reaches-63 DEG C. Along with the reduction of service temperature, the mechanism of fracture of pipeline steel tube gathers type from micropore and turns into transcrystalline cleavage type, and fracture feature turns into crystalloid from threadiness, and toughness obviously declines, and material turns into brittle state from ductile states. Safety for meeting under this kind of cold condition is on active service, and pipe line steel must have big toughness deposit.

Big 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 to be had good very low temperature impelling strength. Stretch and all require that with impact experiment the refinement of the more thick core structure of steel plate is more difficult, how to be quickly cooled to steel plate heart portion, prevent grain growth after controlled rolling in the sampling of steel plate heart portion, be also a greatly challenge to water-cooled condition. After pipe made by steel plate, also need through too much road moulding process and thermal treatment, thus so that pipe fitting has bigger added value and the market requirement.

Summary of the invention

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

The composition (by weight percentage) of the steel plate of the present invention 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 the 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 cools �� pile cold �� sampling, inspection �� warehouse-in, shipping fast.

In slab casting+controlled rolling and controlled cooling technological process, controling parameters is:

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

(2) by walking beam heating furnace by heating steel billet to design temperature 1170��1220 DEG C, heat-up time, 280-450min, ensured the abundant austenitizing of steel billet;

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

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

The finish rolling stage: start rolling temperature: 760-820 DEG C, finishing temperature: 750-800 DEG C, roll speed: 2.0-5.0m/s.

(4) rolling rear steel plate and enter ACC section cooling, begin to cool down temperature and control at 740-790 DEG C, final cooling temperature controls at 400-500 DEG C, and rate of cooling controls at 7-20 DEG C/s;

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

Think gauge X70, X80 pipe fitting pipe line steel produced by above-mentioned operation, steel plate thickness specification covers 30mm��60mm; Mechanical property of steel plate Indexes Comparison is stablized, and armor plate strength index is good, and plasticity, toughness coupling is better.

Accompanying drawing explanation

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

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

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

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

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

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

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

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

Embodiment

According to composition provided by the invention design and production method, smelting 300,400mm continuously cast bloom in 100 tons of converters, difference rolling 30��60mm steel plate on 4300mm wide and heavy plate mill, its chemical composition is in table 1, rolling technological parameter is in table 2, table 3 and table 4, and hot-rolled steel sheet behavior pattern 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: steel plate thickness 1/2 place is taken from stretching, impact sample.

Claims (2)

1. high-grade think gauge pipe fitting hot rolled slab produced by a continuously cast bloom, it is characterised 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; Use 300,400mm continuously cast bloom, producing steel plate thickness range is 30-60mm.

2. a production method for pipe fitting 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 cools �� pile cold �� sampling, inspection �� warehouse-in, shipping fast; It is characterized in that, in slab casting+controlled rolling and controlled cooling technological process, the technical parameter of control is:

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

(2) by walking beam heating furnace by heating steel billet to design temperature 1170��1220 DEG C, heat-up time, 280-450min, made steel billet austenitizing;

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

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

The finish rolling stage: start rolling temperature: 760-820 DEG C, finishing temperature: 750-800 DEG C, roll speed: 2.0-5.0m/s;

(4) rolling rear steel plate and enter ACC section cooling, begin to cool down temperature and control at 740-790 DEG C, final cooling temperature controls at 400-500 DEG C, and rate of cooling controls at 7-20 DEG C/s;

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