RU2471003C1 - Manufacturing method of rolled metal with increased resistance to hydrogen and hydrosulphuric cracking - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: steel is molten and continuously poured into slabs; slabs are heated, pre-rolled and finally rolled and cooled in accelerated manner; at that, steel contains the following, wt %: C 0.02-0.10, Mn 0.5-1.5, Si 0.10-0.50, Nb 0.010-0.10, Al 0.01-0.05, Ti 0.005-0.05, N 0.003-0.012, S 0.002 and less, P 0.001-0.015, Ca 0.0002-0.005, Fe is the rest; at ratio of 0.03≤[C]×[Mn]≤0.12, slabs are heated to 1100-1300°C, pre-rolled with total deformation degree of 50-70% in the direction that is perpendicular to axis slab, and then, in temperature zone of 900-750°C in the direction that is longitudinal to slab axis with total deformation degree of 65-80%, cooled in accelerated manner in temperature zone of (Ar₃±30°C)-(600-400°C), first, to temperature of 600-500°C at the rate of 15-30 deg/s, and then, at the rate of 10-15 deg/s; after that, they are cooled slowly from temperature of 400°C to room temperature at the rate of 0.05-0.15 deg/s.

EFFECT: providing improved strength properties at simultaneous increase in cold resistance, low-temperature viscosity and resistance to hydrogen and hydrosulphuric cracking.

2 cl, 4 tbl, 1 ex

Description

The invention relates to the field of metallurgy, and more particularly to rolling production, and can be used to obtain rolled products for the production of hydrogen sulfide-resistant gas and oil pipes.

A known method of producing rolled steel from low alloy steel, including heating slabs to a temperature of 1160-1190 ° C, rough rolling, finishing rolling with a total relative compression of at least 70% at a temperature of the end of rolling not higher than 820 ° C. After rolling, the sheets are quenched with water at a temperature of 900-950 ° C and tempered at a temperature of 600-730 ° C. In this case, low alloy steel has the following chemical composition, wt.%:

Carbon 0.07-0.12 Manganese 1.4-1.7 Silicon 0.15-0.50 Vanadium 0.06-0.12 Niobium 0.03-0.05 Titanium 0.01-0.03 Aluminum 0.02-0.05 Chromium no more than 0,3 Nickel no more than 0,3 Copper no more than 0,3 Sulfur no more than 0,005 Phosphorus no more than 0.015 Nitrogen no more than 0.10 Iron the rest [1]

The disadvantages of this method are that the rental has low cold resistance, weldability and resistance to hydrogen sulfide cracking. In addition, additional thermal improvement of rolled products makes its production more expensive.

There is also known a method for the production of rolled steel of strength category X65 from low alloy steel of the following composition, wt.%:

Carbon 0.06-0.12 Manganese 1.4-1.7 Silicon 0.20-0.45 Vanadium 0.06-0.10 Niobium 0.04-0.08 Titanium 0.005-0.035 Aluminum 0.02-0.05 Molybdenum 0.01-0.50 Chromium 0.01-0.30 Nickel 0.01-0.30 Copper 0.01-0.30 Sulfur no more than 0,006 Phosphorus no more than 0.015 Boron no more than 0,006 Nitrogen no more than 0,010 Iron rest

Wherein

and

The method includes heating the slabs to a temperature of 1170-1420 ° C, their rough rolling to an intermediate thickness and finishing rolling in the temperature range of 910-710 ° C with a total relative compression of 60-80% [2].

The disadvantages of this method are that it does not provide high cold resistance and resistance against hydrogen sulfide cracking.

The closest analogue in terms of the set of features and the achieved results to the proposed invention is a method for the production of rolled steel from low alloy steel of the following chemical composition, wt.%:

Carbon 0.12-0.17 Manganese 1.3-1.6 Silicon 0.3-0.6 Vanadium and / or Niobium 0.01-0.05 Aluminum 0.02-0.06 Chromium no more than 0,3 Nickel no more than 0,3 Copper no more than 0,3 Sulfur no more than 0,006 Phosphorus no more than 0.015 Calcium no more than 0,02 Nitrogen no more than 0,010 Iron rest

The method includes heating slabs to a temperature of 1220-1280 ° C, multi-pass rough rolling to an intermediate thickness, finishing rolling from a temperature of the end of rolling of 820-880 ° C and accelerated cooling with water to a temperature of 580-660 ° C [3].

The main disadvantages of the known methods of production are insufficient strength, poor performance toughness, cold resistance of the obtained hire and low resistance to hydrogen and hydrogen sulfide cracking.

Flat products for the manufacture of high-strength cold-resistant gas and oil pipes used for transportation of hydrogen sulfide-containing hydrocarbons must meet the following set of properties (Table 1):

Table 1 Properties of sheet metal for hydrogen sulfide-resistant gas and oil pipes σ _in , N / mm ² σ _t , N / mm ² δ ₅ ,% KCV ^-20 , J / cm ² CLR,% σ _then ,% no less than 550 not less than 450 not less than 22 not less than 150 no more than 5 not less than 70%

Known methods for the production of rolled steel from low alloy steel do not provide a simultaneous combination of high strength, cold resistance and resistance to hydrogen sulfide cracking, because an increase in strength due to an increase in the degree of alloying of steel inevitably affects its weldability and resistance to hydrogen sulfide cracking, and reduces the plastic and viscous properties of rolled products at low temperatures.

The technical result of this invention is the production of sheet metal for gas and oil pipes with increased strength, while improving cold resistance, low temperature viscosity and high resistance to hydrogen and hydrogen sulfide cracking without compromising weldability.

The specified technical result is achieved by the fact that in the method for the production of plate products from high-strength and cold-resistant steel, including steel smelting, continuous casting into billets, heating slabs, preliminary and final rolling and accelerated cooling, according to the invention, the rolling is made of steel of the following chemical composition, wt. % :,

C 0.02-0.10

Mn 0.5-1.5

Si 0.10-0.50

Nb 0.010-0.10

Al 0.01-0.05

Ti 0.005-0.05

N, 0.003-0.012

S 0.002 and less

P 0.001-0.015

Ca 0.0002-0.005

Fe - the rest

with a ratio of 0.03≤ [C] × [Mn] ≤0.12,

where [C] × [Mn] is the product of carbon and manganese content in steel.

After heating to temperatures of 1100-1300 ° C, the slabs are pre-rolled with a total degree of deformation of 50-70% in the direction perpendicular to the axis of the slab, and then in the temperature range 900-750 ° C in the direction longitudinal to the axis of the slab, with a total deformation of 65-80 %, after which the rolled products are rapidly cooled in the temperature range (Ar ₃ ± 30 ° C) - (600-400 ° C), and first to temperatures of 600-500 ° C at a speed of 15-30 deg / s, and then at a speed of 10 -15 deg / s; then from 400 ° C to room temperature it is cooled slowly at a rate of 0.05-0.15 deg / s.

The composition of the steel can introduce one or more elements from the series Mo, V, Ni, Cu, Cr, B in the following amount, wt.%:

Mo 0.05-0.35

V 0.01-0.15

Ni 0.01-0.50

Cu 0.01-0.50

Cr 0.01-0.50

B 0.0005-0.005

while with the simultaneous content of Mo, Ni, Cu and Cr, their sum should not exceed 1.0%.

The selected limits of carbon content in combination with manganese and niobium ensure that the rolled products manufactured according to the proposed regimes provide a dispersed ferrite-bainitic structure and achieve high values of temporary resistance, yield strength, elongation, high resistance to hydrogen and hydrogen sulfide cracking while maintaining good weldability. The stated contents of silicon and aluminum provide the necessary purity of steel for non-metallic inclusions and oxygen. The titanium content within the stated limits provides nitrogen binding to stable nitrides, and a very low sulfur content ensures high impact strength at low temperatures and high resistance to hydrogen and hydrogen sulfide cracking.

Calcium has a modifying (spheroidizing) effect on nonmetallic inclusions, which makes it possible to increase the toughness at low temperatures and prevents the initiation of hydrogen cracking at the sulfide-matrix interface.

Niobium within the stated content limits inhibits the growth of austenite grain upon heating, inhibits recrystallization in the temperature range corresponding to a temporary pause between preliminary and final rolling, which contributes to the creation of additional centers for the formation of a new phase (ferrite) during γ → α transformation and, consequently, grinding of ferrite grain . In addition, the release of dispersed niobium carbonitrides contributes to an increase in the strength characteristics of steel due to dispersion hardening.

The declared modes of preliminary rolling, final rolling and stepwise accelerated cooling to bainitic transformation temperatures at 600-400 ° C contribute to the formation of a homogeneous, dispersed, stripless ferrite-bainitic structure with increased strength, cold resistance, weldability and high hydrogen resistance (CLR → 0) and hydrogen sulfide cracking (σ _pore. not less than 0.7σ _t ).

An example implementation of the method.

Steel was smelted in an oxygen converter. After the release of the metal, it was processed in a ladle and cast in a continuous casting machine. During out-of-furnace processing of metal in the ladle, final deoxidation, refining, purging with neutral gas, and modifying treatment with calcium were performed. As a result of smelting and after-furnace treatment, steel of the following chemical composition (wt.%) Was obtained: C - 0.05; Mn 1.26; Si 0.18; Nb 0.43; Ti - 0.011; Cu 0.15; Ni - 0.21; Al is 0.02; N is 0.005; S is 0.001; P is 0.012; Fe is the rest.

Slabs of 246 × 1550 mm in size were rolled onto a sheet 18.7 mm thick using a 5000 single-strand reversing mill. The slabs for rolling were heated to a temperature of 1170 ± 10 ° C. Preliminary deformation in the direction perpendicular to the axis of the slab was carried out in 5 passes and completed at a temperature of 980 ° C, while the total deformation perpendicular to the axis of the slab was 63%. The thickness of the tackle was 90 mm. The final deformation in the direction longitudinal to the axis of the slab was carried out in 12 passes at a temperature of 900-780 ° C, with a total degree of deformation of 79%. After completion of the final rolling, the rolled products were accelerated cooling from a temperature of 790 ° C at a speed of 23.0 deg / s to a temperature of 550 ° C, then at a speed of 12.0 deg / s to a temperature of 400 ° C. Subsequent cooling of the roll to room temperature was carried out slowly at a speed of 0.10 deg / s.

The composition of the steel, technological modes of rolling and a set of obtained properties are shown in tables 2, 3, 4.

table 2 The chemical composition of experimental swimming trunks No. of swimming trunks Mass fraction of elements,% C Si Mn Cr Ni Cu Nb Mo Ti V Al B P S one 0.05 0.18 1.26 0,027 0.21 0.15 0,043 - 0.011 - 0,021 - 0.014 0.001 2 0.056 0.21 1,50 0.024 0.22 0.16 0,074 0.245 0.016 - 0.015 - 0.013 0.002 3 0,039 0.18 1.12 0.016 0.21 0.15 - - 0.013 0,072 0.009 - 0.014 0.003 four 0,034 0.22 1.32 0,026 0,030 0.014 0,042 - 0.016 0,042 0.013 0.003 0.013 0.002 5 0,093 0.21 1.20 0.63 0.21 0.20 0,076 0.02 0.013 0,092 0,026 - 0.007 0.002

Table 4 Mechanical properties of experimental steels No. of swimming trunks σ _in , N / mm ² σ _t , N / mm ² δ ₅ ,% KCV ^-20 , J / cm ² CLR,% σ _then ,% one 645 506 29.2 240 0 80 2 692 580 22.5 170 0 70 3 527 403 25,4 215 6.5 70 four 718 564 32.1 94 0 Less than 60 5 728 543 24.0 147 18.5 Less than 70 Prototype 510 395 22 Less than 150 21.8 Less than 70 Note: CLR,% - the relative length of the cracks when tested for resistance to hydrogen cracking

From the data given in table 4, it follows that in cases of the implementation of the proposed method (options No. 1-2), an increase in sheet strength, cold resistance and resistance to hydrogen and hydrogen sulfide cracking is achieved. With exorbitant values of the declared parameters (options No. 3-5), there is a decrease in low-temperature viscosity (No. 4), or strength (No. 3) and resistance to hydrogen sulfide cracking of sheet metal (No. 3-5).

The proposed method allows to obtain rolled products with increased strength indicators, while improving cold resistance, low temperature viscosity and high resistance to hydrogen and hydrogen sulfide cracking without compromising weldability.

Information sources

1. Patent of the Russian Federation No. 2255123, IPC C21D 8/02, C22C 38/58, 2005

2. Patent of the Russian Federation No. 2241769, IPC C21D 8/02, C22C 38/58, B21B 1/26, 2004

3. Patent of the Russian Federation No. 2262537, IPC C21D 8/02, C22C 38/46, 2005 - prototype.

Claims (2)

1. Method for the production of plate from high-strength and cold-resistant steel, including steel smelting, continuous casting into slabs, heating slabs, preliminary and final rolling and accelerated cooling, characterized in that they produce steel of the following chemical composition, wt.%:
FROM 0.02-0.10 Mn 0.5-1.5 Si 0, 10-0.50 Nb 0.010-0.10 Al 0.01-0.05 Ti 0.005-0.05 N 0.003-0.012, S 0.002 and less R 0.001-0.015 Sa 0.0002-0.005 Fe rest,
when the ratio 0.03 ≤ [C] × [Mn] <0.12,
where [C] × [Mn] is the content of carbon and manganese in the steel, while the slabs are heated to a temperature of 1100-1300 ° C, then the slabs are pre-rolled with a total degree of deformation of 50-70% in the direction perpendicular to the axis of the slab, and finally in the temperature range 900-750 ° C in the direction longitudinal to the axis of the slab with a total degree of deformation of 65-80%, after which the rolled products are accelerated to cool in the temperature range (Ar ₃ ± 30 ° C) - (600-400 ° C), and first to temperatures of 600-500 ° C at a speed of 15-30 degrees / s, and then at a speed of 10-15 degrees / s, after which from a temperature of 400 ° C to room temperature temperatures carry out delayed cooling at a rate of 0.05-0.15 deg / s. 2. The method according to claim 1, characterized in that the steel further comprises one or more elements from the series Mo, V, Ni, Cu, Cr, B in the following amount, wt.%:
Mo 0.05-0.35 V 0.01-0.15 Ni 0.01-0.50 Cu 0.01-0.50 Cr 0.01-0.50 AT 0.0005-0.005,
the sum of the elements Mo, Ni, Cu, and Cr does not exceed 1.0%.