CN102154593A - X80 steel grade anti-corrosion low-temperature seamless line pipe - Google Patents

Abstract

The invention provides an X80 steel grade anti-corrosion low-temperature seamless line pipe which comprises the following components in percentage by weight: 0.08 to 0.14 percent of C, 0.20 to 0.35 percent of Si, 1.10 to 1.40 percent of Mn, less than or equal to 0.015 percent of P, less than or equal to 0.005 percent of S, 0.10 to 0.20 percent of Mo, 0.020 to 0.060 percent of Al, 0.02 to 0.05 percent of Nb, 0.05 to 0.10 percent of V, 0.10 to 0.20 percent of Cu, 0.10 to 0.20 percent of Ni, less than or equal to 0.015 percent of Ti, less than or equal to 0.15 percent of Cr, 0.0015 to 0.0060 percent of Ca, less than or equal to 0.0005 percent of B, less than or equal to 0.012 percent of N, less than or equal to 0.43 percent of CEV, less than or equal to 0.23 percent of Pcm and trace amount of ferrum and impurity elements. The line pipe has the rigidity of less than or equal to 250 HV10 and grain size of more than or equal to 8 levels, and passes tests of hydrogen induced cracking (HIC) and sulfide stress corrosion (SSC) corrosion tests at the ductile-brittle transition temperature of below -60 DEG C. The line pipe has the advantages that the integral tissue of a pipe body is uniform, the equivalent carbon content is less than the that of the requirement of the American petroleum institute (API) 5L standard, the welding performance is high, the low-temperature toughness and anti-corrosion performance are excellent, the cost is low, and the requirement of users on the X80 steel grade seamless line pipe can be met completely.

Description

The anticorrosive low temperature seamless tube of X80 grade of steel spool

Technical field

The invention belongs to the weldless steel tube manufacturing technology of metallurgical industry, relate to the anticorrosive low temperature seamless tube of a kind of X80 grade of steel spool.

Background technology

Pipeline transportation is the mode of movement of the big and economic oil of a kind of scale, Sweet natural gas, can not only transfer oil, Sweet natural gas, also can be used as the significant transportation means of coal and other solid matter.The four big natural gas fields of China (sweet peaceful, Qaidam, Qinghai, Shan, Tarim Basin, South Sinkiang, Chongqing of Sichuan) resource is away from the consumption market, so build high pressure length apart from line of pipes be solve over a long time, the major measure of extensive transport natural gas, and China will seek abroad from now on oily resource by sea-freight or pipe-line transportation to domestic.Worldwide pipe line steel grade of steel be along with the raising of transfer pressure to high grade of steel development.By adopting the high grade of steel pipeline steel tube can the riser tubing transfer pressure, improve transport efficiency and attenuate pipeline wall thickness, correspondingly reduce welding material consumption, thereby save the investment of building line of pipes.

The development of the progress of metallurgical technology and microalloying pipe line steel, make produce have high strength, high tenacity, good welds pipe line steel become a reality, and mainly concentrates at present on two grade of steels of X65, X70, X80 is the newer grade of steel of development in recent years.Adopt modifier treatment, because the restriction of the carbon equivalent of pipe line steel, satisfy high grade of steel, good welding property but has great difficulty.The patent that manufactures and designs the aspect at the high grade of steel pipeline of API 5L has X80 at present, the X100 grade of steel, but these patents all are at welded tube, and also do not have at the pipeline patent of weldless steel tube X80 grade of steel.Along with pipe-line transportation pressure towards high pressure development with reduce the trend of investment, also can increase gradually the demand of X80 grade of steel weldless steel tube, particularly have the weldless steel tube of anticorrosive low-temperature performance.

Summary of the invention

For solving the problem that exists in the above-mentioned technology, the purpose of this invention is to provide the anticorrosive low temperature seamless tube of a kind of X80 of being applicable to grade of steel spool, satisfy the needs of market to X80 grade of steel weldless steel tube.Can reach the X80 grade of steel performance of API 5L regulation by the seamless tube spool of this method manufacturing, and have good anticorrosive and low-temperature performance.

For achieving the above object, technical solution of the present invention provides the anticorrosive low temperature seamless tube of a kind of X80 grade of steel spool, and the weight proportion of the steel grade component of this line pipe is:

C:0.08～0.14%, Si:0.20～0.35%, Mn:1.10～1.40%, P≤0.015%, S≤0.005%, Mo:0.10～0.20%, Al:0.020～0.060%, Nb:0.02～0.05%, V:0.05～0.10%, Cu:0.10～0.20%, Ni:0.10～0.20%, Ti :≤0.015%, Cr :≤0.15%, Ca:0.0015～0.0060%, B :≤0.0005%, N :≤0.012%, CEV≤0.43%, Pcm≤0.23%, all the other are iron, the impurity element trace;

The performance of the anticorrosive low temperature seamless tube of X80 grade of steel spool:

Yield strength 555～705MPa, tensile strength 625～825MPa, yield tensile ratio≤0.92, unit elongation 〉=20%, the summer is than V-type-46 ℃ horizontal full-scale ballistic work 〉=100J, single shear area 〉=80%, on average 〉=90%, ductile-brittle transition temperature is below-60 ℃, hardness≤250HV10, grain fineness number 〉=8 grade are by HIC and SSC corrosion test.

The invention has the beneficial effects as follows: the anticorrosive low temperature seamless tube of this X80 grade of steel spool adopts the micro-alloyed steel design, is fit to the production of the anticorrosive low temperature seamless tube of X80 grade of steel spool, and the body global tissue is even, is uniform tempering bainite+ferrite (B _Return+ F) to organize, grain fineness number is tiny; Carbon equivalent is low, and welding property is good; Special 0.10～0.20% Cu and the Ni of adding makes to reduce cost the usage quantity of saving microalloy element Cr and Mo when this steel grade has good anticorrosive and low-temperature performance, can satisfy the requirement of X80 grade of steel seamless tube spool fully.Compare X80 grade of steel line pipe name SMYS with X70 grade of steel line pipe and improve 14.4%, nominal minimum tensile strength improves 9.6%, and impelling strength does not descend, and has reached good combination of strength and toughness.The ductile-brittle transition temperature of this steel grade is less than-60 ℃, and low-temperature flexibility is good, particularly can be by being strict in the corrosion test of 44 editions requirements of API 5L.Adopt the X80 grade of steel pipeline steel tube can the riser tubing transfer pressure, improve transport efficiency and attenuate pipeline wall thickness, reduce welding material consumption, save the investment of building line of pipes.Use this steel grade to produce X80 grade of steel seamless tube spool and can satisfy the requirement of user the anticorrosive low temperature seamless tube of high grade of steel spool.

Description of drawings

Fig. 1 is Φ 323.80 * 20.00mm X80 seamless tube spool of the present invention center 500X metallograph;

Fig. 2 is a tough-brittle transition curve of the present invention.

Embodiment

Reaching embodiment in conjunction with the accompanying drawings is illustrated the anticorrosive low temperature seamless tube of X80 grade of steel of the present invention spool.

In the anticorrosive low temperature seamless tube of the X80 grade of steel of the present invention spool main moiety being chosen reason is analyzed as follows:

Carbon: most economical, the most basic strengthening element in the steel, the effect by solution strengthening and precipitation strength has tangible effect to the intensity that improves steel, has that cost is low, the good advantage of regulation and control susceptibility.But the shortcoming that content is higher also to have welding property, mechanical property and anti-HIC (hydrogen induced cracking) performance of pair steel to have a negative impact.The strength matching of carbon and steel relation is also particularly important in addition, and proportional with the intensity of steel because of the height of carbon content, but the impelling strength of steel then obviously reduces, and do not satisfy the requirement to the steel high-intensity high-tenacity.Good welding property be gas transmission line the performance that must possess, the low then corresponding welding property of carbon is good.Take all factors into consideration the factor of each side, carbon content is controlled between 0.08～0.14%.

Manganese:, fairly obvious to the net effect of pipeline yield strength and tensile strength by solution strengthening, refined crystalline strengthening and phase transformation strengthening as deoxidation material necessary element in steel-making.Manganese can also improve the toughness of steel when improving intensity, reduce the ductile-brittle transition temperature of steel.American petroleum institute standard (API) regulation: X80 pipe line steel manganese content is not more than 1.90%, reduces the loss of strength that causes to remedy carbon content.According to the characteristics of seamless pipe line steel, manganese content is controlled between 1.10～1.50%.

Niobium: one of main alloy element of the design's steel grade is the micro alloying element that adds, and can improve intensity by refined crystalline strengthening and precipitation strength, can improve the low-temperature impact toughness of steel simultaneously.Thereby niobium reduces the thermoplasticity of steel and has increased the hot cracking tendency that contains niobium steel strand.Take all factors into consideration, X80 pipe line steel content of niobium is controlled between 0.020～0.050%.

Vanadium: one of main alloy element of the design's steel grade, have higher precipitation strength effect and grain refining effect, by the raising surrender and the tensile strength of ferrite precipitation hardening and refinement ferrite crystal grain, but require finishing temperature low and add jointly with elements such as manganese, nitrogen, effect is better.When niobium, the compound use of vanadium microalloy element, vanadium is together by improve the intensity of steel in the ferrite with the VC precipitation strength.Take all factors into consideration, content of vanadium is controlled between 0.05～0.10%.

Molybdenum: one of main alloy element of the design's steel grade, enlarge the austenite phase region, postpone austenite and when ferrite transformation, separate out ferrite formation, promote the principal element of the formation of bainite, phase-change organization plays an important role to control, behind the molybdenum of Xiang Gangzhong adding 0.10～0.20%, even also can obtain tangible bainite structure under slower speed of cooling, while can be so that organize further refinement owing to phase transformation changes to the low temperature direction.Take all factors into consideration, X80 pipe line steel molybdenum content is controlled between 0.10～0.20%.

Aluminium: be reductor, its content is lower than at 0.005% o'clock can not reach this effect, but during too high levels, easily causes inclusion to increase, and produces hairline, reduces toughness and processing characteristics, therefore its content is controlled between 0.020～0.060%.

Nickel: one of main alloy element of the design's steel grade, reinforcement, atmospheric corrosion resistance element, improve intensity and can suitably improve toughness by the ferrite solution strengthening, can obviously improve sea water corrosion resistant with copper or phosphorus coexistence, also can overcome the hot-short phenomenon of Copper Bearing Steel, therefore its content is controlled between 0.10～0.20%.

Copper: one of main alloy element of the design's steel grade, the atmospheric corrosion resistance element adds easily generation " hot-short " and steel surface seminess separately, share with nickel, and effect is obvious, therefore its content is controlled between 0.10～0.20%.

In addition, in order to control the inclusion of steel grade, also carried out the calcium processing, for corrosion resistance and the low-temperature flexibility that improves steel, control S≤0.005%, P≤0.015%, the five-harmful elements sum requires less than 200ppm, finished product nitrogen is less than 120ppm, and finished product oxygen is less than 30ppm, and finished product hydrogen is less than 2ppm.

The anticorrosive low temperature seamless tube of X80 grade of steel of the present invention spool by above-mentioned steel grade component weight item is: C:0.08～0.14%, Si:0.20～0.35%, Mn:1.10～1.40%, P≤0.015%, S≤0.005%, Mo:0.10～0.20%, Al:0.020～0.060%, Nb:0.02～0.05%, V:0.05～0.10%, Cu:0.10～0.20%, Ni:0.10～0.20%, Ti :≤0.015%, Cr :≤0.15%, Ca:0.0015～0.0060%, B :≤0.0005%, N :≤0.012%, CEV≤0.43%, Pcm≤0.23%, all the other are iron, the impurity element trace.

Molten steel after the LF refining is intact is through VD vacuum stripping, and feeding Ca silk carries out calcium to be handled, and the suitable back of temperature is gone up continuous casting platform and carried out continuous casting, and casting process uses terminal induction stirring.

The performance of the anticorrosive low temperature seamless tube of X80 grade of steel of the present invention spool is:

Yield strength 555～705MPa, tensile strength 625～825MPa, yield tensile ratio≤0.92, unit elongation 〉=20%, the summer is than V-type-46 ℃ horizontal full-scale ballistic work 〉=100J, single shear area 〉=80%, on average 〉=90%, ductile-brittle transition temperature is below-60 ℃, hardness≤250HV10, grain fineness number 〉=8 grade are by HIC and SSC corrosion test.

With Φ 323.8 * 20.00mm and Φ 508 * 26.19mm X80 seamless tube spool is that example further specifies:

1, batching smelting, continuous casting

By above-mentioned steel grade component weight item be: C:0.08～0.14%, Si:0.20～0.35%, Mn:1.10～1.40%, P≤0.015%, S≤0.005%, Mo:0.10～0.20%, Al:0.020～0.060%, Nb:0.02～0.05%, V:0.05～0.10%, Cu:0.10～0.20%, Ni:0.10～0.20%, Ti :≤0.015%, Cr :≤0.15%, Ca:0.0015～0.0060%, B :≤0.0005%, N :≤0.012%, CEV≤0.43%, Pcm≤0.23%, all the other are iron, the impurity element trace.

Molten steel after the LF refining is intact is through VD vacuum stripping, and feeding Ca silk carries out calcium to be handled, and the suitable back of temperature is gone up continuous casting platform and carried out continuous casting, and casting process uses terminal induction stirring, continuously cast bloom diameter of phi 350mm and Φ 400mm.Working control alloying constituent such as following table (w%):

Steel grade	C	Si	Mn	P	S	Ni	Cr	Mo	Cu
										1	0.08	0.34	1.40	0.008	0.003	0.18	0.15	0.19	0.19
2	0.09	0.32	1.38	0.006	0.004	0.17	0.12	0.18	0.18

3	0.10	0.30	1.35	0.007	0.003	0.16	0.10	0.17	0.17
										4	0.11	0.28	1.30	0.010	0.004	0.15	0.09	0.16	0.16
5	0.12	0.26	1.25	0.009	0.003	0.14	0.07	0.15	0.15
										6	0.13	0.24	1.20	0.008	0.004	0.13	0.05	0.14	0.14
7	0.14	0.22	1.15	0.007	0.003	0.11	0.04	0.12	0.12
										Steel grade	Al	V	Nb	Ti	N	Ca	B	CEV	Pcm
1	0.034	0.10	0.05	0.008	0.0089	0.0031	0.00024	0.43	0.20
										2	0.041	0.09	0.04	0.012	0.0073	0.0037	0.00035	0.42	0.21
3	0.038	0.08	0.04	0.009	0.0067	0.004	0.00019	0.42	0.21
										4	0.056	0.07	0.04	0.014	0.0071	0.0052	0.00030	0.41	0.22
5	0.051	0.07	0.04	0.007	0.0068	0.0028	0.00041	0.41	0.22
										6	0.047	0.07	0.04	0.007	0.0056	0.0035	0.00032	0.40	0.23
7	0.029	0.06	0.03	0.011	0.0048	0.0049	0.00024	0.39	0.23

Annotate: steel grade 2 is produced Φ 323.8 * 20.00mm; Steel grade 4 is produced Φ 508 * 26.19mm.

2, Φ 323.8 * 20.00mm and Φ 508 * 26.19mm X80 seamless tube spool the finished product performance

(1) stretches

Get the pole sample of vertical Φ 12.7mm, tensile property result such as following table according to the standard-required tensile property.

Steel grade	Temperature	Orientation	Rt0.5(MPa)	Rm(MPa)	Rt/Rm	A％
							1	22	Vertically	590	670	0.88	28
2	22	Vertically	600	685	0.88	27
							3	22	Vertically	610	690	0.88	26
4	22	Vertically	625	710	0.88	25

(2) impact

The horizontal V8 impact specimen of employing 10mm * 10mm * 55mm carries out-46 ℃ shock test, impact property result such as following table.

(3) hardness

H.7.3.3.2 require to measure the horizontal Vickers of pipe (HV10) hardness according to 44 editions appendix of API 5L, interior outer surface is respectively measured 4 points and is averaged, hardness result such as following table.

(4) grain fineness number

Φ 323.8 * 20.00mm pipe is carried out metallurgical analysis, and as shown in Figure 1, it is organized as tempering bainite+ferrite (B _Return+ F), grain fineness number is 9 grades.

(5) series is impacted

Adopt the horizontal V8 impact specimen of 10mm * 10mm * 55mm to carry out from 0 to-80 ℃ serial shock test, impact results such as following table, the tough-brittle transition curve of having drawn Φ 323.8 * 20.00mm is as shown in Figure 2.

(6) corrosion test

According to NACE TM 0177-2005 standard X80 line pipe mother metal is vertically carried out four-point bending SSC test, sample applies 80% of actual yield strength, soaks 720h in standardized solution NACE-A, and it is 2.7 that solution begins pH value, finishing pH value is 3.5, and test temperature is 23～27 ℃.According to NACE TM 0284-2003 standard X80 line pipe mother metal is vertically carried out the HIC test, at NACE-A solution soaking 96h.Corrosion test result such as following table.

Claims (1)

1. the anticorrosive low temperature seamless tube of X80 grade of steel spool, the weight proportion of the steel grade component of this line pipe is:

C:0.08～0.14%, Si:0.20～0.35%, Mn:1.10～1.40%, P≤0.015%, S≤0.005%, Mo:0.10～0.20%, Al:0.020～0.060%, Nb:0.02～0.05%, V:0.05～0.10%, Cu:0.10～0.20%, Ni:0.10～0.20%, Ti :≤0.015%, Cr :≤0.15%, Ca:0.0015～0.0060%, B :≤0.0005%, N :≤0.012%, CEV≤0.43%, Pcm≤0.23%, all the other are iron, the impurity element trace;

The performance of the anticorrosive low temperature seamless tube of X80 grade of steel spool:

Yield strength 555～705MPa, tensile strength 625～825MPa, yield tensile ratio≤0.92, unit elongation 〉=20%, the summer is than V-type-46 ℃ horizontal full-scale ballistic work 〉=100J, single shear area 〉=80%, on average 〉=90%, ductile-brittle transition temperature is below-60 ℃, hardness≤250HV10, grain fineness number 〉=8 grade are by HIC and SSC corrosion test.

Images