CN101020986A - N80 level petroleum pipe produced with micro alloyed medium carbon steel and its production process - Google Patents

Abstract

The present invention is process of producing N80 level petroleum pipe with microalloyed medium carbon steel 34Mn2VN. The present invention is developed based on the research in the effects of micro alloy elements V and N content and the rolling and cooling process on the performance of steel pipe. The production process without on-line normalizing has low power consumption, less production steps, short production period, lowered production cost, raised steel pipe size stability and other advantages.

Description

Non-hardened and tempered steel is produced N80 steel grade petroleum pipeline and technology thereof

One, technical field

Belong to metallurgical technology field, particularly a kind of Technology that adopts microalloying non-hardened and tempered steel and temperature-controlled rolling explained hereafter N80 steel grade petroleum pipeline.

Two, background technology

At present, both at home and abroad N80 steel grade petroleum pipeline production technique is mostly for adopting modified thermal treatment after the thermal distortion, and this process energy consumption height, operation are many, cause the production cost height.

, international online retrieval domestic and network data library searching by " non-quenched and tempered N 80 steel grade petroleum pipeline and production technique thereof " carried out, retrieve 12 pieces of pertinent literatures, it is comprehensively compared, analyzes, can think: " non-quenched and tempered N 80 steel grade petroleum pipeline and production technique thereof " adopting no online normalizing controlled rolling process and V, the production of N microalloying to meet API 5CT standard N80 grade of steel 34Mn ₂On the VN steel petroleum pipeline, not seeing has identical patent documentation and open report both at home and abroad.

Three, summary of the invention

The purpose of this invention is to provide a kind of employing microalloying non-hardened and tempered steel and temperature-controlled rolling explained hereafter N80 steel grade petroleum pipeline; because this steel grade just possesses good comprehensive mechanical properties in rolling state; thereby realize the online normalizing of petroleum pipeline or the modifier treatment operation of this grade of steel of cancellation; simplify its production technique; enhance productivity, reduce production costs.

Because N80 steel grade petroleum pipeline product is except that requiring to have the high strength, also need satisfy product in use to the technical requirements of plasticity, toughness etc., therefore, the content proportioning of carbon and alloying element is scientific and reasonable in the steel, and makes every effort to harmful element, nonmetal inclusion and gas content in the steel are dropped to bottom line.

For this reason, have only the carbon content in the suitable reduction steel, could satisfy steel pipe in use to plasticity and flexible requirement, the present invention adopts the dual technology of alloy strengthening and process strengthening to reach high strength and makes it have certain plasticity and toughness.

Based on above-mentioned mentality of designing and process imagine, the present invention selects to adopt the basic chemical ingredients and the suitable alloying route that adds trace Cr, Mo, Nb, V element of low-carbon high-manganese at first, has drafted the testing program of N80 steel grade petroleum pipeline steel two cover chemical ingredientss.By test, check, analysis, contrast, optimize the chemical ingredients of the N80 steel grade petroleum pipeline non-hardened and tempered steel that can satisfy the API standard-required substantially earlier.Then test-results and practical condition are carried out comprehensive analyses and comparison, with this as the foundation that chemical ingredients is screened, adjusted, then, carry out new test again, in test, further the test steel grade is carried out check, the analysis of chemical ingredients and mechanical property, up to finding optimum chemical composition and the process system that meets API standard N 80 steel grade petroleum pipeline non-hardened and tempered steels.In order to achieve the above object, not only want the stagnation point of determination test steel grade, also will analyze content and the relational degree of mechanical property and the interaction relation of each alloying element of each alloying element, the content of each alloying element of properly distributed.Take turns test through several, according to the analytical results of port test steel grade chemical ingredients with property relationship, with reference to the pertinent data introduction, Cr, Mo alloying element are no longer added in decision, and improve the steel pipe over-all properties by adding V, and decision employing 34Mn ₂The V steel is produced N80 steel grade petroleum pipeline pipe as a trial.The chemical ingredients (wt%) of its test molten steel is

C	Si	Mn	P	S	Al	V
							0.32-0.36	0.32-0.25	1.66-1.61	0.019-0.017	0.005	0.028-0.020	0.09-0.10

Test-results shows, adopts 34Mn ₂V produces the N80 steel grade petroleum pipeline, handles through online normalizing, and the tensile strength of steel pipe, unit elongation, impelling strength have all reached API standard value, particularly notched bar impact strength and exceeded the API standard more than 2 times, and is bigger than the increase rate of not handling through normalizing process; Though yield strength has also reached the API standard value, be in the standard value lower limit.For a change this situation has been done further test.

According to the data introduction, containing the V steel increases N content and can effectively improve intensity, and every increase by 0.001% nitrogen can increase the intensity of 6Mpa, for checking, still adopts 34Mn ₂The V steel is as the test steel grade, and replaces the V-Fe alloy to add the V-N alloy, adds a small amount of Ti simultaneously, with this explained hereafter the effective steel of 4 stove N80 steel level oils.

To with above-mentioned 4 stove steel rolling and see with the result that the fished pipe that different normalizing process are handled carries out service check; its intensity and impelling strength all reach the requirement of in the API standard N80 steel grade petroleum pipeline being stipulated; yield strength also all reaches this standard-required, than the nearly 50Mpa of yield strength mean height that tested steel last time.Think that this mainly is because interaction forms VN or V (C, N) tissue in N in the steel and V each different process section in system steel process, thereby has brought into play due to the different physical metallurgy effects.

This test has also been carried out adding Al and has not been added the influence test of Al to steel tube performance when adding the V-N alloy, and through check, the one heat steel of no Al is all more on the low side than the yield strength that contains the Al heat, and unit elongation and notched bar impact strength then are more or less the same.

The influence of different finishing temperatures to heterogeneous microstructure also studied in experiment.4 kinds of finishing temperatures have been selected in experiment for use, and each temperature has been selected 3 kinds of cooling rates for use.Simulation finish rolling after strain, can determine by the check microtexture: finishing temperature is that 850 ℃～820 ℃, cooling rate are controlled at 0.8 ℃/s, can obtain comparatively ideal microtexture.

Experiment conclusion is thought, under the prerequisite of proof strength, for improving its plasticity toughness index, can realize the highly malleablized of product by following measure:

(1) obtaining tiny ferrite+pearlitic structure, be to improve the flexible effective measure, and suitable speed of cooling has very big promoter action to the elimination of banded structure, the refinement of crystal grain.

(2) the timely phase critical point of correctly measuring this steel grade could provide reliable foundation for the correct process system of formulating.

(3), need do dynamic phase transformation test and control cold simulation test for measuring each phase transition temperature interval and finding best speed of cooling.

For production meets API standard N 80 steel grade petroleum pipelines, the service check result according to the test steel has formulated each process system of production scene.

Determine that best rolling technology route is: heating → perforation → MPM tandem rolling → sizing → cold bed blower fan cooling.

Temperature schedule is according to the characteristic of 34Mn2VN steel grade and varying in size of pipe diameter and difference to some extent: (1), to the minor diameter pipe, because its thermal capacity is little, can make full use of fume afterheat, both energy-conservation, do not influence heating quality again; (2), taking to heat at a slow speed below 750 ℃, taking rapid heating more than 750 ℃, too fast and plasticity is reduced to avoid grain growth, also can avoid occurring heating quality defectives such as hot tearing; (3), according to rolling rhythm, suitably adjust each section temperature, rolling when very fast, adopt the upper limit of temperature, when roll speed is slow, adopt the lower limit of temperature; (4), finishing temperature is controlled at 830-860 ℃, is good with 850 ℃; Perforation back hollow billet temperature is controlled at 1210 ± 10 ℃; (5), rate of heating selects 7-8cm/min for use, for big pipe, should guarantee the homogeneity of heating of pipe blank heat-up time greater than 3.5 hours, reduces the section temperature difference; (6), when shut down or the time to be rolled more in short-term; carry out cooling system to be rolled, shut down when handling overlong time when having an accident, temperature should be reduced to below the Ar3 line (725 ℃); avoid at high temperature the residence time long, produce heating quality defectives such as grain growth, overheated, segregation, serious decarburization.

By measuring dynamically cooling CCT curve continuously, studied 34Mn2VN steel phase transformation law in the continuous cooling process after distortion, promptly as 2 ℃/s 〉=U _{Cooling rate}Can obtain comparatively ideal tissue during＞0.8 ℃/s.

By controlling cold and hot simulated experiment, research different cooling speed impact flexible influences, and analytical data shows that the cooling rate effect of 0.8 ℃/s is better, can obtain more tiny ferrite piece and can avoid occurring bainite structure again.

Utilize processing method of the present invention to produce 52365.509 tons of non-quenched and tempered N 80 steel grade petroleum pipelines,, meet every performance requriements of API standard fully through check.

Adopt non-hardened and tempered steel following advantage to be arranged: (1) save energy than the well casing that produces oil with quenched and tempered steel; (2) reduce production process, improve the stability of fished pipe dimensional precision; (3) simplify production technique, shorten the production cycle, reduce cost; (4) improve working conditions, realize cleaner production.

The present invention is through with N80 1 class petroleum pipeline must be through the history of normalizing process or online normalizing, for the production of N80 1 class petroleum pipeline provides a kind of new process program, for the development of microalloying non-hardened and tempered steel provides big industrial examples of many successful.

Four, embodiment

At first, according to the test steel grade two cover chemical ingredients schemes of drafting, melting in the 150Kg intermediate frequency furnace, 24 stove steel are refined in examination altogether, cast little steel ingot respectively, be swaged into the sample (its compression ratio is 5.7) of 20 * 100mm again, will forge sample and carry out 860 ± 10 ℃ of normalizing air coolings processing, carry out chemical ingredients and every service check then, first to overlap into the result of offshoot program as shown in table 1:

Table 1 test actual chemical ingredients of steel (wt%) and performance

C	Si	Mn	P	S	Cr	Al	Nb	V	Carbon equivalent	Rt0.5 (Mpa)	Rm (Mpa)	A2″ (％)	Horizontal AKL (J)	Vertical AKL (J)
															0.24- 0.32	0.19- 0.33	1.38- 1.91	0.022- 0.026	0.010- 0.017	0.26- 0.23	0.004 - 0.002	0.035 - 0.038	0.081 - 0.084	0.54 - 0.69	577- 385	638- 876	29.5 - 17.0	147- 12	107- 11

Wherein, the intermediate frequency furnace of 2 stove 32Mn6,1 stove 20# steel test steel sees Table 2 with big chemical ingredients and the mechanical property comparing result of producing steel

Table 232Mn6, test of 20# steel port and big composition (wt%) and the performance comparison of producing

Steel grade	C	Si	Mn	P	S	Al	Rt0.5 (Mpa)	Rm (Mpa)	A2″ (％)	Horizontal AKL (J)	Vertical AKL (J)	Remarks
													32Mn6	0.31	0.24	1.44	0.026	0.010	0.013	442	672	27	40	56	Port
32Mn6	0.30	0.21	1.38	0.023	0.010		426	650	26	62	46	Port
													20#	0.19	0.24	1.38	0.025	0.010	0.003	280	437	32	28	45	Port
32Mn6	0.32	0.25	1.27	0.022	0.009	0.017	463	687	27.6	42	37	Big production
													20#	0.21	0.27	1.45	0.016	0.008	-	341	471	27	93	82	Big production

By comparing, can judge by the forging sample of the steel grade of the designed first cover chemical ingredients scheme examination refining and can represent actual rolling state in the production substantially, and composition be screened with reference to the API standard, adjust in good time and carry out second after the design and take turns test.

According to chemical ingredients testing program and the test method newly drafted, smelt 11 stoves in the intermediate frequency furnace test, smelt existing sophisticated 32Mn6 (2 stove) and 20# (1 stove) steel simultaneously, behind the forging sample, check every performance index.

Test-results shows that the mechanical property after the normalizing of port test steel is suitable substantially with the performance data of actual production, can be used as the reference value of THE INDUSTRIAL TRIAL.Wherein have every index of 1 stove all to reach the API standard-required, just yield strength and impelling strength are limit on the lower side, and therefore, on this composition basis, further analyzing influence yield strength and flexible principal element are adjusted in the test of next round port again.

Detected result has been carried out the yield strength grey interaction analysis of effect factors, mainly analyzed C, Mn, Cr, the Al influence degree to yield strength (Rt0.5), promptly relational degree is: rCr=rMn＞rC＞rAl.

Hence one can see that, and C, Mn, Cr, Al are Cr=Mn＞C＞Al to the Rt0.5 influence degree successively.

Think that the optimum content of Mn is 1.5-1.8%, and Cr too high levels impact is unfavorable, can consider to add a little Mo elements, take all factors into consideration each influence factor after, drafted second and taken turns the test composition range.

Second takes turns the test steel smelts at the 150kg intermediate frequency furnace equally, smelt 9 stoves altogether, and to different normalizing temperatures (promptly 860 ℃, 820 ℃, the 780 ℃) check carried out of every performance afterwards, assay sees Table 3,4.

Table 3 second is taken turns the test actual chemical ingredients of steel (%)

Scheme	C	Si	Mn	P	S	Al	Cr	Mo	Nb	V	Carbon equivalent
												1-9	0.29- 0.43	0.27- 0.15	1.39- 1.86	0.023- 0.030	0.013- 0.005	0.012- 0.030	0.50- 0.30	0.52- 0.30	0.033- 0.046	0.15- 0.086	0.73- 0.89

Table 4 second is taken turns the test steel mechanical property

Numbering	Forge attitude				860 ℃ of normalizings
									Rt 0.5(Mpa)	Rm(Mpa)	A2(％)	AKL(J)	Rt0.5(Mpa	Rm(Mpa)	A2″(％)	AKL(J)
	1-9	722.5- 615.0	1155.0- 900.0	13.5- 17.5	20.0- 7.4	630.0- 492.5	1260- 987.5	17.0- 14.5									9.7- 43.8
Numbering									820 ℃ of normalizings				780 ℃ of normalizings
	Rt 0.5(Mpa)	Rm(Mpa)	A2(％)	AKL(J)	Rt0.5(Mpa	Rm(Mpa)	A2″(％)	AKL(J)
									1-9	642.5- 760.0	935.0- 1260.0	13.5- 19.0	6.9- 20	512.5- 885.0	920.0- 1335.0	13.0- 19.0	8.8- 17.3

As seen contrast two takes turns test-results: first round test steel carbon equivalent is in the 0.54-0.69 scope, and corresponding yield strength extends in 21.5-29.5%, impact of collision 42-147J, transverse impact 34-107J at 433-577Mpa after 860 ℃ of normalizings.Second takes turns in the test carbon equivalent 0.73-0.89 scope, and after same 860 ℃ of normalizings, yield strength extends in 15-16% at 515-630Mpa, impelling strength 10-20J.By analyzing as can be known, if will guarantee that yield strength is higher, the also corresponding raising of carbon equivalent, should be about 0.7, so but can not guarantee impelling strength, and carbon equivalent is lower when impelling strength is higher, and will obtain the non-modified composition of the N80 steel grade petroleum pipeline that high strength, a high tenacity matches, its selectable narrow range.

Guaranteeing under the sufficiently high carbon equivalent situation of yield strength, also will find out the interaction relation of each alloying element, and each constituent content of properly distributed.

According to the analytical results of port test steel grade chemical ingredients and property relationship, Cr, Mo are no longer added in decision, and improve the steel pipe over-all properties by adding V, and 34Mn is adopted in decision ₂The V steel is produced 3 boiler tube bases, and specification is Φ 180mm.Test molten steel chemical ingredients (finished product) sees Table 5.

Table 5 molten steel chemical ingredients (wt%)

Melting number	C	Si	Mn	P	S	Al	V
								01202514	0.32	0.32	1.66	0.019	0.005	0.028	0.10
01500495	0.36	0.28	1.63	0.018	0.005	0.021	0.09
								01500496	0.36	0.25	1.61	0.017	0.005	0.020	0.09

Pipe gas content (wt%) sees Table 6.

Table 6 pipe gas content (wt%)

Melting number	O	N
			01200514	0.00095	0.00610
01500495	0.00149	0.00651

Φ 180mm pipe is rolled into Φ 139.7 * 9.17mm N80 steel grade petroleum pipeline, has formulated different normalizing process, promptly 820 ℃, 860 ℃, 900 ℃ and through high pressure water and without the simultaneous test of high pressure water, test-results sees Table 7.

Table 7 steel pipe assay

Numbering	Mechanical property			Impact			Metallographic examination (level)			Technology
											Rt 0.5(Mpa)	Rm(Mpa)	A2″(％)	Vertically (J)			A	B	Grain fineness number
	1A	649	852	28	90	88	90	0.5	0.5											8.5-9	Not normalizing
2A										566	755	30.5	106	94	100	0.5	0.5	9-9.5	Come out of the stove for 820 ℃
	3A	608	761	32.5	96	96	90	0.5	1											9-9.5	Come out of the stove for 860 ℃
4A										564	775	30.5	99	98	98	0.5	0.5	9-9.5	Come out of the stove for 900 ℃
	5A	535	792	30.5	43	42	36	0.5	0.5											9-9.5	Come out of the stove for 860 ℃
2B										507	722	32.5	100	106	100	0.5	0.5	9-9.5	Come out of the stove for 820 ℃
	3B	525	735	31	74	84	70	0.5	1											9-9.5	Come out of the stove for 860 ℃
4B										574	789	30.5	110	111	106	0.5	0.5	9-9.5	Come out of the stove for 900 ℃

Annotate: on behalf of steel pipe, numbering A pass through high pressure water; On behalf of steel pipe, numbering B do not pass through high pressure water;

Test-results shows, adopts 34Mn ₂V produces the N80 steel grade petroleum pipeline, handles through online normalizing, and steel pipe tensile strength, unit elongation, impelling strength have all reached API standard value, particularly notched bar impact strength and exceeded the API standard more than 2 times, than the normalizing process increase rate is not bigger; Though yield strength reaches the API standard value, be in the standard value lower limit.

According to the data introduction, containing the V steel increases N content and can effectively improve intensity, and every increase by 0.001% nitrogen can increase the intensity of 6Mpa, is checking, and the present invention adopts 34Mn ₂The V steel grade also replaces the V-Fe alloy with the V-N alloy, adds a small amount of Ti simultaneously, and in order to produce the effective steel of 4 stove N80 steel level oils, the pipe specification is Φ 230mm.

The V-N alloy adds after refining, and the every stove of add-on (80 tons of converters) is 100-105kg, is equivalent to 0.00125-0.00131%, and nitrogen in steel content assay sees Table 8.

N content (%) in table 8 steel

Melting number	Refining adds the preceding N content of V-N alloy	Refining adds N content behind the V-N alloy	The pipe gas content		The steel pipe gas content
							V	N	O	N
			1	0.00413	0.01188	0.00352					0.01320	0.00283- 0.00243	0.01343- 0.01361
2	0.00366	0.01190					0.00210	0.01197	0.00256	0.01264
			3	Sample is bad	0.01422	0.00226					0.01412	0.00154-0.00184	0.01525-0.01440
4	0.00471	Sample is bad					0.00266	0.01434	0.00245	0.01448

N content assay by the test steel is seen, test adopts the V-N alloy to replace in the N80 grade of steel molten steel of V-Fe production, N content adds average 0.0040% before the V-N alloy by refining and increases to and add average 0.0130% behind the V-N alloy, has increased nearly 0.0090%.To the fished pipe check, N content reaches 0.0130%-0.0145%.

Pipe is carried out metallographic examination, and the result shows that nitrogen content does not have influence to the sufur printing and the high power inclusion of pipe.To rolling fished pipe carried out the chemical ingredients check, assay sees Table 9.

Table 9 production tube composition (%)

Melting number	Lot number	C	Si	Mn	P	S	Al	V	Ti
										1*	1-1 1-2 1-3	0.361 0.355 0.361	0.282 0.282 0.281	1.700 1.780 1.820	0.0176 0.0178 0.0182	0.0058 0.0059 0.0054	＜0.005 ＜0.005 ＜0.005	0.094 0.094 0.094	0.013 0.015 0.014
2		0.321 0.352 0.359	0.240 0.212 0.211	1.716 1.603 1.603	0.0172 0.0175 0.0172	0.0071 0.0079 0.0079	0.015 0.017 0.016	0.096 0.098 0.098	0.020 0.021 0.020
										3	3-1 3-2 3-3	0.347 0.349 0.352	0.278 0.274 0.276	1.730 1.730 1.720	0.0176 0.0179 0.0176	0.0051 0.0054 0.0058	0.013 0.013 0.014	0.092 0.093 0.094	0.017 0.018 0.018
4		0.392	0.386	1.954	0.0156	0.0081	0.016	0.100	0.016

Annotate: a stove of marking * number is no aluminum steel, and all the other have been aluminum steel.

By the specification that is rolled into to two stove different aluminum content is that the N80 steel grade petroleum pipeline of Φ 244.5 * 8.94mm carries out the mechanical property simultaneous test, and has carried out 860 ℃, 900 ℃, the 950 ℃ online normalizing Processing Test of differing temps, and its assay sees Table 10.

Table 10 steel tube performance assay

Melting number	Lot number	Performance			Impact of collision AKV (J)	Technology
							Rt 0.5(Mpa)	Rm(Mpa)	A2″(％)
		1*	1-1	565-605						792-860	27-29	49-72	Come out of the stove for 860 ℃
1-2	570-595				795-820	27-29	56-72	900 ℃ of mountain stoves
			1-3	575-600					785-815	28-31	58-60	Come out of the stove for 950 ℃
3	3-1				575-643	780-851	25-29	54-66					Come out of the stove for 860 ℃
		3-2	575-630	780-865					27-29	54-68	Come out of the stove for 900 ℃
	3-3				575-630	810-790	27.5-26	48-56				950 ℃ of mountain stoves
		API		552-758					≥689	≥18.5	≥32.8

Annotate: impact toughness sample is 7.5 * 10 * 55; A stove of marking * number is no aluminum steel, and all the other are for there being aluminum steel.

Through to different normalizing process rolling fished pipe service check result see; intensity and impelling strength all reach the requirement of in the API standard N80 steel grade petroleum pipeline being stipulated; yield strength also all reaches standard-required, than the nearly 50Mpa of yield strength mean height of previous test.

This test has also been carried out the performance comparison that Al arranged and do not have Al when adding the V-N alloy, a stove that does not wherein have Al is all more on the low side than the yield strength that contains the Al heat, and unit elongation and notched bar impact strength are more or less the same.

By simultaneous test, chemical ingredients and production technique are determined again.Chemical ingredients sees Table 11.

Table 11 chemical ingredients scope (%)

C	Si	Mn	P	S	Al	V	Ti
								0.34-0.38	0.25-0.35	1.65-1.85	≤0.025	≤0.020	0.02-0.05	0.08-0.12	0.015-0.020

Through test of many times, determine that best process flow is: heating → perforation → MPM tandem rolling → sizing → cold bed blower fan cooling.

The result shows, obtains tiny ferrite+pearlitic structure, be to improve the favourable measure of flexible, and speed of cooling has very big influence to the elimination of banded structure, the refinement of crystal grain.

(YB/T5127-93) stagnation point of steel is measured according to " the critical point determination method (plavini) of steel ", stagnation point is respectively: Ac ₃=797 ℃, Ac ₁=715 ℃; Ar ₃=725 ℃, Ar ₁=602 ℃.

By measuring dynamically cooling CCT curve continuously, studied 34Mn2VN steel phase transformation law in the continuous cooling process after distortion, promptly as 2 ℃/s 〉=U _{Cooling rate}Can obtain comparatively ideal tissue during＞0.8 ℃/s.

By controlling cold and hot simulated experiment, the influence of research different cooling speed impact flexible.The cooling rate that experiment is selected for use is respectively: 0.8,1,2 ℃/s experimentizes on Gleeble-1500 thermal analogy machine.The impact specimen specification is 5 * 10 * 55mm, and 0 ℃ of test temperature obtains vertical 1/2Akv (0 ℃) value shown in table 12,13.By the table in data we as can be seen, the cooling rate effect of 0.8 ℃/s is better.

The ballistic work that table 12 different cooling speed obtains

Speed of cooling ℃/s	0.8	1.5	2	Finished product tubing
					Vertical 1/2A kv(0℃)J	31.5	27.4	25.6	15.0

Speed of cooling ℃/s	0.8	1.5	2
				Vertical 1/2A kv(0℃)J	19	27	25
Rockwell hardness HRC	22.5	25	25.6

The performance that table 13 different cooling speed obtains

The influence of different finishing temperatures to heterogeneous microstructure also studied in experiment.

4 kinds of finishing temperatures have been selected in experiment for use, and each temperature has been selected 3 kinds of cooling rates for use, simulates the finish rolling after strain, can determine by the difference of observing microtexture: finishing temperature be 850 ℃～820 ℃, cooling rate about 0.8 ℃/s, microtexture is more satisfactory.

In order to obtain qualified API standard N 80 steel grade petroleum pipelines that meet, can assay according to the test rigidity, formulate the process system of production scene.

Heating cycle:, take different heating cycles according to the characteristic and the pipe diameter difference of 34Mn2VN steel grade.1,, can make full use of the fume afterheat heating to the minor diameter pipe; 2, taking to heat at a slow speed below 750 ℃, taking rapid heating more than 750 ℃; 3, according to rolling rhythm, suitably adjust each section temperature, rolling when very fast, adopt the upper limit of temperature, when roll speed is slow, adopt the lower limit of temperature; 4, finishing temperature is controlled at 830-860 ℃, is good with 850 ℃; Perforation back hollow billet temperature is controlled at 1210 ± 10 ℃; 5, rate of heating is selected 7-8cm/min for use, and for big pipe, heat-up time was greater than 3.5 hours; 6, when shut down or the time to be rolled more in short-term; carry out cooling system to be rolled, shut down when handling overlong time when having an accident, temperature should be reduced to below the Ar3 line (725 ℃); avoid at high temperature the residence time long, produce heating quality defectives such as grain growth, overheated, segregation, decarburization be serious.

Roll speed (summary).

Every index of body and service check situation are shown in table 14,15

The every index performance of table 14 body

	Specification	The performance rate % that once is up to the standards	Service check qualification rate %	Lumber recovery %	Qualification rate %	Ratio of first-grade products %
							Standard value	mm	95		85	92
Test value	φ 114.3 * 6.35 (22 stove)	100 (22 stoves)	100 (22 stoves)	85.87	93.24	78.92
							φ 139.7 * 7.72 (316 stove)	(91.8 290 stove)	(96.83 306 stove)	88.89	96.67	90.26
	φ 177.8 * 8.05 (145 stove)	(95.2 138 stove)	100 (145 stoves)	86.58	96.05	79.36
							Add up to 483 stoves	93.17	96.48	88.23	96.56	87

Table 15 mechanical property and impact assay cartogram

		Yield strength (Rr0.5) MPa	Tensile strength (Rm) MPa	Unit elongation (A) %	Ballistic work (Akv) J (vertical, 1/2 size, 0 ℃)
						Standard value		552-758	≥689	≥16	≥15
Test value	Mean	620	838	25	44
						Minimum value	440	695	13.5	13.33
	Maximum value	729	949	33.5	98.79

Finished product composition test value statistics sees Table 16

Table 16 phosphorus, sulphur content finished product composition test value statistical unit: %

		P	S
				Standard value		≤0.030	≤0.030
Test value	Mean	0.0166	0.0075
				Minimum value	0.009	0.005
	Maximum value	0.024	0.019

After adopting result of study, every index performance of body and mechanical properties test situation see Table 17,18.

The every index performance statistics of table 17 body

	Specification	The performance rate % that once is up to the standards	Service check qualification rate %	Lumber recovery %	Qualification rate %	Ratio of first-grade products %
							Standard value	mm	95		85	92
Test value	φ 114.3 * 6.35 (22 stove)	100 (22 stoves)	100 (22 stoves)	85.87	93.24	78.92
							φ 139.7 * 7.72 (30 stoves	(96.7 29 stove)	100 (30 stoves)	88.65	95.40	89.28
	φ 177.8 * 8.05 (26 stove)	100 (26 stoves)	100 (26 stoves)	96.73	96.61	85.94
							Add up to by (78 stove)	98.41	100	90.65	94.83	86.89

Table 18 mechanical property and impact assay cartogram

		Yield strength (Rt0.5) MPa	Tensile strength (Rm) MPa	Unit elongation (A) %	Ballistic work (Akv) J (0 ℃ of vertical 1/2 size)
						Standard value		552-758	≥689	≥16	≥15
Test value	Mean	627	834	25.5	51
						Minimum value	560	757	21	29
	Maximum value	729	965	29.5	92

Claims (7)

1, a kind of non-hardened and tempered steel is produced N80 steel grade petroleum pipeline and technology thereof, it is characterized in that chemical ingredients scope (%) is C0.34-0.38, Si 0.25-0.35, Mn 1.65-1.85, P≤0.025, S≤0.020, Al 0.02-0.05, V 0.08-0.12, Ti 0.015-0.020, N 0.0130-0.0145; The rolling technology route is: heating → perforation → MPM tandem rolling → sizing → cold bed blower fan cooling; Finishing temperature is that 860 ℃～820 ℃, cooling rate are at 2 ℃/s 〉=U _{Cooling rate}＞0.8 ℃/s.

2, a kind of non-hardened and tempered steel as claimed in claim 1 is produced N80 steel grade petroleum pipeline and technology thereof, the process system that it is characterized in that heating because its thermal capacity is little, can make full use of fume afterheat for (1), to the minor diameter pipe, both energy-conservation, do not influence heating quality again; (2), taking to heat at a slow speed below 750 ℃, taking rapid heating more than 750 ℃, too fast and plasticity is reduced to avoid grain growth, also can avoid occurring heating quality defectives such as hot tearing; (3), according to rolling rhythm, suitably adjust each section temperature, rolling when very fast, adopt the upper limit of temperature, when roll speed is slow, adopt the lower limit of temperature.

3, a kind of non-hardened and tempered steel as claimed in claim 1 is produced N80 steel grade petroleum pipeline and technology thereof, it is characterized in that finishing temperature is controlled at 820-860 ℃, is good with 850 ℃.

4, a kind of non-hardened and tempered steel as claimed in claim 1 is produced N80 steel grade petroleum pipeline and technology thereof, and the back hollow billet temperature that it is characterized in that boring a hole is controlled at 1210 ± 10 ℃;

5, rate of heating is selected 7-8cm/min for use, and for big pipe, should guarantee the homogeneity of heating of pipe blank heat-up time greater than 3.5 hours, reduces the section temperature difference;

6, a kind of non-hardened and tempered steel as claimed in claim 1 is produced N80 steel grade petroleum pipeline and technology thereof; it is characterized in that working as shutdown or time to be rolled more in short-term; carry out cooling system to be rolled; shut down when handling overlong time when having an accident; temperature should be reduced to below the Ar3 line (725 ℃); avoid at high temperature the residence time long, produce heating quality defectives such as grain growth, overheated, segregation, serious decarburization.

7, a kind of non-hardened and tempered steel as claimed in claim 1 is produced N80 steel grade petroleum pipeline and technology thereof, it is characterized in that its stagnation point is respectively: Ac ₃=797 ℃, Ac ₁=715 ℃; Ar ₃=725 ℃, Ar ₁=602 ℃.

8, a kind of non-hardened and tempered steel as claimed in claim 1 is produced N80 steel grade petroleum pipeline and technology thereof, it is characterized in that the V-N alloy adds after refining, and add-on is 0.00125-0.00131%.