CN104789858A

CN104789858A - Economical low-temperature seamless tube suitable for -75 DEG C and manufacturing method thereof

Info

Publication number: CN104789858A
Application number: CN201510125586.9A
Authority: CN
Inventors: 张清廉; 王起江; 翟国丽
Original assignee: Baoshan Iron and Steel Co Ltd
Current assignee: Baoshan Iron and Steel Co Ltd
Priority date: 2015-03-20
Filing date: 2015-03-20
Publication date: 2015-07-22
Anticipated expiration: 2035-03-20
Also published as: CN104789858B

Abstract

The invention discloses an economical low-temperature seamless tube suitable for -75 DEG C. The economical low-temperature seamless tube comprises the following chemical elements in mass percentage: 0.12% or lower of C, 0.05-0.2% of Si, 0.05-1.2% of Mn, 0.005-0.04% of Al, 0.001-0.01% of B and the balance of Fe and other inevitable impurities. The invention further discloses a manufacturing method of the economical low-temperature seamless tube suitable for -75 DEG C. The manufacturing method comprises the following steps: performing smelting; performing casting to obtain a tube blank; heating the tube blank; carrying out perforating, emptying reduction and continuously rolling; performing reheating and heat preservation; performing tension reduction; performing air cooling; performing heating to austenitize a steel tube, and heat preservation, wherein the heating temperature is 870-920 DEG C and the heat preservation period is 10-60 min; performing air cooling again. The low-temperature seamless tube has relatively high low-temperature yield strength, low-temperature tensile strength and elongation, good low-temperature impact performance and tensile performance, and low production cost.

Description

A kind of economical low temperature seamless tube and manufacture method thereof being applicable to-75 DEG C

Technical field

The present invention relates to a kind of pipe fitting and manufacture method thereof, particularly relate to a kind of seamless tube and manufacture method thereof.

Background technology

In essence, low temperature environment is mainly divided into two classes, and a class is at low temperatures in order to realize a certain processing requirement, such as, preparing propylene by dehydrogenating propane, another kind of, be conveying after liquefaction of gases or storage in order to raise the efficiency, the long distance pipelines such as the former such as Sweet natural gas, the latter is liquefied gas bottle such as.For metal, austenitic stainless steel can meet above-mentioned requirements because it does not have obvious ductile-brittle transition temperature, but lack competitiveness because its valency is high, therefore, the ferrite type low-temperature steel that cost performance is high is the focus of investigation of materials and the emphasis of engineer applied.From element to low-temperature flexibility, it is generally acknowledged that C, Si, P, S and N etc. are harmful elements, especially P, its harm is maximum, Mn and Ni is then beneficial element.Such as, ferrite type cryotron mainly relies on Ni and Mn element, and especially Ni element can realize low-temperature performance.Usually, often increase the Ni of 1wt%, the fragility critical transition temperature of steel can reduce about 20 DEG C, but, add the high cost of Ni.

In American Standard cryotron system, A333 is because of containing 5 temperature provinces totally 9 cryotron trades mark and the most comprehensive.Although do not limit Ni content in Gr.1, namely do not need Ni to realize its low-temperature performance, its minimum use temperature is only-45 DEG C.Although Gr.6 and Gr.10 has corresponding requirement for Ni content, but, Gr.6 and Gr.10 only defines the upper limit of Ni, and the two minimum use temperature is also only-45 DEG C and-60 DEG C respectively, does not need to realize its low-temperature performance by Ni so also can regard as.The pipe fitting of other trade mark, the minimum use temperature of such as Gr.7 and Gr.9 is-75 DEG C, and Ni content (intermediate value) is respectively 2.3wt.% and 1.92wt.%.The minimum use temperature of Gr.3 and Gr.4 is-100 DEG C, and Ni content (intermediate value) is respectively 3.5wt.% and 0.725wt.%.Although the minimum use temperature of Gr.8 and Gr.11 can reach-195 DEG C, but the Ni content in the pipe fitting of these two kinds of trades mark is respectively up to 9wt.% and 36wt.%.

At present, China mainly contains the low temperature seamless tube included in GB/T18984 and GB150 standard and has 4 temperature grades totally 7 trades mark.From component system, adopt with Mn for Ni, and generate carbonitride by V and Nb element, in order to reduce the bad effect of the harmful elements such as C, N, reach the object of crystal grain thinning and raising low-temperature flexibility.In these low temperature seamless tubes, except 16MnDG is C-Mn system carbon steel, all the other are all low alloy steel, and wherein, the Ni content of 09MnNiD and 06Ni3MoDG is respectively 0.55wt.% and 3.1wt.%.On Applicable temperature, 16MnDG, 10MnDG and 09DG are applicable to the Working environment of temperature >=-45 DEG C, 09MnD is applicable to the Working environment of temperature >=-50 DEG C, 9Mn2VDG and 09MnNiD is applicable to the Working environment of temperature >=-70 DEG C, and 06Ni3MoDG is applicable to the Working environment of temperature >=-100 DEG C.

Publication number is CN101545077A, and publication date is on September 30th, 2009, the Chinese patent literature that name is called " a kind of Cryogenic Steel and manufacture method thereof ".This patent documentation describes a kind of C:0.060% ~ 0.090%, Si :≤0.20%, Mn:1.10% ~ 1.50%, P≤0.015%, S :≤0.003%, ALS:0.040% ~ 0.070%, Cu:0.05% ~ 0.45%, Ni:0.05 ~ 0.35%, Cr:0.05% ~ 0.30%, Ti:0.007% ~ 0.011%, Nb:0.007% ~ 0.020%, N≤0.0040%, Ca:0.001% ~ 0.005%, all the other are for Fe and be inevitably mingled with.Manufacturing technology steps described in this patent documentation makes steel plate can obtain excellent low-temperature flexibility and can bear the steel plate of Large Heat Input Welding.

Publication number is CN103114250A, publication date is on May 22nd, 2013, the Chinese patent literature that name is called " level-B steel of a kind of anti-subzero 70 degree of low-temperature impacts and preparation method thereof " discloses a kind of level-B steel of anti-subzero 70 degree of low-temperature impacts, and each chemical composition of this level-B steel is made up of the Fe of C, Si, Mn, P, S, Cr, Ni, V, Re, Cu and surplus.This preparation method comprises step: 1) add lime in basic electric arc furnace, and steel scrap and electrode join carbon, are heated to scrap melting; 2) add iron ore in molten steel, intensification is skimmed; 3) add Fe-Mn alloy again, lime, fluorite, silica brick and carbon dust, obtain white slag molten steel; 4) add various alloy and electrode, use Al deoxidation, add rare earth Re silk after tapping, after cast, obtain level-B steel; 5) secondary normalizing treatments B level steel is adopted.

Summary of the invention

The object of the present invention is to provide a kind of economical low temperature seamless tube being applicable to-75 DEG C, it has larger low temperature yield strength, tensile strength and unit elongation, and this low temperature seamless tube also possesses the comprehensive cryogenic mechanics performance such as good cryogenic stretching performance and excellent low temperature impact properties.In addition, of the present invention being applicable to does not contain Ni alloying element in the economical low temperature seamless tube of-75 DEG C.

To achieve these goals, the present invention proposes a kind of economical low temperature seamless tube being applicable to-75 DEG C, its chemical element mass percentage content is:

C：≤0.12％，

Si：0.05～0.2％，

Mn：0.05～1.2％，

Al：0.005～0.04％，

B：0.001～0.01％，

Surplus is Fe and other inevitable impurity.

The principle of design of each chemical element be applicable in the economical low temperature seamless tube of-75 DEG C of the present invention is:

Carbon: in the inventive solutions, C is the harmful element of the low-temperature performance damaging steel.In principle, its content should be more low better.But C in seamless tube of the present invention is outwardness, and exceedingly reduce C content and uneconomical, moreover the too low intensity for material of C content also can have a negative impact.For this reason, should control as≤0.12wt.% in the C content be applicable in the economical low temperature seamless tube of-75 DEG C of the present invention.One more preferred embodiment under, need C content to control as≤0.10wt.%.

Silicon: Si is also the harmful element that can have an impact to low-temperature performance, but it can improve the intensity of material by solution strengthening.Because the ability of the deteriorated low-temperature performance of Si element is lower than C element, therefore, adopt low carbon content to coordinate and ensure certain strength of materials, the mass percentage of the Si element be applicable in the economical low temperature seamless tube of-75 DEG C of the present invention is 0.05wt.% ~ 0.20wt.%.More preferably, this mass percentage being applicable to the Si element in the economical low temperature seamless tube of-75 DEG C controls as 0.10wt.% ~ 0.18wt.%.

Manganese: Mn is also the beneficial element that can have an impact to low-temperature performance, and can improve the intensity of material.But when Mn too high levels, microstructure segregation in material tendency increases the weight of, hydrogen-type corrosion can forming core on the carbide in segregation line, and crackle has the trend expanded along low-temperature transformation product (martensite or bainite).In order to give full play to the beneficial effect of Mn and suppress its deleterious effect, the content of Mn element in the inventive solutions should control as 0.05wt.% ~ 1.20wt.%.Preferably, the content of Mn element may be controlled to 0.10wt.% ~ 1.00wt.%.

Aluminium: Al is the beneficial element being conducive to low-temperature performance.But, during too high Al element, be easy to cracking during rolling, thus the lumber recovery of seamless tube can be reduced.For the purpose of the every chemical element equilibrium material, the content of the Al element in technical scheme of the present invention should control be: 0.005wt.% ~ 0.040wt.%.Preferably, the content of the Al element in technical scheme of the present invention should control as 0.010wt.% ~ 0.035wt.%.

Boron: B can crystal grain thinning, and can improve crystal grain bonding force and intensity.Material cracks is caused in order to prevent Al too high.Although can significantly improve intensity during B too high levels, the yield tensile ratio of Cryogenic Steel is advisable lower than 0.9, moreover too high B content is also unfavorable for processing characteristics.Therefore, the content of the B be applicable in the economical low temperature seamless tube of-75 DEG C of the present invention is set as 0.001wt.% ~ 0.010wt.%.Further, the content of above-mentioned B can also be set as 0.003wt.% ~ 0.007wt.%.

In the inventive solutions, P and S is main residual harmful element.Be produced into for the ease of manufacturing, reducing and improve the overall mechanical property of seamless tube, what control this case respectively is applicable to P≤0.015wt.% in the economical low temperature seamless tube of-75 DEG C and S≤0.008wt.%.Preferably, can respectively P be controlled lower than 0.010wt.% and S be controlled lower than 0.005wt.%, to reduce the side effect of harmful element further,

The economical low temperature seamless tube being applicable to-75 DEG C of the present invention does not add Ni element, on the basis of adding certain content Mn element, by the suitable harmful element such as control C, Si, P, S, and add Al and B element, coordinate the manufacturing process of postorder again, to realize crystal grain thinning and to reduce anisotropy tendency, namely make low temperature seamless tube of the present invention have higher isotropy, thus realize the cryogenic mechanics performance of low temperature seamless tube-75 DEG C time, especially low temperature impact properties.

Further, the microtexture being applicable to the economical low temperature seamless tube of-75 DEG C of the present invention is ferrite and pearlite, wherein pearlitic Phase Proportion 0 < P≤5%.

Further, the grain fineness number being applicable to the economical low temperature seamless tube of-75 DEG C of the present invention is higher than 7 grades.

Further, the ratio being applicable to the equiax crystal of the economical low temperature seamless tube of-75 DEG C of the present invention is greater than 55%.

Correspondingly, another object of the present invention is to provide a kind of manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C, it comprises step:

(1) smelt;

(2) casting obtains pipe;

(3) by heating of pipe blank;

(4) subtracted and tandem rolling by perforation, sky;

(5) reheat and be incubated;

(6) open and subtract;

(7) thermal treatment is incubated after making steel pipe austenitizing: Heating temperature is 870 ~ 920 DEG C, and soaking time is 10 ~ 60min;

(8) air cooling.

Why heating controls with incubation step after making steel pipe austenitizing by the technical program: Heating temperature is 870 ~ 920 DEG C, soaking time is 10 ~ 60min, be because: when soaking time is more than 10min, just can guarantee that the alloying elements such as Al dissolve in matrix, and not in crystal boundary enrichment, soaking time is controlled at below 60min meanwhile, then can prevent excessive grain from growing up, thus guarantee the overall performance of steel pipe.

Further, in the manufacture method of the economical low temperature seamless tube being applicable to-75 DEG C of the present invention, in above-mentioned steps (3), Heating temperature is 1200 ~ 1300 DEG C.

Further, in the manufacture method of the economical low temperature seamless tube being applicable to-75 DEG C of the present invention, in above-mentioned steps (4), tube rolling temperature is 1000 ~ 1150 DEG C.

Further, in the manufacture method of the economical low temperature seamless tube being applicable to-75 DEG C of the present invention, in above-mentioned steps (5), reheating temperature is 960 ~ 1000 DEG C, and soaking time is 15 ~ 45min.

Further, in the manufacture method of the economical low temperature seamless tube being applicable to-75 DEG C of the present invention, in above-mentioned steps (6), a desuperheat degree is 930 ~ 980 DEG C.

The economical low temperature seamless tube being applicable to-75 DEG C of the present invention has good low temperature impact properties.

In addition, the economical low temperature seamless tube being applicable to-75 DEG C of the present invention has higher low temperature yield strength, tensile strength and unit elongation.

In addition, the economical low temperature seamless tube being applicable to-75 DEG C of the present invention has excellent tensile property.

Meanwhile, because of the present invention being applicable to does not add Ni element in the economical low temperature seamless tube of-75 DEG C, its cost of alloy is low, and Productive statistics is saved.

By the manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C of the present invention can produce obtain intensity and unit elongation high, low temperature impact properties is good, good and the seamless tube that isotropy is excellent of tensile property, this seamless tube can be suitable for the Working environment of low temperature (lower than-75 DEG C).

Accompanying drawing explanation

Fig. 1 is the micro-aobvious organization chart of the low temperature seamless tube in embodiment A 3.

Fig. 2 is that embodiment A 3 samples the comparison diagram of radial indentation low-temperature impact work with the longitudinal direction of the Gr.7 in American Standard A333.

Fig. 3 is that embodiment A 3 samples the comparison diagram of radial indentation low-temperature impact work with the hoop of the Gr.7 in American Standard A333.

Fig. 4 is that embodiment A 3 samples the comparison diagram of longitudinal breach low-temperature impact work with the hoop of the Gr.7 in American Standard A333.

Fig. 5 is embodiment A 3 and the comparison diagram of the low temperature yield strength of the Gr.7 in American Standard A333.

Fig. 6 is embodiment A 3 and the comparison diagram of the low temperature tensile strength of the Gr.7 in American Standard A333.

Fig. 7 is embodiment A 3 and the comparison diagram of the unit elongation of the Gr.7 in American Standard A333.

Embodiment

Illustrate below in conjunction with accompanying drawing and be applicable to the economical low temperature seamless tube of-75 DEG C and manufacture method makes further explanation with specific embodiment to of the present invention, but this explanation and explanation do not form improper restriction to technical scheme of the present invention.

The economical low temperature seamless tube being applicable to-75 DEG C in embodiment A 1-A6 is manufactured according to following step:

1) smelt: smelting molten steel, refining the mass percent proportioning controlling each chemical element in steel are as shown in table 1.;

2) cast: casting obtains pipe, and observes pipe with or without defect;

3) heat: by heating of pipe blank, Heating temperature is 1200 ~ 1300 DEG C;

4) perforation, sky subtract and tandem rolling: tube rolling temperature is 1000 ~ 1150 DEG C;

5) reheat and be incubated: reheating temperature is 960 ~ 1000 DEG C, and soaking time is 15 ~ 45min;

6) open and subtract: a desuperheat degree is 930 ~ 980 DEG C;

7) thermal treatment is incubated after making steel pipe austenitizing: Heating temperature is 870 ~ 920 DEG C, and soaking time is 10 ~ 60min;

8) air cooling.

Concrete technology parameter in each step involved by above-mentioned manufacture method is in detail see table 2.

Table 1 lists the mass percentage content of each chemical element made in the low temperature seamless tube of embodiment A 1-A6.

Table 1. (wt.%, surplus is Fe and other the inevitable impurity except P and S)

Sequence number	C	Si	Mn	Al	B	P	S
								A1	0.12	0.05	0.10	0.005	0.001	0.015	0.008
A2	0.07	0.12	1.20	0.010	0.005	0.008	0.006
								A3	0.03	0.10	0.75	0.035	0.003	0.005	0.004
A4	0.10	0.15	0.05	0.020	0.010	0.007	0.005
								A5	0.08	0.20	0.35	0.040	0.006	0.010	0.003

A6

0.05

0.18

1.00

0.032

0.007

0.006

0.005

Table 2 lists the processing parameter of the manufacture method of the low temperature seamless tube in embodiment A 1-A6.

Table 2.

The economical low temperature seamless tube being applicable to-75 DEG C after test to obtain mechanical property parameters as shown in table 3, table 3 lists the every mechanical property parameters being applicable to the economical low temperature seamless tube of-75 DEG C in embodiment A 1-A6.

Table 3 lists every mechanical property parameters of the low temperature seamless tube in embodiment A 1-A6.

Table 3.

Sequence number	Yield strength (MPa)	Tensile strength (MPa)	Unit elongation (%)	Yield tensile ratio (%)
					A1	310	530	45	55.47
A2	482	615	30	78.37
					A3	380	609	35	62.40
A4	309	530	37	58.30
					A5	315	543	35	58.01
A6	510	665	32	76.69
					Comparative example Gr.7	≥240	≥450	≥22	53.33

As can be seen from Table 3, compare to comparative example Gr.7, yield strength >=the 294MPa of the low temperature seamless tube in this case embodiment A 1-A6, tensile strength >=530MPa, unit elongation >=30%, and yield tensile ratio >=55.47%, illustrate thus, the tensile mechanical properties of the low temperature seamless tube in embodiment A 1-A6 all gets a promotion, and especially yield strength is significantly improved, and the raising of yield strength is conducive to the thinning wall thickness of seamless tube.Above-mentioned low temperature seamless tube possesses excellent cryogenic mechanics performance.The economical low temperature seamless tube being applicable to-75 DEG C of the present invention can substitute in prior art containing Ni element Gr.7 and Gr.9 cryotron and under-75 DEG C of pole low-temperature working environment can be widely used in.

Fig. 1 display be the microtexture of low temperature seamless tube in embodiment A 3, as can be seen from Figure 1, its microtexture is that wherein, pearlitic Phase Proportion is lower than 5% with ferrite for a small amount of pearlitic close grain microtexture of advocating peace.The grain fineness number of this microtexture about 7 grades, it is fine grained steel; Equiax crystal is more, the ratio of equiax crystal is greater than 55%, and do not have obvious banded structure, from microtexture, such microtexture not only ensure that low temperature seamless tube possesses higher impelling strength, also assures that each consistence to impelling strength of low temperature seamless tube.

Fig. 2 to Fig. 4 respectively illustrates the relativity between every low-temperature impact work of the Gr.7 in embodiment A 3 and American Standard A333.

The mean value of the comparative example in above-mentioned figure and minimum value are all selected from the Gr.7 in American Standard A333.As shown in Figure 2, Figure 3 and Figure 4, when test temperature is low to moderate-75 DEG C, the longitudinal direction of embodiment A 3 samples radial indentation low-temperature impact work, hoop sampling radial indentation low-temperature impact work and hoop and samples longitudinal breach low-temperature impact work all far above the performance index of every low-temperature impact work of the Gr.7 in American Standard A333, illustrate that low temperature seamless tube low temperature impact properties of the present invention is excellent, the specification of quality of impact property when meeting-75 DEG C.In the prior art, usually the banded structure along rolling direction can be formed in the operation of rolling, cause the mechanical property property of there are differences of all directions, that is, be subject to the impact of banded structure, the lateral performance of pipe fitting comes low than longitudinal performance, and time serious, its lateral performance is lower than longitudinal performance by 30% ~ 50%.But, because embodiment A 3 has microtexture as shown in Figure 1, therefore, under the test temperature of-70 DEG C, the mean value of the ballistic work of embodiment A 3 have dropped 20%, is starkly lower than the fall of the mean value of the Gr.7 ballistic work at such a temperature in American Standard A333.

Fig. 5 to Fig. 7 respectively illustrates the relativity between the low temperature yield strength of the Gr.7 in embodiment A 3 and American Standard A333, low temperature tensile strength and unit elongation.

As shown in Figure 5, the low temperature yield strength of embodiment A 3 does not reduce significantly along with the reduction of test temperature, increases on the contrary, can predict thus in the test temperature interval of-50 DEG C ~-60 DEG C, when test temperature is-75 DEG C, its low temperature yield strength also will maintain this level.

As shown in Figure 6 and Figure 7, the low temperature tensile strength of embodiment A 3 and unit elongation also do not reduce along with the reduction of test temperature, and along with the decline of temperature, low temperature tensile strength and unit elongation maintain same level substantially.Content from Fig. 5 to Fig. 7 can be known, the cryogenic stretching performance of embodiment A 3 is also all better than the Gr.7 in American Standard A333.In addition, owing to not adding Ni element in embodiment A 3, its production cost is lower than Gr.7, and cost performance is higher than Gr.7.

It should be noted that above enumerate be only specific embodiments of the invention, obviously the invention is not restricted to above embodiment, have many similar changes thereupon.If all distortion that those skilled in the art directly derives from content disclosed by the invention or associates, protection scope of the present invention all should be belonged to.

Claims

1. be applicable to the economical low temperature seamless tube of-75 DEG C, it is characterized in that, its chemical element mass percentage content is:

C：≤0.12％，

Si：0.05～0.2％，

Mn：0.05～1.2％，

Al：0.005～0.04％，

B：0.001～0.01％，

Surplus is Fe and other inevitable impurity.

2. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, its microtexture is ferrite and pearlite, wherein pearlitic Phase Proportion 0 < P≤5%.

3. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, its grain fineness number is higher than 7 grades.

4. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, the ratio of its equiax crystal is greater than 55%.

5. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, Si constituent content is 0.10 ~ 0.18wt.%.

6. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, Mn constituent content is 0.10 ~ 1.00wt.%.

7. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, Al constituent content is 0.010 ~ 0.035wt.%.

8. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, B element content is 0.003 ~ 0.007wt.%.

9. be applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 1, it is characterized in that, C element content is≤0.10wt.%.

10., as the manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C in claim 1-9 as described in any one, it is characterized in that, comprise step:

(1) smelt;

(2) casting obtains pipe;

(3) by heating of pipe blank;

(4) subtracted and tandem rolling by perforation, sky;

(5) reheat and be incubated;

(6) open and subtract;

(7) thermal treatment is incubated after making steel pipe austenitizing: Heating temperature is 870-920 DEG C, and soaking time is 10-60min;

(8) air cooling.

11. manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 10, it is characterized in that, in described step (3), Heating temperature is 1200-1300 DEG C.

12. manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 10, it is characterized in that, in described step (4), tube rolling temperature is 1000-1150 DEG C.

13. manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 10, it is characterized in that, in described step (5), reheating temperature is 960-1000 DEG C, and soaking time is 15-45min.

14. manufacture method being applicable to the economical low temperature seamless tube of-75 DEG C as claimed in claim 10, is characterized in that, in described step (6), a desuperheat degree is 930-980 DEG C.