CN104959784A - Preparation method of P91 seamless steel pipe - Google Patents
Preparation method of P91 seamless steel pipe Download PDFInfo
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- CN104959784A CN104959784A CN201510322995.8A CN201510322995A CN104959784A CN 104959784 A CN104959784 A CN 104959784A CN 201510322995 A CN201510322995 A CN 201510322995A CN 104959784 A CN104959784 A CN 104959784A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
- B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
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Abstract
The invention discloses a preparation method of a P91 seamless steel pipe. The preparation method of the P91 seamless steel pipe is economical and practical, and meets product quality requirements. The method includes the steps of pipe blank heating, perforating, pipe continuous rolling and sizing. P91 steel is forged, annealed and peeled, a round billet is manufactured, a through hole is punched, the diameter of the through hole is 15% to 20% of that of the round billet, and the through hole is blocked through a tagger before the round billet is heated; a segmented heating mode is adopted, the round billet is preheated to 800 DEG C, heat is preserved for 2 h, the round billet is heated to 1280 DEG C at the temperature rise speed not larger than 120 DEG C/h, and heat is preserved for 3 h; in the perforating process, the circumferential speed of a pipe blank does not exceed 3 m/s, and the rotation speed is 70% of that of low alloy steel; rolling is conducted at the large differential speed, and the speed of a core rod is 90% of that of a low alloy steel core rod.
Description
Technical field
The present invention relates to metallurgical material field, particularly relate to a kind of P91 seamless steel pipe preparation method.
Background technology
In recent years, China's power industry develop rapidly, boiler of power plant develops to the super-critical and ultra super-critical power unit of Large Copacity, high parameter, and this proposes requirements at the higher level to boiler steel, and general high-temperature steel will have high creep rupture strength, limited hardness, good toughness.P91 is on the basis of P9 (9Cr-1Mo) steel, while the residual deleterious element content such as restriction C content bound, more strictly control P and S, with the addition of carbide V and Nb of a certain amount of N and trace, reach crystal grain thinning, improve the object of steel pipe creep rupture strength, the novel ferrite type heat-resisting alloy steel of one of formation.P91 has good comprehensive mechanical property, and welding performance and process industrial art performance good.This steel pipe difficult point is that P91 materials processing temperature range is narrow, high temperature hot deformation resistance greatly, easily occurs inside and outside folding, to cooling velocity sensitivity etc.When applying hot rolling technology and producing P91 seamless steel pipe, there is product surface quality and dimensional accuracy is poor, the problems such as rate is lower of becoming a useful person.
Summary of the invention
The technical problem to be solved in the present invention be to provide a kind of economic, practical and meet product quality require P91 seamless steel pipe preparation method.
For reaching above-mentioned purpose, a kind of P91 seamless steel pipe of the present invention preparation method, comprises the following steps:
P91 steel makes round base after forging, anneal, stripping off the skin, and gets through hole, and the front tagger of circle base heating blocks described through hole, carries out heating of pipe blank → perforation → Continuous Seamless Tube Mill → sizing afterwards;
Wherein heating of pipe blank step adopts heat stepwise mode to be heated to 1280 DEG C; During perforation, the peripheral speed of pipe is no more than 3m/s, and rotating speed is 70% of low-alloy steel; Adopt larger differential rolling, Mandrel velocity is 90% of low-alloy steel Mandrel velocity.
The diameter of wherein said through hole is 15% ~ 20% of circle base diameter.
Wherein said heat stepwise mode is: be first preheating to 800 DEG C, insulation 2h, then is heated to 1280 DEG C with the programming rate being not more than 120 DEG C/h, insulation 3h.
The main cause that P91 high alloy is difficult to rolling is: the elevated temperature strength that solution strengthening and secondary phase precipitate and formed.This shows that this alloy has high resistance to deformation characteristic when rolling and other deformation processing.Along with the increase of intensity, at any temperature, particularly in mesophilic range, the percentage elongation of alloy reduces.And the casting microstructure of this alloy is easily decomposed, and also can reduce percentage elongation and increase resistance to deformation characteristic.In general, alloying component is larger, and when solidifying, the trend of segregation is also larger.Therefore, P91 adopts forging stock, can improve organization internal structure, reduces the defects such as component segregation, shrinkage cavity, loose, micro-crack, increases equiaxial crystal ratio, refinement arborescent structure, obtain good forging stock quality.P91 high-alloy steel thermal conductivity factor is lower, and circle blank intermediate throughholes can homogenization temperature field, reduces blank thermal stress, reduces piercing force.But through-hole inner surface produces a large amount of oxide skin in heating process, has an impact to end product quality, especially inner surface quality impact is larger.For this reason, adopt tagger to block the hole at pipe two ends, after heating, inner surface oxide skin obviously reduces.What plug iron plate had can be knocked in transportation, even if do not knocked, and plug iron plate also not influence of rolled process and hollow billet inner surface quality.By production practices, through-hole diameter is the 15% ~ 20% more suitable of circle base diameter, if through-hole diameter is excessive, metal loss is comparatively large, less economical; If through-hole diameter is less, homogeneous temperature field DeGrain, product quality is poor.
The percentage elongation of P91 high alloy steel round blank is than the difference of common material, and pyroconductivity is also low.These factors dictate circle base can not heat too fast, otherwise will crack.Because heat conductivity is poor, when surface heating is too fast, circle base inside is heated up slower.If firing rate is too fast, the stress that surface heat expansion produces is enough to Yuan Picong center to be broken.The speed being controlled furnace temperature rising by a series of time step under normal circumstances.Therefore adopt heat stepwise mode, be first preheating to 800 DEG C, insulation 2h, then be heated to 1280 DEG C with the programming rate being not more than 120 DEG C/h, insulation 3h, can guarantee that whole round base all reaches rolling temperature.
Think, during perforation, the too high meeting of blank temperature causes plasticity to decline, aggravate this is because the peripheral speed (more than 5.4m/s) that during perforation, pipe is too high makes surfaces externally and internally rub, blank temperature is caused to raise (more than 1300 DEG C), cause alpha ferrite in steel to separate out and crystal boundary scaling loss thus, reduce plasticity.Be greater than the condition of 3m/s in deformation velocity under, chap and damping action in producing when pipe front end or rear end distortion, make the rolling of high-alloy steel become comparatively difficulty.During perforation, the peripheral speed of pipe is no more than 3m/s, and rotating speed is 70% of low-alloy steel.
The differential of Mandrel velocity more lower than rolled piece is larger, then differential effect is more obvious, and can reduce roll-force, minimizing is spreaded, and is not only conducive to extending, and is conducive to raising and rolls rear steel pipe sizes precision.But when Mandrel velocity is lower, relative velocity is large, and frictional heat is large, can cause plug quick abrasion, reduces the life-span.Therefore, Mandrel velocity is 90% of low-alloy steel Mandrel velocity.
The invention difference from existing technology is that the present invention achieves following technique effect:
The present invention utilizes advanced PQF unit to produce ferrite stainless steel P 91, respectively the heating cycle of this steel grade, piercing process and rolling mill practice are optimized, P91 can be produced efficiently and roll state seamless pipe, lumber recovery is high, quality is good, fill up the blank of Baogang in high-alloy seamless pipe field, there is good application value.
Detailed description of the invention
Below in conjunction with embodiment, to above-mentioned being described in more detail with other technical characteristic and advantage of the present invention.
A kind of P91 seamless steel pipe of the present invention preparation method, comprises the following steps:
P91 steel makes round base after forging, anneal, stripping off the skin, and gets through hole, and the front tagger of circle base heating blocks described through hole, carries out heating of pipe blank → perforation → Continuous Seamless Tube Mill → sizing afterwards;
Wherein heating of pipe blank step adopts heat stepwise mode to be first preheating to 800 DEG C, insulation 2h, then is heated to 1280 DEG C with the programming rate being not more than 120 DEG C/h, insulation 3h; During perforation, the peripheral speed of pipe is no more than 3m/s, and rotating speed is 70% of low-alloy steel; Adopt larger differential rolling, Mandrel velocity is 90% of low-alloy steel Mandrel velocity.
Embodiment
P91 circle base is Φ 430mm, and rolling state pipe specification is Φ 426mm × 34mm.Lumber recovery and pick material statistics, P91 blank annular furnace distribution and temperature settings, P91 blank annular furnace heating cycle, rolling torsion, tandem mill roll-force distinguish as shown in tables 1 to 5.
Table 1 lumber recovery expects statistics with picking
As can be seen from Table 1, when through-hole diameter is 75mm, lumber recovery is better.
Table 2 P91 blank annular furnace distribution and temperature are arranged
Table 3 P91 blank annular furnace heating cycle (heat time/h)
According to blank annular furnace distribution and the temperature setting of table 2, adopt 3 kinds of heating cycles of table 3.The P91 that mode of heating is produced of system 1 has a small amount of infolding; For cost-saving, the mode of heating of employing system 2 is produced, but perforation and mill load obviously increase, and institute's rolling seamless pipe quality is also undesirable; The P91 seamless pipe that the mode of heating of employing system 3 is produced is substantially identical with heating cycle 1.Therefore, annular furnace mode of heating adopts system 1 to produce P91 comparatively suitable.
Table 4 rolling torsion
As can be seen from Table 4, when high rotating speed 380rpm, card phenomenon during P91 occurs.After adjustment, rotating speed, when 300rpm, does not occur in the P91 operation of rolling that impact torque exceedes the phenomenon of more than punch protection moment of torsion, so just can largely avoid the generation of middle card phenomenon, and to produce seamless pipe quality better.Can reach a conclusion in conjunction with above-mentioned analysis, when rolling P91 product, getting through hole and reducing perforation rotating speed is necessary technique.
Table 5 tandem mill roll-force (kN)
The retained speed reduction of roll-force (1) and roll-force (2) is respectively 970mm/s and 930mm/s.
As can be seen from Table 5, when retained speed reduces to 930mm/s, roll-force is lower.
Above-described embodiment is only be described the preferred embodiment of the present invention; not scope of the present invention is limited; under not departing from the present invention and designing the prerequisite of spirit; the various distortion that those of ordinary skill in the art make technical scheme of the present invention and improvement, all should fall in protection domain that claims of the present invention determines.
Claims (3)
1. a P91 seamless steel pipe preparation method, is characterized in that comprising the following steps:
P91 steel makes round base after forging, anneal, stripping off the skin, and gets through hole, and the front tagger of circle base heating blocks described through hole, carries out heating of pipe blank → perforation → Continuous Seamless Tube Mill → sizing afterwards;
Wherein heating of pipe blank step adopts heat stepwise mode to be heated to 1280 DEG C; During perforation, the peripheral speed of pipe is no more than 3m/s, and rotating speed is 70% of low-alloy steel; Adopt larger differential rolling, Mandrel velocity is 90% of low-alloy steel Mandrel velocity.
2. P91 seamless steel pipe preparation method according to claim 1, is characterized in that: the diameter of described through hole is 15% ~ 20% of circle base diameter.
3. P91 seamless steel pipe preparation method according to claim 1, is characterized in that: described heat stepwise mode is: be first preheating to 800 DEG C, insulation 2h, then is heated to 1280 DEG C with the programming rate being not more than 120 DEG C/h, insulation 3h.
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| CN201510322995.8A CN104959784A (en) | 2015-06-12 | 2015-06-12 | Preparation method of P91 seamless steel pipe |
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Citations (7)
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| JP2001329316A (en) * | 2000-05-22 | 2001-11-27 | Sanyo Special Steel Co Ltd | Manufacturing method of seamless steel tube with less residual stress |
| JP2005248302A (en) * | 2004-03-08 | 2005-09-15 | Sanyo Special Steel Co Ltd | Method for producing long, large diameter, and thin-walled seamless steel pipe having little bending |
| CN101811149A (en) * | 2010-04-14 | 2010-08-25 | 新兴铸管股份有限公司 | Manufacturing method of high alloy seamless steel tube |
| CN102581555A (en) * | 2012-02-21 | 2012-07-18 | 衡阳华菱钢管有限公司 | P91 seamless steel pipe and method for manufacturing same |
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2015
- 2015-06-12 CN CN201510322995.8A patent/CN104959784A/en active Pending
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|---|---|---|---|---|
| JP2001329316A (en) * | 2000-05-22 | 2001-11-27 | Sanyo Special Steel Co Ltd | Manufacturing method of seamless steel tube with less residual stress |
| JP2005248302A (en) * | 2004-03-08 | 2005-09-15 | Sanyo Special Steel Co Ltd | Method for producing long, large diameter, and thin-walled seamless steel pipe having little bending |
| CN101811149A (en) * | 2010-04-14 | 2010-08-25 | 新兴铸管股份有限公司 | Manufacturing method of high alloy seamless steel tube |
| CN102581555A (en) * | 2012-02-21 | 2012-07-18 | 衡阳华菱钢管有限公司 | P91 seamless steel pipe and method for manufacturing same |
| CN104073739A (en) * | 2014-07-25 | 2014-10-01 | 太原钢铁(集团)有限公司 | Heatproof stainless steel seamless steel pipe and manufacture method of stainless steel and seamless steel pipe |
| CN104259244A (en) * | 2014-09-10 | 2015-01-07 | 山东尧程新材料科技有限公司 | Forming process of Nb pipes |
| CN104451381A (en) * | 2014-12-25 | 2015-03-25 | 衡阳华菱钢管有限公司 | Large-caliber Gr3 seamless steel tube applied at low temperature and production method thereof |
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Application publication date: 20151007 |