CN103614594A - Method for removing creases of thermal machining surface of heat-resisting alloy - Google Patents

Abstract

The method relates to a method for removing creases of a thermal machining surface of a heat-resisting alloy and belongs to the technical field of heat-resisting alloy machining. The method is characterized in that technical parameters controlled in the process are that lower-limit hot machining temperature is strictly controlled when a tube-making blank is upset, wherein the lower-limit hot machining temperature is 1050-1100 DEG C, and upper-limit hot machining temperature is 1200-1230 DEG C; the encapsulation is carried out in a blank forming process so as to limit the flow of metal before the outer surface of the metal is contacted with the wall of an extruding cylinder during upsetting, wherein an encapsulation material is carbon steel or stainless steel, and the thickness of the encapsulation material is 3-5mm. The method is suitable for eliminating the surface crease defect caused by the fact that recrystallization does not occur or local recrystallization occurs in the blank forming process of a heat-resisting alloy pipeline of an ultra-supercritical thermal power generating unit at steam temperature of 700 DEG C, so that the surface quality in the blank forming process is improved, the material yield of the alloy is improved, and the production cost is lowered.

Description

A kind of method of eliminating refractory alloy hot-work surface folding

Technical field

The invention belongs to refractory alloy technical field of hot working, particularly relate to a kind of method of eliminating refractory alloy hot-work surface folding, be applicable to eliminate in 700 ℃ of vapor temperature ultra supercritical fired power generating unit refractory alloy pipeline base processes the surface folding defect causing due to non-recrystallization or local recrystallize, surface quality while improving base, improve alloy lumber recovery, reduce production costs.

Technical background

The manufacturing technology of 600 ℃ of ultra supercritical power station large-diameter pipes of China is mature on the whole, and can utilize vertical extrusion technique production specification for Φ 273～1066mm, the steel pipe of wall thickness 20～130mm.700 ℃ of further energy-saving and emission-reduction of ultra supercritical unit, China has set up the 700 ℃ of coal-fired thermal power generating technology of advanced ultra supercritical Innovation Alliances, puts forth effort on and builds 700 ℃ of ultra supercritical Demonstration Stations.600 ℃ of ultra supercritical power stations are Ascalloy with thick-wall and large-diameter tube, can not be applied to 700 ℃, must select Refractoloy to manufacture thick-wall and large-diameter tube.Compare with Ascalloy, Refractoloy resistance to deformation is large, and thermal processing distortion temperature range is narrow, the difficult distortion of large size ingot shape.

At present, power station is ripe with the bigbore Hot-extrusion of heavy wall, and has solved external diameter Φ 273～1066mm for 600 ℃ of ultra supercritical station boilers, the manufacture of wall thickness 20～130mm heavy caliber thick wall seamless steel tube.The production technique of Ascalloy large-diameter steel pipe mainly adopts vertical extrusion technique with manufacture method, refers to patent CN 101706019 B ^[1].And poorer than the deformability of iron for Refractoloy, recrystallization temperature is high, easily occurs fold in base process.Once there is fold, just need a large amount of machinings to eliminate the fold on alloy pipe stock, if serious fold cannot be eliminated, will make compo pipe scrap.Allow to eliminate fold, also increased the compo pipe production cycle, reduced efficiency, also caused raw-material consumption, reduced compo pipe lumber recovery simultaneously.

The invention provides a kind of method of eliminating refractory alloy hot-work surface folding, improve refractory alloy tube-surface quality, improve refractory alloy lumber recovery, reduce the manufacturing cost of refractory alloy pipe.

Summary of the invention

The object of the invention is to provide a kind of method of eliminating refractory alloy hot-work surface folding, has solved the hot-work surface folding problem of existing refractory alloy, improves refractory alloy large-calibre seamless tubing lumber recovery, reduces material manufacturing cost.Be applicable to the parts such as 700 ℃ of vapor temperature ultra supercritical fired power generating unit heavy caliber thick wall boiler tubings and pipe fitting.

The present invention, by restriction refractory alloy lower limit texturing temperature, utilizes jacket restriction surface of steel ingot side direction metal flow simultaneously, can eliminate refractory alloy hot-work surface folding defect.

Refractory alloy chemical composition of the present invention (% by weight) is as follows: Cr21 ?23%; Fe < 1.0%; C0.03 ?0.08%; Mn≤0.5%; Si≤0.25%; Co11 ?13%; Mo8.0 ?10.0%; Ti0.3 ?0.5%; Al0.8 ?1.3%; Cu≤0.15%; P < 0.012%; S < 0.008%; B0.002 ?0.005%; Nb≤1.0%; V≤0.6%; W < 2.0%; N≤0.015%; Ca≤0.01%; Zr≤0.02%; Surplus is nickel and inevitable impurity element.

The present invention is applicable to the refractory alloy of mentioned component, and the technical parameter of controlling in its technique is as follows:

(1) want strict lower control limit hot processing temperature during tubulation base jumping-up, described lower limit hot processing temperature is 1050～1100 ℃, and upper limit hot processing temperature is 1200 ℃～1230 ℃.

(2) to carry out jacket during base, when the object of jacket is jumping-up, before outer metallic surface contact squeeze barrel, limit metal flow; Sheath material is carbon steel or stainless steel, thickness 3-5mm.

Principle of the present invention: refractory alloy recrystallization temperature of the present invention is high, and resistance to deformation is large, hot processing temperature window narrows, its hot ductility curve is as shown in Figure 1.There is " muscle shape " surface folding phenomenon in refractory alloy, as Fig. 2 when 1050 ℃ of thermo compression tests; When carrying out hot tensile test below lower than 1100 ℃, also there is surface folding phenomenon, as shown in Figure 3.In the present invention, this phenomenon is analyzed, when Refractoloy will be grown before hot-work, high-temperature homogenization diffusion annealing is processed, column crystal in ingot casting coarse grains after high-temperature homogenization diffusion annealing when long, and CRYSTALLITE SIZES is inhomogeneous, as shown in Figure 4.During thermo compression, surface folding metallographicobservation is found, grain size is uneven, grain boundaries generation local dynamic station recrystallize, and recrystal grain is tiny.The reason schematic model of surface folding metallographicobservation and formation respectively as shown in Figure 5 and Figure 6.Recrystallization easily forms at high dislocation density place, such as crystal boundary.After grain boundaries forms recrystal grain, strength decreased, shows as softeningly, and intracrystalline intensity is higher than grain-boundary strength, and distortion is carried out along crystal boundary.When blank pressurized, central metal flows to both sides, and the large crystal grain of limit portion is because the local recrystallize of crystal boundary forms rat, and little crystal grain due to compatibility of deformation ability a little less than, form surface recessed, at large and small crystal grain joint, just form surface folding like this.

The technology used in the present invention solution is:

1. when long during the ingot shape hot-work first after High temperature diffusion homogenizing annealing, strict lower control limit thermal processing distortion temperature, texturing temperature will be higher than 1100 ℃.

2. when suitability for industrialized production is carried out jumping-up base, in the time of lower control limit texturing temperature, at blank outside surface, use carbon steel jacket, the object of jacket is to limit metal flow during to jumping-up, eliminates the generation of surface folding.The present invention uses carbon steel or stainless steel jacket, thickness 3～5mm.

Compared with prior art, the invention has the beneficial effects as follows: improve pipe surface quality, for follow-up extruded tube provides surface good hollow billet; Improve refractory alloy seamless tube lumber recovery, reduce material cost.

Accompanying drawing explanation

Fig. 1 refractory alloy hot ductility curve of the present invention.

Macro surface fold during 1050 ℃ of distortion thermo compression of Fig. 2 refractory alloy of the present invention.In figure, be from left to right 1050 ℃ of strain rates difference 0.01,0.1,1,10S successively ^-1surface folding phenomenon during distortion.

Fig. 3 refractory alloy of the present invention is lower than 1100 ℃ of thermal stretch macro surface folds.

Fig. 4 refractory alloy of the present invention is laterally metallographic structure (50 *) after high-temperature homogenization diffusion annealing.

Surface folding section metallographicobservation during Fig. 5 refractory alloy thermo compression of the present invention.

Fig. 6 surface folding produces a schematic model (left side: before compression; In: local recrystallize forms surface folding; Right: without surface folding).

1000 ℃ and 1150 ℃ thermal stretch sample macro surface of Fig. 7 refractory alloy of the present invention are (upper: 1000 ℃; Under: 1150 ℃).

Embodiment

Embodiment 1:

Adopt 50Kg vacuum induction furnace smelting refractory alloy ingot of the present invention, while growing, after high-temperature homogenization diffusion annealing, utilize thermal simulation machine to carry out 1000～1200 ℃ of thermo compression and hot tensile test, carry out macro surface observation.Result shows, lower than the sample deformation district of 1100 ℃ of texturing temperatures, occurs surface folding, and temperature is lower, and fold is more serious; The distorted area smooth surface of 1100～1190 ℃ of interval samples of texturing temperature; In the time of 1200 ℃, thermal stretch shows that thermoplasticity sharply reduces.

Embodiment 2:

Utilize 200Kg vacuum induction furnace smelting refractory alloy ingot two stoves of the present invention, after steel ingot vehicle light, billet is of a size of Ф 200mm, high 300mm, high-temperature homogenization diffusion annealing while growing, then jumping-up, wherein the strict lower control limit texturing temperature of a stove is higher than 1100 ℃ and carry out 3mm carbon steel jacket, and after jumping-up, cooling observation is without surface folding; And another stove example as a comparison, upsetting process temperature, 1050 ℃ of left and right, is processed without jacket, and cooling rear observation surface folding is serious.The serious comparative example of surface folding needs the thicker one deck of turning, and its turning amount of metal is 3 times without surface folding example turning amount of metal.

Embodiment 3:

Industry trial-production: adopt vacuum induction to smelt 5.5 tons of refractory alloy ingots of the present invention of VIM+ vacuum consumable VAR remelting, utilize 1.5 ten thousand tons of blank machine bases of certain company, preforming comprises container jumping-up and punching.Base process is as follows: by No. 45 thick steel plates of surface of steel ingot integument 4mm, joint welds, and steel ingot two circle cross sections do not wrap up, outside surface metal flow when object is restriction jumping-up.When being carried out to high temperature length, steel ingot shove charge after homogenizing diffusion annealing, takes out roller coating glass lubricant on roller coating platform, put into the jumping-up cylinder mould jumping-up of preheating, Upsetting temperature is higher than 1100 ℃, and after jumping-up, mobile blank machine patrix switching mechanism, directly carries out punching.The cooling rear observation of hollow billet, removes surperficial residual glass lubricant etc., and surface quality is good, without surface folding.

Claims (1)

1. eliminate a method for refractory alloy hot-work surface folding, the composition % by weight that is applicable to refractory alloy is: Cr21-23%; Fe < 1.0%; C0.03-0.08%; Mn≤0.5%; Si≤0.25%; Co11-13%; Mo8.0-10.0%; Ti0.3-0.5%; Al0.8-1.3%; Cu≤0.15%; P < 0.012%; S < 0.008%; B0.002-0.005%; Nb≤1.0%; V≤0.6%; W < 2.0%; N≤0.015%; Ca≤0.01%; Zr≤0.02%; Surplus is nickel and inevitable impurity element; It is characterized in that, the technical parameter of controlling in technique is as follows:

(1) want strict lower control limit hot processing temperature during tubulation base jumping-up, described lower limit hot processing temperature is 1050～1100 ℃, and upper limit hot processing temperature is 1200 ℃～1230 ℃.

(2) to carry out jacket during base, while making jumping-up, before outer metallic surface contact squeeze barrel, limit metal flow; Sheath material is carbon steel or stainless steel, thickness 3-5mm.

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