CN103978138A - Method for improving bearing casting blank surface quick-cooling and controlling hot rolling tissues - Google Patents

Abstract

The invention relates to a method for improving bearing casting blank surface quick-cooling and controlling hot rolling tissues. The method comprises the following steps of (1) casting to prepare a blank, i.e. pouring refining liquid steel into a horizontal centrifuge for centrifugally casting pipes, mold stripping at 1200-1250 DEGC after the liquid steel is solidified; sequentially determining the rolling expansion ratio and inner and outer diameters of thermal-state tube blanks according to the sizes of bearing rings; sawing and blanking the thermal-state tube blanks by a steel pipe blanking machine according to the height of the bearing rings to obtain bearing casting blanks; (2) forcibly quick-cooling the surfaces of the casting blank, i.e. spraying normal temperature water mist on the internal and external surfaces of the casting blanks to forcibly quick-cool the surfaces, so that the internal and external surfaces of the casting blanks can be rapidly cooled to 800-850 DEG C, and the central temperature keeps at 950-1050 DEG C; (3) controlling hot rolling, i.e. immediately performing hot rolling on the surface quick-cooled casting blanks, and reasonably controlling rolling feeding speed according to the rolling expansion ratio and the sizes of the bearing rings. According to the method, the bearing casting blank central coarse tissues can be accelerated to be effectively fined, and the integral tissue can be homogenized; the product tissue and performance consistency can be improved; the technical process can be reduced, the energy consumption is reduced, and the efficiency is improved.

Description

A kind of bearing casting billet surface speed is cold-controls heat to roll over the improvement method of organizing

Technical field

The present invention relates to bearing manufacturing technology, be specifically related to a kind of bearing casting billet surface speed cold-control heat to roll over the improvement method of organizing.

Background technology

Bearing is Mechanical Fundamentals part, at many industrial circles, has extensive important application.The matrix of bearing is annular bearing ring (abbreviation bearer ring), and it is most important to the performance of bearing and life-span.At present, in bearer ring production, most widely used technique is forge hot base after heat rolling forming, first forges afterwards and rolles over.This technique can obtain the bearing forging stock of even as-forged microstructure, thereby ensures hot rolling forming ring performance, but forge hot preforming is many, efficiency is low, core material waste is many, so energy consumption is high, stock utilization is low.By casting, obtaining ring-shaped casting blank and directly carry out hot rolling and cast and roll over to be shaped, compare forging shaping, shortened technological process, reduced energy consumption, improved stock utilization, is a kind of ring-shaped work pieces low-consumption high-efficiency new technology, has started at present to be researched and developed.Yet, compare the even as-forged microstructure of forging stock, more, there is the defects such as pore, shrinkage porosite, segregation in the thick inequality of as-cast structure of strand, need to be improved and be eliminated by hot rolling, otherwise can produce serious genetic risk to ring performance.Due to foundry method features, the defects such as the defect(ive) structure of strand and inner shrinkage porosite focus mostly in ring base heart portion, and hot rolling has inhomogeneous deformation feature, ring base heart portion is stagnant zone, deflection is little, and tissue improves weak effect, makes casting roll over that shaping ring exists that surface texture is tiny more and core structure is thick and shrinkage porosite, hole are left over problem, finally cause ring mechanical property distribution uneven, cannot meet instructions for use.Therefore, because casting and hot rolling process characteristic cause continuous casting billet structure can not obtain effective improvement, be, that the Main Bottleneck that forming technology is applied in high-performance bearing ring is manufactured is rolled in restriction casting.

Summary of the invention

For above-mentioned present situation, the present invention proposes a kind of bearing casting billet surface speed, and cold-control heat is rolled over the improvement method of organizing, by controlling strand temperature distribution state and hot rolling deformation parameter, can effectively increase and promote hot rolling process strand heart portion's distortion and structure refinement, improve casting blank deformation uniformity, realize even tissue and improve.

For achieving the above object, technical solution of the present invention is: a kind of bearing casting billet surface speed is cold-and controls heat to roll over and organize improvement method, it is characterized in that comprising following specific implementation step:

(1) casting base: pour refining liquid steel (molten steel) in horizontal centrifuge spun cast pipe, after molten steel (molten steel) has solidified 1200 ℃～1250 ℃ depannings, obtaining hot pipe (explains: hot pipe inside/outside diameter size is cast blank size, be related to rolling deflection, so should provide, tube blank size can be controlled acquisition by casting die); The internal diameter of hot pipe, outside dimension are d ₀, D ₀, according to bearer ring size, press following formula and determine:

$D_0=\frac{(D-d)K^2+(D+d)}{2K},$ $d_0=\frac{-(D-d)K^2+(D+d)}{2K}---\left(1\right)$

Wherein, d, D are respectively the inside and outside diameter of bearer ring; K is rolling ratio, is the ratio of bearing strand sectional area with bearer ring sectional area; For making strand rolling process produce fully distortion thinning microstructure and control inhomogeneous deformation degree, rolling ratio can be by choosing as follows:

K＝1.2+0.027H-1.9×10 ^-4H ² (2)

Wherein, H=(D-d)/2, the wall thickness that H is bearer ring;

With steel pipe blanking machine, hot pipe is pressed to bearer ring height sawing, obtain bearing strand;

(2) it is cold that bearing casting billet surface is forced speed: bearing strand surfaces externally and internally spray normal temperature water smoke is carried out to surface pressure cooling, make strand surfaces externally and internally fast cooling to 800～850 ℃ (and heart portion temperature remains on 950～1050 ℃);

(3) control hot rolling: the fast chill casting base in surface is carried out to hot rolling immediately, and rolling process strand produces fully in order to make, uniform plastic deformation, and rolling feed speed is pressed following formula and determined:

$v=k\frac{2n_d{R}_d{\left(\arctan \mathrm{\μ}\right)}^2}{R_0{(\frac{1}{R_d}+\frac{1}{R_m})}^2}(\frac{1}{R_d}+\frac{1}{R_m}+\frac{1}{R_0}-\frac{1}{r_0})---\left(3\right)$

Wherein, k is constant, gets 0.2～0.5; r ₀=d ₀/ 2, R ₀=D ₀/ 2, be respectively bearing strand inside radius, outer radius; R _dand R _mbe respectively the radius of clean-up of drive roll and core roller; n _dfor drive roll rotating speed; μ is coefficient of friction.

The invention has the beneficial effects as follows: by forcing speed cold to casting billet surface, increase casting billet surface and the heart portion temperature difference, areal deformation drag is sharply increased and heart portion resistance of deformation is substantially constant, plastic zone easier centripetal portion expansion and increase the strain of heart portion and strain rate in hot rolling, is conducive to the as-cast structure transformation of heart portion and shrinkage porosite, hole is forged and closed.By reasonable rolling ratio and rolling speed, select, control strand inhomogeneous deformation, improve deformation uniformity, make strand zones of different tissue obtain even refinement, finally obtain thin even Tissue distribution, improve product structure property uniformity, ensure bearer ring mechanical property.In addition, utilize cast tube waste heat to carry out rolling, removed heating link from, shortened technological process, reduced energy consumption, improved efficiency.

The specific embodiment

In order to understand better the present invention, below in conjunction with embodiment, further illustrate content of the present invention, but content of the present invention is not only confined to the following examples.

Embodiment 1:

Take certain GCr15 bearer ring is example, and its external diameter is that 425mm, internal diameter are 355mm, are highly 30mm, its bearing casting billet surface speed is cold-and controls heat to roll over the improvement method of organizing, realize as follows:

(1) casting base: pour GCr15 molten steel after refining into spun cast pipe in horizontal centrifuge, 1200 ℃ of depannings, obtain hot pipe after solidification of molten steel completes.According to the present invention, rolling determines that than computing formula and bearer ring size rolling is 1.9 than K.Then according to the present invention, hot pipe inside/outside diameter size computing formula, bearer ring size and rolling ratio are determined hot pipe outer diameter D ₀for 212.81mm, inner diameter d ₀for 102.41mm.With steel pipe blanking machine, hot pipe sawing is obtained to height 30mm bearing strand, now casting blank surface temperature is approximately 1100 ℃.

(2) it is cold that casting billet surface is forced speed: strand surfaces externally and internally spray normal temperature water smoke is carried out to surface pressure cooling, make its surface temperature be down to fast approximately 800 ℃.

(3) control hot rolling: the surface cold rear strand of speed is put into Ring Rolling Machine, and rolling process strand produces fully in order to make, uniform plastic deformation.According to rolling feed speed computing formula, in the present embodiment, k gets 0.2, r ₀=d ₀/ 2, R ₀=D ₀/ 2 are respectively 69.38mm and 135.88mm, R _d, R _mbe respectively 285mm and 55mm, n _dfor 1.2r/s; μ gets 0.3, and calculative determination rolling feed speed is 2.43mm/s.

To the present invention's surface speed cold-control heat to roll over bearer ring and conventional casting and roll over forming axis carrier ring and organize and compare.Respectively to two kinds of method lower bearing ring outer surfaces, heart portion, inner surface sampling, carry out crystallite dimension test relatively, result is as shown in table 1: the present invention's surface speed is cold-and controls heat to roll over bearer ring heart portion crystallite dimension and than conventional casting, roll over bearer ring and reduce 29.92%, whole crystal grain nonunf ormity declines 35.97%.

Each region crystallite dimension test result of table 1 bearer ring

Embodiment 2:

Take certain 42CrMo bearer ring is example, and its external diameter is that 320mm, internal diameter are 260mm, are highly 35mm, its bearing casting billet surface speed is cold-and controls heat to roll over the improvement method of organizing, realize as follows:

(1) casting base: pour 42CrMo molten steel after refining into spun cast pipe in horizontal centrifuge, 1250 ℃ of depannings, obtain hot pipe after solidification of molten steel completes.According to the present invention, rolling determines that than computing formula and bearer ring size rolling is 1.84 than K; Then according to the present invention, hot pipe inside/outside diameter size computing formula, bearer ring size and rolling are that 212.81mm, internal diameter are 102.41mm than definite hot pipe internal-and external diameter, cast tube after depanning is obtained to height 35mm bearing strand with steel pipe blanking machine sawing, and now casting blank surface temperature is approximately 1150 ℃;

(2) it is cold that casting billet surface is forced speed: strand surfaces externally and internally spray normal temperature water smoke is carried out to surface pressure cooling, make its surface temperature be down to fast approximately 850 ℃.

(3) control hot rolling: the surface cold rear strand of speed is put into Ring Rolling Machine, and rolling process strand produces fully in order to make, uniform plastic deformation.According to rolling feed speed computing formula, in the present embodiment, k gets 0.5, r ₀=d ₀/ 2, R ₀=D ₀/ 2 are respectively 51.205mm and 106.405mm, R _d, R _mbe respectively 285mm and 55mm, n _dfor 1.2r/s; μ gets 0.3, and calculative determination rolling feed speed is 6.17mm/s.

To the present invention's surface speed cold-control heat to roll over bearer ring and conventional casting and roll over forming axis carrier ring and organize and compare.Respectively to two kinds of method lower bearing ring outer surfaces, heart portion, inner surface sampling, carry out crystallite dimension test relatively, result is as shown in table 2: the present invention's surface speed is cold-and controls heat to roll over bearer ring heart portion crystallite dimension and than conventional casting, roll over bearer ring and reduce 27.04%, whole crystal grain nonunf ormity declines 39.05%.

Each region crystallite dimension test result of table 2 bearer ring

The explanation of above-mentioned example, adopts the inventive method gained bearer ring core structure thinning effect obvious, and global tissue is more evenly distributed, and illustrates that the present invention can effectively improve bearing continuous casting billet structure.

The technology of the present invention method is also applicable to the bearer ring of other material, and its method is identical with above-mentioned example, and effect is also identical, at this particularize embodiment not.

Claims (1)

1. Bearing casting billet surface speed cold-control heat to roll over and organize an improvement method, it is characterized in that comprising following specific implementation step:

   (1) casting base: pour refining liquid steel in horizontal centrifuge spun cast pipe, 1200 ℃～1250 ℃ depannings, obtain hot pipe after solidification of molten steel completes; The internal diameter of hot pipe, outside dimension are d ₀, D ₀, according to bearer ring size, press following formula and determine:

   $D_0=\frac{(D-d)K^2+(D+d)}{2K},$ $d_0=\frac{-(D-d)K^2+(D+d)}{2K}---\left(1\right)$

   Wherein, d, D are respectively the inside and outside diameter of bearer ring; K is rolling ratio, is the ratio of bearing strand sectional area with bearer ring sectional area; For making strand rolling process produce fully distortion thinning microstructure and control inhomogeneous deformation degree, rolling ratio can be by choosing as follows:

   K＝1.2+0.027H-1.9×10 ^-4H ² (2)

   Wherein, H=(D-d)/2, the wall thickness that H is bearer ring;

   With steel pipe blanking machine, hot pipe is pressed to bearer ring height sawing, obtain bearing strand;

   (2) it is cold that bearing casting billet surface is forced speed: bearing strand surfaces externally and internally spray normal temperature water smoke is carried out to surface pressure cooling, make strand surfaces externally and internally fast cooling to 800～850 ℃;

   (3) control hot rolling: the fast chill casting base in surface is carried out to hot rolling immediately, and rolling process strand produces fully in order to make, uniform plastic deformation, and rolling feed speed is pressed following formula and determined:

   $v=k\frac{2n_d{R}_d{\left(\arctan \mathrm{\μ}\right)}^2}{R_0{(\frac{1}{R_d}+\frac{1}{R_m})}^2}(\frac{1}{R_d}+\frac{1}{R_m}+\frac{1}{R_0}-\frac{1}{r_0})---\left(3\right)$

   Wherein, k is constant, gets 0.2～0.5; r ₀=d ₀/ 2, R ₀=D ₀/ 2, be respectively bearing strand inside radius, outer radius; R _dand R _mbe respectively the radius of clean-up of drive roll and core roller; n _dfor drive roll rotating speed; μ is coefficient of friction.