JPS61556A - Hot run table roller - Google Patents

Abstract

PURPOSE:To obtain a lightweight hot run table roller having superior resistance to wear and accidents by uniting an outer shell of high-Cr cast iron having a specified composition and specified hardness and an inner shell of high grade cast iron having a specified composition to one body by welding to form a composite sleeve and by fixing plural pieces of such sleeves on a roller shaft at prescribed intervals. CONSTITUTION:The outer shell of high-Cr cast iron consisting of, by weight, 2.5-3.2% C, 0.5-1.5% Si, 0.5-1.5% Mn, <=0.08% P, <=0.06% S, 1.0-2.0% Ni, 10-23% Cr, 0.5-3.0% Mo and the balance practically Fe and having >=65 hardness Hs and the inner shell of high grade cast iron consisting of 2.5-4.0% C, 2.0-3.0% Si, 0.3-1.0% Mn, <=0.2% P, <=0.06% S, 1.0-2.0% Ni, <=6.0% Cr, <=0.5% Mo and the balance practically Fe are united to one body by welding to form a composite sleeve. Plural pieces of such sleeves are fixed on a roller shaft at prescribed intervals to obtain a hot run table roller.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention relates to a roller used in a hot run table of a hot rolling facility, and more specifically, the present invention relates to a roller used in a hot run table of a hot rolling facility, and more specifically, from a finish rolling process to a cooling header, and from a cooling zone to a rolling head. This relates to a roller used between the coiler and the pinch roll.

Conventionally, hot run table rollers have been made of ordinary steel or ordinary cast steel because they are considered consumables, or Cr-Mowl to which wear resistance has been positively imparted has been used. The former has poor abrasion resistance, requiring frequent replacement of the rollers, while the latter has excellent abrasion resistance, but has the disadvantage of poor accident resistance. In the latter case, in order to improve accident resistance, heat treatment may be performed to reduce hardness, but this results in poor wear resistance and increases wear and tear.

In addition, the rollers on the ridges are manufactured by applying various treatments such as surface heat treatment and overlay to a long tube obtained by continuous centrifugal casting to form an integral sleeve, which is then fixed to the roller shaft. Because of this, the unit weight is large and a large amount of driving energy is required, which is disadvantageous in terms of running costs. Furthermore, since the thickness of the integral sleeve cannot normally be increased due to limitations on the roller diameter, it is necessary to centrifugally cast a long tubular body with a thin and uniform thickness, which is difficult to manufacture.

<Means for Solving the Problems> The present invention was made in view of the above problems, and provides a hot run table roller that has excellent wear resistance and accident resistance, can be driven at low running cost, and is easy to manufacture. That's what we offer! The chemical composition in the column is weight%, C: 2.5-3.2% S: 0.06% or less St
: 0.5~1.5% Ni: 1.0~2.0
%Mn: 0.5-1.5% Cr: 10-23%
P: 0.08% or less Mo: 0.5-3.0
The outer shell is made of high chromium cast iron material, the balance of which is essentially Re, and the chemical composition is in weight percent: C: 2.5 to 4.0% S: 0.06% or less Si:
2.0~3.0% Ni: 1.0~2.0%M
n: 0.3 to 1.0% Cr: 6.0% or less p: 0.2% or less Mo: 0.5% or less The inner shell is welded and integrated with a high-grade cast iron material with the remainder essentially consisting of Fe. The roller shaft is characterized in that a plurality of composite sleeves having a hardness and an outer shell hardness of Hs65 or more are fixed to the roller shaft at intervals.

<Function> According to the ridge means, the roller of the present invention is made of a composite sleeve in which an outer shell of high chromium cast iron of a specific chemical composition and an inner shell of tough high-grade cast iron of a specific chemical composition are welded and integrated. Since a plurality of rollers are fixed to the roller shaft at intervals, the rollers have excellent wear resistance and accident resistance, and can reduce the weight of the roller unit.

Moreover, instead of fixing an integral composite sleeve to the roller shaft, multiple short composite sleeves are fixed to the roller shaft at intervals, so that the composite sleeve is attached to the roller shaft. Furthermore, the residual stress in the axial direction of the composite sleeve is significantly reduced compared to that of a one-piece composite sleeve, and it is possible to ensure an improvement in damage resistance from the viewpoint of the roller structure. Further, there is no need to manufacture a long, thin, one-piece composite sleeve that is difficult to manufacture, and the composite sleeve can be easily manufactured.

<Example> Next, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a hot run table roller l of the present invention, in which a composite sleeve 2 has an outer shell 3 and an inner shell 4 welded together.
A plurality of rollers are fixed to the roller shaft 5 at predetermined intervals.

The outer shell 3 is made of high chromium cast iron material with excellent wear resistance.
Its chemical composition (weight %) is specified based on the following component limitation reasons.

C: 2.5 to 3.2% C should be within the range that stabilizes the (Pe-Cr) 7 C3 type carbide, and should be determined based on the balance with Gr and the desired amount of carbide, but 2 If it is less than .5%, the amount of carbide is small and the effect on wear resistance is insufficient;
．． If the content exceeds 2%, the amount of carbides becomes too large, resulting in significant deterioration in mechanical strength, especially toughness. Therefore, C2,
It is defined as 5-3.2%.

St: 0.5-1.5% St is included for deoxidizing the molten metal, and is 0.5%.
If the content is less than 1.5%, there is no effect, and if the content exceeds 1.5%, the mechanical properties will deteriorate and the Arl transformation point will be lowered, making it difficult to obtain hardness. Therefore, the St content is 0.5
The range is 1.5%.

Mn: 0.5 to 1.5% Mn has an auxiliary effect in deoxidizing Si, and if it is less than 0.5%, no deoxidizing effect can be obtained. However, if the content exceeds 1.5%, the mechanical properties, especially the toughness, will deteriorate significantly. Therefore, the Mn content is also set in the range of 0.5 to 1.5%.

P: 0.08% or less P is preferably as low as possible, especially in roll materials.
It is necessary to keep the content to 0.08% or less in order to make the material brittle.

S F 0.06% or less Similar to P, S is preferably as small as possible, and from the viewpoint of making the material brittle, it must be kept at 0.06% or less.

Ni: 1.0 to 2.0% Ni is added to improve hardenability and actively adjust hardness.If the content is less than 1.0%, it has no effect; If the content exceeds 0.0%, retained austenite will increase, making it difficult to increase hardness, and will also be disadvantageous in terms of seizure resistance.

Therefore, the Ni content is set in the range of 1.0 to 2.0%.

Cr: 10-23%, Cr is contained in a particularly large amount to improve toughness and wear resistance, but if the content is less than 10%, many M and C type carbides will crystallize, resulting in poor toughness. Improvement in properties and fine uniformity of carbides cannot be obtained. Also, if the content exceeds 23%, M23. The amount of C, type carbide increases, and this carbide has lower hardness than M7C3 type carbide, making it impossible to obtain sufficient wear resistance and purity.

Therefore, the Cr content is balanced with the above specified range of C content, and the Cr content is set as the range in which M7C3 type carbide is crystallized.
It is defined as 10 to 23%.

Mo: 0.5-3.0% Mo increases the quenching and tempering resistance, and at the same time reacts with C to increase Mo.
Precipitates carbides to improve strength. Its content is 0.5
If the content is less than 3.0%, this effect will be small, while if the content exceeds 3.0%, the residual austenite in the base will be stabilized, and the seizure resistance will deteriorate. Therefore, the Mo content is 0.5-3
．． The range is 0%.

In addition to the above, the remainder of the outer shell chemical composition consists essentially of Fe, but in place of a part of Fe, particularly effective
can be added.

(2) is effective in making the casting structure finer, and the addition of (2) promotes the precipitation effect and improves wear resistance.

■It has sufficient effect when the content is 1.0% or less, and 1.0%
Even if this value is exceeded, the effect will be saturated and the cost will be disadvantageous.

The inner shell 4, which is integrally welded with the outer shell 3, is made of a high-grade cast iron material with excellent toughness, and its chemical composition (weight %) is specified by the following reason for limiting the composition.

C: 2.5 to 4.0% C is contained to impart toughness and strength, but if it is less than 2.5%, the material will become chilled and the toughness of the inner shell material will significantly decrease; If it exceeds this, graphitization progresses and strength becomes insufficient. In particular, if the strength of the sleeve used for table rollers is insufficient, the wall thickness is thin and a large fitting allowance cannot be achieved when the sleeve and roller shaft are shrink-fitted, resulting in axial displacement of the sleeve and damage from the inside. It leads to the loss of.

Si: 2.0 to 3.0% St is necessary to prevent the inner shell material from becoming brittle due to mixing of Cr in the outer shell, but if it is less than 2%, graphitization is insufficient and cementite is formed. A large amount of crystallization occurs, and the strength of the inner shell deteriorates, making cracks more likely to occur during casting due to residual stress.
．． When it exceeds 0%, graphitization becomes excessive and strength deteriorates.

It is also an effective method to inoculate 0.2 to 6.5% (as Si content) of Ca-3is, Fe-3is, etc. at the time of casting the inner shell. However, in that case, the Si content needs to be lower than the above range and the ψSt% after inoculation needs to be 2.0 to 3.0%.

Mn: 0.3-1.0% Mn combines with S to form MnS and eliminates the adverse effects of S, but if it is less than 0.3%, this effect is almost absent; on the other hand, 1.
If it exceeds 0%, rather than preventing the adverse effects of S, the quality of the material deteriorates significantly.

p: 0.2% or less P increases the fluidity of the molten metal, but makes the material brittle, so it is desirable to have it as low as possible, and Q: 2% or less.

s:0. oe% or less S, like P, makes the material brittle, so the content should be as low as <0.06% or less.

Ni: 1. ．． 0 to 2.0% Ni is contained to stabilize graphite, but if it is contained in excess of 2.0%, there is no significant effect. Further, Ni is also a material-strengthening element and must be contained in an amount of 1.0% or more.
- Cr: 6.0% or less Cr is effective in strengthening the material, but if it exceeds 6%, the material becomes brittle due to the formation of carbides.

In addition, since the outer shell is made of high chromium material, C from the outer shell to the inner shell is
The contamination of r is unavoidable, and in consideration of this, the C of the molten metal is
r should be 1.5% or less.

Mo: 0.5% or less Mo is effective in reinforcing the base, but if it is contained in excess of 0.5%, it becomes too hard, which is not preferable.

In addition to the above-mentioned components, the remainder of the inner shell material is substantially composed of Fe.

A plurality of composite sleeves 2 ((""0°"
11kO-5'A°°°1"1 is dispersed and fixed by shrink fitting, adhesive, etc. According to such a dispersed arrangement of the composite sleeve 2, when the integral composite sleeve is fixed to the roller shaft. On the other hand, the roller unit weight can be significantly reduced, and therefore the driving energy can be reduced, and running costs can be lowered.Furthermore, since the composite sleeve 2 itself has a small sleeve width, It is possible to significantly reduce axial residual stress and significantly improve accident resistance.

The composite sleeve 2 is obtained by appropriately dividing a composite sleeve material into lengths that are easy to cast by centrifugal force casting. The manufacturing method of this composite sleeve material is explained with reference to Fig. 2.The inner surface is coated with refractory material, and sand mold or heat-resistant brick hands 7 are fixed to the inner surfaces of both ends to prevent molten metal from scattering from both ends. Using a power casting mold 6, which is rotated on a centrifugal casting machine, the molten metal for the outer shell is first cast to form the outer shell 3'', and then, while the inner surface is partially or completely unsolidified, Then, the molten inner shell is cast to cast a composite sleeve material 8 in which the outer shell 3° and the inner shell 4′ are completely welded and integrated metallurgically.

In FIG. 2, numeral 9 indicates a rotating roller, numeral 10 a molten metal ladle, and numeral 11 a casting trough.

In the centrifugal casting method illustrated in FIG. 2, an example is shown in which the axis of rotation is horizontal, but it is of course possible to perform centrifugal casting with the axis of rotation inclined.

After the composite sleeve material 8 manufactured according to the ridges is divided into desired dimensions, each divided portion is subjected to a prescribed heat treatment,
A plurality of composite sleeves 2 having an outer shell hardness of Hs65 or more are obtained.

The divided portion before the heat treatment has a structure in which high-hardness Cr carbide is precipitated in a matrix of retained austenite and martensite.
C, precipitates secondary carbides in the base, and then cools and tempers at a cooling rate of 100°C/Hr or higher to convert residual austenite to martensite, and this heat treatment results in a hardness of Hs65 or higher. To obtain a composite sleeve 2 having high wear resistance and seizure resistance.

According to such a manufacturing method, there is no need to manufacture a thin-walled, long, one-piece composite sleeve that is difficult to cast, and residual stress can be significantly reduced because the cast composite sleeve material 8 is divided and used as appropriate. This makes it possible to improve accident resistance.

The composite sleeves 2 obtained as described above are individually fixed to the roller shaft 5 by shrink fitting or the like to obtain a hot run table roller l, but the composite sleeves 2 are considerably smaller than an integrated product. , the fixing work is extremely easy.

Next, more specific embodiments of the present invention will be described in detail.

Product oily Riichi φ310 +n, body length L = 180 (Jam
Example of manufacturing a hot run table roller (1) The outer shell high chromium cast iron molten metal shown in Table 2 was placed in a centrifugal casting mold (rotation speed 80 Orpm') with an inner diameter of φ300 + n x 1200 + nρ as shown in Figure 2. Thickness 40n
(casting weight: 341 kg), and was cast at a casting temperature of 1,400°C.

(2) Six minutes after starting to cast the outer shell, pour the inner shell molten metal shown in Table 1 onto the inner surface of the outer shell with a thickness of 40+n (247 kg).
, and was cast at a casting temperature of 1400°C.

(3) Twenty minutes after the start of casting the outer shell, the inner shell was completely solidified. After that, the composite sleeve material was molded and held in a furnace to remove any strain. Table 1 shows the product chemical composition of the sleeve material.

(4) After removing the distortion, remove 150 pieces from each end of the sleeve material, divide the sleeve into 4 parts, and heat each divided part to 950°C.
It was kept in the furnace for 5 hours and then air cooled until the surface temperature reached 500℃.
The temperature was then kept at 550°C in the furnace again to cool it down. As a result, the hardness on the sleeve surface was Hs71
Met.

(5) By machining the inner and outer surfaces of each divided part, the outer diameter φ
Four composite sleeves with a diameter of 310 mm, an inner diameter of 200 m1, and a width of 200 mm were obtained. The four composite sleeves are assembled as shown in Figure 1.
A desired hot runtable roller was obtained by shrink fitting to a 535C roller shaft having an outer diameter of φ200W at a shrink fit ratio of 6/1000 at intervals of 200 cages.

(6) As a result of ultrasonic testing and disassembly of the sleeve surface, it was found that the outer shell and inner shell of the composite sleeve were completely welded together and were structurally continuous.

When this roller was installed and used in an actual machine, it was found that the lifespan was approximately 1.5 times longer than that of conventional ordinary cast steel rollers.

Next <Effects of the Invention> As explained above, the hot run table roller of the present invention is formed by welding and integrating an outer shell made of high chromium cast iron with excellent wear resistance and an inner shell made of high grade cast iron with excellent toughness. Since a plurality of composite sleeves are fixed to the roller shaft at intervals, it has excellent wear resistance and accident resistance, is lightweight, and therefore requires less driving energy. The production of the sleeve itself and the work of fixing it are also very easy, and the economic value of the roller of the present invention is significant.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of an embodiment of the hot run table roller of the present invention, and FIG. 2 is a schematic cross sectional view showing a method for manufacturing a composite sleeve material related to the hot run table roller of the present invention. DESCRIPTION OF SYMBOLS 1... Hot run table roller, 2... Composite sleeve, 3... Outer shell, 4... Inner shell, 5... Roller shaft, 6... Centrifugal force casting mold, 8... - Composite sleeve material.

Claims (1)

[Claims] 1. Chemical composition in weight%: C: 2.5-3.2% Si: 0.5-1.5% Mn: 0.5-1.5% P: 0.08 % or less S: 0.06% or less Ni: 1.0 to 2.0% Cr: 10 to 23% Mo: 0.5 to 3.0% The remainder is an outer shell made of high chromium cast iron material consisting essentially of Fe. ,
Chemical composition in weight%: C: 2.5-4.0% Si: 2.0-3.0% Mn: 0.3-1.0% P: 0.2% or less S: 0.06% The following Ni: 1.0 to 2.0% Cr: 6.0% or less Mo: 0.5% or less An inner shell made of high-grade cast iron material, the remainder of which is essentially Fe, is welded and integrated with the outer shell hardness. 1. A hot runtable roller comprising a plurality of composite sleeves having a diameter of Hs 65 or more fixed to a roller shaft at intervals.