JPS61557A - Hot run table roller - Google Patents

Abstract

PURPOSE:To obtain a lightweight hot run table roller having superior seizing and cracking resistances by uniting an outer shell of graphite-crystallized high-Cr cast iron having a specified composition and specified hardness and an inner shell of ductile 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 graphite-crystallized high-Cr cast iron consisting of, by weight, 2.4-3.4% C, 2.0-3.4% Si, 0.5-1.5% Mn, <=0.1% P, <=0.08% S, 4.5-10% Ni, 5-10% Cr, 0.4-1.5% Mo and the balance essentially Fe and having >=65 hardness Hs and an inner shell of ductile cast iron consisting of 3.0- 3.8% C, 1.8-3.0% Si, 0.3-1.0% Mn, <=0.1% P, <=0.06% S, <=2.0% Ni, <=5.0% Cr, <=1.0% Mo, 0.02-0.1% Mg and the balance essentially 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 hot run table for hot rolling equipment.
More specifically, it relates to rollers used from the finish rolling process to the cooling header, and from the cooling zone to the pinch roll of the take-up coiler.

Conventionally, hot run table rollers have been made of ordinary steel or ordinary cast steel considering they are consumables, or Cr-Mo steel to which wear resistance has been positively imparted. The former type has poor abrasion resistance and requires frequent replacement of the rollers, while the latter type has excellent abrasion resistance but is inferior in seizure resistance, crack resistance, and accident resistance. There were drawbacks. 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, rollers on ridges are usually manufactured by applying various treatments such as surface heat treatment and overlay to a long tube obtained by centrifugal casting to form an integral sleeve, which is then fixed to the roller shaft. Because of this, it had a large unit weight, required a lot of driving energy, and was 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. In addition, some sleeves have two layers, but in this case it is more difficult to manufacture. In other words, the long, thin-walled two-layer sleeve is manufactured by centrifugal casting, forming an outer shell and an inner shell with uniform thickness in the axial direction, and complete metallurgical welding at the boundary. In order to achieve this, many factors such as mold rotation speed, casting temperature, inner shell casting timing, etc. must be considered, making it difficult to obtain a sleeve of constant quality industrially. In particular, the hot run table roller has a long length (more than 1,500 yen) and has a small number of layers (10 to 20 yen), so the above-mentioned manufacturing difficulties are significant.

Means for Solving the Problems> The present invention has been made in view of the above problems, and has excellent seizure resistance, crack resistance, abrasion resistance, and accident resistance.
The purpose of the present invention is to provide a hot run table roller that can be driven at low running cost and is easy to manufacture. Si: 2.0-3.4% Ni: 4.5
~10%Mn: 0.5~1.5% Cr:5~
10%P: 0. l% or less Mo: 0.4~
An outer shell of graphite-crystallized high chromium cast iron with the remainder essentially consisting of Fe and a chemical composition in weight percent, C: 3. O~3.8% Nt: 2.0% or less S
i: 1.8-3.0% Cr: 5.0% or less Mn: 0.3-1.0% Mo: 1.0
% or less p: o, t% or less Mg,: 0.02
~0.1% s: o, oe% or less The remaining part consists of a plurality of composite sleeves, which are integrally welded with an inner shell made of ductile cast iron material consisting essentially of Fe, and whose outer shell hardness is Hs65 or more, as roller shafts. It is characterized by being fixed to each other with a space provided between them.

<Function> According to the ridge means, the roller of the present invention has an outer shell made of graphite-crystallized high chromium cast iron having a specific chemical composition and an inner shell made of strong ductile cast iron having a specific chemical composition that are welded and integrated. Since multiple composite sleeves are fixed to the roller shaft at intervals, the product has excellent wear resistance, seizure resistance, crack resistance, and accident resistance due to the effects of chromium carbide and crystallized fine graphite. , and the roller unit weight can be reduced. 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 1 according to the present invention, and a composite sleeve 2 in which an outer shell 3 and an inner shell 4 are welded and integrated.
A plurality of roller shafts (Aha) are arranged at predetermined intervals.
It is fixed to 5.

The outer shell 3 is made of graphite-crystallized high chromium cast iron material with excellent seizure resistance, crack resistance, and wear resistance, and its chemical composition (weight %) is specified by the following reason for limitation.

C: 2.4 to 3.4% C combines with Cr to form chromium carbide, and also crystallizes as fine graphite with the graphitization forming elements of Si and Ni, which will be described later. When C is less than 2.4%, chromium carbide decreases and graphite crystallization also disappears, meaning the present invention becomes meaningless. Next, if 0% exceeds 3.4%, there is a relationship with Cr%, but in the case of the present invention, Cr% is limited to 5 to 10%, so supersaturated carbon is high in Si and Ni%, so graphite This results in a large amount of graphite crystallization, resulting in poor wear resistance.

Si: 2.0 to 3.4% Si is necessary to crystallize graphite, a high chromium material.
．． If it is less than 0%, this effect will not occur, and if it exceeds 3.4%, there will be too much graphite, resulting in poor wear resistance.

Regarding Si, it is better to set the Si content at the time of casting to be lower than this range and inoculate it before casting so that the composition of the final product falls within the above range.
It is advantageous in this respect.

Mn2 0.5-1.5% Mn needs to be contained in an amount of at least 0.5% to assist in deoxidizing Si, and if it is less than 0.5%, a sufficient deoxidizing effect cannot be obtained. However, if the content exceeds 1.5%, mechanical properties, especially toughness, deteriorate significantly.

P: 0.1% or less P is preferably as low as possible, especially in roller materials, and is suppressed to 0.1% or less in order to make the material brittle.

S: 0.08% or less For the same reason as P, the smaller the amount of S, the more desirable it is, and its content should be 0.08% or less.

Ni: 4.5-10% Ni is actively included to improve the matrix structure and crystallize graphite. If it is less than 4.5%, graphite crystallization will occur, and if it exceeds 10%, graphite crystallization will occur. When the amount of residual austenite increases, the amount of austenite is not reduced even by subsequent heat treatment, which causes problems in terms of roughness resistance during use.

Cr: 5-10% Cr combines with C to form Cr carbide, but if it is less than 5%, there are few carbides and the wear resistance is inferior, and if it exceeds 10%, crystallization of graphite will occur in the above Nis Si composition range. I can't get it.

Mo: 0.4 to 1.5% Mo is effective in increasing the quenching and tempering resistance and at the same time entering into the carbide to increase the hardness of the carbide and improving the tempering softening resistance. However, if the content exceeds 1.5%, there is a strong tendency towards whitening, and graphite crystallization cannot be obtained.

The outer shell composition contains the above, and the remainder is substantially composed of Fe.

The inner shell 4, which is welded and integrated with the outer shell 3, is made of ductile cast iron having excellent toughness, and its chemical composition is specified by the following limitations. The chemical composition of the molten inner shell must be determined in consideration of the fact that the inner surface of the outer shell is washed and mixed into the molten inner shell during the casting of the inner shell.

C: 3.0 to 3.8% C is included to impart toughness and strength, but if the C content is less than 3.0%, the material will become chilled and the toughness of the inner shell material will significantly decrease. Become. On the other hand, if the content exceeds 3.8%, graphitization will be excessive and the strength of the inner shell material will be insufficient. As a result, the sleeve cannot be removed, leading to axial displacement of the sleeve and damage from the inside. Therefore, Ca is defined as 0 to 3.8%.

Si: 1.8-3.0% Si is necessary to prevent the material from becoming brittle due to mixing with the outer shell Cr, but if the content is less than 1.8%, graphitization will be poor and cementite will be formed. Since a large amount of crystallization occurs and the strength of the inner shell deteriorates, it becomes more likely to crack during casting due to residual stress. On the other hand, if the content exceeds 3.0%, graphitization will be promoted and strength will deteriorate. Therefore, the Si content is 1.8 to 3.0
% range. Note that the Si content can be set within the above-mentioned high range from the time of melting the inner shell molten metal, but when pouring the inner shell molten metal, 0.2
Inoculation of ~0.5% (as Si%) is also a very effective method; in this case, the initial Si content is lower than the above range (and the Si% after inoculation is within the specified range). It is necessary to.

Mn: 0.3-1.0% Mn combines with S and reduces the negative effects of S as MnS, but this effect is less at less than 0.3%, while at 1.0%
If the content exceeds S, the effect of deteriorating the material becomes more pronounced rather than the effect of preventing the adverse effects of S. Therefore, Mn
The content is in the range of 0.3 to j1.0%.

p: o, i% or less P increases the fluidity of the molten metal, but since it makes the material brittle, it is preferably as low as possible, and the content needs to be 0.1% or less.

s: o, oe% or less S, like P, makes the material brittle, so the lower it is, the better. In addition, since the inner shell is made of spheroidal graphite cast iron, it combines with M added in the Mg treatment to form MgS, and j
3 is removed, but a low S content is required to make graphite spheroidal, and 0.06
% or less.

Ni: 2.0% or less Ni is contained for the purpose of stabilizing graphite, and there is no significant effect if it is contained in excess of 2.0%, so it is kept to 2.0% or less.

Cr: 5.0% or less Since the outer shell is made of a high chromium material and contamination of Cr from the outer shell is unavoidable, the lower the Cr content of the inner shell molten metal is, the better it is 0.5% or less. If the content exceeds 0.5%, the content of Cr exceeds 5.0% due to the amount mixed in from the outer shell, resulting in an excessive amount of cementite in the material, resulting in deterioration of toughness.

Mo: 1.0% or less If Mo is contained in an amount exceeding 1.0%, the material becomes too hard, so the content should be 1.0% or less.

Mg: 0.02-0.1% Mg is an element necessary for spheroidizing graphite, but if its residual content is less than 0.02%, spheroidization will be poor, so it is necessary to make the inner shell into a strong spherical shape. Graphite cast iron material cannot be used. On the other hand, if the content exceeds 0.1%, it is unfavorable in terms of Mg's chilling effect and dross. Therefore, M
The residual content of g is in the range of 0.02 to 0.1%. In addition, when treating the inner shell molten metal, it is necessary to add an extra amount of M in order to obtain a predetermined residual amount, taking into account the loss due to the generation of MgS and dross.

The inner shell composition contains the above, and the remainder is substantially composed of Fe.

A plurality of composite sleeves 2, in which an outer shell 3 having excellent seizure resistance, crack resistance, and abrasion resistance on paper and an inner shell 4 having excellent toughness are welded and integrated, are mounted on the roller shaft 5 at intervals after a predetermined heat treatment. are placed, dispersed, and fixed by shrink fitting, gluing, etc. According to the distributed arrangement of the composite sleeves 2, the unit weight of the roller can be significantly reduced compared to the case where an integral composite sleeve is fixed to the roller shaft.Therefore, it is possible to reduce driving energy and reduce running costs. can be done.

Furthermore, since the width of the composite sleeve 2 itself is small, residual stress in the axial direction can be significantly reduced with respect to the integral body, and the accident resistance can be significantly improved.

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 force casting mold 6, which is rotated on a centrifugal force casting machine, the molten metal is first cast to form the outer shell 3'', and then, while the inner surface is partially or completely unsolidified, Then, the molten metal of the 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, 9 indicates a rotating roller, 10 a molten metal ladle, and 11 a casting machine.

In the centrifugal casting method illustrated in FIG. 2, an example is shown in which the axis of rotation is horizontal, but centrifugal casting can also be performed with the axis of thermal 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 above heat treatment is a quenching and tempering heat treatment performed to improve the seizure resistance and wear resistance of the graphite crystallized high chromium cast iron material of the outer shell of the composite sleeve. An associated axial residual stress is generated. That is, compressive stress on the outer surface and tensile stress on the inner surface are generated, and the magnitude thereof is determined by the wall thicknesses of the outer shell and the inner shell. In conventional one-piece long composite sleeves, residual stress in the axial direction was not released, and there was a possibility of cracks occurring from the inner surface and cracking when the roller was used.However, in the present invention, the composite sleeve can be shortened. This made it possible to release residual stress in the axial direction and improve accident resistance.

The composite sleeves 2 obtained as described above are individually fixed to the roller shafts 5 by shrink fitting or the like.
The trantable roller 1 is obtained, and since the composite sleeve 2 is considerably smaller than a single piece, the fixing operation is extremely easy.

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

Production Example (1) of a hot run table roller with product body diameter D = φ310 vn = body length L = 1800 m The outer shell graphite crystallized high chromium cast iron molten metal shown in Table 1 was heated to an inner diameter φ300 w x 1200 m as shown in Figure 2. In a centrifugal force casting mold (rotation speed: 80 rpm) for fin p, a wall thickness of 40 mm (casting weight: 341 kg) and a casting temperature of 140 mm were placed.
It was cast at 0°C.

(2) Six minutes after the start of casting 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+*m (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 was molded and held in the furnace to remove the strain. Table 1 shows the product chemical composition of the sleeve material.

Next Leaf (4) After removing the distortion, remove 150 pieces from each end of the sleeve material, divide the sleeve into 4 parts, hold each divided part in a furnace at 950℃ for 5 hours, and then cool it until the surface temperature reaches 500℃. In this state, it was again held at 550°C in the furnace and cooled.

As a result, the hardness on the sleeve surface was Hs70.

(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 mm, and a width of 200 H were obtained. The four composite sleeves were assembled to <200 mm as shown in Figure 1.
6 /
Shrink fitting was performed at a shrink fit ratio of 1000 to obtain a desired hot run table roller.

(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.

In addition, test pieces were taken from the outer and inner shells after disassembly and their mechanical properties were investigated. The results were as shown in Table 2. The compressive strength at the boundary is 164 kg when compressed in a 45° direction.
/wm2, which was good.

Table 2 <Effects of the Invention> As explained above, the hot run table roller of the present invention has an outer shell made of graphite crystallized high chromium cast iron that has excellent seizure resistance, crack resistance, and wear resistance, and a Multiple composite sleeves, which are formed by welding and integrating ductile cast iron inner shells, are fixed to the roller shaft at intervals, resulting in seizure resistance, crack resistance, abrasion resistance, and accident resistance. The roller of the present invention has excellent economical value because it is both excellent in both properties, is lightweight, requires less driving energy, and is very easy to manufacture and fix.

[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 of 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: 2.4-3.4% Si: 2.0-3.4% Mn: 0.5-1.5% P: 0.1 % or less S: 0.08% or less Ni: 4.5 to 10% Cr: 5 to 10% Mo: 0.4 to 1.5% The remainder consists essentially of Fe with an outer shell of graphite crystallized high chromium cast iron , the chemical composition is in weight%: C: 3.0-3.8% Si: 1.8-3.0% Mn: 0.3-1.0% P: 0.1% or less S: 0.06 % or less Ni: 2.0% or less Cr: 5.0% or less Mo: 1.0% or less Mg: 0.02 to 0.1% The balance is welded and integrated with the inner shell of ductile cast iron, which essentially consists of Fe. 1. A hot runtable roller comprising: a plurality of composite sleeves having an outer shell hardness of Hs65 or more, which are fixed to a roller shaft at intervals.