JPS6044114A - Rolling roll having tough neck part and its manufacture - Google Patents

Abstract

PURPOSE:To develop a composite high alloy-steel roll having neck parts excellent in toughness by reasonably improving the shapes and dimensional ratios and the material at each part of a rolling roll. CONSTITUTION:A roll used for hot strip rolling is so formed that its neck length lN is larger and its body diam. DB is smaller than those of conventional ones, and the ratio lN/lB between the neck length lN and the body length lB is 0.8-1.2, and the ratio lN/DN between the length lN and the neck diam. DN is 3.8-13.0. In manufacturing the roll, a body outer-shell part 4 required to have resistances to wear, surface roughening, and crack is manufactured by casting a high-alloy grain material by using a quenching mold such as a metallic one, and a slow cooling mold such as a sand one is used for a neck part 5 required to have toughness. Further, a ductile cast iron or a graphite steel is used for a body axial part 6 and a neck part 5, which are cast into one body to form a blank material of composite roll. The material after rough machining is hardened by an intermediate frequency hardening device and is machined for finish forming it.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the provision of a composite roll suitable for a rolling roll having an elongated neck shape, a special shape requiring particular toughness at the neck end, and usage characteristics. This invention relates to an improved high-alloy grain roll.

Since the properties required for the body and neck of rolling rolls are different, composite rolls are often used in which the III/i outer shell, body shaft core, and neck are made of different materials, but in recent years New types of hot strip mills for rolling steel plates are emerging to control the shape of steel plates.

In other words, these methods include a method in which the work roll is shifted in the axial direction, a method in which the work roll is forcibly bent, a method in which two work rolls are crossed with respect to the axis of a backup roll, etc. .

Therefore, work rolls used in these rolling methods tend to have smaller body diameters.

Furthermore, due to the type of rolling mill, the length of the neck needs to be longer than that of conventional rolls, and the diameter of the neck is also made smaller. In addition, in this type of neck part, a larger stress is generated in the neck than in the past, and particularly toughness is required.

The conventional general shape roll is shown in Figure 1, and the above new rolling method 0
The specially shaped roll used in the formula is shown in FIG. 2 in comparison, and the specific differences in shape and dimensions are summarized as follows.

Mu lN/1m D) I Mu/DN, DB Conventional 10
00 0.52 ,,J, shape~14oo~o, 7.340-. ．． 500
2,0,3,6 650,8401N: Neck length (
m-) 1m: Body length (-m) DN: Neck diameter (bo) DB: Body diameter (,,) As mentioned above, in the rolls used for this new rolling method,
Ratio of neck length to torso length is approximately 1. ．． / Eight is 0.8-1.2
Or is the ratio of neck length to neck diameter 7? N/D, I is 3.8~
It is characterized by an elongated neck shape in the range of 13.0 mm.

By the way, the usage characteristics of the body and the neck part as a whole are also different for such specially shaped rolling rolls, and as shown in Fig. 3, the body part jl) in contact with the rolling strip has wear resistance, Roughness resistance, rug resistance, etc. are required.

On the other hand, the required characteristics of the neck part differ further in the axial direction.The bearing part (2) near the body part 11+ requires wear resistance and toughness against friction with the bearing, and the other part from the body part (1) The remote neck ends (3) are elongated in shape and require particular toughness as they must withstand large stresses. "Also, with this specially shaped roll, as shown in Figures 2 and 3, the neck end t3) K has a portion with a smaller diameter than the neck diameter D'N, and depending on the rolling method, for example, A large thrust stress is generated on the side (W), and a large torsional stress is generated on the drive side (D), so toughness is particularly required for this portion.

In particular, the necks of recent post-stage work rolls have complex shapes and small diameters, resulting in large thrusts and
Twisting and bending forces act on the corners of the neck, and damage due to the development of microcracks on the surface becomes a problem, so toughness is required at the corners of the neck.

In this way, the ratio lx/im of the neck length to the torso length is 0.
．． It has an elongated neck shape with a ratio lN/DN of 8 to 1.2 or neck length to neck diameter of 3.8 to 13.0, and is suitable for special rolling rolls that generate large stress at the neck end. An object of the present invention is to provide a rolling roll in which the neck corner of a composite roll is made tough, and a method for manufacturing the same. Therefore, its characteristics are that the body outer shell is made of high-alloy grain material, and the body axis and neck are made of ductile cast iron or graphite steel. The core of the trunk is integrally welded, and the surface layer of the corner of the neck is hardened, and a rapid cooling mold is placed in the trunk and a slow cooling mold is placed in the neck. A composite roll material is cast by bath coat integrated casting using a high-grade gold grain material for the core part and ductile cast iron or graphite steel material for the body axis and neck part, and the body part and neck part of the roll material are roughly machined. After that, the surface layer of the corner portion of the neck portion is medium-frequency hardened using a medium-frequency hardening device.

The present invention will be explained in detail below.

For example, the work roll for the latter stage of the hot strip mill finishing stand has an outer shell (4
) is made of high-grade gold grain material, and includes a neck part (6) consisting of a bearing part (2) and a neck end part (3), and a trunk shaft core part (6).
) is made of ductile cast iron or graphite steel,
The trunk outer shell part (4) and the trunk shaft core part (6) are integrated into the bathrobe. The dimensions of each part of this roll are as described above.

The manufacturing method for the roll described above is as follows: First, a rapid cooling mold is placed in the body, a slow cooling mold is placed in the neck, a high-alloy grain material is placed in the body outer shell (4), a body shaft core (6), and a slow cooling mold is placed in the neck. (6) Dakuquill! ! #Cast a composite roll material by welding and integral casting using iron or graphite steel.

As mentioned above, the shell outer shell, part (4), is required to have wear resistance, roughness resistance, crack resistance, etc., so it must be aimed at microstructural refinement and uniformity. Alternatively, casting is performed using a rapidly cooling mold with a relatively thin layer of refractory applied onto the mold.

A cold mold such as a sand mold is used for the neck part (5) in order to strengthen the neck part, prevent internal cavities, and replenish unsolidified bath water to the mold part.

If a mold is used for the neck, since the diameter of the neck is smaller than that of the body, the neck will solidify earlier than the body, and a shrinkage cavity will occur in the center of the body. Therefore, a slow cooling mold is used for the neck part, but since the neck part is slowly cooled, its toughness is inferior to that when the neck part is rapidly cooled. Here, due to constraints in the manufacturing process, the mechanical properties required for the mating part are sacrificed.

Therefore, in the present invention, in order to prevent the above-mentioned fraud, after rough processing the body and neck of the roll material, the surface layer of the corner 17i of the neck (5) is heated using a medium frequency hardening machine. Frequency hardening imparts toughness.

The reason for using medium frequency hardening is that the thrust load on the roll neck is large, and hardening only near the bottom is not effective, so a certain degree of hardening depth is required. With induction hardening or flame hardening, only a very shallow surface layer is hardened, and the toughness (
;The effect of J is small.

Next, the medium frequency heat treatment of the roll neck will be explained in detail.

As shown in Figures 4 and 5, a medium frequency hardening device I+o consisting of one medium frequency coil, 8) and a water cooling coil (91),
Install it at the neck corner (7) at a uniform distance from the surface.

Next, the medium frequency coil (8) is energized, the medium frequency energy is adjusted, and the temperature of the neck corner (7) is gradually raised.
Get 1 perversion point or higher. At this time, the temperature of the neck portion other than the roll body and the corner hardly increases.

Following this, the female of the water cooling coil (9): 9 l (I
Quenching is performed by jetting cooling water from J). This results in
The surface layer of the neck corner portion (7) has high hardness over a predetermined depth, and the inside where the temperature rise is small has the characteristic of having toughness unique to ductile or graphite steel.

After the medium frequency quenching described above, the roll is subjected to normal heat treatment to relieve residual stress in the neck portion and to bring the roll body to the target quality.

Examples of the present invention will be described below.

<Example> Target roll; Material of the work roll for the latter stage; Trunk outer shell part: High alloy grain material Trunk shaft core and neck part: Ductile cast iron roll dimensions; Trunk part 570φx x, 45o /Neck minimum diameter part 200φX 100' Frequency 11; Then medium frequency hardening was performed.

First, power is applied to the medium frequency coil (8) at the neck corner (
After heating 7) for 30 molecules at 300°C, the temperature was further raised to 500°C and 30 molecules were heated. Thereafter, the temperature was raised and maintained at 900°C for 20 minutes.

After that, turn off the current and use the two water cooling nozzles (ll) to
Water cooling was performed using K97an' water pressure.

After medium frequency quenching, the equipment is removed and the entire roll is heated to 350°C.
After heat treatment at ℃, the roll was disassembled.

As a result of the above, the hardness of the neck part is H at the corner part (7).
H846 was obtained at s57 and other parts. Figure 8 shows the change in hardness in the radial direction.

Hardness indicates the stress σf at a certain percentage of strain in a stress-strain diagram, and when the hardness increases, the tensile strength also increases. The results of this tensile test are shown in the table below.

Tensile test results As detailed above, according to the present invention, the body has the characteristics necessary for a roll, the neck has a high surface hardness,
In addition, the inside of the roll is rich in toughness, making it necessary for hot strip millwork rolls to have an elongated neck shape, a neck surface with high hardness, and a neck interior with high toughness. For the role that
It exhibits excellent effects.

Note that medium frequency hardening can be applied not only to the neck corner portions but also to the entire surface of the neck portion.

[Brief explanation of the drawing]

Figure 1 is a side view showing an example of the shape of a conventional rolling roll;
The figure is a side view showing an example of the shape of a rolling roll that is the subject of the present invention, Figure 3 is a partially enlarged side view of the rolling roll that is the subject of the present invention, and Figure 4 is a front view of a medium frequency hardening device. 5 is a sectional view of the same, FIG. 6 is a plan view of a part of the embodiment of the present invention, and FIG. 7 is a sectional view of the embodiment of the present invention, and FIG.
Figure 8 is a graph showing the hardness distribution. (4) ... Torso outer shell part, (5) ... Neck part, (6)
...Body shaft core part, (7)...Corner part, 1101...
・Medium frequency hardening equipment. Figure 1 Figure 3 Figure 5 Figure 61 Figure 7

Claims (1)

[Claims] 1. Neck length (/, ) and body length (in) O ratio 1m/
It has an elongated neck shape with a h of 0.8 to 1.2, or a ratio is/Dw of neck length (7N) to neck diameter (D) of 3.8 to 13.0, with a particularly strong structure at the neck end. In the required roll, the outer shell part is made of high-alloy grain material, the core part and neck part are made of ductile cast iron or graphite steel, and the outer shell part and the core part of the body are made of ductile cast iron or graphite steel. A rolling roll having a tough neck part, which is welded to solidified and has a hardened corner surface layer. 2. Neck length (lH) Torso length (lB) (D ratio i
It has an elongated neck shape with a s/is force of 0.8-1.2 or a ratio lN/DN of neck length (lN) and neck diameter (D-) of 3.8-13.0, and is particularly strong at the neck end. This is a method for manufacturing rolls that require high performance, in which a rapid cooling mold is placed in the body, a slow cooling mold is placed in the neck, high-alloy grain material is used in the outer shell of the body, and ductile is used in the core and neck of the body. A composite roll material is cast by welding and integral casting using cast iron or graphite steel, and the body and neck of the roll material are rough-processed. After 7ζ, the surface layer of the corner part of the neck is heated using a medium direction wave hardening device. A method for manufacturing a rolling roll with a strong neck portion, which comprises medium-frequency hardening.