JPH08121464A - Roll for heat roll plant winding machine - Google Patents

Abstract

PURPOSE: To prolong the service life by forming a hardening padding welding layer of specific hardness or higher in a barrel part surface of an iron system roll, and further forming thereon a self melting hardening alloy flame spraying layer, so as to prevent occurrence and spalling of a flame spraying layer cracking. CONSTITUTION: A hardening padding welding layer B of Hs50 or higher hardness is formed on a barrel part surface of an iron system roll C, further to form thereon a self fusing hardening alloy flame spraying layer A. Here, also hardness of the self fusing hardening alloy flame spraying layer A is set to Hs50 or higher, thickness of the hardening padding welding layer B is set to 3mm or more of single padding and thickness of the self fusing hardening alloy flame spraying layer A is set to 0.1mm or more of single padding, also preferable to apply fusing treatment to this flame spraying layer A. Thus, by using an iron system as the roll material C particularly using a low carbon low alloy system material of good weldability, and by combining the hardening padding layer B and the self fusing alloy flame spraying layer A applied, quality of a product is improved, also to increase its durability with use for a long period made capable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a self-hardening weld metal built up on the surface of the body of a roll for a hot rolling mill winding machine such as a wrapper roll for a hot rolling mill winding machine or an upper and lower pinch roll. The present invention relates to a roll for a winder of a hot rolling factory, which has a self-hardening alloy sprayed layer sprayed thereon.

[0002]

2. Description of the Related Art Rolls for hot rolling mills such as wrapper rolls and upper and lower pinch rolls for hot rolling mills
Due to severe operating conditions such as surface pressure and slip, wear, corrosion,
The life of the roll is short due to seizure, etc., and there are many problems in terms of rolling cost. As a countermeasure against this, each roll manufacturer is researching new roll materials and new processing methods. Forging and casting rolls, which have the highest degree of utilization than ever, are more resistant to wear, corrosion, and seizure. There are limits to meeting the conditions.

[0003] A spalling-resistant and wear-resistant roll, in which the surface of the body of an iron-based roll is subjected to hardfacing welding under certain conditions and a thermal sprayed layer of self-fluxing alloy type is further deposited thereon, It is proposed in Japanese Laid-Open Publication No. 55-149710. However, its use was generally said to be useful as a steelmaking roll. Various self-fluxing alloy sprayed rolls have also been developed, but the compatibility with the bare roll is poor, and wear resistance, seizure resistance, spalling resistance, and bead mark resistance are all achieved by spraying the self-fluxing alloy alone. It was insufficient to make an excellent roll for a winder.

[0004]

Since the self-fluxing alloy thermal spray material is generally hard and brittle, when it is thermally sprayed on a roll of a steel mill, a roller, especially a large shape roll such as a winder roll, thermal stress It is easy for cracks to occur due to unbalance.
Further, the self-fluxing alloy sprayed layer is 900 to 13 during fusing.
Since it is melted at a high temperature of about 00 ° C, naturally the surface of the base material of the roll is also heated by the heat, and the base material such as mild steel or carbon steel is softened and the hardness distribution as shown in Fig. 2 is obtained. It is easy to become.

Moreover, at the time of cooling after fusing, there is a risk of cracking unless the sprayed layer is annealed to remove stress, but the annealing also tends to soften the base material. Due to the above factors, the self-fluxing alloy sprayed roll having the hardness distribution as shown in Fig. 2 is likely to be cracked near the boundary between the base material and the sprayed layer due to the contact pressure impact during use, which may cause spalling. Therefore, it is not used for rolls with high load and high impact.

In order to solve the above problems, the present invention combines wear overlay welding with a suitable self-fluxing alloy spray overlay to provide wear resistance having a gradient of hardness distribution as shown in FIG.
Aiming to provide rolls for hot rolling mill winders, such as hot rolling mill winder wrapper rolls and upper and lower pinch rolls, which have epoch-making performance in corrosion resistance, seizure resistance, spalling resistance, and bead mark resistance. I am trying.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the inventors of the present invention have conducted extensive studies and as a result, as a roll material, an iron-based material, particularly a low carbon or low alloy material having good weldability. Based on this, it was found that it is important to apply a combination of a hardfacing layer and a self-fluxing alloy sprayed layer to this, and the present invention has been completed. That is, the present invention made on the basis of the above-mentioned findings is characterized in that a hardfacing welding layer having a hardness of Hs 50 or more and a self-fluxing alloy sprayed layer are further formed on the body surface of the iron-based roll. The main point is a roll for a hot rolling mill winder. A roll for a hot rolling mill winder having a self-hardening alloy sprayed layer with a hardness of Hs 50 or more is also the subject matter of the present invention. A roll for a hot rolling mill winder having a thickness of the sprayed layer of 0.1 mm or more and having a fusing treatment applied to the self-hardening alloy sprayed layer is also the subject matter of the present invention.

[0008]

The structure and operation of the present invention will be described. In the present invention, the roll material used is an iron-based material, particularly a low-carbon, low-alloy-based material having good weldability because of its relationship with the self-fluxing alloy sprayed layer. That is, the sprayed self-fluxing alloy layer is not transformed during cooling, and the shrinkage is uniform during the cooling process. However, the iron-based element roll in contact with the sprayed layer exhibits a unique expansion phenomenon due to martensitic transformation. This expansion amount increases as the amount of C in the roll material and the amount of hardening component increase, so that if the material of the roll material is erroneously selected, cracks will be generated in the self-fluxing alloy sprayed layer. Therefore, the C content is preferably 0.40% or less.

Next, the hardness of the hardfacing weld layer is set to Hs 50 or more, but a relatively low carbon material is selected as the weld metal to be built up, and the expansion transformation amount is made smaller than that of the roll material. Therefore, as will be apparent from the examples described below, the amount of C is preferably 0.30% or less, and overlay welding is performed using a welding material containing high Cr, Mo, V, etc. in order to make the structure martensitic. Do.

On the other hand, the material of the weld metal is required to have a desired hardness even if it is subjected to a heat cycle (heat during fusing and annealing) during spraying of the self-fluxing alloy. The weld metal is preferably a low carbon martensite system in which a softening structure is less likely to occur even if the weld layer is cooled after the austenite transformation fairly slowly. That is,
A hardened structure with a reduced expansion amount.

The thickness of the overlay welding layer is set to 3 mm or more on each side. When the thickness of the overlay welding layer is less than 3 mm on one side, deformation due to surface pressure during use occurs, the effect of the present invention is reduced, and it becomes difficult to absorb the transformation expansion of the roll. Therefore, overlay welding with a wall thickness in the above range is preferably performed.

Subsequently, self-fluxing alloy thermal spraying is performed on the surface of the roll barrel portion on which the weld metal having good self-hardening property has been built up in advance. The thickness of this sprayed layer is set to 0.1 mm or more per piece. The practical thickness of the sprayed layer is preferably thin in view of prevention of cracking during construction and economical efficiency, but about 2 mm is suitable. It is preferable to use a Ni-based, Co-based, or Fe-based self-fluxing alloy material for the sprayed layer. The hardness of the self-fluxing alloy sprayed layer is Hs considering the wear resistance and the scratch resistance.
50 or more.

After fusing the sprayed layer, the roll is held at a predetermined temperature for a certain time during cooling in order to relieve stress in the sprayed layer. A holding temperature of 500 ° C or higher is required, and an annealing effect is given to the material and the overlay. Since the temperature at the time of fusing of the thermal sprayed layer is about 900 to 1300 ° C, the overlay welding layer below the thermal sprayed layer rises to a temperature close to the fusing temperature and is austenitized, but after that, for a short time in the annealing process. Select a material that is less likely to cause softening in the retention of
Since the amount of transformation expansion is small, there is no cracking even after being completely cooled after annealing.

[0014]

EXAMPLES The present invention will be specifically described with reference to Examples.
This does not limit the invention. Example A wrapper roll of a hot rolling mill winding machine according to the present invention will be described. Table 1 shows the components of the self-fluxing alloy spray material applied to the roll, Table 2 shows the raw material components of the roll, and Table 3 shows the components of the hardfacing weld metal.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

Of these specific examples, the diameter 35 of the body of the roll
0mm x body length 1730mm x total length 2300mm (Table 2: Material No. 6), hardfacing welding was performed on one side of the blank 3.
The thickness was 5 mm (Table 3: Material No. 9), and spray coating was performed on the surface with a thickness of 1.5 mm (Table 1: Material No. 3), and then fusing was performed at 1000 to 1200 ° C. In the cooling process after fusing, the temperature was held at 700 ° C. for 5 hours and then gradually cooled. The hardness distribution of the obtained roll cross section is
The sprayed layer is Hs80, the overlay welding layer is Hs65, and the base metal is Hs.
It was 23.

In the process for producing a hot-rolled steel sheet, the roll of the present invention and the roll of the conventional example (a roll material directly sprayed with a self-fluxing alloy material of Table No. 3 having a material thickness of 1.5 mm) are used. When comparing the use results, compared to the conventional example roll, the roll of the present invention, the recess due to the flaw of the threading plate top,
There was no occurrence of cracks in the sprayed layer and no spalling, and the service life was more than doubled.

[0020]

Since the present invention is configured as described above, the quality of the product is improved and the durability thereof is improved as compared with the conventional hot rolling mill winder wrapper roll and the upper and lower pinch rolls. It has an excellent effect that it can be used for a long period of time and is extremely useful in industry.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of hardness distribution of a roll of the present invention.

FIG. 2 is an explanatory diagram of hardness distribution of a conventional roll having only a self-fluxing alloy sprayed layer.

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Claims (4)

[Claims] 1. A winder for a hot rolling mill, comprising a hardfacing weld layer having a hardness of Hs 50 or more and a self-hardening alloy sprayed layer formed on the body surface of an iron-based roll. For rolls. 2. The roll for a hot rolling mill winder according to claim 1, wherein the hardness of the self-hardening alloy sprayed layer is Hs 50 or more. 3. The hardfacing welding layer has a thickness of 3 mm or more per piece,
The roll for a hot rolling mill winder according to claim 1 or 2, wherein the thickness of the self-hardening alloy sprayed layer is 0.1 mm or more. 4. The roll for a hot-rolling mill winder according to claim 1, which is a self-fluxing alloy sprayed layer that has been subjected to a fusing treatment.