KR102218407B1 - Hot leveller carriage frame for thick steel sheet and method of manufacturing the same - Google Patents

Abstract

According to one aspect of the present invention, provided are a hot leveler carriage frame for a thick plate increasing abrasion resistance due to improvement of hardness while maintaining peeling resistance and corrosion resistance of the hot leveler carriage frame for a thick plate repetitively used at high temperature and high pressure for a long period of time, and a method for manufacturing the same. According to one embodiment of the present invention, provided are the hot leveler carriage frame for a thick plate comprising a main body unit having a concave unit and a convex unit where a roll chock is secured, wherein a first buttering layer is formed on the convex unit and a second buttering layer is formed on the first buttering layer, and the method for manufacturing the same.

Description

Hot leveler carriage frame for thick plate and its manufacturing method {HOT LEVELLER CARRIAGE FRAME FOR THICK STEEL SHEET AND METHOD OF MANUFACTURING THE SAME}

The present invention relates to a hot leveler carriage frame for a thick plate and a manufacturing method thereof.

In general, a carbon steel material containing carbon (C) is refined by making pig iron containing a large amount of carbon (C) in order to secure excellent machinability, removing impurities in the steel making process, and alloying the components. Next, a solidified slab is made through a continuous casting process, reheated to a constant temperature before hot rolling, and then put into a rolling mill, and the thickness is reduced by continuous rolling action to form a strip plate of constant thickness. It can be used as a thick plate or hot-rolled plate after being hot-processed with a furnace, or sent to a cold-rolling process to be cold-rolled to produce a cold-rolled plate.

At this time, the Hot Leveler Carriage Frame used in the calibration process after hot rolling for the production of thick plate is the heat treatment process, temperature variation, and cooling rate of the thick plate obtained through slab rolling in a rolling mill. It is operating as a core facility of the quality of thick plates as a hot correction device to precisely match the deformation and local thickness deviation according to the constant thickness and shape. That is, in the hot-leveler carriage frame, in order to correct the surface of the steel sheet rolled by the rolling mill during the hot rolling process, the surface of the steel sheet and the deformation due to temperature deviation in the center or width direction, etc. It acts to induce to maintain the flatness of.

The Hot Leveller Carriage Frame is composed of several facilities. Most of the equipment repeats movement according to the material during rolling. The Hot Leveler Carriage Frame equipment includes several straightening rolls above and below the frame, and this straightening roll They are assembled by respective roll chocks, and the assembled roll chocks are connected and coupled to the cross section of the mounting table formed on the hot leveler carriage frame. The straightening rolls are driven by electrical energy, and the upper and lower roll intervals are controlled by hydraulic pressure. After hot rolling, the pulled out thick plate is passed through a multi-stage straightening roll, and at this time, the longitudinal and lateral deformations, distortions, and bent shapes of the thick plate are calculated in conjunction with the roll dia for optimal hot calibration. After the roll gap is set, it is calibrated by passing between the calibration rolls at a constant speed in a hot state of 550°C to 950°C.

However, during such a hot calibration (hot leveler) process, a repetitive and continuous roll force of 10,000 tons or more is applied to the thick plate, and as a result, it is in contact with the hot leveler roll choke. The surface of the seating table of the Hot Leveler Carriage Frame is also damaged and acts as a factor that hinders the control of the gap of the calibration roll.

On the other hand, the reduction in thickness relative to the total area due to abrasion, corrosion, and subsidence is managed within 0.1mm, and if the reduction in section thickness of the mounting table is 0.1mm or more, the calibration capability is lost. The driving is stopped, which causes a phenomenon that significantly deteriorates the quality of the thick plate, and the roll choke seat of the Hot Leveler Carriage Frame is repeatedly processed and used to reduce the total cross-sectional thickness of the seat to more than 3mm. If worn or settled, the facility cannot be used, so it is replaced with a new one after disposal.

1 is a picture of a conventional hot leveler carriage frame. The material of the conventional hot leveler carriage frame is SM490YA or similar welded structural steel, C: 0.2% or less, Si: 0.55% or less, Mn: 1.60% or less, 　P: 0.035% or less, S: It contains less than 0.035% of components, has a tensile strength of about 490N/mm2, and has a ferrite structure. These welded structural steels have characteristics in that their surfaces are easily oxidized, corroded, and worn by cyclic loads, high heat and moisture, and impact loads.

To solve this, a surface hardening layer of 3-6 μm is formed on the surface of the roll chalk mounting table through surface hardening heat treatment, acid-nitridation treatment, etc. to improve abrasion resistance, peeling resistance, and corrosion resistance, etc. Although the desired technology has been developed, there is a limit in improving the life of the thick plate hot leveler carriage frame that is repeatedly used for a long period of time at high temperature and high pressure.

Accordingly, a thick plate hot leveler carriage that is repeatedly used for a long period of time at high temperature and high pressure, while maintaining the peeling resistance and corrosion resistance of the frame, while improving the abrasion resistance according to hardness improvement. Development of a frame is required.

One aspect of the present invention is a thick plate hot leveler carriage that is repeatedly used for a long period of time at high temperature and high pressure, while maintaining the peeling resistance and corrosion resistance of the frame, and a thick plate hot leveler carriage capable of increasing abrasion resistance according to hardness improvement. frame And it is intended to provide a manufacturing method.

One embodiment of the present invention includes a body portion having a convex portion and a concave portion on which a roll choke is seated, and a thick plate hot leveler carriage frame having a first buttering layer on the convex portion and a second buttering layer formed on the first buttering layer. to provide.

Another embodiment of the present invention comprises the steps of preparing a body portion having a convex portion and a concave portion; A first buttering welding step of buttering welding such that a first buttering layer is formed on the convex portion; A second buttering welding step of performing a second buttering welding such that a second buttering layer is formed on the first buttering layer; And air-cooling the body portion on which the first buttering layer and the second buttering layer are formed. It provides a method of manufacturing a thick plate hot leveler carriage frame.

According to one aspect of the present invention, a thick plate hot leveler carriage capable of enhancing abrasion resistance according to hardness improvement while maintaining peeling resistance and corrosion resistance of a thick plate hot leveler carriage frame frame And it can provide a manufacturing method.

In addition, it is possible to solve the increase in cost due to replacement and purchase of a carriage frame caused by frequent damage.

1 is a picture of a conventional hot leveler carriage frame.
2 is a photograph of an observation of a buttering layer of a thick plate hot leveler carriage frame according to an embodiment of the present invention.
FIG. 3 is a schematic diagram of a thick plate hot leveler carriage frame corresponding to the AA′ area shown in FIG. 2.

2 is a photograph of an observation of a buttering layer of a thick plate hot leveler carriage frame according to an embodiment of the present invention. 3 is a schematic diagram of a thick plate hot leveler carriage frame corresponding to a region A-A' shown in FIG. 2. Hereinafter, the present invention will be described with reference to FIGS. 2 and 3.

The thick plate hot leveler carriage frame 100 according to an embodiment of the present invention includes a body portion 30 having a convex portion 10 and a concave portion 20 on which a roll choke (not shown) is seated, and the convex A first buttering layer 40 is formed on the portion 10 and a second buttering layer 50 is formed on the first buttering layer 40. In this way, by forming the first buttering layer and the second buttering layer on the convex portion on which the roll choke is seated, corrosion or wear or local peeling even in the case of oxidation due to impact, thermal stress, friction, and moisture caused by repeated use for a long time By preventing the phenomenon from occurring, the lifespan of the thick plate hot carriage frame is improved, and through this, frequent replacement and the resulting cost increase can be prevented in advance. Meanwhile, in the present invention, the shape and number of the convex portions and the concave portions are not particularly limited.

The main body portion 30 of the present invention has a convex portion 10 and a concave portion 20, as shown in FIG. 2, and a roll choke is mounted on the upper side of the convex portion 10. A straightening roll is connected to the roll choke, and the roll choke is driven by hydraulic and electrical control to adjust the gap between the vertical straightening rolls. More specifically, in the hot leveler carriage frame, several calibration rolls are installed at regular intervals on the top and bottom, and the gap between the top and bottom calibration rolls is adjusted by driving a roll choke connected to the calibration roll. Depending on the thickness of the plate, the setting of the interval between the upper and lower straightening rolls may be different. Meanwhile, a bearing block provided with a roll choke may be mechanically coupled to the concave portion using a bolt and a nut.

The main body part applied to the thick plate hot leveler carriage frame of the present invention may be made of SM490YA material commonly used in the art or a welded structural steel material having an alloy composition similar thereto, for example, C: 0.2% or less, Si: 0.55 % Or less, Mn: 1.60% or less, 　P: 0.035% or less, S: 0.035% or less, the balance may have a composition containing Fe and other inevitable impurities, and the tensile strength is about 490N/mm2, and may have a ferrite structure. have.

On the other hand, the first buttering layer by weight%, C: 0.09 to 0.11%, Si: 0.65 to 0.72%, Mn: 0.59 to 6.15%, Cr: 19.0 to 19.6%, Ni: 8.95 to 9.20%, Mo: 0.55 It is preferable to contain ~0.65%, N: 0.10 ~ 0.16%, Ti: 0.04 ~ 0.07%, the balance Fe and other inevitable impurities.

C: 0.09~0.11%

The C is added to prevent cracking of the buttering layer due to the generation of chromium carbide (Cr ₂₃ C ₆ ), and if it is less than 0.09%, the above effect and the effect of improving hardness cannot be sufficiently obtained, and if it exceeds 0.10% Locally, the hardness is improved, which may cause cracking. Therefore, it is preferable that the content of C has a range of 0.09 to 0.11%.

Si: 0.65~0.72%

Si is an element that is very effective in improving high-temperature oxidation properties as the amount of Si added increases, and also improves sag resistance, elongation, high-temperature strength and phase stability (grain growth resistance). When the Si content is less than 0.65%, the above effect cannot be sufficiently obtained, and when the Si content exceeds 0.72%, a problem may occur in that the elongation is sharply decreased. Therefore, the Si content is preferably in the range of 0.65 ~ 0.72%.

Mn: 0.59~6.15%

Mn is an element that is advantageous in improving sag resistance, high temperature oxidation resistance, and phase stability as the amount of Mn increases. If the Mn is less than 0.59%, the above effect cannot be sufficiently obtained, and if it exceeds 6.15%, the elongation may be rather lowered, thereby lowering the moldability. Therefore, it is preferable that the content of Mn has a range of 0.59 to 6.15%.

Cr: 19.0~19.6%

Cr is an important element for strengthening corrosion resistance, and the higher the amount added, the better the high-temperature oxidation characteristics. When the Cr is less than 19.0%, the above effect cannot be sufficiently obtained, and when it exceeds 19.6%, high temperature strength, hot workability at high temperature, and elongation may be reduced. Therefore, it is preferable that the content of Cr has a range of 19.0 to 19.6%.

Ni: 8.95~9.20%

Ni refines the structure of the steel and strengthens the base by solidifying it well in austenite and ferrite. Moreover, when it coexists with Cr or Mo, it shows excellent hardenability. Ni remarkably improves the low-temperature toughness of steel and does not impair the weldability and malleability. In addition, since Ni slows the diffusion of C or N, deterioration is prevented and physical properties such as expansion rate, stiffness rate, and permeability are improved. When the content of Ni is less than 8.95%, the above effect cannot be sufficiently obtained, and when it exceeds 9.20%, Ni is eluted, and moldability may be deteriorated. Therefore, it is preferable that the content of Ni has a range of 8.95 to 9.20%.

Mo: 0.55~0.65%

Mo has an effect of improving hardenability up to 10 times that of Ni, and plays a role of imparting tempering embrittlement resistance by preventing tempering brittleness. In addition, since Mo forms carbides, it exhibits excellent effects as an alloying element in high-end cutting tools and increases the crystal grain coarsening temperature. Regarding the hardenability, it is more effective in combination with Cr than Mo alone. When the Mo content is less than 0.55%, the above effect cannot be sufficiently obtained, and when it exceeds 0.65%, tempering embrittlement resistance is lowered and formation of carbides may be difficult. Therefore, it is preferable that the content of Mo has a range of 0.55 to 0.65%.

N: 0.10~0.16%

Even in the presence of a very small amount of N, it has a great influence on the mechanical properties of the steel. It increases the tensile strength and yield strength, but has the property of lowering the elongation. In particular, it is effective in reducing the impact of the steel and increasing the transition temperature. N is an interstitial element like C, has a fast diffusion rate in steel, and shows a continuous change in solubility from about 0.1% (580℃) to 0.003% (room temperature) for ferrite. It has different characteristics from the element. For this reason, steel exhibits various brittleness and age hardening properties. When the content of N is less than 0.10%, the effect of improving mechanical properties cannot be sufficiently obtained, and when it exceeds 0.16%, brittleness and age hardenability are excessively increased, and the elongation may be deteriorated. Therefore, it is preferable that the content of N has a range of 0.10 to 0.16%.

Ti: 0.04~0.07%

Ti shows a strong affinity with any element such as O, N, C, S, and H, and is particularly commonly used for deoxidation, denitrification and deoiling (脫硫). In addition, the ability to form carbides is also stronger than that of Cr, and is an element that is advantageous in miniaturizing crystal grains. When the content of Ti is less than 0.04%, the above effect cannot be sufficiently obtained, and when it exceeds 0.07%, the ability of forming carbides is excessively high, resulting in a disadvantage that the hardness exceeds the reference value. Therefore, the Ti content is preferably in the range of 0.04 to 0.07%.

It is preferable that the first buttering layer contains the balance Fe and other inevitable impurities.

It is preferable that the first buttering layer has an austenitic structure. In addition, it is preferable that the first buttering layer has an age-hardening property, and it is possible to improve product life by securing a property of increasing strength even with repeated use for a long time. Meanwhile, the first buttering layer may be formed by buttering welding. For example, when the thickness of the welding layer formed during welding corresponding to one pass during buttering welding is about 2 mm, it is directly applied to the surface of the body part. It is not easy to maintain a single austenite phase because the one-pass welding layer formed of is mixed with the one-pass welding layer while the body portion is partially melted. It is not easy to maintain the single austenite phase as a part of the 1-pass welding layer is also mixed when forming the 2-pass welding layer, but as a number of passes progress, the closer to the upper side of the first buttering layer, the more the austenite single phase is obtained. Organization can be obtained. That is, when looking at the first buttering layer as a whole, it is not an austenite single-phase structure, but the upper side of the first buttering layer has a single-phase austenite structure, and the lower side has a microstructure consisting of austenite + second phase. . The second phase may include at least one of ferrite, pearlite, austenite, and martensite. On the other hand, the first buttering layer acts as an intermediate material between the body part and the second buttering layer to mitigate the difference in microstructure and hardness between the body part and the second buttering layer to suppress the phenomenon that the second buttering layer is peeled off from the body part. . In addition, by absorbing the high load and the impact load transmitted to the second buttering layer to reduce the transmission to the body portion, it is possible to improve the buffering effect even in repeated use. The first buttering layer has a thickness of 10 mm or more so that not only the above effect, but also corrosion, abrasion, and local peeling phenomena are not generated by repetitive impact, thermal stress, friction, and oxidation by moisture, and set mechanical and physical properties are exhibited. It is preferable to have. In addition, when the thickness of the first buttering layer is less than 10 mm, mechanical and physical properties set due to the influence of the fraction between the heat-affected zone (HAZ) of the main body and the metal structure during buttering welding may shorten the product life. On the other hand, when the thickness of the first buttering layer exceeds 15 mm, there is a disadvantage such as an increase in cost.

Meanwhile, the second buttering layer is in wt%, C: 0.055 to 0.068%, Si: 0.63 to 0.99%, Mn: 1.23 to 1.50%, Cr: 13.30 to 13.70%, Ni: 3.10 to 3.40%, Mo: 0.79 to It is preferable to include 0.85%, V: 0.47 to 0.52%, Co: 1.25 to 1.31%, the total amount of W, Nb, N and Ti: 0.59 to 0.74%, the balance Fe and other unavoidable impurities.

C: 0.055~0.068%

The C is added to prevent cracking of the buttering layer due to the formation of chromium carbide (Cr ₂₃ C ₆ ), and when it is less than 0.055%, the above effect cannot be sufficiently obtained, and when it exceeds 0.068%, cracking occurs. Disadvantages can occur. Therefore, it is preferable that the content of C has a range of 0.055 to 0.068%.

Si: 0.63~0.69%

Si is an element that is very effective in improving high-temperature oxidation properties as the amount of Si added increases, and also improves sag resistance, elongation, high-temperature strength and phase stability (grain growth resistance). When the Si is less than 0.63%, the above effect cannot be sufficiently obtained, and when it exceeds 0.69%, the elongation is rather rapidly deteriorated. Therefore, the Si content is preferably in the range of 0.63 ~ 0.69%.

Mn: 1.23~1.50%

Mn is an element that is advantageous in improving sag resistance, high temperature oxidation resistance, and phase stability as the amount of Mn increases. When the Mn is less than 1.23%, the above effect cannot be sufficiently obtained, and when it exceeds 1.50%, the elongation is rather lowered, thereby reducing the moldability. Therefore, it is preferable that the content of Mn has a range of 1.23 to 1.50%.

Cr: 13.30~13.70%

Cr is an important element for strengthening corrosion resistance, and the higher the amount added, the better the high-temperature oxidation characteristics. When the Cr is less than 13.30%, the above effect cannot be sufficiently obtained, and when it exceeds 13.70%, high temperature strength, hot workability at high temperature, and elongation may be reduced. Therefore, it is preferable that the content of Cr has a range of 13.30 to 13.70%.

Ni: 3.10-3.40%

Ni refines the structure of the steel and strengthens the base by solidifying it well in austenite and ferrite. Moreover, when it coexists with Cr or Mo, it shows excellent hardenability. Ni remarkably improves the low-temperature toughness of steel and does not impair the weldability and malleability. In addition, since Ni slows the diffusion of C or N, deterioration is prevented and physical properties such as expansion rate, stiffness rate, and permeability are improved. When the content of Ni is less than 3.10%, the above effect cannot be sufficiently obtained, and when it exceeds 3.40%, Ni is eluted, and moldability may be deteriorated. Therefore, it is preferable that the content of Ni has a range of 3.10 to 3.40%.

Mo: 0.79~0.85%

Mo has an effect of improving hardenability up to 10 times that of Ni, and plays a role of imparting tempering embrittlement resistance by preventing tempering brittleness. In addition, since Mo forms carbides, it exhibits excellent effects as an alloying element in high-end cutting tools and increases the crystal grain coarsening temperature. Regarding the hardenability, it is more effective in combination with Cr than Mo alone. When the Mo content is less than 0.79%, the above effect cannot be sufficiently obtained, and when it exceeds 0.85%, the hardenability is high, and thus a disadvantage of exceeding the designed hardness value may occur. Therefore, it is preferable that the content of Mo has a range of 0.79 to 0.85%.

V: 0.47~0.52%

V plays a role of improving the strength of the steel through the precipitation strengthening effect by the formation of precipitates. In addition, since V has a high carbide-forming ability to make fine-grained carbides to refine the structure of steel, it is widely used from high-tensile steel to various tool steels. Tempering softening resistance is also better than Mo, and high-temperature strength is greatly improved. When the content of V is less than 0.47%, the above effect cannot be sufficiently obtained, and when it exceeds 0.52%, the designed hardness value may be exceeded, and an oxide such as V ₂ O ₅ which is evaporated at high temperature due to high vapor pressure is formed. There may be disadvantages of doing this. Therefore, it is preferable that the content of V has a range of 0.47 to 0.52%.

Co: 1.25~1.31%

Most of the alloying elements are added in a small amount to improve the hardenability of steel, but Co shows the opposite tendency as an exception, and because it is expensive, it is not used in general steel, but is used to improve properties by adding magnets, advanced cutting tools, and heat-resistant materials. I am using it. In particular, Co is effective in improving the high temperature strength of steel. When the Co content is less than 1.25%, the above effect cannot be sufficiently obtained, and when it exceeds 1.31%, a disadvantage of excessively reducing the hardenability may occur. Therefore, it is preferable that the content of Co has a range of 1.25 to 1.31%.

Total amount of W, Nb, N and Ti: 0.59~0.74%

The W, Nb, N, and Ti are elements added to stabilize the metal structure of the heat-affected zone of the first buttering layer and improve impact resistance, strength, hardness, heat resistance, and corrosion resistance. In order to sufficiently secure the above effect, it is preferable that the total amount of W, Nb, N, and Ti is 0.59% or more.However, if it exceeds 0.74%, brittleness and age hardenability become too large, and disadvantages of lowering the elongation may occur. In addition, there is a disadvantage in that the formation ability of carbide is too high to cause a disadvantage in that the hardness exceeds the reference value, and it is disadvantageous in terms of cost.

It is preferable that the second buttering layer has an austenitic structure. In addition, it is preferable that the second buttering layer also has an age-hardening property, and the product life can be improved by securing a property of increasing strength even with repeated use for a long time. In addition, the second buttering layer has a higher level of corrosion resistance, impact resistance, abrasion resistance, ductility, and hardness than the first buttering layer, so that it has a repetitive high load (about 10000-13000 tons) and resistance to impact loads. Can improve. It is preferable that the fraction of austenite is 100% by area in order to sufficiently obtain the above effect in the second buttering layer. On the other hand, the second buttering layer absorbs high loads and impact loads that are directly transmitted to reduce transmission to the body portion and the first buttering layer, thereby improving product life. It is preferable that the second buttering layer has a thickness of 10 mm or more so that corrosion, abrasion, and local peeling phenomena do not occur not only by the above effect, but also by repeated impact, thermal stress, friction, and oxidation by moisture. In addition, when the thickness of the second buttering layer is less than 10 mm, a part of the first buttering layer changes martensite during welding, resulting in cracks and peeling into pieces, resulting in defects in quality and equipment. On the other hand, when the thickness of the second buttering layer exceeds 15 mm, there is a disadvantage such as an increase in cost.

As mentioned above, in the thick plate hot leveler carriage frame of the present invention, the body portion has a first hardness, the first buttering layer has a second hardness, and the second buttering layer has a third hardness. It is preferable that the 1st hardness, 2nd hardness and 3rd hardness satisfy the conditions of Equation 1 below. The first buttering layer formed on the body portion and the second buttering layer formed on the first buttering layer are metal-bonded by buttering welding, and have the same hardness gradient, so that the first buttering layer from the body portion is It is possible to prevent peeling or peeling of the second buttering layer from the first buttering layer. In addition, since the second buttering layer has a higher hardness than the body portion, impact resistance and abrasion resistance are maximized, thereby improving product life. On the other hand, although not particularly limited in the present invention, the body portion may have a hardness of 22 to 25 Hs, the first buttering layer may have a hardness of 38 to 46 Hs, and the second buttering layer may have a hardness of 52 to 60 Hs Can have

[Equation 1]

1st hardness <2nd hardness <3rd hardness

Hereinafter, an embodiment of a method for manufacturing a thick plate hot leveler carriage frame according to the present invention will be described.

The manufacturing method of the thick plate hot leveler carriage frame of the present invention comprises: preparing a body portion having a convex portion and a concave portion; A first buttering welding step of buttering welding such that a first buttering layer is formed on the convex portion; A second buttering welding step of performing a second buttering welding such that a second buttering layer is formed on the first buttering layer; And air-cooling the body portion on which the first buttering layer and the second buttering layer are formed.

Buttering welding refers to surface-coating welding of a metal of a different kind from the object to be welded. In the present invention, the buttering welding conditions are not particularly limited, and those of ordinary skill in the art can form the first buttering layer and the second buttering layer through the buttering welding without any difficulty.

After the formation of the first buttering layer and the second buttering layer, it is preferable to perform air cooling, and through this, an effect such as stabilization of the metallic structure of the buttering layer can be obtained. On the other hand, in the present invention, it is characterized in that preheating treatment before welding or heat treatment after welding, which are commonly performed in the art, is not performed. If, in the case of performing the pre-heat treatment or post-welding heat treatment of the present invention, the interlayer temperature of the welded portion may be increased, and thus, chromium (Cr) carbide is generated and thus cracking is promoted.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are only examples for explaining the present invention in more detail, and do not limit the scope of the present invention.

(Example)

After preparing a body part made of SM490YA having a convex part and a concave part, a first buttering layer having an alloy composition of Table 1 is formed on the convex part by buttering welding, and then buttering welding on the first buttering layer. After the second buttering layer having the alloy composition of Table 3 was formed, it was air-cooled to prepare a thick plate hot leveler carriage frame. Before the formation of the second buttering layer, the high-temperature tensile strength, abrasion resistance, hardness, corrosion resistance, and age hardenability of the first buttering layer were evaluated, and the results are shown in Table 2 below, and the high-temperature tensile strength of the second buttering layer. After evaluating the strength, abrasion resistance, hardness, corrosion resistance and age hardenability, the results are shown in Table 4 below. On the other hand, in the conventional example, only the body part made of SM490YA is used.

For the high-temperature tensile strength, 6 tensile specimens were collected, and the average value was calculated by measuring the tensile strength in the range of 700 to 800°C.

For wear resistance, six disc-shaped specimens are taken, rotated, and the friction coefficient of the material is measured by scratching the surface with a ceramic ball, and the depth-profile of the surface is measured through an alpha-step device. It was carried out in the same way. Thereafter, the surface depth-profile of the test piece used for the friction coefficient measurement was measured using an α-step device, and the degree of quantitative abrasion was confirmed by integrating based on the surface (depth=0).

The hardness was measured using a Shore hardness tester after taking six specimens, and the average value was calculated.

Corrosion resistance was achieved by performing a salt spray test for 4 hours (JISZ2371 ``Salt Spray Test Method'') after polishing the surface of the specimen with #600, and then measuring the rust area rate.If the rust area rate is 10% or less If it exceeded 10%, it was judged as bad.

The aging hardenability was evaluated as good if the hardness increased after performing 20 hits to drop a 5Kg object from a height of 100 mm, and then 72 hours later, and if there was no change in hardness as bad.

division Alloy composition (% by weight) C Si Mn Cr Ni Mo N Ti Conventional example 0.20 0.3 1.55 11.50 5.60 - - - Example 1 0.09 0.68 6.05 19.6 9.15 0.6 0.16 0.05 Example 2 0.09 0.65 6 19.5 9.2 0.65 0.12 0.04 Example 3 0.11 0.68 6.15 19 9 0.62 0.1 0.06 Example 4 0.1 0.72 5.95 19 8.95 0.55 0.1 0.07

division High temperature tensile strength (MPa) Abrasion resistance (1×10 ^-13 m ³ /m) Hardness(Hs) Corrosion resistance Age hardening Conventional example 85~115 830~850 22-25 Bad Bad Example 1 180~200 650~670 38~42 Good Good Example 2 175~195 660~680 38~42 Good Good Example 3 185~205 630~650 42~46 Good Good Example 4 190~210 610~630 40~44 Good Good

division Alloy composition (% by weight) C Si Mn Cr Ni Mo V Co W+Nb+N+Ti Conventional example 0.20 0.3 1.55 11.50 5.60 - - - - Example 1 0.063 0.69 1.23 13.3 3.25 0.85 0.52 1.31 0.610 Example 2 0.06 0.65 1.3 13.6 3.3 0.85 0.48 1.25 0.650 Example 3 0.055 0.67 1.5 13.5 3.4 0.83 0.51 1.27 0.685 Example 4 0.068 0.63 1.45 13.7 3.1 0.79 0.47 1.28 0.720

division High temperature tensile strength (MPa) Abrasion resistance (1×10 ^-13 m ³ /m) Hardness(Hs) Corrosion resistance Age hardening Conventional example 85~115 830~850 22-25 Bad Bad Example 1 230-240 190~210 55~59 Good Good Example 2 225~235 210~230 53~57 Good Good Example 3 220~230 230~250 52~56 Good Good Example 4 235~245 200~220 56~60 Good Good

As can be seen from Tables 1 to 4, Examples 1 to 4 having a two-layered buttering layer proposed by the present invention and satisfying the alloy composition of the present invention are excellent in high temperature tensile strength, wear resistance, hardness, corrosion resistance and aging It can be seen that it has hardenability.

On the other hand, it can be seen that the conventional example, which is a thick plate hot leveler carriage frame using only the existing main body, has lower high-temperature tensile strength, abrasion resistance, and hardness compared to Examples 1 to 4, and also has poor corrosion resistance and age hardenability.

10: convex
20: recess
30: main body
40: first buttering layer
50: second buttering layer
100: thick plate hot leveler carriage frame

Claims (9)

A body portion having a convex portion and a concave portion on which the roll choke is seated, a first buttering layer on the convex portion and a second buttering layer on the first buttering layer,
The second buttering layer is in wt%, C: 0.055 to 0.068%, Si: 0.63 to 0.99%, Mn: 1.23 to 1.50%, Cr: 13.30 to 13.70%, Ni: 3.10 to 3.40%, Mo: 0.79 to 0.85 %, V: 0.47~0.52%, Co: 1.25~1.31%, the total amount of W, Nb, N and Ti: 0.59~0.74%, the balance contains Fe and other inevitable impurities,
The body portion has a first hardness, the first buttering layer has a second hardness, the second buttering layer has a third hardness, and the first hardness, the second hardness, and the third hardness are expressed in Equation 1 below. Plate hot leveler carriage frame that meets the requirements.
[Equation 1]
1st hardness <2nd hardness <3rd hardness
The method according to claim 1,
The first buttering layer is in wt%, C: 0.09 to 0.11%, Si: 0.65 to 0.72%, Mn: 0.59 to 6.15%, Cr: 19.0 to 19.6%, Ni: 8.95 to 9.20%, Mo: 0.55 to 0.65 %, N: 0.10~0.16%, Ti: 0.04~0.07%, the balance of Fe and other unavoidable impurities. Thick plate hot leveler carriage frame.
The method according to claim 1,
The first buttering layer is a thick plate hot leveler carriage frame having an austenitic structure.
The method according to claim 1,
The first buttering layer is a thick plate hot leveler carriage frame having a thickness of 10 to 15 mm.
delete The method according to claim 1,
The second buttering layer is a thick plate hot leveler carriage frame having a single austenite structure.
The method according to claim 1,
The second buttering layer is a thick plate hot leveler carriage frame having a thickness of 10 to 15 mm.
delete Preparing a body portion having a convex portion and a concave portion;
A first buttering welding step of buttering welding such that a first buttering layer is formed on the convex portion;
A second buttering welding step of performing a second buttering welding such that a second buttering layer is formed on the first buttering layer; And
Air-cooling the body portion on which the first buttering layer and the second buttering layer are formed; includes,
The second buttering layer is in wt%, C: 0.055 to 0.068%, Si: 0.63 to 0.99%, Mn: 1.23 to 1.50%, Cr: 13.30 to 13.70%, Ni: 3.10 to 3.40%, Mo: 0.79 to 0.85 %, V: 0.47~0.52%, Co: 1.25~1.31%, the total amount of W, Nb, N and Ti: 0.59~0.74%, the balance contains Fe and other inevitable impurities,
The body portion has a first hardness, the first buttering layer has a second hardness, the second buttering layer has a third hardness, and the first hardness, the second hardness, and the third hardness are expressed in Equation 1 below. A method of manufacturing a thick plate hot leveler carriage frame satisfying the conditions.
[Equation 1]
1st hardness <2nd hardness <3rd hardness

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