JP6473720B2 - Liner material for red hot coke conveying bucket and method for producing the same - Google Patents

Description

The present invention relates to a liner material for a red-hot coke transport bucket used for an inner liner of a bucket that receives high-temperature red-hot coke discharged from a coke oven and transports it to a coke dry fire extinguishing equipment, and a method for manufacturing the same.
More specifically, after casting a molten metal containing a large amount of V and containing Fe and inevitable impurities in the balance, heat treatment is performed at 700-1050 ° C. for 3-10 hours, and the cooling rate to room temperature is 10 ° C.-100 ° C./hour. The present invention relates to a liner material for a red hot coke transport bucket, which is manufactured by cooling, is strong against impact caused by dropping of red hot coke, and has excellent wear resistance against sliding after contact with red hot coke.

Coke is a fuel obtained by carbonizing coal to leave only a carbon portion, and a furnace used for this carbonization is called a coke oven.
In order to protect the members of the coke oven from impact and abrasion, a liner is attached to the surface layer portion thereof.
For example, a coke bucket for conveying coke discharged from a coke oven to a coke dry fire extinguishing facility is provided with a liner on the inner surface thereof. This liner protects the inner surface of the bucket from impact caused by the fall of red hot coke and wear due to sliding after contact.

Conventionally, spheroidal graphite cast iron has been used as a liner material for a red heat coke conveyance bucket. Spheroidal graphite cast iron is cast iron having a spherical structure with improved spherical shape and improved strength and ductility, and is therefore used for its excellent wear resistance and impact resistance (crack resistance).
However, since the temperature of the reddish coke produced in the kiln exceeds 1000 ° C, even if spheroidal graphite cast iron is used for the liner material for buckets, cracks are likely to occur and the wear is severe, so the usable period is short and must be replaced frequently. There is a problem that there is.

In addition to spheroidal graphite cast iron, various liner materials for buckets have been developed so far.
For example, Patent Document 1 discloses an inexpensive high temperature wear resistant material while ensuring wear resistance in a high temperature environment.
Specifically, the composition is C: 0.2-0.5 wt%, Si: 0.2-1.5 wt%, Mn: 16-24 wt%, Cr: 12-20 wt%, N: 0.1-0 A high-temperature wear-resistant material containing 0.5 wt% and the balance consisting of Fe and inevitable impurities is used for the liner material. That is, it is described that it can be manufactured at low cost by not containing expensive Ni, and high-temperature wear can be ensured by increasing the content of Mn.

Patent Document 2 discloses an inexpensive high-temperature wear-resistant material that exhibits excellent wear resistance and crack resistance in a high-temperature environment.
Specifically, C: 0.2-0.5 wt%, Si: 0.2-1.5 wt%, Mn: 10-24 wt%, Cr: 12-20 wt%, Ni: less than 4.0 wt, N: A high-temperature wear-resistant material containing less than 0.1 wt% and the balance being Fe and inevitable elements is used as the liner material. By not adding N at the time of casting, the inspection of N on the finished product is omitted, an inexpensive high temperature wear resistant material is realized, and the content of other alloy elements is limited to a predetermined range. It is described that the wear resistance and crack resistance equivalent to the invention can be exhibited.

However, the inventions described in Patent Document 1 and Patent Document 2 require a larger amount of alloy to be added than the spheroidal graphite cast iron, which is often used as a conventional liner material, and it is unavoidable to increase the cost compared to the spheroidal graphite cast iron. It is clear that there is no.
Although the invention described in Patent Document 2 can be manufactured relatively easily and inexpensively by omitting the N inspection at the time of manufacture compared to the invention described in Patent Document 1, the impact resistance, mechanical strength, and hardness are conventional. (Refer to Examples in Patent Documents 1 and 2). If the impact resistance and wear resistance are the same as before, the invention described in Patent Document 2 needs to be replaced frequently as in Patent Document 1, and the manufacturing cost can be reduced because it can be easily manufactured. Even if it can be suppressed, it is difficult to significantly reduce the cost of use as a bucket liner as a result.
Therefore, there is a demand for a liner material having a low liner replacement frequency and excellent durability.

JP 2009-221554 A JP 2014-181360 A

  The present invention has been made to solve the above-mentioned problems of the prior art, and after casting a molten metal containing a large amount of V and containing Fe and unavoidable elements in the balance, The present invention provides a liner material for reddish coke conveyance buckets that is manufactured by heat treatment for 10 hours and cooling at a cooling rate of 10 ° C. to 100 ° C./hour to room temperature.

  The invention according to claim 1 is: C: 0.35-0.42 wt%, Si: 0.80-1.20 wt%, Mn: 0.30-0.50 wt%, Ni: 0.50 wt% or less, Cr : 4.80-5.50 wt%, Mo: 1.20-1.60 wt%, V: 0.50-1.10 wt%, the balance is composed of Fe and inevitable elements, The present invention relates to a liner material for a red heat coke conveyance bucket.

  The invention according to claim 2 is: C: 0.35-0.42 wt%, Si: 0.80-1.20 wt%, Mn: 0.30-0.50 wt%, Ni: 0.50 wt% or less, Cr : 4.80-5.50 wt%, Mo: 1.20-1.60 wt%, V: 0.50-1.10 wt%, the remainder of the molten metal consisting of Fe and inevitable elements after casting, It is related with the manufacturing method of the liner material for red hot coke conveyance buckets characterized by heat-processing at 700-1050 degreeC for 3 to 10 hours, and cooling at the cooling rate of 10 to 100 degreeC / hour to room temperature.

According to the invention which concerns on Claim 1, it can be set as the liner material for red hot coke conveyance buckets which has the outstanding abrasion resistance by containing more V than the liner material for conventional red hot coke conveyance buckets.
Specifically, V forms a very stable carbide with a strong bonding force with C, and is a base ferrite stabilizing element. Therefore, when V is added at 0.50 to 1.10 wt%, the ferrite is stabilized. Therefore, the addition of V has the effect of increasing the compressive strength at high temperatures.

According to the invention which concerns on Claim 2, it contains more V than the conventional liner material for red hot coke conveyance buckets, and after casting a molten metal, it heat-processes at 700-1050 degreeC for 3-10 hours, and cools to room temperature By cooling at a rate of 10 ° C. to 100 ° C./hour, a liner material for a red hot coke conveyance bucket having excellent impact resistance and wear resistance can be produced.
Specifically, V forms a very stable carbide with a strong bonding force with C, and is a base ferrite stabilizing element. Therefore, when V is added at 0.50 to 1.10 wt%, the ferrite is stabilized. Therefore, the addition of V has an effect of increasing the high temperature compressive strength under rapid heating under the use conditions of the liner for the red hot coke conveying bucket.
Furthermore, conventional liner materials for red hot coke conveying buckets (spheroidal graphite cast iron) are often used as cast without heat treatment after casting. Patent Document 1 (particularly, paragraph [0018]) and Patent Document 2 ( In particular, the invention described in paragraph [0025]) is prepared by applying a water toughness treatment in which water is rapidly cooled by water cooling after heating to 1100 ° C. In contrast, the present invention heat-treats at 700-1050 ° C. for 3-10 hours, and gradually cools at a cooling rate of 10 ° C.-100 ° C./hour to room temperature (so-called annealing), thereby forming a base ferrite. It has the effect of removing internal strain during casting, softening the structure, and improving the spreadability. The softening of the structure makes it difficult for cracking to occur even when red hot coke falls, and imparts wear resistance by dispersing hard vanadium carbide.
Therefore, the liner material for red hot coke conveyance buckets with excellent durability and long service life can be produced.

It is a figure which shows the composition of the alloy of the Example and comparative example of this invention. It is a figure which shows the comparison of the coke contact surface structure | tissue of the Example (A) of this invention, and a comparative example (B). It is a figure which shows the comparison of the high temperature compressive strength under rapid heating of the Example and comparative example of this invention.

1. The following content of each alloying element, the preferred embodiment of the red hot coke conveying bucket liner material according to the present invention will be described in detail.
The liner material for red hot coke conveyance buckets of this embodiment is C: 0.35-0.42 wt%, Si: 0.80-1.20 wt%, Mn: 0.30-0.50 wt%, Ni: 0.00. 50 wt% or less, Cr: 4.80-5.50 wt%, Mo: 1.20-1.60 wt%, V: 0.50-1.10 wt%, with the balance being Fe and inevitable elements It is a liner material for red hot coke conveyance buckets characterized by these.

Each element contained in the liner material for the red hot coke conveyance bucket according to the present embodiment will be described below.
C is an element effective for improving high-temperature strength and wear resistance. In the alloy of this embodiment, VC-based carbides that cause excellent high-temperature compressive strength are generated and dispersed in the metal structure. It is a necessary element (for details, see the description of V below).
The lower limit of the C content is 0.35 wt%, preferably 0.37 wt%, more preferably 0.39 wt%, and the upper limit is 0.42 wt%, preferably 0.41 wt%, more preferably 0.40 wt%. It is. If the C content is less than the above lower limit, the required strength and wear resistance may not be ensured. On the other hand, if the content of C exceeds the above upper limit, the toughness may be lowered, and cracking due to insufficient toughness may occur.

Si has an effect of ensuring castability by preventing oxidation and deoxidation at the time of melting and improving the flow of hot water at the time of casting. Moreover, it has a ferrite stabilizing effect, and has the effect of increasing the ferrite disappearance temperature and increasing the high temperature strength.
The lower limit of the Si content is 0.80 wt%, preferably 0.85 wt%, more preferably 0.90 wt%, and the upper limit is 1.20 wt%, preferably 1.10 wt%, more preferably 1.00 wt%. It is. If the Si content is less than the above lower limit, the necessary good hot water flow, castability, and heat resistance may not be ensured. On the other hand, if the Si content exceeds the above upper limit, the toughness may be reduced, and cracking due to insufficient toughness may occur.

Mn has a deoxidizing action, stabilizes austenite, and has an effect of improving corrosion resistance, heat resistance, and toughness.
The lower limit of the Mn content is 0.30 wt%, preferably 0.33 wt%, more preferably 0.35 wt%, and the upper limit is 0.50 wt%, preferably 0.45 wt%, more preferably 0.40 wt%. It is. If the Mn content is less than the above lower limit, the effect of stabilizing austenite and the necessary corrosion resistance, heat resistance, and toughness may not be obtained. On the other hand, Mn has an austenite stabilizing effect and lowers the ferrite disappearance temperature. Therefore, if the upper limit is exceeded, the high temperature strength may be lowered.

Ni has an action of improving corrosion resistance, heat resistance and toughness.
The upper limit of the Ni content is 0.50 wt%, preferably 0.47 wt%, more preferably 0.45 wt%. Since Ni has an austenite stabilizing action and lowers the ferrite disappearance temperature, if the Ni content exceeds the upper limit, the high temperature strength may be lowered.

Cr has the effect of increasing the strength of the base material by forming a solid solution, forming carbides and increasing the high temperature strength. Furthermore, it has a ferrite stabilizing action, increases the ferrite disappearance temperature, and increases the high temperature strength.
The lower limit of the Cr content is 4.80 wt%, preferably 4.90 wt%, more preferably 5.00 wt%, and the upper limit is 5.50 wt%, preferably 5.40 wt%, more preferably 5.30 wt%. It is. If the Cr content is less than the above lower limit, the necessary high temperature strength and ferrite stabilizing action may not be obtained. On the other hand, when the above upper limit is exceeded, coarse chromium carbides segregate at the grain boundaries, which may reduce toughness.

Mo, like V, is a carbide forming element having a ferrite stabilizing effect.
The lower limit of the Mo content is 1.20 wt%, preferably 1.25 wt%, more preferably 1.30 wt%, and the upper limit is 1.60 wt%, preferably 1.55 wt%, more preferably 1.50 wt%. It is. If the Mo content is less than the lower limit, a sufficient ferrite stabilizing effect may not be obtained. On the other hand, when the above upper limit is exceeded, Mo ₆ C carbides having a low matrix solid solution temperature increase, and as a result, VC carbides having a high matrix solid solution temperature decrease, which may reduce the high temperature compressive strength.

V combines with carbon to form a VC-based carbide having a one-to-one atomic ratio of vanadium and carbon. This VC-based carbide is not a covalent bond as seen in other carbides, but also has an ionic bond, so the bonding force between V and C is large and extremely stable. It remains without being decomposed to a high temperature.
In addition, V is a ferrite stabilizing element and raises the ferrite disappearance temperature, so that ferrite exists stably up to a high temperature. The VC-based carbide and the remaining ferrite are different in phase from austenite, which is the main base at high temperatures, and have a function of suppressing migration and proliferation of transitions responsible for plastic deformation. Higher stress is required to cause plastic deformation under such conditions. For this reason, the addition of V has the effect of increasing the high temperature compressive strength.
The lower limit of the V content is 0.50 wt%, preferably 0.60 wt%, more preferably 0.70 wt%, and the upper limit is 1.10 wt%, preferably 1.00 wt%, more preferably 0.90 wt%. It is. If the V content is less than the lower limit, the amount of VC-based carbide produced may be reduced and the high temperature compressive strength may be reduced. On the other hand, if the above upper limit is exceeded, coarse VC carbides segregate at the grain boundaries, which may reduce toughness.

Inevitable elements are 0.05 wt% or less for each element.
For example, since S combines with Mn to become MnS, excessive inclusion of S deteriorates toughness. For this reason, S is desirably 0.03 wt% or less. P is preferably 0.04 wt% or less. Here, S and P are positioned as inevitable elements.

2. Heat treatment step and cooling step after casting The liner material for the red hot coke conveyance bucket of the present invention has C: 0.35-0.42 wt%, Si: 0.80-1.20 wt%, Mn: 0.30-0. 50 wt%, Ni: 0.50 wt% or less, Cr: 4.80-5.50 wt%, Mo: 1.20-1.60 wt%, V: 0.50-1.10 wt%, the balance being Fe And after casting the molten metal which consists of an inevitable element, it heat-processes at 700-1050 degreeC for 3 to 10 hours, and is manufactured by cooling at the cooling rate of 10 to 100 degreeC / hour to room temperature.

  In this way, by performing the so-called annealing operation after heat treatment, so-called annealing, the liner material for the red hot coke conveyance bucket of the present invention is converted into base ferrite, the internal strain during casting is removed, the structure is softened, and the ductility Can be improved. The softening of the structure makes it difficult for cracking to occur even when red hot coke falls, and the dispersion of hard vanadium carbide imparts wear resistance.

  Hereinafter, the effect of the present invention will be made clearer by showing examples relating to the liner material for a red hot coke conveyance bucket according to the present invention. However, the present invention is not limited to the following examples.

<Manufacture of liner material for red heat coke conveyor bucket>
(Example 1-3)
An alloy of Example 1-3 having the composition shown in FIG. 1 was cast.
After casting, it was heat-treated at 700-1050 ° C. for 3-10 hours, and cooled at a cooling rate of 10 ° C.-100 ° C./hour to room temperature. These were made into Example 1-3.

(Comparative Example 1)
TSR21 (manufactured by Kurimoto Steel Works) was used as Comparative Example 1. In Comparative Example 1, an as-cast product obtained by pouring a molten metal having the composition shown in FIG. 1 was heat-treated under the following conditions, and cut into a required size to prepare a test piece.
(Heat treatment conditions)
Heating temperature: 1100 ° C
Heating rate: 100 ° C./hour Holding time: 5.5 hours Cooling method: Water cooling (screw stirring)

(Comparative Example 2)
KM16IM (manufactured by Kurimoto Steel Works) was used as Comparative Example 2. Comparative Example 2 is a high-temperature wear-resistant material described in Patent Document 1, and an as-cast product obtained by pouring a molten metal having the composition shown in FIG. 1 is heat-treated under the following conditions and cut into a required size. A test piece was prepared.
(Heat treatment conditions)
Heating temperature: 1100 ° C
Heating rate: 100 ° C./hour Holding time: 5.5 hours Cooling method: Water cooling (screw stirring)

(Comparative Example 3)
Spheroidal graphite cast iron FCD450 defined in JIS G5502 was used as Comparative Example 3. The molten metal having the composition shown in FIG. 1 was used as cast after casting.

Various tests for confirming the performance were performed on the materials of the experimental example and the comparative example.
<Observation of coke contact surface>
Example 1 and Comparative Example 1 were used in actual operation for 18 months as bucket liner materials for transporting red hot coke from a drying furnace for coke production used in a blast furnace at a factory in Kitakyushu, a major steel mill. The structure of the surface after use was observed under a microscope.
The result is shown in FIG.

Example 1 and Comparative Example 1 do not have an oxide film before being exposed to a high temperature, and an oxide film is formed only after being exposed to a high temperature.
As shown in FIG. 2A, Example 1 has an oxide film remaining on the surface. This indicates that the surface oxide film formed under the use environment at a high temperature remains even after the coke is dropped. On the other hand, as shown in FIG. 2B, Comparative Example 1 shows no oxide film on the surface after use. This is because the adhesion between the surface oxide film formed during use at high temperature and the base is low, and it is considered that the red hot coke dropped off.

  As described above, Example 1 means that the oxide film has better base adhesion than Comparative Example 1, and the oxide film is dense. Formation of an oxide film excellent in adhesion to the base results in suppression of subsequent oxidation, resulting in less reduction in wall thickness due to oxidation of the base in use, leading to an extended service life. Further, it is easily estimated that this oxide film has a high hardness and wear when the coke is dropped.

<High temperature compressive strength under rapid heating>
Example 1-3 and Comparative Example 1-2 were heated to 1100 ° C. under the following test conditions (Comparative Example 3 was heated to 900 ° C.), and then subjected to a compressive stress and immediately before plastic deformation began. The compression yield strength was investigated.
(Test conditions)
Test device: Fuji Electric Koki Co., Ltd., hot processing reproduction test device (Thermo Mecha Master Z)
Sample shape: 8 mmφ × 12 mm length Heating method: High frequency heating temperature: 1100 ° C. (Comparative Example 3 only 900 ° C.)
Temperature rising time: 60 seconds Time from reaching 1100 ° C. to applying a compressive load: 2 seconds Deformation speed: 0.1 mm / second Deformation amount: 2.4 mm
The load and strain during the compression load were recorded, a stress-strain curve was obtained, and the compressive yield stress was calculated. In the calculation, the stress value immediately before the transition from elastic deformation to plastic deformation was taken as the compressive yield stress value.
Considering that Comparative Example 3 is spheroidal graphite cast iron, its melting point is as low as 1150 ° C., it is difficult to perform a high-temperature compression test at 1100 ° C., and the actual upper limit temperature for use is generally around 900 ° C. The test temperature was 900 ° C. Since Example 1 and Comparative Example 1-2 were steel, their melting points were about 1350 ° C. or higher, so the test temperature was 1100 ° C.
The results are shown in FIG.

As mentioned above, Example 1-3 means that compression yield strength is higher than Comparative Example 1-3. That is, it is shown that Example 1-3 becomes a liner material that is softer in structure and less susceptible to cracking than Comparative Example 1-3.
This is considered to be due to the fact that V was added to Example 1-3 and / or so-called annealing in which annealing was performed after heat treatment was performed.

  The liner material for a red hot coke transport bucket according to the present invention is suitably used as a liner material disposed on the inner surface of a coke bucket for transporting coke discharged from a coke oven to a coke dry fire extinguishing facility.

1 Liner material for red heat coke conveyor bucket 2 Oxide film

Claims (2)

C: 0.35-0.42 wt%, Si: 0.80-1.20 wt%, Mn: 0.30-0.50 wt%, Ni: 0.50 wt% or less, Cr: 4.80-5.50 wt% %, Mo: 1.20 to 1.60 wt%, V: 0.50 to 1.10 wt%, with the balance being Fe and inevitable impurities,
A liner material for a red-hot coke conveyance bucket , wherein the base is ferrite and vanadium carbide is dispersed .   C: 0.35-0.42 wt%, Si: 0.80-1.20 wt%, Mn: 0.30-0.50 wt%, Ni: 0.50 wt% or less, Cr: 4.80-5.50 wt% %, Mo: 1.20 to 1.60 wt%, V: 0.50 to 1.10 wt%, and after casting a molten metal consisting of Fe and unavoidable impurities, A method for producing a liner material for a red hot coke conveyance bucket, characterized by heat treatment for 10 hours and cooling at a cooling rate of 10 ° C to 100 ° C / min to room temperature.

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