JP6518161B2 - Thermal spray installation method - Google Patents
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- JP6518161B2 JP6518161B2 JP2015147921A JP2015147921A JP6518161B2 JP 6518161 B2 JP6518161 B2 JP 6518161B2 JP 2015147921 A JP2015147921 A JP 2015147921A JP 2015147921 A JP2015147921 A JP 2015147921A JP 6518161 B2 JP6518161 B2 JP 6518161B2
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- 239000007921 spray Substances 0.000 title claims description 28
- 238000000034 method Methods 0.000 title claims description 22
- 238000009434 installation Methods 0.000 title 1
- 239000002184 metal Substances 0.000 claims description 52
- 229910052751 metal Inorganic materials 0.000 claims description 52
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 38
- 239000001301 oxygen Substances 0.000 claims description 38
- 229910052760 oxygen Inorganic materials 0.000 claims description 38
- 239000000843 powder Substances 0.000 claims description 36
- 239000007789 gas Substances 0.000 claims description 26
- 239000000463 material Substances 0.000 claims description 16
- 238000002485 combustion reaction Methods 0.000 claims description 14
- 238000007751 thermal spraying Methods 0.000 claims description 11
- 239000012159 carrier gas Substances 0.000 claims description 7
- 238000004880 explosion Methods 0.000 claims description 5
- 238000012546 transfer Methods 0.000 claims description 5
- 230000000694 effects Effects 0.000 claims description 4
- 239000000428 dust Substances 0.000 claims description 3
- 239000011863 silicon-based powder Substances 0.000 description 24
- 238000005507 spraying Methods 0.000 description 13
- 239000006185 dispersion Substances 0.000 description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 7
- 239000011449 brick Substances 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000002360 explosive Substances 0.000 description 2
- 230000005855 radiation Effects 0.000 description 2
- 239000011819 refractory material Substances 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 229910001111 Fine metal Inorganic materials 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000005350 fused silica glass Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 238000009718 spray deposition Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000003832 thermite Substances 0.000 description 1
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- Coating By Spraying Or Casting (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Description
本発明は、テルミット溶射法による溶射施工方法に関する。 The present invention relates to a thermal spray application method by a thermit thermal spraying method.
工業用窯炉の炉壁を補修する技術の一つとして、耐火原料粉及び金属粉を主材として含む溶射材を、酸素又は酸素を含有するガスを搬送ガスとしてノズル先端から被施工面（被補修面）に吹き付け、金属粉の燃焼発熱を利用して耐火原料を溶融付着させるテルミット溶射法が知られている。 As one of the techniques for repairing the furnace wall of industrial kilns, a sprayed material containing refractory raw material powder and metal powder as a main material and oxygen or a gas containing oxygen as a carrier gas is used as a carrier gas from the nozzle tip There is known a thermit spraying method in which a refractory material is melted and attached by spraying on a repair surface and utilizing the heat of combustion of metal powder.
このようにテルミット溶射法に使用する溶射材は金属粉を含むことから、必然的に発火が生じやすいという問題がある。一般的に発火現象は、以下の３条件が揃った際に発生する。
１）適用金属粉の粉塵濃度が爆発下限界濃度以上であること。
２）発火するに必要な着火源（スパーク）が存在すること。
３）酸素が存在していること。
As described above, since the thermal spray material used in the thermit thermal spraying method contains metal powder, there is a problem that ignition tends to occur. In general, the ignition phenomenon occurs when the following three conditions are met.
1) The dust concentration of the applied metal powder must be above the lower explosion limit concentration.
2) The presence of an ignition source (spark) necessary for ignition.
3) The presence of oxygen.
ここで、テルミット溶射方法では、３）の条件は原理上回避できないため、１）又は２）のいずれか又は双方を回避しておく必要がある。また、２）に関しては、適用する金属粉によって最小着火エネルギーがあることが知られているが、テルミット溶射法では溶射材の搬送時に発生するスパークや配管内静電気といった着火源が生じやすく、さらに金属粉の燃焼発熱によりノズル先端が加熱されることから、２）の条件を回避することは非常に難しい。したがって、テルミット溶射法において発火現象を抑制するには、１）の条件を回避することが基本となる。従来技術も１）の条件に関連するものが多く、例えば特許文献１には、金属粉（金属Ｓｉ粉）のメジアン径が小さいと、微細な金属Ｓｉ粉が凝集して擬似粒子を形成することで、金属Ｓｉ粉の活性が低下し、爆発下限界濃度が急激に高くなって発火しにくくなるこという知見に基づき、金属Ｓｉ粉のメジアン径を１０μｍ以下にする技術が開示されている。 Here, in the thermit thermal spraying method, the condition 3) can not be avoided in principle, so it is necessary to avoid either 1) or 2) or both. With regard to 2), it is known that there is a minimum ignition energy depending on the metal powder to be applied, but in the thermit spraying method, ignition sources such as sparks generated during transportation of the thermal spray material and static electricity in piping are easily generated. It is very difficult to avoid the condition 2) because the nozzle tip is heated by the combustion heat of the metal powder. Therefore, in order to suppress the ignition phenomenon in the thermit spraying method, it is basic to avoid the condition 1). Prior art also has many things related to the condition of 1). For example, in Patent Document 1, when the median diameter of metal powder (metal Si powder) is small, fine metal Si powder is aggregated to form pseudo particles. Then, based on the finding that the activity of the metal Si powder decreases and the lower limit concentration of explosion rapidly increases and it becomes difficult to ignite, a technology is disclosed to make the median diameter of the metal Si powder 10 μm or less.
一方、テルミット溶射法においては、上述した発火現象の他に、金属粉の燃焼発熱による燃焼火焔がノズル先端を経て材料切り出しホッパーまで逆流する逆火現象が発生することが知られている。したがってテルミット溶射法においては、発火現象と逆火現象の双方を抑制する対策を講じることが求められる。この点、特許文献２には、吐出導管の流路を形成する少なくとも一部を樹脂又はゴムで構成することで発火現象を抑制するとともに、吐出導管のストレート部の内径及び噴出ノズルのノズル孔径を限定することで逆火現象を抑制する技術が開示されている。 On the other hand, it is known that, in the thermit thermal spraying method, in addition to the above-mentioned ignition phenomenon, a flash fire phenomenon occurs in which a combustion flame due to combustion heat of metal powder flows back to the material cutting hopper through the nozzle tip. Therefore, in the thermit spraying method, it is required to take measures to suppress both the ignition phenomenon and the flashback phenomenon. In this respect, in Patent Document 2, the ignition phenomenon is suppressed by forming at least a part of the flow path of the discharge conduit with resin or rubber, and the inner diameter of the straight portion of the discharge conduit and the nozzle diameter of the jet nozzle The technique which suppresses a flashback phenomenon by limiting is disclosed.
しかし、この特許文献２の技術は、噴出ノズル内及び吐出導管内における逆火現象の進展の抑制には効果があるものの、ノズル先端から吐出された金属粉の燃焼発熱による燃焼火焔が逆流するという逆火現象の根本的な発生原因を解消することはできず、実際の溶射施工の現場においては、依然として逆火現象を散見する。 However, although the technology of this patent document 2 is effective in suppressing the development of the flashback phenomenon in the jet nozzle and the discharge conduit, it is said that the combustion flame by the heat of combustion of the metal powder discharged from the tip of the nozzle flows back. The root cause of the flashback phenomenon can not be eliminated, and in the actual thermal spray application site, the flashback phenomenon is still spotted.
本発明が解決しようとする第１の課題は、テルミット溶射法による溶射施工方法において逆火現象を抑制することにあり、第２の課題は、逆火現象とともに発火事象を抑制することにある。 The first problem to be solved by the present invention is to suppress the backfire phenomenon in the thermal spray application method by thermit spraying method, and the second problem is to suppress the ignition event together with the backfire phenomenon.
本発明の一観点によれば、次の溶射施工方法が提供される。
酸素又は酸素を含有するガスを搬送ガスとして金属粉を含む溶射材をノズル先端から被施工面に吹き付け、金属粉の燃焼発熱で被施工面に溶融付着させる溶射施工方法において、
ノズル先端からの酸素又は酸素を含有するガスの吐出線流速を（１）式で表される速度Ｖmin（ｍ/ｓ）以上とすることを特徴とする溶射施工方法。
ここで、
λ：酸素と金属粉との平均熱伝導率（ｋｃａｌ／ｍ・℃・ｈｒ）
ρ：酸素と金属粉との平均密度（ｋｇ／Ｎｍ３）
Ｃ：酸素と金属粉との平均比熱（ｋｃａｌ／ｋｇ・℃）
ｂ：燃焼帯長さ（ｍ）
Ｔｂ：燃焼時の最高温度（℃）
Ｔｚ：予熱帯の温度（℃）
Ｔｕ：粉塵雲の初期温度（℃）
ｋ：輻射伝熱の効果を補正する係数でｋ＝１．１
According to one aspect of the present invention, the following thermal spray application method is provided.
In the thermal spraying application method, a thermal spray material containing metal powder is sprayed from the tip of the nozzle onto the work surface from the tip of the nozzle using oxygen or oxygen-containing gas as the carrier gas, and melted and adhered to the work surface by combustion heat of the metal powder,
A thermal spray application method characterized in that the discharge linear flow velocity of oxygen or oxygen-containing gas from the tip of the nozzle is set to a velocity Vmin (m / s) or more represented by equation (1).
here,
λ: Average thermal conductivity of oxygen and metal powder (kcal / m · ° C · hr)
ρ: Average density of oxygen and metal powder (kg / Nm 3 )
C: Average specific heat of oxygen and metal powder (kcal / kg · ° C)
b: Length of combustion zone (m)
Tb: Maximum temperature during combustion (° C)
Tz: Temperature of preheating zone (° C)
Tu: Initial temperature of dust cloud (° C)
k: coefficient to correct the effect of radiant heat transfer k = 1.1
この本発明の溶射施工方法において特徴的な前記（１）式は、本発明者らによる以下のような発想及び知見により導き出されたものである。 The characteristic (1) in the thermal spray application method of the present invention is derived from the following idea and knowledge by the present inventors.
まず本発明者らは、逆火現象を抑制する点から、ノズル先端から吐出する、溶射材（金属粉）を含む搬送ガス（酸素又は酸素を含有するガス）の吐出線流速を火焔伝播速度以上にしようという発想を得、さらに、テルミット溶射法における火焔伝搬速度の評価に、可燃混合ガスの火焔伝搬速度Ｖを表すMallard-Chatlierの式を適用しようという発想を得た。 First, from the point of suppressing the flashback phenomenon, the present inventors set the discharge linear flow velocity of the carrier gas (oxygen or gas containing oxygen) containing the thermal spray material (metal powder) discharged from the nozzle tip to the flame propagation velocity or more. The idea of applying the Mallard-Chatlier equation, which represents the flame propagation velocity V of the combustible mixed gas, to the evaluation of the flame propagation velocity in the thermit spraying method was obtained.
Mallard-Chatlierの式とは次の（２）式である。
ここで、
Ｖ：火焔伝搬速度（ｍ／ｓ）
λ：可燃混合ガスの熱伝導率（ｋｃａｌ／ｍ・℃・ｈｒ）
ρ：可燃混合ガスの密度（ｋｇ／Ｎｍ３）
Ｃ：可燃混合ガスの比熱（ｋｃａｌ／ｋｇ・℃）
ｂ：燃焼帯長さ（ｍ）
Ｔｂ：燃焼時の最高温度（℃）
Ｔｚ：予熱帯の温度（℃）
Ｔｕ：可燃混合ガスの初期温度（℃）
The Mallard-Chatlier equation is the following equation (2).
here,
V: flame propagation speed (m / s)
λ: Thermal conductivity of combustible mixed gas (kcal / m · ° C · hr)
ρ: density of combustible mixed gas (kg / Nm 3 )
C: Specific heat of combustible mixed gas (kcal / kg · ° C)
b: Length of combustion zone (m)
Tb: Maximum temperature during combustion (° C)
Tz: Temperature of preheating zone (° C)
Tu: Initial temperature of combustible mixed gas (° C)
本発明者らは、このMallard-Chatlierの式をテルミット溶射法に適用するにあたり、これまでのテルミット溶射法に関する種々の知見に基づき検討した結果、Mallard-Chatlierの式におけるλ、ρ及びＣは、テルミット溶射法では、それぞれ、酸素と金属粉との平均熱伝導率、平均密度及び平均比熱に置き換え、かつ、Mallard-Chatlierの式におけるｂ、Ｔｂ、Ｔｚ及びＴｕは、使用条件に則した値を代入してテルミット溶射法における火焔伝搬速度を算出した。 As a result of examining the present inventors on the basis of various findings on the thermit spraying method so far in applying this Mallard-Chatlier formula to the thermit spraying method, λ, 及 び and C in the Mallard-Chatlier formula are In thermite thermal spraying method, the average thermal conductivity, the average density and the average specific heat of oxygen and metal powder are replaced, respectively, and b, Tb, Tz and Tu in the Mallard-Chatlier equation are values according to the use conditions The flame propagation velocity in the thermit spraying method was calculated by substitution.
しかし、本発明者らが、搬送ガス（酸素又は酸素を含有するガス）の吐出線流速を前記Mallard-Chatlierの式に基づき算出した火焔伝播速度Ｖとして試験したところ、依然として逆火現象が発生した。その原因について本発明者らが検討したところ、テルミット溶射法では、ノズル先端から吐出される搬送ガスに金属粉が含まれることから、その熱伝達は熱伝導に加え輻射伝熱が加わり、結果として、前記のMallard-Chatlierの式に基づき算出される火焔伝播速度よりも、実際の火焔伝播速度が速くなるためと考えられた。 However, when the present inventors tested the discharge linear flow velocity of the carrier gas (oxygen or a gas containing oxygen) as the flame propagation velocity V calculated based on the above-mentioned Mallard-Chatlier equation, a flashback phenomenon still occurred. . When the present inventors examined the cause, in the thermit spraying method, since the metal powder is contained in the carrier gas discharged from the tip of the nozzle, the heat transfer is added to the heat conduction and the radiation heat transfer, and as a result The actual flame propagation speed is considered to be faster than the flame propagation speed calculated based on the above-mentioned Mallard-Chatlier equation.
以上より、本発明者らは、前記のMallard-Chatlierの式をテルミット溶射法に適合するように上述の置き換えを行うとともに、輻射伝熱の効果を補正する係数ｋを導入することに想到した。さらに種々の検討及び試験の結果、係数ｋ＝１．１が適当であることを突き止め、前記（１）式を完成させた。 From the above, the present inventors conceived to introduce the coefficient k for correcting the radiation heat transfer effect as well as performing the above-mentioned replacement so as to make the above-mentioned Mallard-Chatlier equation compatible with the thermit spraying method. Further, as a result of various examinations and tests, it was found that the coefficient k = 1.1 was appropriate, and the above equation (1) was completed.
この（１）式で表される速度Ｖmin（ｍ／ｓ）は、テルミット溶射法における火焔伝搬速度に相当する。したがって、ノズル先端からの酸素又は酸素を含有するガスの吐出線流速を火焔伝搬速度Ｖmin（ｍ／ｓ）以上とすることで、逆火現象を抑制することができる。 The velocity Vmin (m / s) represented by the equation (1) corresponds to the flame propagation velocity in the thermit spraying method. Therefore, the backfire phenomenon can be suppressed by setting the discharge linear flow velocity of oxygen or oxygen-containing gas from the nozzle tip to the flame propagation velocity Vmin (m / s) or more.
以上のとおり本発明の溶射施工方法によれば逆火現象を抑制することができ、安全な溶射施工が可能となる。 As described above, according to the thermal spray application method of the present invention, it is possible to suppress the backfire phenomenon and enable safe thermal spray application.
表１は、溶射材に含有する金属粉を金属Ｓｉ粉とし、酸素と金属Ｓｉ粉との固気比、すなわち酸素中の金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）を変化させて、前記（１）式により火焔伝搬速度Ｖmin（ｍ／ｓ）を算出した結果を示す。また、図１は、その算出結果をプロットしたものである。 In Table 1, the metal powder contained in the thermal spray material is metal Si powder, and the solid-gas ratio of oxygen to metal Si powder, that is, the dispersion amount of metal Si powder in oxygen (kg / Nm 3 ) is changed. 1) The results of calculating the flame propagation velocity Vmin (m / s) by the equation are shown. Moreover, FIG. 1 plots the calculation result.
以下、具体的に火焔伝搬速度Ｖmin（ｍ／ｓ）の算出方法について示す。 Hereinafter, a method of calculating the flame propagation speed Vmin (m / s) will be specifically described.
まず、表１におけるρ、λ、Ｃの算出例を以下に示す。
算出例として、酸素の熱伝導率＝０．０２（ｋｃａｌ／ｍ・℃・ｈｒ）、酸素の密度＝１．１７（ｋｇ／Ｎｍ３）、酸素の比熱＝０．２２（ｋｃａｌ／ｋｇ・℃）、金属Ｓｉ粉の熱伝導率＝７１．９７（ｋｃａｌ／ｍ・℃・ｈｒ）、金属Ｓｉ粉の比熱＝０．１６（ｋｃａｌ／ｋｇ・℃）、金属Ｓｉ粉分散量＝０．１０（ｋｇ／Ｎｍ３）の場合について以下に示す。
ρ＝１．１７＋０．１０＝１．２７（ｋｇ／Ｎｍ３）
λ＝{（１．１７／１．２７）×０．０２}＋{（０．１０／１．２７）×７１．９７}＝５．７０（ｋｃａｌ／ｍ・℃・ｈｒ）
Ｃ＝{（１．１７／１．２７）×０．２２}＋{（０．１０／１．２７）×０．１６}＝０．２２（ｋｃａｌ／ｋｇ・℃）
First, calculation examples of ρ, λ, and C in Table 1 will be shown below.
As a calculation example, the thermal conductivity of oxygen = 0.02 (kcal / m · ° C · hr), the density of oxygen = 1.17 (kg / Nm 3 ), the specific heat of oxygen = 0.22 (kcal / kg · ° C) ), Thermal conductivity of metal Si powder = 71.97 (kcal / m · ° C · hr), specific heat of metal Si powder = 0.16 (kcal / kg · ° C), metal Si powder dispersion amount = 0.10 (k It shows below about the case of kg / Nm < 3 >.
ρ = 1.17 + 0.10 = 1.27 (kg / Nm 3 )
λ = {(1.17 / 1.27) × 0.02} + {(0.10 / 1.27) × 71.97} = 5.70 (kcal / m · ° C. · hr)
C = {(1.17 / 1.27) × 0.22} + {(0.10 / 1.27) × 0.16} = 0.22 (kcal / kg · ° C.)
平均密度ρは酸素の密度と金属Ｓｉ粉分散量の加算値である。
平均熱伝導率λは、質量分率×酸素と金属Ｓｉ粉各々の熱伝導率の総和であり、平均比熱Ｃは質量分率×酸素と金属Ｓｉ粉各々の比熱の総和である。
上記算出方法により、金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）の値に応じた平均密度ρ、平均熱伝導率λ、平均比熱Ｃを算出した。
The average density ρ is the sum of the density of oxygen and the metal Si powder dispersion amount.
The average thermal conductivity λ is the sum of the mass fraction × the thermal conductivity of each of oxygen and metal Si powder, and the average specific heat C is the sum of the mass fraction × the specific heat of each of oxygen and the metal Si powder.
The average density ρ, the average thermal conductivity λ, and the average specific heat C according to the value of the metal Si powder dispersion amount (kg / Nm 3 ) were calculated by the above calculation method.
また、ｂ、Ｔｂ、Ｔｚ及びＴｕの値は、ｂ＝１ｍｍ（０．００１ｍ）、Ｔｂ＝１６５０℃、Ｔｚ＝６００℃、Ｔｕ＝２５℃とし、これらの値を定数とした。 The values of b, Tb, Tz and Tu were b = 1 mm (0.001 m), Tb = 1650 ° C., Tz = 600 ° C., Tu = 25 ° C., and these values were used as constants.
上記手法により算出したρ、λ、Ｃ及び上記ｂ、Ｔｂ、Ｔｚ及びＴｕの値を式（１）に代入し、金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）の値に応じて火焔伝搬速度Ｖmin（ｍ／ｓ）を算出し、図１に示す関係を求めた。 Substituting the values of ρ, λ, C and the values of b, Tb, Tz and Tu calculated by the above method into the equation (1), the flame propagation speed Vmin according to the value of the metal Si powder dispersion amount (kg / Nm 3 ) (M / s) was calculated to obtain the relationship shown in FIG.
このようにあらかじめ図１の関係を求めておけば、あとはその溶射施工における金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）に応じて、ノズル先端からの酸素又は酸素を含有するガスの吐出線流速（以下、単に「ガスの吐出線流速」という。）を火焔伝搬速度Ｖmin（ｍ／ｓ）以上とすれば良い。これにより、ノズル先端からの溶射材の吐出量が５０（ｋｇ／ｈｒ）以上のような大量吐出を行う場合であっても、逆火事象を抑制できる。 Thus, if the relationship of FIG. 1 is previously obtained, the discharge linear velocity of oxygen-containing gas or oxygen-containing gas from the tip of the nozzle according to the metal Si powder dispersion amount (kg / Nm 3 ) in the thermal spraying application (Hereinafter, simply referred to as "gas discharge linear flow velocity") may be set to the flame propagation velocity Vmin (m / s) or more. As a result, even in the case where a large amount of discharge such as 50 (kg / hr) or more of the discharge amount of the thermal spray material from the tip of the nozzle is performed, it is possible to suppress a backfire event.
ここで、金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）は、発火現象を抑制する点から爆発下限界濃度以下とすることが好ましい。したがって、例えば、爆発下限界濃度が０．３ｋｇ／Ｎｍ３の金属Ｓｉを使用する場合、金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）は０．３ｋｇ／Ｎｍ３を上限とし、この上限の金属Ｓｉ粉分散量＝０．３ｋｇ／Ｎｍ３で溶射施工する場合は、ガスの吐出線流速は図１（前記（１）式）に従い、２６．８０（ｍ／ｓ）以上に設定する。 Here, it is preferable to set the metal Si powder dispersion amount (kg / Nm 3 ) to the explosive lower limit concentration or less in order to suppress the ignition phenomenon. Thus, for example, if the lower explosive limit concentration is the use of metal Si of 0.3 kg / Nm 3, a metal Si powder dispersion amount (kg / Nm 3) is capped at 0.3 kg / Nm 3, metallic Si in the upper In the case of thermal spraying with a powder dispersion amount of 0.3 kg / Nm 3 , the discharge linear flow velocity of the gas is set to 26.80 (m / s) or more according to FIG. 1 (the above equation (1)).
なお、金属Ｓｉ粉以外の金属粉においても、同様に前記（１）式に基づきガスの吐出線流速を火焔伝搬速度Ｖmin（ｍ／ｓ）以上に設定すれば良く、この場合も、金属粉分散量（ｋｇ／Ｎｍ３）は爆発下限界濃度以下とすることが好ましい。 Also for metal powders other than metal Si powder, the discharge linear flow velocity of gas may be set to the flame propagation velocity Vmin (m / s) or more based on the above equation (1) as well, and also in this case, metal powder dispersion The amount (kg / Nm 3 ) is preferably below the lower explosion limit concentration.
このように、本発明は、ガスの吐出線流速を火焔伝搬速度Ｖmin（ｍ／ｓ）以上にすることで逆火現象を抑制するもので、逆火現象を抑制する点からはガスの吐出線流速の上限を規定する必要はない。ただし、溶射施工における付着歩留りを確保するなどの点からは、ガスの吐出線流速は、前記(１)式において係数ｋ＝２としたときの速度Ｖmax（ｍ/ｓ）以下とすることが好ましい。 As described above, the present invention suppresses the flashback phenomenon by setting the discharge linear flow velocity of gas to the flame propagation velocity Vmin (m / s) or more, and from the point of suppressing the flashback phenomenon, the discharge line of the gas is There is no need to specify the upper limit of the flow rate. However, from the viewpoint of securing the adhesion yield in the thermal spraying, it is preferable to set the discharge linear flow velocity of the gas to a velocity Vmax (m / s) or less when the coefficient k = 2 in the equation (1). .
表２は、本発明の実施例を比較例と共に示す。 Table 2 shows examples of the present invention along with comparative examples.
金属粉として、酸素雰囲気下で測定した爆発下限界濃度が０．４ｋｇ／Ｎｍ３又は０．４５ｋｇ／Ｎｍ３の金属Ｓｉ粉を使用し、金属Ｓｉ粉１５質量％に対し、非金属の耐火材料粉としてシリカ質粉を８５質量％加え、溶射材とした。シリカ質粉としては、天然石英粉、溶融シリカ粉、珪砂、珪石粉、あるいはこれらの成分を主体とした耐火物粉等が挙げられる。
なお、表２における火焔伝搬速度は、金属Ｓｉ粉分散量の値に対応する火焔伝搬速度を図１から読み取った。
As the metal powder, the explosion lower limit concentration measured under an oxygen atmosphere using a metal Si powder 0.4 kg / Nm 3 or 0.45 kg / Nm 3, to a metal Si powder 15 wt%, the refractory material of the non-metallic As a powder, 85% by mass of siliceous powder was added to obtain a thermal spray material. Examples of the siliceous powder include natural quartz powder, fused silica powder, silica sand, silica powder, and refractory powder mainly composed of these components.
In addition, the flame propagation speed in Table 2 read the flame propagation speed corresponding to the value of metal Si powder dispersion amount from FIG.
各例の溶射材を被施工面であるれんが表面に溶射施工し、その溶射施工時の逆火、発火の有無を評価した。 The thermal spray material of each example was thermally sprayed on the surface of the brick which is the application surface, and the presence or absence of flashback and ignition during the thermal spray deposition was evaluated.
溶射施工には一般的な溶射装置を用い、タンクの底部に備え付けたテープフィーダをもって溶射材を切り出し、酸素で搬送し、ノズル先端かられんが表面に向けて吹き付けた。れんが表面とノズル先端との距離は８０ｍｍとし、１回あたり３ｋｇの溶射材をれんが表面に吹付けた。 The thermal spray application was carried out using a general thermal spray apparatus, and a thermal spray material was cut out with a tape feeder provided at the bottom of the tank, transported with oxygen, and sprayed from the nozzle tip toward the brick surface. The distance between the surface of the brick and the tip of the nozzle was 80 mm, and 3 kg of sprayed material was sprayed onto the surface of the brick at one time.
溶射施工時の逆火（発火）の有無は、上述の溶射施工を繰り返し１００回行い、逆火（発火）が１回も発生しなかったものを「無」、逆火（発火）が１回でも発生したものは「有」と評価した。 The presence or absence of backfire (ignition) at the time of thermal spray construction repeats the above-mentioned thermal spray construction 100 times, and those with no backfire (ignition) at least once are "No" and 1 backfire (ignition) However, what occurred was evaluated as "presence".
各例の金属Ｓｉ粉分散量は、「金属Ｓｉ粉分散量（ｋｇ／Ｎｍ３）＝溶射材吐出量（ｋｇ／ｈｒ）×金属Ｓｉ濃度０．１５÷酸素流量（Ｎｍ３／ｈｒ）」により算出される。 The amount of metal Si powder dispersed in each example is according to “metal Si powder dispersed amount (kg / Nm 3 ) = spray amount of sprayed material (kg / hr) × metal Si concentration 0.15 × oxygen flow rate (Nm 3 / hr)” It is calculated.
実施例１〜３は、いずれもノズル先端からのガスの吐出線流速を、前記（１）式（図１）から得た火焔伝搬速度Ｖmin（ｍ／ｓ）以上に設定したもので、逆火も発火も発生しなかった。 In all of Examples 1 to 3, the discharge linear flow velocity of the gas from the nozzle tip was set to the flame propagation velocity Vmin (m / s) or more obtained from the equation (1) (FIG. 1). Neither fire nor fire occurred.
一方、比較例１は、ノズル先端からのガスの吐出線流速を、前記（１）式においてｋ＝１として得た速度に設定したもので、逆火が発生した。 On the other hand, in Comparative Example 1, flash discharge occurred because the discharge linear flow velocity of the gas from the nozzle tip was set to the velocity obtained as k = 1 in the equation (1).
Claims (4)
ノズル先端からの酸素又は酸素を含有するガスの吐出線流速を（１）式で表される速度Ｖmin（ｍ／ｓ）以上とすることを特徴とする溶射施工方法。
ここで、
λ：酸素と金属粉との平均熱伝導率（ｋｃａｌ／ｍ・℃・ｈｒ）
ρ：酸素と金属粉との平均密度（ｋｇ／Ｎｍ３）
Ｃ：酸素と金属粉との平均比熱（ｋｃａｌ／ｋｇ・℃）
ｂ：燃焼帯長さ（ｍ）
Ｔｂ：燃焼時の最高温度（℃）
Ｔｚ：予熱帯の温度（℃）
Ｔｕ：粉塵雲の初期温度（℃）
ｋ：輻射伝熱の効果を補正する係数でｋ＝１．１ In the thermal spraying application method, a thermal spray material containing metal powder is sprayed from the tip of the nozzle onto the work surface from the tip of the nozzle using oxygen or oxygen-containing gas as the carrier gas, and melted and adhered to the work surface by combustion heat of the metal powder,
A thermal spray application method characterized in that the discharge linear flow velocity of oxygen or oxygen-containing gas from the tip of the nozzle is set to a velocity Vmin (m / s) or more represented by equation (1).
here,
λ: Average thermal conductivity of oxygen and metal powder (kcal / m · ° C · hr)
ρ: Average density of oxygen and metal powder (kg / Nm 3 )
C: Average specific heat of oxygen and metal powder (kcal / kg · ° C)
b: Length of combustion zone (m)
Tb: Maximum temperature during combustion (° C)
Tz: Temperature of preheating zone (° C)
Tu: Initial temperature of dust cloud (° C)
k: coefficient to correct the effect of radiant heat transfer k = 1.1
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