JPS5922768B2 - Surface treatment agent and surface treatment method for cold rolled steel sheets - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a surface treatment agent and a surface treatment method for cold rolled steel sheets,
More specifically, a surface treatment agent for cold-rolled steel sheets that makes it possible to simultaneously perform anti-graphitization treatment and anti-seizure treatment on a steel sheet during an annealing process of a steel sheet whose surface has been cleaned by cold rolling or electrolytic cleaning after cold rolling. and surface treatment methods.

The cold-rolled steel sheet product obtained by the treatment of the present invention exhibits an excellent surface appearance without surface defects caused by baking between the steel sheets or surface stains due to precipitation of graphite and/or sooty carbon.

During the annealing process of cold-rolled steel strip coils, welding or seizure often occurs between the contact surfaces of the cold-rolled steel strip coils, so that when the cold-rolled steel strip coils are unwound after annealing, seizure wrinkles may occur, and in severe cases, the plate may be damaged. There may be holes in the copper strip, and even the copper strip may break.

Furthermore, after annealing, the surface of the cold-rolled steel strip coil may be stained black, resulting in a defect that significantly impairs the surface appearance.

This black stain may occur when the gas atmosphere during annealing contains carbon-containing substances, such as CH4 or CO. It is thought that this is the precipitate.

However, it has been recognized that they also appear in the absence of carbon sources such as αt and CO in the gas atmosphere.

In this case, the graphite precipitated on the surface of the cold-rolled steel strip coil is considered to be carbon contained in the steel, for example, carbon in cementite in the steel precipitates on the surface as graphite during annealing.

To solve these problems, in order to prevent seizure during annealing, by applying an appropriate amount of a compound having siloxane bonds to the surface of the steel sheet before annealing, an ultra-thin porous film or scattered dots are formed on the surface of the steel sheet during the annealing process. Efforts have been taken to prevent seizure by precipitating a compound whose main component is silicon.

In this method, the organic content of the silicon-containing organic compound is scattered during annealing, and the siloxane bond portion remains on the surface as a silicon compound with Si-0 bonds, forming an extremely thin porous film or scattered dots. In a cold-rolled steel strip coil wrap, it prevents the steel sheets from coming into close contact with each other and has the effect of preventing seizure.

However, although organic compounds having siloxane bonds may have a remarkable effect on preventing seizure, they may not have any effect on preventing black color, and they tend to promote graphite precipitation due to the scattering of organic components during the annealing process.

Silicon compounds remaining on the surface of the steel sheet after annealing are removed during pre-painting treatment (chemical conversion treatment such as phosphate treatment) of the finished steel sheet.
Effective contact between the chemical conversion treatment liquid and the steel plate surface may be hindered, and a good chemical conversion coating may not be obtained.

Further, carbon present on the surface of the steel sheet exhibits a black color and impairs the appearance of the surface, and like silicon compounds, tends to inhibit the chemical conversion treatment properties of the steel sheet.

To prevent black color caused by carbon, which is another problem during annealing, a conventional method is to apply an appropriate amount of a compound containing sulfur as a negative catalyst for carbon precipitation to the surface of a cold-rolled steel sheet before annealing. There are times when it happens.

For example, K2S, Na2S2O7, K2S2O5, N
It is known that graphite precipitation on the surface of a cold-rolled steel strip coil can be effectively suppressed by applying a2S, KHSO3, etc. in the form of an aqueous solution or suspension.

However, if the amount of these negative catalysts applied is too large, the surface of the steel sheet may turn brown after annealing even if the blackening of the surface of the steel sheet can be prevented.

In addition, this type of substance has almost no effect on preventing annealing seizure in an applied amount effective for preventing graphite precipitation.

The present inventors have worked diligently to solve these drawbacks and to obtain a surface treatment agent for annealing and a surface treatment method as a pre-annealing treatment that can prevent seizure and black coloring at the same time and do not interfere with post-processing. As a result of our efforts and research, we have completed the present invention.

That is, the present invention provides a phosphate ester salt represented by the general formula and C→ CRO(C2H40)n-P (-0-)-2)
aXb and) [(RO(C2H40)n)2-P-0-]aXb
Phosphite ester salt represented by (in the formula, R has 4 to 2 carbon atoms)
represents an alkylphenyl group or dialkylphenyl group having 2 saturated or unsaturated linear or branched alkyl groups or an alkyl group having 4 to 18 carbon atoms;
X represents a metal, a hydrogen atom, an oxyalkylene group, or a polyoxyalkylene group, and in the formula, X represents Pb, A1
Must contain one of 1Cr.

a represents 1.2 or 3, n represents a number from 0 to 20, and b represents 1 or 2.

The present invention provides a surface treatment agent for cold rolled steel sheets comprising one or more compounds selected from the group consisting of (1) and an annealing pretreatment method using such a treatment agent.

In the compound represented by the formula (a) to) of the present invention,
When b=2, one X is one of Pb, AI, Cr
and the other one X is an alkali metal or alkaline earth metal, or when b=2 in the compound of formula (a) to), one XfJ''-Pb
, Al, and Cr, and the other X is preferably an oxyethylene group or a polyoxyethylene group (the number of moles of oxyethylene added is 1 to 6).

The surface treatment agent for cold rolled steel sheets according to the present invention is added to cold rolling oil and applied onto the steel sheet in a step before the annealing process, or applied to the steel sheet by a coating method such as spraying or roll coating. In other words, the effects of the present invention can be achieved by providing a coating step before annealing and applying the surface treatment agent according to the present invention to the surface of the steel sheet.

However, as is clear from its chemical structure, when the surface treatment agent according to the present invention is used in the presence of water, it undergoes hydrolysis when the pH is high at 9 or higher, or when the pH is low at 3 or lower. It cannot be used in combination with an alkaline degreasing solution or an acid solution under such usage conditions, such as electrolytic cleaning or acid cleaning processes, because it will form a foreign substance and will not be able to exhibit its effects.

The surface treatment agent according to the present invention is 0.05~
A coating weight of 500 .mu./m@2 is preferred.

If the coating amount is less than 0.05 cm/m', it is practically difficult to uniformly apply the surface treatment agent of the present invention to the surface of the steel plate, and it is difficult to obtain the expected effect.

Moreover, if the coating amount exceeds 500 m9/rrl, although the anti-seizing function is exhibited, the effect of preventing surface blackening is hindered due to precipitation of carbon due to decomposition of organic components, which is disadvantageous.

The phosphoric acid ester salt and the phosphorous acid ester salt according to the present invention are produced by a generally known method.

For example, a hydroxy compound having 4 to 22 carbon atoms or a product obtained by adding ethylene oxide to this hydroxy compound is reacted with phosphorus pentoxide in a molar ratio of 3 to 10 to obtain a sesquiphosphate, and then a sesquiphosphate is obtained. Alternatively, the sesquiphosphate is reacted with acetate to form a Pb, Cr or AI salt, and if necessary, the remaining free acid is converted into a Na salt with caustic soda, or ethylene oxide is added to form the phosphoric acid according to the present invention. An ester salt is obtained.

A phosphite salt is prepared by reacting a hydroxy compound having 4 to 22 carbon atoms or a product obtained by adding ethylene oxide to this hydroxy compound with, for example, phosphorus trichloride, and similarly producing a Pb, Cr, or AI salt of the phosphite ester. shall be.

If necessary, the remaining acid is converted into Na salt or ethylene oxide is added to obtain the phosphorous acid ester salt according to the present invention.

In this case, the hydroxy compound having 4 to 22 carbon atoms used as a raw material may be a higher alcohol obtained from nature or a synthetic alcohol, or may be an alkylphenol or a dialkylphenol.

The present invention will be explained in more detail below using reference examples and examples.

Reference example 1 Phosphate ester of 3 moles of ethylene oxide added to lauryl alcohol (50% monoester, 50% diester)
% and has an acid value of 154) and 584P is heated to 70°C to form aluminum isopropoxide 107P (about 1.0 of the acid value equivalent).
After 2 hours of reaction, unreacted aluminum isopropoxide and free isopropyl alcohol were removed to form a yellow viscous liquid with an acid value of 70. 535 g of phosphoric acid ester salt was obtained (synthesis product A).

By the same operation, a product with an added mole of ethylene oxide of 10 moles (composite B) and a product with the same number of moles of ethylene oxide added of 15 mole (composite C) were obtained.

Reference example 2 Phosphoric ester of octyl alcohol (monoester 50
%, contains 50% diester and has an acid value of 315) 266 g.
Heat to 0℃ and add 244f lead acetate. (approximately 1.0 of acid value equivalent)
5 times) was added, heated to 130°C, stirred under normal pressure in a nitrogen gas atmosphere, and after reacting for 3 hours, lead acetate and free acetic acid were removed to form phosphoric acid ester salt 3, a yellow viscous liquid with an acid value of 130.
88? was obtained (composite D).

Bridge [ By the same operation, a salt of a phosphoric acid ester (containing 50% monoester and 50% diester, acid value 141) obtained by adding 5 moles of ethylene oxide to octyl alcohol was obtained (composite E).

Further, similar operations were performed to obtain a phosphoric ester salt (compound F) obtained by the reaction of the phosphoric ester of octyl alcohol with aluminum acetate (basic) and a phosphoric ester salt (compound G) obtained by the reaction with chromium acetate (e). .

Reference example 3 Phosphite diester of oleyl alcohol (acid value 96)
58.6S' was heated to 50°C, aluminum acetate (basic) 63.5S' (about 1.05 times the acid value equivalent) was added, further heated to 130°C, and stirred under normal pressure in a nitrogen gas atmosphere. After a 3-hour reaction wave, aluminum acetate, free acetic acid, etc. were removed, and a brown viscous liquid phosphoric acid ester salt with an acid value of 29 was obtained. (Synthesis H).

A similar operation was carried out to form a phosphoric acid ester salt produced by the reaction of the oleyl alcohol phosphite and chromium acetate.
Compound I) was obtained.

Reference Example 4 Compound D (acid value 130) was partially neutralized with a 50% caustic soda aqueous solution, and water was removed to obtain a phosphoric acid ester salt containing lead and sodium as a yellow viscous liquid with an acid value of 75 ( Composite J).

Compounds F and G are neutralized by the same operation, and L
I got it.

Reference example 5 Compound D43N for adding ethylene oxide to active hydrogen?
Ethylene oxide 131 (approximately three times the acid value equivalent) was added thereto and reacted at 100° C. and 3 atm for 3 hours to obtain 52 g of a yellow viscous liquid with an acid value of 92 after the reaction (composite M).

Compound M was soluble in spindle oil.

Example: Apply a predetermined amount of a surface treatment agent or a solution of mineral oil or rolling oil as a surface treatment agent to a steel plate with a width of 30 mm and a length of 50 mm and a thickness of Q, and then stack the coated steel plates with a load of 46 kg. /cI
? Annealing was performed at 700°C for 6 hours in a gas containing 5% hydrogen and 95% nitrogen having a dew point of -40°C.

The peel strength after annealing was measured and evaluated as follows.

Further, a steel plate having a width of 100mm, a length of iomm, and a thickness of 0.8mm was coated with the surface treatment agent in the same manner, annealed in the same manner, and after annealing, the surface was observed with the naked eye and with an optical microscope to evaluate black stains.

The results are shown in Table 1. The composition of rolling oil (I) is as follows.

Paraffinic mineral oil 82% Ester 10% 1′: H2 °″ 3%

Claims (1)

[Claims] 1. A phosphoric acid ester salt represented by the following general formula and e→ CRO(C2H40) n P + O+2
) aXb and )C(RO(C2H+0)n)2P -0:)aXb
Phosphite ester salt represented by (in the formula, R has 4 to 2 carbon atoms)
represents an alkylphenyl group or dialkylphenyl group having 2 saturated or unsaturated linear or branched alkyl groups or an alkyl group having 4 to 18 carbon atoms;
X represents a metal, a hydrogen atom, an oxyalkylene group, or a polyoxyalkylene group, and in the formula, X represents Pb, Al
, Cr. a represents 1.2 or 3, n represents a number from 0 to 20, and b represents 1 or 2. ) A treatment agent for preventing graphitization and seizure during annealing of cold rolled steel sheets, which comprises one or more compounds selected from the group consisting of: 2 In the compound of formula (a) to), when b=2,
The treatment agent according to claim 1, wherein one X is one of Pb, AI, and Cr, and the other X is an alkali metal or an alkaline earth metal. 3 In the compound of formula (a) to), when b=2,
Claim 1, wherein one X is one of Pb, AI, and Cr, and the other X is an oxyethylene group or a polyoxyethylene group (number of added moles = 1 to 6) treatment agent. 4 Prior to annealing, a phosphate ester salt represented by the following general formula and (/υ CRO(C2H40)n-P(-0-)-2) are applied to the surface of the cold rolled steel sheet.
aXb and (-)C(RO(C2H40)n)2P-0-'']a
Phosphite ester salt represented by Xb (in the formula, R has 4 carbon atoms)
represents an alkylphenyl group or dialkylphenyl group having ~22 saturated or unsaturated linear or branched alkyl groups or an alkyl group having 4 to 18 carbon atoms, and X is a metal, a hydrogen atom, an oxyalkylene group, or a polyoxy represents an alkylene group, and in the formula, X is Pb,
Always includes one of AI and Cr. a represents 1.2 or 3, n represents a number from 0 to 20, and b represents 1 or 2. ) A surface treatment agent for cold rolled steel sheets consisting of one or more compounds selected from the group consisting of 0.05 to 500yn9
1. A treatment method for preventing graphitization and seizure during annealing of a cold rolled steel sheet, characterized by applying a coating of "/rn".