JPS6243764B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for suppressing the formation of scale when heating steel materials and improving the removability of the generated scale. (Technical background) When steel materials are hot worked, they are usually heated to 1000℃ or more in a heating furnace.
After being heated to 1300℃, it is transferred to a processing machine.
At this time, the surface of the steel material is oxidized due to contact with the oxygen-containing atmosphere in the heating furnace and the atmosphere during transportation, and so-called scale is generated. Formation of scale causes loss of steel material, and if it gets caught between the steel material and the tool during machining, it can damage the tool or cause the scale to be press-fitted into the steel material, causing surface scratches and degrading the quality of the product. (Prior Art) Various methods have been used to suppress scale formation. The most common method is to apply so-called scale inhibitors to the steel before heating it. For example, Japanese Patent Publication No. 53-43124 discloses applying a composition consisting of chromium oxide and other materials to steel materials for the purpose of inhibiting scale formation. Mixtures of various metals or non-metals are known as scale inhibitors. However, with conventional methods, not only is scale suppression insufficient, but even after applying a scale inhibitor, the generated scale and scale inhibitor firmly adhere to the steel material, and the scale is removed before processing. Even if you try to remove it with a breaker, it will not be removed completely and the above problems will occur. Due to the above-mentioned current situation, there is a strong desire for a steel processing method that can sufficiently suppress the formation of scale, and even if some scale does occur, it can be easily removed. (Object of the Invention) The present invention suppresses scale formation and improves the removability of the generated scale. The object is to provide an improved method for processing steel materials. (Structure of the Invention) The present invention is characterized in that the surface of steel is coated with two coating layers each having a different composition.
That is, the present invention coats the surface of a steel material with a composition containing a binder and carbon powder, and then coats the surface of the composition layer with (a) aluminum, chromium, titanium, manganese,
10 to 50 parts by weight of powder of a metal selected from copper, nickel, cobalt, magnesium and iron, (b) Powder of oxide of the metal listed in (a) above
5 to 30 parts by weight, (c) 10 to 100 parts by weight of silicic anhydride, (d) 10 to 100 parts by weight of powder of kaolin, montmorillonite, and dolomite refractories, (e) 20 to 80 parts by weight of water glass, (t) ) This is a method for improving the formation of scale during heating of steel materials and the removability of the generated scale, which is characterized by coating the steel with a composition containing an appropriate amount of water. The components of the present invention will be explained in detail below. (Lower layer composition) In the present invention, as the carbon powder, one or more of graphite, carbon black, charcoal powder, etc. can be used, and as the binder for the carbon powder, water glass or a water-soluble polymer substance can be used. Can be done. As water-soluble polymeric substances, derivatives of natural polymeric substances such as carboxymethylcellulose and synthetic polymeric substances such as polyacrylic acid can be widely used. After the carbon powder and the binder are mixed uniformly, if necessary, water is appropriately added to adjust the viscosity so that the composition can be easily applied. At this time, it is desirable that the ratio of carbon powder to binder is larger than that of binder in terms of weight ratio. The carbon powder-containing composition prepared in this manner will be referred to as a lower layer composition in the following description. (Metal Powder and Metal Oxide Powder) In the present invention, aluminum, chromium, and titanium are particularly desirable among the components (a), and particularly desirable among the components (b) are aluminum oxide and chromium. and titanium oxide. This is because the use of these metals and metal oxides is particularly effective in suppressing scale formation. (Top layer composition) To produce a composition containing the substances (a) to (g) above (hereinafter referred to as the top layer composition),
After uniformly mixing the substances (a) to (e), water is added as necessary to adjust the consistency in order to facilitate application to steel materials. (Coating amount) In the present invention, the coating amounts of the lower layer and upper layer compositions to be applied to the surface of the steel material are desirably 2 mg/cm ² or more for the lower layer and 5 mg/cm ² or more for the upper layer as dry weight. The reason for this is that, as shown in Figures 2 and 3, if the coating amount of the lower layer is less than 2 mg/cm ² , the scale removability is poor, and if the coating amount of the upper layer is less than 5 mg/cm ^{2 .}
This is because if it is less than that, the effect of suppressing scale generation will be poor. The coating amount of the lower layer is preferably 5 mg/cm ² or more, and the coating amount of the upper layer is 5 mg/cm ² or more, preferably 20 mg/cm ² or more. (Actions and Effects of the Invention) The effects of the present invention are obtained by forming a lower layer composition and an upper layer composition [the composition containing the substances (A) to (G) above is referred to as the upper layer composition. ] is expressed by two coating layers formed from the above. When a composition is prepared by mixing carbon powder and the above-mentioned upper layer composition, and this is applied to the surface of the steel material to form a single coating layer, the scale suppression effect is inferior, and in addition, the generated scale and fixed Difficult to remove scale inhibitors. In the present invention, if the application of the upper layer composition is omitted, or if the order of applying the lower layer composition and the upper layer composition is reversed, the carbon powder will easily oxidize and disappear during heating, so no effect will be produced. . Furthermore, even if the coating of the lower layer composition of the present invention is omitted and the steel material is coated with only the upper layer composition, the effect of blocking the atmosphere and suppressing scale can be obtained to some extent, but it is not sufficient, and the generated scale can be removed. is difficult. Moreover, this upper layer composition itself is also sintered in the heating furnace to form a strong fixed layer on the surface of the steel material. This fixed layer is difficult to remove and remains even when a scale breaker is used, causing damage to tools and steel materials. If steel materials are processed by the method of the present invention, the generation of scale can be suppressed to an extremely small amount, thereby increasing the yield of steel materials and contributing to resource conservation. In addition, if steel materials are treated by the method of the present invention, the scale including the treatment agent can be easily removed using a scale breaker, for example, so that there is no risk of damaging tools during hot working or from steel materials. No surface scratches will occur. In the method of the present invention, the effects of the two layers covering the surface of the steel material are estimated as follows. First, the upper layer composition temporarily prevents oxygen from reaching the steel surface from the atmosphere through its reducing action and physical shielding effect. Next, the lower layer composition finally prevents the relatively low partial pressure of oxygen that could not be prevented by the upper layer composition from reaching the steel surface through the reducing action of carbon and the physical shielding effect of the layer.
Prevents scale from forming. Furthermore, the presence of the lower layer suppresses the adhesion of the upper layer composition to the steel material, making it easier to peel off scale including the upper layer composition. (Example) Next, the present invention will be specifically described with reference to Examples. However, the present invention is not limited to these in any way. (Processing method) In each of the following examples, a pre-weighed steel material (SPCC, 80 x 60 x 1.2 mm) was used as a test piece, and the lower layer composition was kneaded well on both sides and applied uniformly with a brush. After drying at ℃ for 30 minutes, it was weighed to determine the coating amount of the lower layer composition as the dry coating amount. Next, on the coating layer of the lower layer composition, the upper layer composition was thoroughly kneaded and applied with a brush, and the coating amount of the upper layer composition was determined in the same manner as for the lower layer composition. After heating the steel specimen coated with the two-layered scale inhibitor in this way in an electric furnace in an air atmosphere at 1200°C for 1 hour, it was taken out and the following method was used to improve the scale inhibition effect and scale removability. The effectiveness was evaluated. (Evaluation method of scale suppression effect and scale removability) FIG. 1 is a perspective view of the main parts of the test device, and the arrow in the figure indicates the direction of movement of the test piece. The steel specimen 1 is moved horizontally in the longitudinal direction and passed through a total of four nozzles 2, two on the top and two on the top, arranged as shown in Fig. and the scale inhibitor was removed, dried at 110°C for 30 minutes, and weighed. The weight at that time was defined as W ₁ . The operating conditions of the test equipment are as follows. Discharge pressure (each nozzle) 100Kg/cm ² nozzle diameter 1.7mmφ Discharge rate 17/min Distance between nozzle and test piece 50mm Distance between parallel nozzles 30mm Moving speed of test piece 2mm/sec Even after the above treatment The attached scale and scale inhibitor were completely removed by mechanical impact and weighed. weight at that time
I set it as W ₂ . The weight of the steel plate test piece before application of the scale inhibitor was taken as W ₀ , and the oxidation loss rate and scale removal rate were determined using the following equations. Oxidation loss rate = [(W ₀ − W ₂ ) / W ₀ ] × 100% Scale removal rate = [(W ₀ − W ₁ ) / W ₀ − W ₂ ] × 100% The smaller the oxidation loss rate, the more effective it is to suppress scale. It is evaluated that the larger the scale removal rate is, the better the scale removability is. Example 1 As a lower layer composition, 16 parts by weight of graphite, 6 parts by weight of water glass, and 30 parts by weight of water were mixed and kneaded well, and the mixture was uniformly applied to both sides of a steel specimen. After determining the coating amount using the above method, apply aluminum powder on top of this coating layer.
30 parts by weight, 22 parts by weight of aluminum oxide powder, 55 parts by weight of silicic acid powder, 55 parts by weight of kaolin, 50 parts by weight of water glass
The upper layer composition prepared by mixing 15 parts by weight of water and 15 parts by weight of water was applied, and the coating amount was determined by the method described above. The coating amount was 20 mg/cm ² for the lower layer and 80 mg/cm ² for the upper layer. Next, the oxidation loss rate and scale removal rate were determined in accordance with the above-mentioned order. The results are shown in Table 1 below. Example 2 The coating amount of the lower layer composition in Example 1 was changed to 10 mg/
cm ² and treated and tested in exactly the same manner as in Example 1. The results are shown in Table-2. Example 3 The lower layer composition and the upper layer composition of Example 1 were both coated at 20 mg/cm ² each, and other treatments were carried out in the same manner as in Example 1 for testing. The results are shown in Table-1. Comparative Example 1 The upper layer composition was applied directly to the test piece without applying the lower layer composition of Example 1. The amount of application is
It was 100mg/ ^cm2 . The rest was treated and tested in the same manner as in Example 1. The results are shown in Table-1. Comparative Example 2 Only the lower layer composition of Example 1 was applied, and the upper layer composition was not applied. The coating amount was 80 mg/cm ² . The rest was treated and tested in the same manner as in Example 1. The results are shown in Table-1. Comparative Example 3 16 parts by weight of graphite, 30 parts by weight of aluminum powder, 22 parts by weight of aluminum oxide powder, 55 parts by weight of anhydrous silicic acid powder, 56 parts by weight of water glass, and 45 parts by weight of water were mixed and applied. The coating amount was 100 mg/cm ² . The rest was treated and tested in the same manner as in Example 1. The results are shown in Table-1.

[Table] As shown in the above examples, when steel materials are treated by the method of the present invention, the oxidation loss rate is small and the scale removal rate is high. This shows that when steel materials are treated by the method of the present invention, the amount of scale generated on the steel materials can be suppressed, and the peelability of the generated scales and the scale removal rate can be improved.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a test apparatus used for evaluation tests of scale suppression effect and scale removability. FIG. 2 is a graph showing the oxidation reduction rate according to Example 1. FIG. 3 is a graph showing the scale removal rate according to Example 1. 1...Test piece, 2...Nozzle.

Claims (1)

[Scope of Claims] 1. The surface of a steel material is coated with a composition containing a binder and carbon powder, and then the surface of the composition layer is coated with (a) aluminum, chromium, titanium, manganese,
10 to 50 parts by weight of powder of a metal selected from copper, nickel, cobalt, magnesium and iron, (b) Powder of oxide of the metal listed in (a) above
5 to 30 parts by weight, (c) 10 to 100 parts by weight of silicic anhydride, (d) 10 to 100 parts by weight of powder of kaolin, montmorillonite, and dolomite refractories, (e) 20 to 80 parts by weight of water glass, (t) ) A method for improving the formation of scale during heating of a steel material and the removability of the generated scale, the method comprising coating with a composition containing an appropriate amount of water.