JPS62199778A - Formation of oxalate film on cr-ni stainless steel - Google Patents

Abstract

PURPOSE:To rapidly form an oxalate film on a Cr-Ni steel when the steel is subjected to oxalate film forming treatment as pretreatment for cold working, by treating the steel with sulfuric acid immediately before the oxalate film forming treatment so as to activate the surface. CONSTITUTION:A Cr-Ni stainless steel is subjected to oxalate film forming treatment as pretreatment for cold working. At this time, the steel is treated with sulfuric acid having 10-50g/l concn. immediately before the oxalate film forming treatment so as to activate the surface. By the activation, the parkerizing time can be shortened, so Fe and Cr ions hardly dissolve in a parkerizing soln. from the steel and the service life of the soln. is remarkably prolonged.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention is directed to Cr-Ni stainless steel (hereinafter simply Cr-Ni stainless steel).
Regarding the method for forming an oxalate film carried out as a pretreatment for cold working of steel (sometimes referred to as steel), in detail, the method for forming an oxalate film on Cr-Ni steel that reliably and efficiently provides an oxalate film on the surface of the material. It is related to.

[Prior art] When drawing Cr-Ni steel in a broad sense including 18-8 stainless steel, Cr-Nt is drawn in advance to improve the lubricant's adhesion.
It is widely practiced to chemically convert @ to form a lubricating carrier consisting of an oxalate film on the surface. A typical method for forming such an oxalate film is the Ferbond method manufactured by Nippon Barker Rising Co., Ltd. This is done by immersing Cr-Ni steel in the treatment mixture shown in Table 1 below (hereinafter referred to as Barker solution), and coating the surface with an insoluble oxalate film (ferrous oxalate: approx. 98%
%).

Table 1 To describe the above Parker treatment more specifically, A, and A
2 to a predetermined concentration, and
It is common to add A C+ a every time steel is processed.

[Problems to be solved by the invention] However, when the material to be treated is a general-purpose material such as 18-8 stainless steel (SUS 304) among Cr-N1m, it is necessary to form a sufficient oxalate film by the above method. However, as shown in Table 2, the carbon content is low even among Cr-Ni steels, and Cr.

In the case of special stainless steels with high amounts of Ni, Mo, etc. (hereinafter sometimes simply referred to as special steels), it is difficult to form an oxalate film even if the above chemical conversion treatment is performed, and in some cases it is not possible to form much. .

(Left below) ゛・.

Table 2 This shows that the annealing scale that forms on the surface of the above-mentioned special steel due to the annealing performed prior to drawing is so acid resistant that a salt bath is required to remove it. This is because it is strong and does not react with Barker's solution or has very weak reactivity.

On the other hand, in the conventional oxalate film generation treatment, in order to process steel materials of various types, sizes, and quantities in a practical line,
It has also been pointed out that bath management of the processing mixture is difficult. In other words, if the ideal conditions shown in Table 1 are maintained through bath management, the chemical conversion treatment will progress relatively smoothly, but depending on the type of treatment, the appropriate bath composition will be slightly different, and
The consumption status of Parker liquid differs depending on each treatment (i.e. A+, A2, AC+a depending on the type of treatment).
As a practical matter, it is difficult to manage the bath. Therefore, even if a bath is adjusted to have an appropriate composition at the time of bath preparation, continuous treatment will gradually change the composition, causing the composition to become unbalanced. However, accurate analysis of the concentration of each component in the Barker liquid is difficult because the raw materials are in a completely mixed state, and at most the concentration of the AI agent can be managed by point (qualitative) measurement, and point management is difficult. A.Although it is possible depending on the amount of drug input, A2. AC,I.

cannot be known without quantitative analysis. Quantitative analysis takes time and cannot be used as a moment-to-moment adjustment. Moreover, in the Parker solution, there is also self-reaction between the constituent components, which makes concentration control even more difficult. As the oxalate chemical conversion treatment of Cr-Mogl is continued using the Barker solution described above, the Cr ion concentration and Fe ion concentration in the treatment mixture gradually rise, reacting with oxalic acid and producing sludge (ferric oxalate). This will inhibit chemical conversion treatment. In this way, in the conventional oxalate chemical treatment method, the bath composition changes;
There were problems such as large accumulation of sludge, and it was necessary to periodically renew a part of the treatment mixture and remove the sludge.

The present invention was developed as a result of intensive studies to solve these various disadvantages, and it is possible to reliably and efficiently form an oxalate coating not only on general-purpose Cr-Ni steel but also on the above-mentioned special stainless steel. The object of the present invention is to provide a method for forming an oxalate film on Cr-Ni steel.

[Means for Solving the Problems] The method of the present invention that achieves the above object is based on Cr-Ni
When performing oxalate film formation treatment as a pretreatment for cold working steel, the gist is that sulfuric acid treatment is performed immediately before the oxalate film formation treatment.

[Operations] The present invention will be explained with reference to FIG. 1 (flow explanatory diagram showing the steps of the embodiment).

Material heat treated (annealed) for drawing (Cr-NivA)
is descaled by pickling or using a salt bath, washed with water, and then sent to a sulfuric acid tank. The surface of the material treated with sulfuric acid is activated (has a reducing property) by the material that has been treated with nitrofluoric acid or the material that has been temporarily stored, so A Cr-Ni stainless steel, which has strong acid resistance, is , the initial reaction with Barker's liquid is strong, and the formation of an oxalate film is rapid and reliable. Regarding the sulfuric acid concentration of the sulfuric acid bath in the present invention, Parker (r!
2 is desirable. When the sulfuric acid concentration becomes less than 10g/JZ,
The above-mentioned initial reaction may deteriorate depending on the type of steel or the storage conditions after pickling (retention days or aether atmosphere), and if it exceeds 50 g/Il, the strength of the Parker coating will weaken due to excessive sulfuric acid content. In addition, as mentioned above, material feeding to the sulfuric acid bath may be carried out immediately after washing with the pickling solution, or may be carried out after temporary storage, but pickling and immersion in the sulfuric acid bath should be carried out as close as possible to each other. Desirable for activating the surface of the material. However, in practical production lines, there is often a state of waiting for barker treatment, so there are few cases in which the pickled material is immersed in a sulfuric acid bath and treated with parker immediately after washing with water, and therefore it is often stored temporarily. Therefore, more desirable treatment effects can be obtained by simply carrying out pickling and water washing once again after temporary storage and before feeding to the sulfuric acid bath.

Next, in the present invention, the material immersed in the sulfuric acid bath is immediately subjected to Parker treatment. As mentioned above, the surface of the material is activated by immersion in the sulfuric acid bath, and since the material with sulfuric acid still attached to the surface is immersed in the Parker bath, the initial reaction between the material surface and the Parker solution is rapid, and the subsequent formation of the oxalate film is accelerated. Growth also progresses rapidly. In this way, in the present invention, the oxalate film forming reaction proceeds rapidly, so the Parker treatment time is short, and the elution of metal ions such as Fe ions and Cr ions from the material into the Parker solution is extremely small, resulting in sludge. The life of the Barker liquid will be dramatically increased because there will be less generation of such substances.

Furthermore, in the present invention, since the sulfuric acid immersion treatment is performed immediately before the Parker treatment step, it is possible to form a sufficient oxalate film even on special steel, for which it was difficult to form an oxalate film using conventional methods. For example, 21 Cr -40N i -3M
It has been impossible to form an oxalate film on highly corrosion-resistant stainless steels such as No. The pretreatment with sulfuric acid ensured the formation of a film, making it possible to provide the same processing rate as 18-8 stainless steel.

Because of its strong film-forming ability, when applied to 18-8 series general-purpose stainless steel, an oxalate film is formed at about twice the rate of conventional stainless steels.

When the Parker treatment is completed as described above, the treated material is dried, coated with a lubricant, subjected to a drawing process, and drawn into a desired shape.

[Example] According to the process shown in Fig. 1, materials [A] to [B] (third
The results shown in Table 3 were obtained when Parker treatment and drawing were performed on each of the samples (listed in the table). On the other hand, the conventional method (
According to the process shown by the broken line in Figure 1), the same < [A] to [
The material of [C] was subjected to Parker treatment and drawing, and the results are also listed in Table 3. The evaluation criteria for Parker treatment and drawing are as shown in Table 4.

As shown in Table 3, in the case of the conventional example, 17Cr-1λN
Almost satisfactory results were obtained with general-purpose materials such as i-2,5Mo steel, but with 25Cr-21Ni steel and 2
When using special steel like 1Cr-4ONi-3MovA, it was not possible to obtain a good Parker film, and the drawing property was also deteriorated. On the other hand, it was confirmed that the method of the present invention provides good Parker coating and drawability for all of the same general-purpose materials [A], special steels [B], and [Cr].

[Effects of the Invention] The present invention is configured as described above, and can obtain the effects summarized below.

(1) By performing sulfuric acid immersion treatment immediately before Parker treatment, the surface of the material is activated, and as a result, the nucleation of the film on the surface of the material and the formation of the oxalate film can be carried out quickly.

(2) Since the Parker treatment can be completed in a short time, there is less elution of metal ions such as Cr ions and Fe ions from the material into the Parker solution, and the sludge caused by the reaction between these metal ions and oxalic acid is reduced. Less generation is required. As a result, the life of the Parker liquid can be dramatically extended.

(3) As mentioned above, pre-soaking in sulfuric acid increases the reactivity between the material and the Parker solution, making it possible to efficiently perform the Parker treatment on special steel with a Ni content of 20% or more, which was previously considered impossible. be able to. Also 18-8
For general-purpose materials such as stainless steel, the processing efficiency has been improved, and Parker processing can be completed in approximately 1/2 the time required by conventional methods.

(4) As processing efficiency improves, less steam is needed to heat the Parker liquid, allowing economical processing.

[Brief explanation of drawings]

FIG. 1 is a flow explanatory diagram showing a method according to an embodiment of the present invention and a conventional method.

Claims (1)

[Claims] A Cr characterized in that when performing oxalate film formation treatment as a pretreatment for cold working Cr-Ni stainless steel, sulfuric acid treatment is performed immediately before the oxalate film formation treatment.
- A method for forming an oxalate film on Ni-based stainless steel.