JPH0119464B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to high manganese steel with excellent pickling properties.
In particular, the present invention relates to a high manganese steel that has excellent pickling properties, with a small amount of base iron dissolved in pickling after water toughening, and a good surface smoothness after pickling. High manganese steel with a basic composition of C: 0.9 to 1.5% and Mn: 10 to 15% is also called Hud-field steel, and shows a completely austenitic structure.
As mechanical properties, it has both extremely excellent work hardenability and good toughness, so it is widely used in parts that require wear resistance and impact resistance. [Prior art] This high manganese steel is manufactured by casting, hot-rolling, or rolling, but if it is cast, hot-melted, or rolled, it is extremely brittle due to the precipitation of carbides at grain boundaries. Be sure to perform water toughness treatment to impart toughness and impact resistance. Water toughness treatment is about 1000~1100
This is a process in which the carbide is completely dissolved by heating to a temperature of °C and then rapidly cooled. Water cooling is usually used for rapid cooling, but if the plate is thin, air cooling may be used. The heat treatment in this water toughness treatment is usually carried out using a heating furnace fueled by heavy oil, liquefied petroleum gas, coke gas, etc., and the interior of the furnace is an oxidizing atmosphere, causing oxide scale to adhere to the surface. For this reason, pickling with sulfuric acid or hydrochloric acid is usually performed to remove the oxide scale formed on the surface after water toughening treatment. [Problems to be solved by the invention] Water-toughened high-manganese steel castings, forged products, and rolled products manufactured through the conventional melting and refining processes of electric furnaces, converters, and degassing. When pickling is performed after treatment, the following problems occur. In other words, if the entire product is pickled sufficiently to completely remove oxide scale, the rate of dissolution of the base metal under the scale is high, resulting in a drop in yield and large variations in dimensional accuracy due to pickling, resulting in localized The surface of the product exhibits a pock-like uneven pattern due to the difference in the amount of dissolved base metal. If this pock-like uneven pattern is polished to a smooth surface, it will further reduce the yield and cause poor dimensional accuracy. Due to the significant work hardening of the surface layer introduced by the polishing process, there was also the problem of a high incidence of cracking due to working. The purpose of the present invention is to solve the above-mentioned problems of the prior art, and to provide a high manganese steel with excellent pickling properties, which has a small amount of base iron dissolved during pickling after water toughening, and has a good surface smoothness after pickling. is to provide. [Means and effects for solving the problem] The present inventors have investigated water toughness with respect to the type and content of impurity elements inevitably included in the normal melting and refining process of high manganese steel and optionally added alloying elements. As a result of detailed investigation into the relationship between pickling properties after treatment, it was discovered that pickling properties were significantly improved by limiting the content of Ni, Mo, and Cr to a certain level, which led to the completion of the present invention. be. The gist of the present invention is as follows.
That is, in terms of weight ratio, C: 0.9 to 1.5%, Si:
The basic composition is 0.80% or less, Mn: 10-15%, Cr: 0.10-1.0%, and Ni and Mo are each Ni: 0.05%.
Hereinafter, it is a high manganese steel with excellent pickling properties, characterized by having a Mo content of 0.010% or less, which has a small amount of base iron dissolved in pickling after water toughening, and has good surface smoothness after pickling. . Next, the reason for limiting the components in the present invention will be explained. C: C stabilizes austenite and requires a minimum content of 0.9% or more to impart high strength, but 1.5% is required.
If it exceeds this amount, it becomes difficult to dissolve carbides during heating during water toughening treatment, so it was limited to a range of 0.9 to 1.5%. Si: Si is effective in deoxidizing during melting and increasing yield strength, but if it exceeds 0.80%, cracks are likely to occur during casting, so the upper limit was limited to 0.80%. Mn: 10% or more of Mn is required to stabilize austenite, but if it exceeds 15%, hot workability deteriorates, so it is limited to a range of 10 to 15%. Cr: When the content of Cr is less than 0.10%, the following occurs.
Even if Ni: 0.05% or less and Mo: 0.010% or less, the pickling property deteriorates, so the lower limit was limited to 0.10%.
On the other hand, since Cr is an expensive element, the upper limit was limited to 1.0% from the economic point of view. Ni, Mo: Limiting the content of Ni and Mo is important for improving the pickling properties of the present invention, and Ni: 0.05
% or less, Mo: 0.010% or less, the amount of pickling dissolution of the base iron is significantly reduced, and the surface after pickling can be smooth enough to make polishing treatment unnecessary in practice. , in the present invention, Ni:
Mo content was limited to 0.05% or less, Mo: 0.010% or less. It should be noted that in conventional high manganese steel melting and refining methods, Ni:
The content was about 0.10 to 0.30%, and Mo: about 0.030 to 0.050%. As mentioned above, the present invention includes C, Si, Mn, Cr, Ni,
Although Mo is limited, it can be used as a deoxidizing element during melting and refining.
Although 0.1% or less of Al may be added, the effects of the present invention are maintained even in this case. In addition, as for P and S as unavoidable impurities, the amount contained in ordinary melting and refining methods is allowable without affecting the effects of the present invention, but from the viewpoint of workability and weldability, P: 0.080% Below, S: 0.040
% or less is desirable. In addition, in high manganese steel, 2% or less of Cu, Ti, Zr,
V, Nb and W may be added alone or in combination, but even in such cases the excellent pickling properties of the present invention are maintained. [Example] High manganese steel whose composition is shown in Table 1 was melted by high frequency melting to produce a 50 kg steel ingot. After removing surface flaws from the steel ingot, a steel plate with a thickness of 2.0 mm was obtained through the steps of hot rolling, annealing, pickling, and cold rolling, and this was used as a test material. Regarding these nine types of test steel plates,
After water toughness treatment by heating in a heating furnace at 1000℃ for 5 minutes and cooling in air, the 80%
A pickling treatment was performed by immersing the sample in a 20% sulfuric acid aqueous solution at ℃ for 80 seconds, and the occurrence of a pock-like uneven pattern on the surface after pickling was observed. In addition, after water toughening treatment, the surface layer of the steel was mechanically removed by 0.2 to 0.3 mm along with the oxide scale formed on the surface, and then immersed in a 20% sulfuric acid aqueous solution at 80℃ for 80 seconds to determine the amount of dissolved steel. It was measured.

[Table] The results of these observations and measurements are shown in Table 2. In Table 2, the degree of occurrence of the pock-like uneven pattern was expressed according to the following criteria. No occurrence...No unevenness occurred at all.Minor level of occurrence: An uneven level difference of 10μ or less occurred.Small...An uneven level difference of more than 10μ and less than 20μ occurred.Medium...An unevenness level difference of more than 20μ and 30μ or less occurred.Large...Unevenness level difference is more than 30 μ If the unevenness level difference is 10 μ or less, no practical inconvenience will occur even if the polishing removal process is not performed and the product is used as is.

【table】

〔Effect of the invention〕

As is clear from the above examples, the present invention limits the content of C, Si, Mn, Cr, Ni, and Mo in high manganese steel, thereby reducing the amount of dissolved base iron during pickling after water toughening treatment. Since the surface is smoothed after pickling, the product yield is improved, plate thickness accuracy is improved, and there is no need for polishing after pickling, which eliminates the process, resulting in economical effects and improved workability. We were able to obtain many results. In addition, in the steel of the present invention, the dissolution rate of the base iron decreases during pickling compared to conventional steel, but this decrease does not cause the problem that the descaling ability during pickling decreases and the required pickling time increases. .

Claims (1)

[Claims] 1 The basic composition in terms of weight ratio is C: 0.9 to 1.5%, Si: 0.80% or less, Mn: 10 to 15%, Cr: 0.10 to 1.0%, Ni and Mo each, Ni: 0.05% or less,
A high-manganese steel with excellent pickling properties, characterized by having a Mo content of 0.010% or less, which has a small amount of base iron dissolved in pickling after water toughening, and has good surface smoothness after pickling.