JPH04289157A - Cast steel product in which generation of burr at the time of cold working is controlled - Google Patents

Abstract

PURPOSE:To reduce burrs in a cost steel product generated at the time of cold working by providing a soft cast steel product with a surface hardened layer having hardness higher than that on the inside. CONSTITUTION:In a soft cast steel product by a precision casting, large burrs are easy to generate at the time of partial mechanical working, and many man-hours are required for removing the above burrs. Accordingly, by nitriding treatment, carburizing treatment or the like, it is provided with a surface hardened layer by which the hardness of the surface part is higher than that on the inside of the main body by >=100Hv, so that burrs generated at the time of cold working can be reduced, and the improvement of the efficiency in its finish working and the reduction of man-hours for removing burrs will be permited.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cast steel product in which a part of a relatively soft cast material is machined and burrs generated during the machining are controlled.

0002

[Prior Art] Cast products made using the precision casting method have excellent dimensional accuracy and have the advantage of being able to mass-produce products with complex shapes.
Various parts are manufactured for use in many industrial fields. Among these, the expansion into electrical and electronic fields, which require particularly high quality, is remarkable. For example, the yokes in computer-related magnetic circuits are made of low-alloy cast material and are machined with high precision. The yoke material is usually made of S8C to S15C low carbon steel, which is machined after being magnetically annealed, provided that it has low magnetic resistance. However, since these materials have low hardness and high ductility, when cold working as shown in FIG. 1 is performed under the cutting conditions shown in Table 1, machining burrs as shown in FIG. 2 are generated at the edges of the workpiece. This deburring process requires a large amount of man-hours.

[0003] Conventionally, extra man-hours were required to minimize burrs generated by special processing methods or to remove generated burrs. As for the above-mentioned special processing methods, for example, the material of the tool, the depth of cut, the number of processing times, etc. have been studied, and as methods for removing burrs, barrel polishing, deburring with a projectile material, etc. have been investigated, but none of them have been considered. It was not sufficient due to the cost and man-hours involved.

[0004]Also, a method for reducing punching burrs during press forming is disclosed in JP-A-1-255626, but in the case of cast steel products, this method is not satisfactory due to the product shape, processing location, or material. . In other words, if the surface hardened layer shown in the above patent is limited to within 5% of the plate thickness, the depth of the hardened layer may be less than 0.1 mm, causing a problem in burr resistance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cast steel product in which burrs generated during machining of a part of the cast product after soft cast steel are cast are controlled.

[0005]

[Means for Solving the Problem] As a result of various studies to solve the above problems, the inventor noticed that the softer the cast steel product and the greater the ductility, the larger the burrs generated during machining. However, in order to control the occurrence of burrs, the inventors have found that making the surface of the cast product harder than the inside of the main body has a significant effect, leading to the completion of the present invention.

That is, the first aspect of the present invention is a cast steel of either ferritic type, austenitic type, or martensitic type in an annealed state, and the hardness of the inside of the main body is Vickers hardness (HV). 250 or less,
A cast steel product with controlled burr generation during cold working, characterized by having a hardened surface layer whose surface portion has a hardness (HV) 100 or more higher than the hardness inside the main body;
This is a cast steel product in which burr generation during cold working is controlled, according to the first invention, in which the surface hardening layer is a carburized layer or a nitrided layer.

The cast materials targeted by the present invention are soft materials with a hardness of (HV) 250 or less inside the main body, ie, ferritic or austenitic cast steel, and annealed materials with a hardness of (HV) 250 or less during machining. It also includes martensitic cast steel or pure iron in a better state. The above-mentioned cast steel is generally a soft material with a hardness of (HV) 250 or less, and burrs are generated significantly when cold finishing of the sprue part or precision finishing of a part of the cast product is performed after casting.

According to the present invention, from the internal hardness of the cast steel body,
By providing a surface hardening layer with a high (HV) of at least 100, it is possible to significantly control the occurrence of burrs. If the hardness of the hardened layer is only within a range of less than (HV) 100 higher than the internal hardness of the cast steel body, it will be less effective in controlling the occurrence of burrs. do. The depth of the surface hardening layer is appropriately determined depending on the hardness inside the body of the cast material, the purpose of the cast product, machining conditions, etc., but it is preferably 0.2 to 0.8 mm deep from the surface of the cast product. It is sufficient. To measure the hardness of the hardened surface layer, the surface of the cast product can be checked using a Vickers hardness meter. By applying a hardened layer of appropriate hardness to the surface of a soft cast steel product in this way, burrs are less likely to occur in the hardened layer during cutting, and even if cutting continues deep beyond the hardened layer, When the cutting edge of the tool reaches near the surface of the cast steel product, it penetrates into the hardened layer, thereby significantly controlling burr generation.

[0009] The means for applying the above-mentioned surface hardening layer is not particularly limited, but it is preferable to use relatively simple and inexpensive treatment methods such as carburizing, nitriding, and shot blasting. In addition, since the hardened layer partially remains in the product, it does not impair the characteristics of the product, and the hardened layer also has other effects such as providing wear resistance to sliding parts.
In order to unnecessarily promote tool wear during machining, consideration should be given to reducing the hardness of the hardened layer appropriately.

0010

EXAMPLES The present invention will be explained below based on examples.

(Example 1) As a test steel, C:
0.14%, Si: 0.63%, Mn: 0.8%, P
: 0.015%, S: 0.012%, Al: 0.0
A ferrite-based low magnetic resistance material of 8% and the balance Fe was melted in the atmosphere in a high frequency induction melting furnace. The molten metal from the melting furnace was precision cast into a ring-shaped mold to obtain a test piece. The ring test piece that was subjected to mold removal was subjected to magnetic annealing and then 580
Surface hardening treatment by salt bath nitriding was performed at different times at °C. The flat part of the obtained ring test piece was subjected to cutting and lathe processing under the conditions shown in Table 1, and the lengths of burrs generated at specific positions were measured. The results are shown in Table 2. We also measured the magnetic properties of the lathe-processed ring specimens.
The results are shown in Table 3.

0012

[Table 1]

[0013]

[Table 2]

[0014]

[Table 3]

The depth of the hardened layer varied depending on the difference in surface hardening treatment time, and the measured results were 0.2 to 0.8 mm. When these test pieces were cut, the burr lengths were all 0.15 mm or less, and the hardening depth was particularly 0.5 mm.
mm and 0.8 mm, there were some areas where no burrs were generated. However, in the test specimens of comparative materials that were not subjected to surface hardening treatment, the maximum burr length was 0.3 mm, and burrs were observed in all cases. In addition, the hardening depth is 0.1
When the thickness was less than mm, no effect of surface hardening treatment was observed. Even in lathe processing, the burr length was 0.3 mm or less in the material of the present invention, whereas burrs were generated in the comparative material with a length 8 to 9 times that of the inventive material. Furthermore, as a result of measuring the magnetic properties, no particularly large deterioration was observed in the material of the present invention compared to a comparative material that was not subjected to surface hardening treatment.

(Example 2) As a test steel, C:
0.08%, Si: 1.08%, Mn: 1.51%,
Ni: 11.86%, Cr: 17.75%, balance Fe
An austenitic stainless steel having the composition was precision cast into a ring test piece having the same shape as in Example 1, and then shot blasting was performed. Projection conditions are projection speed: 73m/se
c. Projection time: 20 minutes. Projection material: 0.8 mm stainless steel cut wire. The average hardness of the inside and surface of the main body after treatment is (HV) 185 and (
HV) 378. As a result of cutting the flat surface of the as-cast ring and the ring that was shot-blasted after casting and measuring the length of the burr that was generated, it was found that the shot-blasting treatment was performed at a burr length ratio of approximately 3:1. It was confirmed that the burr length of the sample material was short.

(Example 3) As a test steel, C:
0.40%, Si: 0.26%, Mn: 0.75%,
Ni: 1.88%, Cr: 0.75%, Mo: 0.
A cast steel having a composition of 21% Fe with the balance being Fe was precision cast into a ring-shaped mold and then annealed in a carburizing gas. In addition, as a comparative test steel, we also prepared a ring that was only annealed without using carburizing gas. The average hardness of both bodies was 224 (HV), and the surface hardness of the carburized ring was 356 (HV). As a result of measuring the length of burrs generated by cutting the flat parts of these rings, it was found that the length of burrs was shorter in the sample material that had been carburized at a ratio of approximately 4:1. It was confirmed. The machined ring was then quenched and tempered to produce a product.

[0018]

[Effects of the Invention] As described above, the present invention can significantly reduce the burrs that occur when cold working a part of soft cast steel products, improve the efficiency of finishing work, and significantly reduce the number of deburring steps. It is extremely effective for mass production of cast steel products.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing cutting processing.

FIG. 2 is a schematic diagram showing the burr shape of a conventional product after processing.

FIG. 3 is a schematic diagram showing the form of the product of the present invention after processing.

Claims (2)

[Claims] Claim 1: A cast steel made of ferritic, austenitic, or annealed martensitic steel, and the hardness of the inside of the main body is Vickers hardness (HV
) 250 or less, 0.1 mm or more 1.5 from the surface layer
The hardness of the surface part is less than mm than the hardness inside the main body (HV)
A cast steel product with controlled burr generation during cold working, characterized by having a hardened surface layer with a hardness of 100 or more. 2. The cast steel product with controlled burr generation during cold working according to claim 1, wherein the surface hardening layer comprises a carburized layer or a nitrided layer.