JPS58154451A - Casting - Google Patents

Abstract

PURPOSE:To provide a casting which can be produced efficiently and inexpensively like forgings and forging castings, by remelting the surface layer by a moving heat source thereby removing surface defects such as shrinkage cavities and decreasing impurity concn. CONSTITUTION:A stainless steel roll 1 which is produced by a centrifugal casting method is placed on a turntable (not shown), and while the roll is rotated in an arrow (a) direction, a heat source 3 is moved in an arrow (b) direction from the end A to the end B to melt the surface of the roll spirally over the entire part. As the source 3 moves in the circumferential arrow (b') direction of the roll 1, impurities remain in a molten pool 4, and the amt. of the impurities in a solidified part 2 decreases. The impurities of high concn. remain in the final solidified part at the end B in the final, and said part is machined away if necessary. A TIG welding device or the like is usable for the source 3, and the inside of slag or the like is effective in removing impurities as the atmosphere in the stage of melting. Residual stresses are removed by a post-treatment such as heat treatment according to need.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a casting that takes advantage of the excellent manufacturability of casting, removes all the defects peculiar to casting, and retains the characteristics of forged or molten products.

In the case of castings, it is almost impossible to eliminate casting defects including minute cavities. These casting defects lower the quality of cast products compared to forged products, and as a result, despite their excellent manufacturability, the use of cast products is completely hindered. Among defects, defects near the surface have a particularly large influence.

The following is an example of how defects near the surface affect the quality of castings.

(1) When stainless steel castings are used in an aqueous solution, it becomes a starting point for pitting corrosion.

(2) In the case of heat-resistant steel castings, carburizing resistance is reduced (e.g., cranking tubes for ethylene cracking furnaces are generally used by machining both sides of centrifugally cast tubes such as HK40, but (Due to low carburizing resistance, in some cases it is unavoidable to use expensive fused pipes.)

(3) During induction hardening, quenching cracks occur at all starting points of casting defects.

(4) When a fluctuating load is applied, it becomes the starting point for fatigue cracks and causes a decrease in strength.

(5) Defects may appear after processing and the product may be discarded.

(6) It can cause defects in surface treatments such as plating.

Generally, the properties of metal products, such as strength, corrosion resistance, and carburization resistance, are largely controlled by the properties of their surfaces. The same is true for castings, as described in (1) to (6) above ((especially dominated by casting defects existing near the surface).

Therefore, in the present invention, the advantages of the manufacturing technology of casting are utilized as is, and only the surface layer of the cast product has properties similar to those of forged or molten products.

That is, the present invention relates to a casting characterized in that the surface layer can be melted by a moving heat source.

The casting of the present invention can be used for cracking tubes for ethylene plants, size press rolls for paper machines, induction hardening rolls,
It can be applied to plated rolls, centrifuge bowl heads, suction rolls, and various other cast products that dislike surface defects.

Hereinafter, the casting of the present invention will be explained in detail by giving specific examples.

Specific Example 1 Stainless steel fi [5O813] for paper machines [A roll is first manufactured by a centrifugal casting method. .

This roll 1 is shown in FIG.
As shown in the cross-sectional view of FIG. The arrow b' in Figure 1 (2) indicates the movement of the heat source 6 in the circumferential direction of the roll 1.
], when the entire surface is melted in a spiral manner, impurities remain in the bath melt layer 4, and the amount of impurities in the solidified portion 2 decreases. Eventually, a high concentration of impurities will remain in the final solidified part at the B end, and this part naturally tends to cause cracks and other defects, but since this part is extremely small, it can be deleted. In addition, defects such as cracks and cavities on the surface can also be removed by the above-mentioned melting process.

In addition, in order to effectively remove all surface defects or to make the molten layer as shallow as possible, it is necessary to roughen the roll surface to remove the casting surface prior to the above melting. desirable. In addition, the heat source is not particularly limited, but for example, TIG welding equipment or plasma welding equipment can be used, and the atmosphere during melting may be inert gas, vacuum, slag (for example, Examples include slag for door arc welding, etc., and slag is particularly effective for removing impurities in molten metal. Furthermore, residual stress is generated during melting, so if there is a risk of stress corrosion cracking, it is desirable to perform post-treatment such as heat treatment. One method is to use water cooling on the circular surface of the roll.

In addition, in the present invention, when it is desired to further reduce the impurity concentration or obtain surface layer performance superior to that of the base material,
High purity filler metals of the same or different materials can be added. When 5US316L'i was used as this dissimilar filler material, the corrosion resistance was measured.

The effects of the casting of the present invention obtained as described above are summarized as follows.

(1) Since there are no defects on the surface of the paper machine roll 1 that comes into contact with the corrosive liquid, a remarkable improvement in corrosion resistance can be obtained, and properties comparable to those of forged rolls and welded rolls can be obtained.

(2) The energy required for production is small (about 100 to 100 units of #forming rolls and welding rolls).

(3) Complex shapes can be easily obtained.

(4) Products comparable to forged or molten products can be obtained with a rho value.

(5) Surface defects such as cavities are eliminated.

(6) Impurity concentration decreases.

(7) Crystal grains become finer.

(8) There is no need to repair defects or dispose of the machine after processing.

Specific Example 2 A racking tube made of heat-resistant steel (HK40) for use in an ethylene plant is first centrifugally cast.

After rough-machining the inner surface of the tube 5, as shown in the partially cutaway vertical cross-sectional view of FIG. , the heat source 6 is moved in the axial direction C to melt the entire inner surface of the tube 5 from the left end to the right end. Note that in order to make the inner surface even smoother, machining may be performed subsequently.

In this case as well, it is possible to use the same atmosphere as in Example 1, water cooling the outer surface, post-heat treatment, or melting and grinding the same or different materials.

The effects obtained in this example are as follows.

(1) Since surface defects are eliminated, carburization resistance is improved.

(2) By making the molten layer shallower, the decrease in creep strength will be reduced, and the original strength of castings (greater than that of forged products) can be maintained.

(3) Other effects similar to those of Example 1 can be obtained.

Specific Example 3 A roll similar to that in Specific Example 1 is melted, polished, and plated to obtain a plated roll. In this case, the following effects can be obtained.

(1) Significant occurrence of pinholes, which are defects in plating□ It is possible to obtain a good plating ball.

(2) The number of plugs required to repair all the concave defects in Table 1m is significantly reduced.

(3) Other effects similar to those of Specific Example 1 can be obtained.

Specific Example 4 After casting a roll made of BC42, the surface is melted, and then the roll is hardened by induction hardening. In this case, the following effects can be obtained.

(1) Surface defects that become starting points for quench cracking are eliminated, and a good surface-hardened roll can be obtained.

(2) There is no starting point for fatigue failure during use.

(3) Other effects similar to those of Example 1 can be obtained.

Also, instead of the above induction hardening, O: 0.25%,
Mn: 1.67%, Si: 0.67%, Or:
2.41%, Mo: 0.61%, F'e: Solving power of high hardness material with remaining components 1) rA is added simultaneously with surface melting to obtain a surface hardened roll. In this case, the following effects can be obtained.

(1) The hardness of the base material was about Hv-1.70, but the hardness increased by cutting to about 1111, I Hv-460.

(2) There is no need to perform the entire curing process.

(3) Other effects similar to those of Example 1 can be obtained.

[Brief explanation of the drawing]

FIGS. 1 (1), (2) and 2 are diagrams showing an example of an embodiment for obtaining a casting according to the present invention. Sub-agents 1) Post-Morning agent Ryo Hagiwara - Figure 1, Figure 2, Figure 2

Claims (1)

[Claims] A casting characterized by the fact that the surface layer is remelted by a moving heat source.