The method of hardening the surface of steel products

 

(57) Abstract:

Usage: chemical and thermal processing of metals. The inventive Surface of the steel product is heated electrically short arc reverse the polarity of the carbon electrode, and then cooled to a temperature of phase transformations. Create pressure to plastic deformation parallel to the two lateral boundary flows seam heating separate tool. Thus is saturated carbon steel, plastic deformation and hardening with increasing wear of the product by increasing surface hardness and reduce roughness. 1 C.p. f-crystals, 1 tab., 2 Il.

The invention relates to chemical-heat treatment of steel and can be used for surface hardening of steel products.

Known methods of hardening steel products, including heating surface to the melting temperature, the saturation of its carbon and quenched by rapid cooling in an environment of refrigerant (see and.with. N 53326 class. C 23 C 8/08; N 589286 class. With 38 8/06; N 1104102 class. With 7 patents great Britain).

The disadvantages of the known analogues are low mechanical properties, since it is formed of coarse-grained austenite and m is the development and education of the wavy surface.

The prototype of the invention is a method of hardening the surface of steel products, including heating surface to the melting temperature electrical short reverse polarity arc carbon electrode [1]

The disadvantage of the prototype is the lack of durability of the hardened surface and its low quality due to heterogeneity of the microhardness and roughness.

The purpose of the invention increase the durability of the product by increasing the surface microhardness and reduce surface roughness.

This goal is achieved by the fact that after processing, the surface is cooled to a temperature of phase transformations, then smoothing tool create pressure to plastic deformation with simultaneous quenching surface, and a smoothing tool is cooled by the refrigerant, the pressure to plastic deformation creates parallel to the boundary surface heating of the treated and untreated surface separate tools.

In Fig. 1 shows a General view of a device for hardening the surface of steel products on the way. In Fig. 2 shows a top view in Fig. 1. The device includes processed the rotation of the product 1, in parallel with two smoothing tool in the form of elastic plates 3 fixed in the rotary beam 4 bolt 5 installed in the screw axis 6, on the uprights 7 of the casing 8 is clamped in a support plate of the machine by bolts 9. Through the slots of the smoothing plate 3 by bolts 10 attached water radiators 11 on the other side of the plate 3 are based on an adjustable screw support 12.

The method is as follows. The product is 1 result in rotation with a linear speed of 2 to 10 m/min Electrode 2 is put into rotation counter surface 1 and serves on the electric voltage of the opposite polarity.

Between the electrode 2 and the surface of the product 1 set short electric arc with a current strength of 100 to 1000 A. Set the processing mode to the sealing surface 1, i.e., about 1540oC. Here is intense diffusion saturation of the molten bath carbon and temperature of crystallization is reduced to the melting temperature of iron 1156oC. After the arc contact thermocouple (not shown) determine the cooling zone of the treated surface of the product 1 to the temperature of phase transformations 900 600oWith due to internal heat dissipation), where set is the second surface) on the product 1 is mounted an adjusting screw jacks 12. At the same time through the radiators 11 pumped water.

When fusing the surface of the product 1 under the action of a plasma arc pressure in the bath of molten metal on the limits of the heat generated longitudinal seams across the width "A" of the bath and with a height of lateral flows. Especially in conditions of intensive treatment modes. When the movement of the plates 3, each of which plastically deforms flows "In" and aligns them. When this occurs, additional refinement of the structure of the metal, the formation of martensite deformation of residual austenite and mechanical work hardening. At the same time smoothing plate 3, having a low temperature, cooled rapidly deformed surface layer of the product 1, which stops the phase transformation, prevents the growth of crystals and stabilize supersaturated solid solution of carbon in iron austenite and martensite, i.e., is immediately hardened steel with increased dispersion and microhardness of structural components. With step-by-step movement of the arc of the cylindrical surface in the direction of V (arrow) lateral inflow suture from treated and untreated surfaces are in various conditions of thermal treatment. Side Napoli always heated a second time, what is the reason for the leave, reduction of microhardness and its large spread in the width of the seam A.

When the secondary thermal effects as promotion tool, when the influx is from the processed surface, the secondary remelting of metal, recrystallization and phase transformations in the underlying zone under the molten surface. The initial state of the structure, namely, its dispersion, which is embedded in the first cycle of melting and deformation has a significant impact due to heredity on the process of structure formation is the lateral inflow from surface re-melting and deformation.

Separately dvuhtokovoe thermal and combined with it mechanical impact, carried out in stages, it is possible to increase the average hardness due to its alignment in the cross section "A" seam. This greatly increases the dispersion melted and the underlying zone, the uniformity of hardening and surface quality.

Water radiators 11 secured by bolts 10 in the slots, can travel to the heating zone, they help to remove the excess heat generated is the possibility of their longitudinal extension to the melting zone and are fastened by the bolts 5. The beam is capable of rotational movement around the screw axis 6, mounted in the uprights 7 of the casing 8, which is fixed in the support plate of the machine by bolts 9.

The implementation of the method is illustrated by examples.

Example 1. The product blank with a diameter of 100 mm of steel grade NM (billet) is fixed in the Chuck of a lathe. Disk carbon electrode with a diameter of 150 mm, thickness 5 mm set with a gap with the surface of the workpiece. Set the linear speed of movement of the surface of the workpiece 2 m/min, step 3.5 mm and treat the surface of the workpiece to melt electrical short reverse polarity arc current of 300 A, the voltage 23,0 Century

After processing, the workpiece is cooled, cut the samples across the joint and produce sections. Measure the surface roughness and microhardness across the joint. The data are summarized in table 1.

Example 2. In example 1 after the electrode thermocouple determine the area of the cooling surface to 900oC, where the set on the whole caliper smoothing tool with Silvaniei smoothing 1000 H to obtain a smooth surface. Through shirt smoothing tool pumped water.

After processing zagotovka Verdot across the joint. The data are summarized in table.

Example 3. In example 2 establish two separate smoothing tool along the borders of the heating zone. After processing, the workpiece is cooled, cut the samples across the joint and produce sections. Measure the surface roughness and microhardness across the joint. The data are summarized in table 1.

The table shows that the application of a smoothing tool surface roughness of from 0.3 mm was reduced to 0.1 mm.

The table shows that the hardness of the hardened surface using a smoothing tool increases the hardness of the surface without mechanical treatment at 200 to 600 MPa. When processing a separate smoothing, compared to the whole, the hardness of the surface hardening on the limits of surface temperature increased by 115 270 MPa.

Thus, the application of the proposed method by increasing the homogeneity of the structure of a deformable surface and its microhardness allows to increase the average hardness and mechanical properties of the workpiece.

1. The method of hardening the surface of steel products, including heating surface to the melting temperature of an electrical short arc reverse polarity is poverhnosti microhardness and reduce surface roughness, after processing, the surface is cooled to a temperature of phase transformations, then smoothing tool create pressure to plastic deformation with simultaneous quenching surface, and a smoothing tool is cooled by the refrigerant.

2. The method according to p. 1, characterized in that the pressure to plastic deformation creates a boundary surface heating of the treated and untreated surfaces of the product separate tools.

 

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FIELD: rolling-mill machinery.

SUBSTANCE: the invention presents an installation for rolled metal cooling and is dealt with metal rolling, in particular with cooling of rolled metal. The installation for rolled metal cooling contains a body with an inlet branch-pipe and two rows of outlet branch-pipes displaced from each other by a half step. Value of a step of the outlet branch pipes in each row does not exceed four internal diameters of the branch-pipes. Across the body opposite to an entry of the inlet branch-pipe a dissector is installed. Along the body opposite to the outlet branch-pipes there are two entire central plates and two fragmentary lateral plates forming two longitudinal funnel-shaped cavities, turned by their narrow parts to each row of outlet branch-pipes. Fragmentariness of the lateral plates is created at the expense at least of one cutout in the base of each plate, at the longitudinal butts of which there are two perpendicularly fixed damping plates facing inside the funnel-shaped cavities. The invention allows to increase evenness, flexibility and efficiency of the rolling metal cooling process and ensures reliable operation of the installation.

EFFECT: the invention allows to increase evenness, flexibility and efficiency of the rolling metal cooling process and ensures reliable operation of the installation.

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