DD204106A1 - PROCESS FOR SURFACE HARDENING IRON-CARBON ALLOYS - Google Patents

Abstract

The invention relates to the field of the metalworking industry. The aim of the invention is to increase hardness and wear resistance in the surface area substantially. The invention has for its object to provide sufficient and coordinated process parameters. According to the invention, the object is achieved by irradiating the surface of an iron-carbon alloy, preferably with> equal to 0.4% by mass C content, with a continuously radiating CO deep-2 power laser, the surface moving almost perpendicularly to the beam becomes. The starting material contains mainly ferrite and cementite of a crystallite size in at least one dimension <10 / micrometer and a dislocation density> equal to 10 high 10 / cm high 2. The relative speed between surface and laser beam is 1 to 10mm / s and the surface is doing a power density between 20 and 300kW / cm high 2 exposed. The laser beam is focused to a diameter <equal to 0.8mm. Fields of application of the invention are parts made of an iron-carbon alloy containing> equal to 0.4% by mass of carbon and requiring a hard and wear-resistant surface.

Description

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Process for surface hardening of iron-carbon alloys

Field of application of the invention

The invention relates to the field of the metalworking industry. Objects in which their application is possible and expedient are parts of an iron-carbon alloy, which preferably contains 0.4 mass / pound or more of carbon, which may be a hard and soft one Wear-resistant surface must have, such as crankshafts, bearings, housing parts, cutting and Ümformwerkzeuge.

Characteristic of the known technical solutions

It is known [lj? * Goiowko, WS Kovalenko, V. 3 «Chernenko, 77.?. Garashchuk, P, A, Vasilez, A. A, Svirgin, Elektronnaya obrabotka materialov o_ (1980) 26 ?. a method in which carbon steels are irradiated with 0.2% of 1.2% by weight of Ce, the surface of which is Zn-phosphated for better radiation coupling, under atmospheric conditions with a continuous radiative CO "power laser. The power density of the laser is

at 5 to 200 k ', 7 / cm ~ and the relative velocity zvrisclien surface and laser beam 10 to 70 mm / s. The surface layer achieves hardness values around 1000 EV, in exceptional cases a maximum of 1200 HV.

The disadvantage of this method is that due to insufficiently specified and coordinated

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drive parameters ·; the hardness and the wear resistance in the surface area is too low.

Object of the invention

The aim of the invention is to substantially increase hardness and wear resistance in the surface area.

Explanation of the essence of the invention

The object of the invention is to provide adequate and coordinated process parameters. According to the invention, the object is achieved by irradiating the surface of an iron-carbon alloy, preferably with > 0.4% by mass C content, with a continuously radiating COp power laser with the surface being moved nearly perpendicular to the beam * The starting material contains predominantly ferrite and cementite of crystallite size in at least one dimension

10 2

<10 / μm and a dislocation density> 10 / cm. The surface is metallically pure and defined radiation-absorbing prepared · The irradiation is carried out in an inert gas atmosphere, and the movement between laser beam and surface takes place with -a relative speed between 1 and 10 mm / s * The surface is doing a power density between 20 and 300 KsiZ / cm exposed and set the diameter of the laser beam on the surface <0.8 mm · The metallic pure and defined radiation-absorbing surface is achieved by Peinschleifen. As an inert gas atmosphere preferably nitrogen is used,

embodiments

Example 1:

The surface of a Fe-C alloy disk of 0.63 mass - $> C should be hardened.

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grit first and then sanded with emery paper of 220 grain size. The starting material has a structure of ferrite grains or ferrite and cementite fins in the Bsr lite grains, which are smaller than 10 μm at least in one dimension and has a

10.2 'dense clay 1.10 / cm ♦ For irradiation, a COp laser with a dower output of 200 W is used, whose beam is focused on the surface. · The focus has a diameter of 0.5 mm and an average effective power density of 90 ° kW / cm. The irradiation takes place in an atmosphere of technical nitrogen and the disk is thereby moved at a constant speed of 4.2 mm / s perpendicular to the laser beam. The heating and cooling rate is calculated to be 2.10 K / s and the holding time to the austenitizing temperature 1 ms · The surface of the disc after this treatment shows microhardness HV _{Q Q5} of: 1600 ·

Example 2:

An Fe-C alloy with 1.0 mass% C is to be surface hardened. For this purpose, the surface is prepared as described in Example T. The Ausgangsm _a material has a structure of Zementitkömem or ferrite and Zementitlamellen in the Perlitkömern, which are smaller than 10 / at least in one dimension. The dislocation density

10 2

contributes 1 · 10 / cm. The same laser and atmosphere are used as in Example 1. The speed at which the disk is moved perpendicular to the laser beam is 2.1 mm / s.

4 heating and cooling rate of 1.10 K / s and a holding time on the Austenitisierungstemperatur of 2 ms calculated · Hach this treatment shows the surface of the alloy has a microhardness HVq q ^ of 1650,

Example 3 '·

The surface of an Fe-C alloy with 2 _? 35% by weight of C is to be hardened. The surface is first coarse and then sanded with emery paper 220 grit.

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fen ". The starting material "has a structure of crystallites" or * graphite lamellae, which are smaller than 10 / at least in one dimension and has a dislocation density

10? from 1.10 / cm. The same laser is used as in Example 1. The irradiation takes place in an atmosphere of technical nitrogen and the material is thereby moved at a constant speed of 4 × 2 mm / s perpendicular to the laser beam. The heating and cooling rate is calculated under these conditions to 2.10 K / s and the holding time at the Austenitisierungstemperatur to 1 ms. After this treatment, the surface of the material shows microhardness HV _{n nt} - of 1500.

Even when the method is applied to cast iron, substantial increases in microhardness are achieved compared to conventional hardening technologies, which can reach up to HVq _Λ! - = 1250 ..

Claims (3)

238584 4 -s Srfindungsanspruch · Process for the surface hardening of iron-carbon. Alloys, preferably mil; ^ 0.4 mass% C content by irradiation with a continuously radiating COp power laser, wherein beam and surface are moved relative to each other, characterized in that as starting material a microstructure consisting mainly of ferrite and cementite a crystal size in at least one 10 2 dimension <10 μm and a dislocation density> 10 / cm is used, the surface is metallically pure and defined radiation absorbing prepared, the irradiation is carried out in an inert gas atmosphere, the movement between the laser beam and the surface at a relative speed between 1 and 10 mm / s, the surface is exposed to a power density between 20 and 300 R'üT / cm and the diameter of the laser beam is set on the surface <0.8 mm. 2. Method according to item 1, characterized in that the metallically pure and defined radiation-absorbing surface is achieved by fine grinding * 3. Method according to item 1, characterized in that nitrogen is preferably used as inert gas atmosphere «