US-12617034-B2 - Method of making a tool

Abstract

A method of making a tool having a joining a maraging steel joining partner and a cemented carbide joining partner by brazing and a tool made according to the method is provided. The method includes depositing a Ni coating onto the maraging steel joining partner prior to applying the filler material having at least 70 wt % Cu. The braze joint shows excellent shear strength.

Inventors

• Leif Dahl
• Tim ULITZKA

Assignees

• AB SANDVIK COROMANT

Dates

Publication Date

20260505

Application Date

20220815

Priority Date

20211103

Claims (8)

1. 1 . A method of making a tool by joining a cemented carbide joining partner with a maraging steel joining partner, the method comprising the steps of: applying a Ni coating with a thickness of between 0.5 and 15 μm on a joining surface of the maraging steel joining partner; placing a filler material including at least 70 wt % Cu between the cemented carbide joining partner and the Ni coated joining surface of the maraging steel joining partner; subjecting the cemented carbide joining partner and the maraging joining partner with the filler material in between to a brazing process at an elevated temperature in a vacuum furnace at a temperature between 90° and 1200° C., for a time period of between 1 and 60 minutes; and subjecting the joined cemented carbide joining partner and maraging joining partner to a tempering process at a temperature of between 30° and 600° C. for between 5 minutes and 12 hours.
2. 2 . The method according to claim 1 , wherein the filler material includes at least 99 wt % Cu.
3. 3 . The method according to claim 1 , wherein the Ni coating has a thickness of between 2 and 10 μm and is deposited using a PVD technique.
4. 4 . The method according to claim 1 , wherein the maraging steel comprises 8 to 25 wt % Ni, one or more alloying elements selected from Co, Mo, Ti, Al and Cr in a total amount of between 7 to 27 wt %, less than 0.03 wt % C and a balance of Fe and impurities.
5. 5 . The method according to claim 1 , wherein the maraging steel comprises 11 to 25 wt % Ni, 7 to 15 wt % Co, from 3 to 10 wt % Mo, 0.1 to 1.6 wt % Ti, from 0 to 0.15 wt % Cr, from 0 to 0.2 wt % Al, and less than 0.03 wt % C with a balance of Fe and impurities.
6. 6 . The method according to claim 1 , wherein the maraging steel comprises 15 to 25 wt % Ni, 8.5 to 12.5 wt % Co, from 3 to 6 wt % Mo, 0.5 to 1.2 wt % Ti, from 0 to 0.15 wt % Cr, from 0 to 0.2 wt % Al, less than 0.03 wt % C with a balance of Fe and impurities.
7. 7 . The method according to claim 1 , wherein the brazing process takes place at a temperature of between 95° and 1170° C. for between 5 and 30 minutes.
8. 8 . The method according to claim 1 , wherein the tempering process takes place at a temperature of between 400 and 600° C. for between 2 and 5 hours.

Description

RELATED APPLICATION DATA This application is a § 371 National Stage Application of PCT International Application No. PCT/EP2022/072751 filed Aug. 15, 2022 with priority to SE 2130220-3 filed Aug. 16, 2021 and EP 21206226.9 filed Nov. 3, 2021. TECHNICAL FIELD The present invention relates to a method of making a tool comprising a joining a maraging steel joining partner and a cemented carbide joining partner by brazing. The present invention also relates to a tool made according to this method. BACKGROUND Joining steel with cemented carbide by brazing or welding has been known for a long time in the art of making tools. There are several challenges when joining steel with cemented carbide, e.g. differences in CTE (coefficient of thermal expansion), strength of the braze joint, undesired hardness profiles in the steel etc. There are several solutions that can improve each of these problems individually, but the solutions often result in problems in other areas and not all problems can be solved. The principle of brazing is that you use a filler material that joins two pieces when heated. There are several ways to heat the braze joint, where one of the most common way is induction heating using an induction coil. One of the benefits with using a coil is that only the local area around the braze joint is heated and leaving the rest of the tool unaffected. This local heating can however lead to unwanted hardness profiles in the steel part which can cause problems when the steel part will be provided with threading etc., for fastening rotary tools and other cutting tools etc. SUMMARY One object of the present invention is to provide a tool which have both a strong braze joint and a steel part with an even hardness profile and a high hardness and consequently an improved wear resistance. Another object of the present invention is to provide a process of joining steel and cemented carbide which is easy to use and lead to a predictable joint with high strength and a steel part that has a predictable hardness. The present invention relates to a method of making a tool by joining a cemented carbide joining partner with a maraging steel joining partner comprising the steps of: applying a Ni coating with a thickness of between 0.5 and 15 μm on a joining surface of the maraging steel joining partner;placing a filler material comprising at least 70 wt % Cu in contact with the cemented carbide joining partner and the joining surface of the maraging steel joining partner;subjecting the cemented carbide joining partner and the maraging joining partner with the filler material in between to an elevated temperature in a vacuum furnace at a temperature between 90° and 1200° C., for a time period of between 1 and 60 minutes;subjecting the joined cemented carbide joining partner and maraging joining partner to a tempering process at a temperature of between 30° and 600° C. for between 5 minutes and 12 hours. Maraging steel is a type of steel, which is hardened by precipitation of intermetallic compounds. Maraging steels suitably contains from 8 to 25 wt % Ni and one or more alloying elements selected from Co, Mo, Ti, Al and Cr in a total amount of between 7 to 27 wt %, preferably between 7 to 23 wt % of alloying elements. Maraging steels typically contain less carbon than conventional steel, suitably 0.03 wt % or less. The balance being Fe and impurities. In one embodiment of the present invention, the maraging steel according to the present invention contains from 11 to 25 wt % Ni, preferably 15 to 25 wt % Ni. The alloying elements are suitably Co in an amount of from 7 to 15 wt %, preferably 8.5 to 12.5 wt % Co, Mo in an amount of from 3 to 10 wt %, preferably 3 to 6 wt % Mo, Ti in an amount of from 0.1 to 1.6 wt %, preferably from 0.5 to 1.2 wt % Ti, from 0 to 0.15 wt % Cr, Al in an amount of from 0 to 0.2 wt % and less than 0.03 wt % C. The balance being Fe and impurities. In one embodiment of the present invention, the maraging steel has a composition of from 17 to 19 wt % Ni, from 8.5 to 12.5 wt % Co, from 4 to 6 wt % Mo, from 0.5 to 1.2 wt % Ti, from 0 to 0.15 wt % Cr, from 0 to 0.2 wt % Al and less than 0.03 wt % C. The balance being Fe and impurities. By impurities is herein meant any element that can be present in the maraging steel in such small amounts that it does not have any influence on the properties of the steel. The total amount of impurities is below 0.50 wt %, preferably below 0.15 wt %. Examples of such elements are Mn, P, Si, B and S. In one embodiment of the present invention, the amount of Mn is less than 0.05 wt %, the amount of P is less than 0.003 wt %, the amount of Si is less than 0.004 wt % and the amount of S less than 0.002 wt %. The Ni coating can be deposited using any coating technique known in the art of depositing Ni coatings, e.g., galvanization or PVD. The thickness of the Ni coating is between 0.5 and 20 μm, preferably between 2 and 10 μm. In one embodiment of the present invention, the Ni