Hanomag Lohnhärterei
Corporate brand
UnclaimedGerman contract heat-treatment group specialising in the hardening of steel and aluminium, founded in 1986 out of the Hanomag machinery works.
Last updated September 28, 2026
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Overview
Hanomag Lohnhärterei is a German industrial service group based in Hannover that specialises in contract heat treatment — the hardening, case-hardening, tempering and related thermal processing of steel, aluminium and other metallic materials — together with complementary mechanical machining and measuring/testing services. The business traces its origins to the in-house hardening shop of the Hannoversche Maschinenbau AG (Hanomag), the historic Hannover machinery builder founded in 1835 by Georg Egestorff, whose product range once spanned locomotives, tractors, construction vehicles and racing cars. In 1986 the hardening operation was spun out of Hanomag AG and reconstituted as Hanomag Lohnhärterei GmbH, with participation from the Hanomag GmbH holding company and Konrad Seehafer. Since 1993 the company has been owned by the Seehafer family. The group operates as a network of heat-treatment plants rather than a single site. From its Hannover base it expanded across Germany — Berlin (1992), Gommern (1995), Gevelsberg and Wernigerode (1998), a new-build in Hannover-Marienwerder (2004), Hildesheim (2018), Penzberg (2023) and Uhldingen-Mühlhofen (2023) — and internationally into Poland (Poznań, 2015) and Austria (Taufkirchen an der Pram, 2019). The official website describes the group as one of Germany's leading contract hardening businesses, with more than 30 years of activity, modern plant technology at 13 locations, and a service portfolio covering the full spectrum of heat-treatment processes plus upstream and downstream operations, measurement and testing. At many sites mechanical machining centres have been integrated so that the group can supply a complete process chain from raw part to inspected, ready-to-install finished component. Hanomag Lohnhärterei serves demanding industrial sectors — automotive, machinery and other technology-driven fields — and positions itself around quality, continuity and sustainability. Its stated vision is to be the market reference in surface technology and component processing for sophisticated technological areas. The group pursues a decarbonisation target of halving CO₂ emissions per customer component by 2030 against a 2019 baseline, and its sustainability performance is assessed through platforms such as NQC, EcoVadis and SupplyOn. Quality and environmental management are certified to automotive and ISO standards across the locations, and the group has invested in process innovation, including a patent for low-pressure carburising. Leadership has passed to the next generation: Karsten Seehafer, son of founder Konrad Seehafer, joined the management in 2000 and is a public face of the group. In 2026 the company marks 40 years since its founding.
History
The roots of Hanomag Lohnhärterei lie in the Hannoversche Maschinenbau AG (Hanomag), a Hannover machinery manufacturer founded in 1835 by Georg Egestorff. Over more than a century Hanomag built an unusually broad product range — locomotives, tractors, construction vehicles and racing cars — and maintained its own in-house hardening shop (Betriebshärterei) for the heat treatment of components. By the 1980s the Hanomag group was in difficulty. In April 1984 the entrepreneurs Alfred Gassmann, Helmut Gassmann and Günter Papenburg founded a holding company, Hanomag GmbH, to take over parts of the business. Two years later, in 1986, the hardening operation was spun out of Hanomag AG and reconstituted as Hanomag Lohnhärterei GmbH, with participation from Hanomag GmbH and Konrad Seehafer. This 1986 spin-out is the founding date the company itself uses, and the group celebrated its 40th anniversary in 2026. Ownership consolidated in the Seehafer family from 1993. Growth then proceeded through a series of new sites and acquisitions. In 1992 the group established Hanomag Härtol Lohnhärterei GmbH in Berlin; in 1995 a further site followed in Gommern. In 1998 two more locations were added — Gevelsberg and, under the Hanomag Härtol name, Wernigerode. In 2000 Karsten Seehafer, son of founder Konrad Seehafer, joined the management of Hanomag Lohnhärterei GmbH, marking the transition to the next generation. In 2004 the group built new premises in Hannover-Marienwerder for both Hanomag Lohnhärterei GmbH and Hanomag Härtecenter GmbH, consolidating its Hannover operations. The following decade was shaped by certification and process innovation. In 2006 all group locations were certified to ISO/TS 16949 (the automotive quality standard), followed by an environmental management system to ISO 14001 in 2009 and an energy management system to ISO 50001 in 2013. In 2010 the group obtained a patent for low-pressure carburising, an important modern case-hardening technology. International expansion began in 2015 with the founding of Hanomag Heat Treatment International Sp.z.o.o. in Poznań, Poland. In 2018 the group acquired Herbst Zerspanungs- und Messtechnik GmbH in Hildesheim, adding machining and measuring capability; in 2019 it established a site in Taufkirchen an der Pram, Austria, under Hanomag Heat Treatment International GmbH & Co. KG. The most recent phase has broadened the group's material and service scope. In 2021 Hanomag Aluminium Solutions GmbH was founded with sites in Kassel and Baunatal, extending the group's aluminium heat-treatment offering. In 2023 the group took over a site in Penzberg and acquired HTU Härtetechnik Uhldingen-Mühlhofen GmbH. Today the group describes itself as one of Germany's leading contract hardening businesses, active for more than 30 years, with modern plant technology at 13 locations and a service range covering the full heat-treatment spectrum plus mechanical machining, measurement and testing. It positions itself around quality, continuity and sustainability, with a stated decarbonisation goal of halving CO₂ emissions per customer component by 2030 versus 2019.
- 2026
Group marks 40 years since its founding (1986–2026).
- 2023
Takeover of the Penzberg site and acquisition of HTU Härtetechnik Uhldingen-Mühlhofen GmbH.
- 2021
Hanomag Aluminium Solutions GmbH founded with sites in Kassel and Baunatal.
- 2019
Site established in Taufkirchen an der Pram, Austria.
- 2018
Acquisition of Herbst Zerspanungs- und Messtechnik GmbH in Hildesheim.
- 2015
Hanomag Heat Treatment International Sp.z.o.o. founded in Poznań, Poland.
- 2013
Energy management system to ISO 50001 introduced.
- 2010
Group receives patent for low-pressure carburising.
- 2009
Environmental management system to ISO 14001 introduced.
- 2006
All group sites certified to ISO/TS 16949.
Products and positioning
Market reference in surface technology and component processing for demanding technological sectors, built on quality, continuity and sustainability.
Heat treatment of steel
Heat treatment of aluminium
Low-pressure carburising
Mechanical machining (prototypes, pre-series, series)
Measuring and testing services
Material consulting
Sources6 sources
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