Research on Forge
Processing Technology
Kiichiro Toyoda anticipated that as advances were made in
casting technology, cast components would replace forged components. Therefore,
when the Koromo Plant was constructed, investment in forging facilities was
limited. Kiichiro explained his reasoning as follows:
I am ashamed to say that we are still using a primitive
method. The workers are quite used to the processes, so even if the methods are
primitive, the products themselves are fairly accurate... I had research
conducted on forging machines and one-heat process forging in preparation for
mass production, but the workers were rather unenthusiastic, and as a result
the design of the Koromo Plant used the old style.
The "primitive method" that Kiichiro refers to was
hammer forging, which indicates production methods such as those using free
hammer and stamping hammer with a forging die. The forging machinery installed
at the Koromo Plant included not only hammer forging equipment, but also
forging machines that perform die forging. The latter is a type of horizontal
press known as an upsetter and is used to machine the ends of long materials to
form rear axles and other components.
Rear axle shaft formation
process using upset forging
However, the workers were not accustomed to the upset
forging machinery manufactured by Eumuco in Germany, and initially it was not
used. Later, when it was learned that the dies for three processes could be
arranged and three-step formation performed with a single heating, the workers
recognized the efficiency of one heat forging and started using the upset
forging equipment in 1940.
Research on
Alternative Steel
Nickel supplies became extremely tight across the globe as a
result of the outbreak of the Second World War in September 1939 and exports to
Japan were interrupted. As a result, the Ministry of Commerce and Industry
issued regulations on August 20, 1940 restricting the use of nickel, and
emergency standards on alternative steels that use limited amounts of nickel
were adopted. Alternative steels were manufactured within Japan based on those
standards.
Article on
substitutes for nickel steels in Automotive Industries, an American publication
On March 19, 1941, the Machinery Materials Department of the
Japan Society of Mechanical Engineers and the Automotive Steel Materials
Research Center of the Iron and Steel Institute of Japan held a combined
symposium to discuss alternatives to nickel chrome steel with a focus on
automotive steels. During the meeting, the use of chrome molybdenum steel in
place of nickel chrome steel was discussed.
The United States also experienced a nickel shortage, and
the American Iron and Steel Institute issued a pamphlet entitled 'Possible
Substitutes for Nickel Steels' as a countermeasure. Kiichiro submitted an
abstract of an article on this problem for the June 1942 issue of Journal of
the Japan Society of Mechanical Engineers. In this way, research on steels was
conducted by making reference even to foreign publications.
Toyota Motor Co., Ltd. conducted research on heat treatments
of each steel type with the aim of switching to a different steel. Specific
areas of research included the transformation temperature, quench hardening
ability, tempering ability, and other characteristics of steels with different
compositions and properties depending on the temperature, the effects of
different masses on quenching hardness and depth according to the size and
thickness of the material, quenching deformation, and so on. In 1941, a switch
was made from nickel chrome steel to chrome molybdenum steel.
Later, molybdenum also became scarce, and it became
necessary to switch from chrome molybdenum steel to chrome steel. This problem
was resolved around 1943. Research was also conducted on switching from alloy
steels to carbon steel for some components, and a shortage of chrome steel
necessitated testing on the practicality of switching to all-carbon steel.
As a result of this research, the properties of various
steels were determined, making it possible to use the steel best suited for the
application. Although they were first referred to as alternative steels, when
used in appropriate applications, they were no longer simply alternatives.3
Truck Production and
the Steel Shortage
In 1935, when the Automotive Department of Toyoda Automatic
Loom Works, Ltd. launched the G1 truck, Japan's annual domestic steel
production amounted to 3.81 million tons (3.74 million tons of regular steel,
70,000 tons of special steel). Most of the raw material for Japan's iron and
steel production was provided from scrap metal, the consumption of which
reached 2.98 million tons in that year. The industry relied on scrap metal
imports of more than one million tons a year from the United States, but these
were interrupted in 1940, sparking an increasingly serious iron and steel
shortage in Japan. The pre-war, mid-war peak of iron and steel production was
reached in 1943, with 7.65 million tons, for which 4.17 million tons of scrap
metal was consumed (99 percent from domestically-produced sources).
In addition to this quantitative shortage, steel for
automotive use also faced major problems in terms of quality. Aware of the
importance of steel materials, Kiichiro Toyoda's initial policy was to
establish a steelworks to carry out research and development into steel
materials; when successful development of the necessary steel varieties was
assured, their production would be commissioned to a specialist steel
manufacturer. However, the material produced by steel manufacturers-who used
scrap metal as their main raw material-was contaminated with surplus alloy
constituents, so that the composition and properties of the steel varied
between different manufacturers even for a steel variety of the same
specification. Dimensions and shape were also subject to variation, making it
unsuitable for mass production.
Therefore, if Toyota wanted to obtain steel material of
confirmed quality, it would have to produce it in its own steelworks. In Kiichiro's
opinion, the mass production of good quality automobiles required steel
material of good machinability and excellent durability.
In 1939, to cope with increased production at Toyota Motor
Co., Ltd., the Steelmaking Department of Toyoda Automatic Loom Works took steps
to increase production capacity: using space freed up after the completion of
the Koromo Plant, two additional 4-ton electric furnaces were installed, which
began operation in May of the same year.
As mentioned previously, from January 1940 until the end of
the year, the steelworks was under the guidance of the engineer Louis Henry
Berry. In spring of that year, Shoichi Saito, Manager of the Auditing and
Improvement Section, was posted to the steelworks, where he worked as
interpreter and assistant to Berry, and in six months learned about grain size3
and other aspects of steel manufacturing technology.
After listening to advice from Berry, Kiichiro came to
realize that the purity of the steel manufacturing raw material was an
important factor. To obtain pure raw material for steelmaking rather than scrap
metal contaminated with other constituents, Kiichiro therefore sent Saito to
mainland China in September 1940 on an investigative mission. At the same time
as researching pure raw materials for steelmaking, Kiichiro explored various
strategies to deal with the raw material shortage, but resolving the absolute
shortage of steel materials proved difficult.
The Model KC truck
catalogue (1943)
Truck development and production thus proceeded against a
background of insufficiencies in both the quality and the quantity of steel
material. In January 1940, the GB truck was upgraded. Among the improvements
were an increase in engine output from 75 hp to 78 hp, improved engine cooling
efficiency, and enhancements in the suspension area.
Meanwhile, the Ministry of Commerce and Industry's
Automobile Technology Committee (established in August 1939), which was working
on the creation of standard vehicle specifications, called for an increase in
truck load capacity. In response, Toyota Motor Co., Ltd. took the decision to
develop a new truck model based on a substantial upgrade of the GB truck. In
March 1942, it began production of the KB truck with a 4-ton load capacity.
On July 14 of the next year, 1943, the Automobile Technology
Committee officially decided the specifications of a wartime truck. Based on
these specifications, Toyota Motor Co., Ltd. developed the KC truck and used it
to replace the KB in November of the same year. To adapt to the steel shortage,
the design of the KC truck achieved a saving of around 30 percent (260 to 300
kilograms) in the use of steel material compared to previous trucks.
Source: TOYOTA MOTOR CORPORATION
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